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Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]5 <title>Writing an LLVM Compiler Backend</title>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]6 <link rel="stylesheet" href="llvm.css" type="text/css">
7</head>
8
9<body>
10
Chris Lattner611944b2008-11-11 19:31:26 +0000[diff] [blame]11<div class="doc_title">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]12 Writing an LLVM Compiler Backend
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]13</div>
14
15<ol>
16 <li><a href="#intro">Introduction</a>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]17 <ul>
18 <li><a href="#Audience">Audience</a></li>
19 <li><a href="#Prerequisite">Prerequisite Reading</a></li>
20 <li><a href="#Basic">Basic Steps</a></li>
21 <li><a href="#Preliminaries">Preliminaries</a></li>
22 </ul>
23 <li><a href="#TargetMachine">Target Machine</a></li>
Chris Lattner528875c2008-11-11 19:34:28 +0000[diff] [blame]24 <li><a href="#RegisterSet">Register Set and Register Classes</a>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]25 <ul>
26 <li><a href="#RegisterDef">Defining a Register</a></li>
27 <li><a href="#RegisterClassDef">Defining a Register Class</a></li>
28 <li><a href="#implementRegister">Implement a subclass of TargetRegisterInfo</a></li>
Chris Lattner528875c2008-11-11 19:34:28 +0000[diff] [blame]29 </ul></li>
30 <li><a href="#InstructionSet">Instruction Set</a>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]31 <ul>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]32 <li><a href="#operandMapping">Instruction Operand Mapping</a></li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]33 <li><a href="#implementInstr">Implement a subclass of TargetInstrInfo</a></li>
34 <li><a href="#branchFolding">Branch Folding and If Conversion</a></li>
Chris Lattner528875c2008-11-11 19:34:28 +0000[diff] [blame]35 </ul></li>
36 <li><a href="#InstructionSelector">Instruction Selector</a>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]37 <ul>
Chris Lattner528875c2008-11-11 19:34:28 +0000[diff] [blame]38 <li><a href="#LegalizePhase">The SelectionDAG Legalize Phase</a>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]39 <ul>
40 <li><a href="#promote">Promote</a></li>
41 <li><a href="#expand">Expand</a></li>
42 <li><a href="#custom">Custom</a></li>
43 <li><a href="#legal">Legal</a></li>
Chris Lattner528875c2008-11-11 19:34:28 +0000[diff] [blame]44 </ul></li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]45 <li><a href="#callingConventions">Calling Conventions</a></li>
Chris Lattner528875c2008-11-11 19:34:28 +0000[diff] [blame]46 </ul></li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]47 <li><a href="#assemblyPrinter">Assembly Printer</a></li>
48 <li><a href="#subtargetSupport">Subtarget Support</a></li>
Chris Lattner528875c2008-11-11 19:34:28 +0000[diff] [blame]49 <li><a href="#jitSupport">JIT Support</a>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]50 <ul>
51 <li><a href="#mce">Machine Code Emitter</a></li>
52 <li><a href="#targetJITInfo">Target JIT Info</a></li>
Chris Lattner528875c2008-11-11 19:34:28 +0000[diff] [blame]53 </ul></li>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]54</ol>
55
56<div class="doc_author">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]57 <p>Written by <a href="http://www.woo.com">Mason Woo</a> and
58 <a href="http://misha.brukman.net">Misha Brukman</a></p>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]59</div>
60
61<!-- *********************************************************************** -->
62<div class="doc_section">
63 <a name="intro">Introduction</a>
64</div>
65<!-- *********************************************************************** -->
66
67<div class="doc_text">
68
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]69<p>
70This document describes techniques for writing compiler backends that convert
71the LLVM Intermediate Representation (IR) to code for a specified machine or
72other languages. Code intended for a specific machine can take the form of
73either assembly code or binary code (usable for a JIT compiler).
74</p>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]75
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]76<p>
77The backend of LLVM features a target-independent code generator that may create
78output for several types of target CPUs &mdash; including X86, PowerPC, Alpha,
79and SPARC. The backend may also be used to generate code targeted at SPUs of the
80Cell processor or GPUs to support the execution of compute kernels.
81</p>
82
83<p>
84The document focuses on existing examples found in subdirectories
85of <tt>llvm/lib/Target</tt> in a downloaded LLVM release. In particular, this
86document focuses on the example of creating a static compiler (one that emits
87text assembly) for a SPARC target, because SPARC has fairly standard
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]88characteristics, such as a RISC instruction set and straightforward calling
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]89conventions.
90</p>
91
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]92</div>
93
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]94<div class="doc_subsection">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]95 <a name="Audience">Audience</a>
96</div>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]97
98<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]99
100<p>
101The audience for this document is anyone who needs to write an LLVM backend to
102generate code for a specific hardware or software target.
103</p>
104
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]105</div>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]106
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]107<div class="doc_subsection">
108 <a name="Prerequisite">Prerequisite Reading</a>
109</div>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]110
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]111<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]112
113<p>
114These essential documents must be read before reading this document:
115</p>
116
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]117<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]118<li><i><a href="http://www.llvm.org/docs/LangRef.html">LLVM Language Reference
119 Manual</a></i> &mdash; a reference manual for the LLVM assembly language.</li>
120
121<li><i><a href="http://www.llvm.org/docs/CodeGenerator.html">The LLVM
122 Target-Independent Code Generator</a></i> &mdash; a guide to the components
123 (classes and code generation algorithms) for translating the LLVM internal
124 representation into machine code for a specified target. Pay particular
125 attention to the descriptions of code generation stages: Instruction
126 Selection, Scheduling and Formation, SSA-based Optimization, Register
127 Allocation, Prolog/Epilog Code Insertion, Late Machine Code Optimizations,
128 and Code Emission.</li>
129
130<li><i><a href="http://www.llvm.org/docs/TableGenFundamentals.html">TableGen
131 Fundamentals</a></i> &mdash;a document that describes the TableGen
132 (<tt>tblgen</tt>) application that manages domain-specific information to
133 support LLVM code generation. TableGen processes input from a target
134 description file (<tt>.td</tt> suffix) and generates C++ code that can be
135 used for code generation.</li>
136
137<li><i><a href="http://www.llvm.org/docs/WritingAnLLVMPass.html">Writing an LLVM
138 Pass</a></i> &mdash; The assembly printer is a <tt>FunctionPass</tt>, as are
139 several SelectionDAG processing steps.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]140</ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]141
142<p>
143To follow the SPARC examples in this document, have a copy of
144<i><a href="http://www.sparc.org/standards/V8.pdf">The SPARC Architecture
145Manual, Version 8</a></i> for reference. For details about the ARM instruction
146set, refer to the <i><a href="http://infocenter.arm.com/">ARM Architecture
147Reference Manual</a></i>. For more about the GNU Assembler format
148(<tt>GAS</tt>), see
149<i><a href="http://sourceware.org/binutils/docs/as/index.html">Using As</a></i>,
150especially for the assembly printer. <i>Using As</i> contains a list of target
151machine dependent features.
152</p>
153
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]154</div>
155
156<div class="doc_subsection">
157 <a name="Basic">Basic Steps</a>
158</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]159
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]160<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]161
162<p>
163To write a compiler backend for LLVM that converts the LLVM IR to code for a
164specified target (machine or other language), follow these steps:
165</p>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]166
167<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]168<li>Create a subclass of the TargetMachine class that describes characteristics
169 of your target machine. Copy existing examples of specific TargetMachine
170 class and header files; for example, start with
171 <tt>SparcTargetMachine.cpp</tt> and <tt>SparcTargetMachine.h</tt>, but
172 change the file names for your target. Similarly, change code that
173 references "Sparc" to reference your target. </li>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]174
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]175<li>Describe the register set of the target. Use TableGen to generate code for
176 register definition, register aliases, and register classes from a
177 target-specific <tt>RegisterInfo.td</tt> input file. You should also write
178 additional code for a subclass of the TargetRegisterInfo class that
179 represents the class register file data used for register allocation and
180 also describes the interactions between registers.</li>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]181
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]182<li>Describe the instruction set of the target. Use TableGen to generate code
183 for target-specific instructions from target-specific versions of
184 <tt>TargetInstrFormats.td</tt> and <tt>TargetInstrInfo.td</tt>. You should
185 write additional code for a subclass of the TargetInstrInfo class to
186 represent machine instructions supported by the target machine. </li>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]187
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]188<li>Describe the selection and conversion of the LLVM IR from a Directed Acyclic
189 Graph (DAG) representation of instructions to native target-specific
190 instructions. Use TableGen to generate code that matches patterns and
191 selects instructions based on additional information in a target-specific
192 version of <tt>TargetInstrInfo.td</tt>. Write code
193 for <tt>XXXISelDAGToDAG.cpp</tt>, where XXX identifies the specific target,
194 to perform pattern matching and DAG-to-DAG instruction selection. Also write
195 code in <tt>XXXISelLowering.cpp</tt> to replace or remove operations and
196 data types that are not supported natively in a SelectionDAG. </li>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]197
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]198<li>Write code for an assembly printer that converts LLVM IR to a GAS format for
199 your target machine. You should add assembly strings to the instructions
200 defined in your target-specific version of <tt>TargetInstrInfo.td</tt>. You
201 should also write code for a subclass of AsmPrinter that performs the
202 LLVM-to-assembly conversion and a trivial subclass of TargetAsmInfo.</li>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]203
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]204<li>Optionally, add support for subtargets (i.e., variants with different
205 capabilities). You should also write code for a subclass of the
206 TargetSubtarget class, which allows you to use the <tt>-mcpu=</tt>
207 and <tt>-mattr=</tt> command-line options.</li>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]208
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]209<li>Optionally, add JIT support and create a machine code emitter (subclass of
210 TargetJITInfo) that is used to emit binary code directly into memory. </li>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]211</ul>
212
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]213<p>
214In the <tt>.cpp</tt> and <tt>.h</tt>. files, initially stub up these methods and
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]215then implement them later. Initially, you may not know which private members
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]216that the class will need and which components will need to be subclassed.
217</p>
218
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]219</div>
220
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]221<div class="doc_subsection">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]222 <a name="Preliminaries">Preliminaries</a>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]223</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]224
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]225<div class="doc_text">
226
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]227<p>
228To actually create your compiler backend, you need to create and modify a few
229files. The absolute minimum is discussed here. But to actually use the LLVM
230target-independent code generator, you must perform the steps described in
231the <a href="http://www.llvm.org/docs/CodeGenerator.html">LLVM
232Target-Independent Code Generator</a> document.
233</p>
Matthijs Kooijman6aa81272008-09-29 11:52:22 +0000[diff] [blame]234
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]235<p>
236First, you should create a subdirectory under <tt>lib/Target</tt> to hold all
237the files related to your target. If your target is called "Dummy," create the
238directory <tt>lib/Target/Dummy</tt>.
239</p>
Matthijs Kooijman6aa81272008-09-29 11:52:22 +0000[diff] [blame]240
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]241<p>
242In this new
243directory, create a <tt>Makefile</tt>. It is easiest to copy a
244<tt>Makefile</tt> of another target and modify it. It should at least contain
245the <tt>LEVEL</tt>, <tt>LIBRARYNAME</tt> and <tt>TARGET</tt> variables, and then
246include <tt>$(LEVEL)/Makefile.common</tt>. The library can be
247named <tt>LLVMDummy</tt> (for example, see the MIPS target). Alternatively, you
248can split the library into <tt>LLVMDummyCodeGen</tt>
249and <tt>LLVMDummyAsmPrinter</tt>, the latter of which should be implemented in a
250subdirectory below <tt>lib/Target/Dummy</tt> (for example, see the PowerPC
251target).
252</p>
Matthijs Kooijman6aa81272008-09-29 11:52:22 +0000[diff] [blame]253
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]254<p>
255Note that these two naming schemes are hardcoded into <tt>llvm-config</tt>.
256Using any other naming scheme will confuse <tt>llvm-config</tt> and produce a
257lot of (seemingly unrelated) linker errors when linking <tt>llc</tt>.
258</p>
Matthijs Kooijman6aa81272008-09-29 11:52:22 +0000[diff] [blame]259
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]260<p>
261To make your target actually do something, you need to implement a subclass of
262<tt>TargetMachine</tt>. This implementation should typically be in the file
263<tt>lib/Target/DummyTargetMachine.cpp</tt>, but any file in
264the <tt>lib/Target</tt> directory will be built and should work. To use LLVM's
265target independent code generator, you should do what all current machine
266backends do: create a subclass of <tt>LLVMTargetMachine</tt>. (To create a
267target from scratch, create a subclass of <tt>TargetMachine</tt>.)
268</p>
269
270<p>
271To get LLVM to actually build and link your target, you need to add it to
272the <tt>TARGETS_TO_BUILD</tt> variable. To do this, you modify the configure
273script to know about your target when parsing the <tt>--enable-targets</tt>
274option. Search the configure script for <tt>TARGETS_TO_BUILD</tt>, add your
275target to the lists there (some creativity required), and then
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]276reconfigure. Alternatively, you can change <tt>autotools/configure.ac</tt> and
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]277regenerate configure by running <tt>./autoconf/AutoRegen.sh</tt>.
278</p>
279
Matthijs Kooijman6aa81272008-09-29 11:52:22 +0000[diff] [blame]280</div>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]281
282<!-- *********************************************************************** -->
283<div class="doc_section">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]284 <a name="TargetMachine">Target Machine</a>
285</div>
286<!-- *********************************************************************** -->
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]287
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]288<div class="doc_text">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]289
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]290<p>
291<tt>LLVMTargetMachine</tt> is designed as a base class for targets implemented
292with the LLVM target-independent code generator. The <tt>LLVMTargetMachine</tt>
293class should be specialized by a concrete target class that implements the
294various virtual methods. <tt>LLVMTargetMachine</tt> is defined as a subclass of
295<tt>TargetMachine</tt> in <tt>include/llvm/Target/TargetMachine.h</tt>. The
296<tt>TargetMachine</tt> class implementation (<tt>TargetMachine.cpp</tt>) also
297processes numerous command-line options.
298</p>
299
300<p>
301To create a concrete target-specific subclass of <tt>LLVMTargetMachine</tt>,
302start by copying an existing <tt>TargetMachine</tt> class and header. You
303should name the files that you create to reflect your specific target. For
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]304instance, for the SPARC target, name the files <tt>SparcTargetMachine.h</tt> and
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]305<tt>SparcTargetMachine.cpp</tt>.
306</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]307
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]308<p>
309For a target machine <tt>XXX</tt>, the implementation of
310<tt>XXXTargetMachine</tt> must have access methods to obtain objects that
311represent target components. These methods are named <tt>get*Info</tt>, and are
312intended to obtain the instruction set (<tt>getInstrInfo</tt>), register set
313(<tt>getRegisterInfo</tt>), stack frame layout (<tt>getFrameInfo</tt>), and
314similar information. <tt>XXXTargetMachine</tt> must also implement the
315<tt>getTargetData</tt> method to access an object with target-specific data
316characteristics, such as data type size and alignment requirements.
317</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]318
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]319<p>
320For instance, for the SPARC target, the header file
321<tt>SparcTargetMachine.h</tt> declares prototypes for several <tt>get*Info</tt>
322and <tt>getTargetData</tt> methods that simply return a class member.
323</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]324
325<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]326<pre>
327namespace llvm {
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]328
329class Module;
330
331class SparcTargetMachine : public LLVMTargetMachine {
332 const TargetData DataLayout; // Calculates type size &amp; alignment
333 SparcSubtarget Subtarget;
334 SparcInstrInfo InstrInfo;
335 TargetFrameInfo FrameInfo;
336
337protected:
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]338 virtual const TargetAsmInfo *createTargetAsmInfo() const;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]339
340public:
341 SparcTargetMachine(const Module &amp;M, const std::string &amp;FS);
342
343 virtual const SparcInstrInfo *getInstrInfo() const {return &amp;InstrInfo; }
344 virtual const TargetFrameInfo *getFrameInfo() const {return &amp;FrameInfo; }
345 virtual const TargetSubtarget *getSubtargetImpl() const{return &amp;Subtarget; }
346 virtual const TargetRegisterInfo *getRegisterInfo() const {
347 return &amp;InstrInfo.getRegisterInfo();
348 }
349 virtual const TargetData *getTargetData() const { return &amp;DataLayout; }
350 static unsigned getModuleMatchQuality(const Module &amp;M);
351
352 // Pass Pipeline Configuration
353 virtual bool addInstSelector(PassManagerBase &amp;PM, bool Fast);
354 virtual bool addPreEmitPass(PassManagerBase &amp;PM, bool Fast);
355 virtual bool addAssemblyEmitter(PassManagerBase &amp;PM, bool Fast,
356 std::ostream &amp;Out);
357};
358
359} // end namespace llvm
360</pre>
361</div>
362
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]363</div>
364
365
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]366<div class="doc_text">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]367
368<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]369<li><tt>getInstrInfo()</tt></li>
370<li><tt>getRegisterInfo()</tt></li>
371<li><tt>getFrameInfo()</tt></li>
372<li><tt>getTargetData()</tt></li>
373<li><tt>getSubtargetImpl()</tt></li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]374</ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]375
376<p>For some targets, you also need to support the following methods:</p>
377
378<ul>
379<li><tt>getTargetLowering()</tt></li>
380<li><tt>getJITInfo()</tt></li>
381</ul>
382
383<p>
384In addition, the <tt>XXXTargetMachine</tt> constructor should specify a
385<tt>TargetDescription</tt> string that determines the data layout for the target
386machine, including characteristics such as pointer size, alignment, and
387endianness. For example, the constructor for SparcTargetMachine contains the
388following:
389</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]390
391<div class="doc_code">
392<pre>
393SparcTargetMachine::SparcTargetMachine(const Module &amp;M, const std::string &amp;FS)
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]394 : DataLayout("E-p:32:32-f128:128:128"),
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]395 Subtarget(M, FS), InstrInfo(Subtarget),
396 FrameInfo(TargetFrameInfo::StackGrowsDown, 8, 0) {
397}
398</pre>
399</div>
400
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]401</div>
402
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]403<div class="doc_text">
404
405<p>Hyphens separate portions of the <tt>TargetDescription</tt> string.</p>
406
407<ul>
408<li>An upper-case "<tt>E</tt>" in the string indicates a big-endian target data
409 model. a lower-case "<tt>e</tt>" indicates little-endian.</li>
410
411<li>"<tt>p:</tt>" is followed by pointer information: size, ABI alignment, and
412 preferred alignment. If only two figures follow "<tt>p:</tt>", then the
413 first value is pointer size, and the second value is both ABI and preferred
414 alignment.</li>
415
416<li>Then a letter for numeric type alignment: "<tt>i</tt>", "<tt>f</tt>",
417 "<tt>v</tt>", or "<tt>a</tt>" (corresponding to integer, floating point,
418 vector, or aggregate). "<tt>i</tt>", "<tt>v</tt>", or "<tt>a</tt>" are
419 followed by ABI alignment and preferred alignment. "<tt>f</tt>" is followed
420 by three values: the first indicates the size of a long double, then ABI
421 alignment, and then ABI preferred alignment.</li>
422</ul>
423
424<p>
425You must also register your target using the <tt>RegisterTarget</tt>
426template. (See the <tt>TargetMachineRegistry</tt> class.) For example,
427in <tt>SparcTargetMachine.cpp</tt>, the target is registered with:
428</p>
429
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]430<div class="doc_code">
431<pre>
432namespace {
433 // Register the target.
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]434 RegisterTarget&lt;SparcTargetMachine&gt;X("sparc", "SPARC");
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]435}
436</pre>
437</div>
438
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]439</div>
440
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]441<!-- *********************************************************************** -->
442<div class="doc_section">
443 <a name="RegisterSet">Register Set and Register Classes</a>
444</div>
445<!-- *********************************************************************** -->
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]446
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]447<div class="doc_text">
448
449<p>
450You should describe a concrete target-specific class that represents the
451register file of a target machine. This class is called <tt>XXXRegisterInfo</tt>
452(where <tt>XXX</tt> identifies the target) and represents the class register
453file data that is used for register allocation. It also describes the
454interactions between registers.
455</p>
456
457<p>
458You also need to define register classes to categorize related registers. A
459register class should be added for groups of registers that are all treated the
460same way for some instruction. Typical examples are register classes for
461integer, floating-point, or vector registers. A register allocator allows an
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]462instruction to use any register in a specified register class to perform the
463instruction in a similar manner. Register classes allocate virtual registers to
464instructions from these sets, and register classes let the target-independent
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]465register allocator automatically choose the actual registers.
466</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]467
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]468<p>
469Much of the code for registers, including register definition, register aliases,
470and register classes, is generated by TableGen from <tt>XXXRegisterInfo.td</tt>
471input files and placed in <tt>XXXGenRegisterInfo.h.inc</tt> and
472<tt>XXXGenRegisterInfo.inc</tt> output files. Some of the code in the
473implementation of <tt>XXXRegisterInfo</tt> requires hand-coding.
474</p>
475
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]476</div>
477
478<!-- ======================================================================= -->
479<div class="doc_subsection">
480 <a name="RegisterDef">Defining a Register</a>
481</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]482
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]483<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]484
485<p>
486The <tt>XXXRegisterInfo.td</tt> file typically starts with register definitions
487for a target machine. The <tt>Register</tt> class (specified
488in <tt>Target.td</tt>) is used to define an object for each register. The
489specified string <tt>n</tt> becomes the <tt>Name</tt> of the register. The
490basic <tt>Register</tt> object does not have any subregisters and does not
491specify any aliases.
492</p>
493
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]494<div class="doc_code">
495<pre>
496class Register&lt;string n&gt; {
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]497 string Namespace = "";
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]498 string AsmName = n;
499 string Name = n;
500 int SpillSize = 0;
501 int SpillAlignment = 0;
502 list&lt;Register&gt; Aliases = [];
503 list&lt;Register&gt; SubRegs = [];
504 list&lt;int&gt; DwarfNumbers = [];
505}
506</pre>
507</div>
508
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]509<p>
510For example, in the <tt>X86RegisterInfo.td</tt> file, there are register
511definitions that utilize the Register class, such as:
512</p>
513
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]514<div class="doc_code">
515<pre>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]516def AL : Register&lt;"AL"&gt;, DwarfRegNum&lt;[0, 0, 0]&gt;;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]517</pre>
518</div>
519
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]520<p>
521This defines the register <tt>AL</tt> and assigns it values (with
522<tt>DwarfRegNum</tt>) that are used by <tt>gcc</tt>, <tt>gdb</tt>, or a debug
523information writer (such as <tt>DwarfWriter</tt>
524in <tt>llvm/lib/CodeGen/AsmPrinter</tt>) to identify a register. For register
525<tt>AL</tt>, <tt>DwarfRegNum</tt> takes an array of 3 values representing 3
526different modes: the first element is for X86-64, the second for exception
527handling (EH) on X86-32, and the third is generic. -1 is a special Dwarf number
528that indicates the gcc number is undefined, and -2 indicates the register number
529is invalid for this mode.
530</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]531
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]532<p>
533From the previously described line in the <tt>X86RegisterInfo.td</tt> file,
534TableGen generates this code in the <tt>X86GenRegisterInfo.inc</tt> file:
535</p>
536
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]537<div class="doc_code">
538<pre>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]539static const unsigned GR8[] = { X86::AL, ... };
540
541const unsigned AL_AliasSet[] = { X86::AX, X86::EAX, X86::RAX, 0 };
542
543const TargetRegisterDesc RegisterDescriptors[] = {
544 ...
545{ "AL", "AL", AL_AliasSet, Empty_SubRegsSet, Empty_SubRegsSet, AL_SuperRegsSet }, ...
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]546</pre>
547</div>
548
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]549<p>
550From the register info file, TableGen generates a <tt>TargetRegisterDesc</tt>
551object for each register. <tt>TargetRegisterDesc</tt> is defined in
552<tt>include/llvm/Target/TargetRegisterInfo.h</tt> with the following fields:
553</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]554
555<div class="doc_code">
556<pre>
557struct TargetRegisterDesc {
558 const char *AsmName; // Assembly language name for the register
559 const char *Name; // Printable name for the reg (for debugging)
560 const unsigned *AliasSet; // Register Alias Set
561 const unsigned *SubRegs; // Sub-register set
562 const unsigned *ImmSubRegs; // Immediate sub-register set
563 const unsigned *SuperRegs; // Super-register set
564};</pre>
565</div>
566
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]567<p>
568TableGen uses the entire target description file (<tt>.td</tt>) to determine
569text names for the register (in the <tt>AsmName</tt> and <tt>Name</tt> fields of
570<tt>TargetRegisterDesc</tt>) and the relationships of other registers to the
571defined register (in the other <tt>TargetRegisterDesc</tt> fields). In this
572example, other definitions establish the registers "<tt>AX</tt>",
573"<tt>EAX</tt>", and "<tt>RAX</tt>" as aliases for one another, so TableGen
574generates a null-terminated array (<tt>AL_AliasSet</tt>) for this register alias
575set.
576</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]577
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]578<p>
579The <tt>Register</tt> class is commonly used as a base class for more complex
580classes. In <tt>Target.td</tt>, the <tt>Register</tt> class is the base for the
581<tt>RegisterWithSubRegs</tt> class that is used to define registers that need to
582specify subregisters in the <tt>SubRegs</tt> list, as shown here:
583</p>
584
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]585<div class="doc_code">
586<pre>
587class RegisterWithSubRegs&lt;string n,
588list&lt;Register&gt; subregs&gt; : Register&lt;n&gt; {
589 let SubRegs = subregs;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]590}
591</pre>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]592</div>
593
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]594<p>
595In <tt>SparcRegisterInfo.td</tt>, additional register classes are defined for
596SPARC: a Register subclass, SparcReg, and further subclasses: <tt>Ri</tt>,
597<tt>Rf</tt>, and <tt>Rd</tt>. SPARC registers are identified by 5-bit ID
598numbers, which is a feature common to these subclasses. Note the use of
599'<tt>let</tt>' expressions to override values that are initially defined in a
600superclass (such as <tt>SubRegs</tt> field in the <tt>Rd</tt> class).
601</p>
602
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]603<div class="doc_code">
604<pre>
605class SparcReg&lt;string n&gt; : Register&lt;n&gt; {
606 field bits&lt;5&gt; Num;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]607 let Namespace = "SP";
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]608}
609// Ri - 32-bit integer registers
610class Ri&lt;bits&lt;5&gt; num, string n&gt; :
611SparcReg&lt;n&gt; {
612 let Num = num;
613}
614// Rf - 32-bit floating-point registers
615class Rf&lt;bits&lt;5&gt; num, string n&gt; :
616SparcReg&lt;n&gt; {
617 let Num = num;
618}
619// Rd - Slots in the FP register file for 64-bit
620floating-point values.
621class Rd&lt;bits&lt;5&gt; num, string n,
622list&lt;Register&gt; subregs&gt; : SparcReg&lt;n&gt; {
623 let Num = num;
624 let SubRegs = subregs;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]625}
626</pre>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]627</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]628
629<p>
630In the <tt>SparcRegisterInfo.td</tt> file, there are register definitions that
631utilize these subclasses of <tt>Register</tt>, such as:
632</p>
633
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]634<div class="doc_code">
635<pre>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]636def G0 : Ri&lt; 0, "G0"&gt;,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]637DwarfRegNum&lt;[0]&gt;;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]638def G1 : Ri&lt; 1, "G1"&gt;, DwarfRegNum&lt;[1]&gt;;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]639...
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]640def F0 : Rf&lt; 0, "F0"&gt;,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]641DwarfRegNum&lt;[32]&gt;;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]642def F1 : Rf&lt; 1, "F1"&gt;,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]643DwarfRegNum&lt;[33]&gt;;
644...
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]645def D0 : Rd&lt; 0, "F0", [F0, F1]&gt;,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]646DwarfRegNum&lt;[32]&gt;;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]647def D1 : Rd&lt; 2, "F2", [F2, F3]&gt;,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]648DwarfRegNum&lt;[34]&gt;;
649</pre>
650</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]651
652<p>
653The last two registers shown above (<tt>D0</tt> and <tt>D1</tt>) are
654double-precision floating-point registers that are aliases for pairs of
655single-precision floating-point sub-registers. In addition to aliases, the
656sub-register and super-register relationships of the defined register are in
657fields of a register's TargetRegisterDesc.
658</p>
659
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]660</div>
661
662<!-- ======================================================================= -->
663<div class="doc_subsection">
664 <a name="RegisterClassDef">Defining a Register Class</a>
665</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]666
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]667<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]668
669<p>
670The <tt>RegisterClass</tt> class (specified in <tt>Target.td</tt>) is used to
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]671define an object that represents a group of related registers and also defines
672the default allocation order of the registers. A target description file
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]673<tt>XXXRegisterInfo.td</tt> that uses <tt>Target.td</tt> can construct register
674classes using the following class:
675</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]676
677<div class="doc_code">
678<pre>
679class RegisterClass&lt;string namespace,
680list&lt;ValueType&gt; regTypes, int alignment,
681 list&lt;Register&gt; regList&gt; {
682 string Namespace = namespace;
683 list&lt;ValueType&gt; RegTypes = regTypes;
684 int Size = 0; // spill size, in bits; zero lets tblgen pick the size
685 int Alignment = alignment;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]686
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]687 // CopyCost is the cost of copying a value between two registers
688 // default value 1 means a single instruction
689 // A negative value means copying is extremely expensive or impossible
690 int CopyCost = 1;
691 list&lt;Register&gt; MemberList = regList;
692
693 // for register classes that are subregisters of this class
694 list&lt;RegisterClass&gt; SubRegClassList = [];
695
696 code MethodProtos = [{}]; // to insert arbitrary code
697 code MethodBodies = [{}];
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]698}
699</pre>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]700</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]701
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]702<p>To define a RegisterClass, use the following 4 arguments:</p>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]703
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]704<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]705<li>The first argument of the definition is the name of the namespace.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]706
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]707<li>The second argument is a list of <tt>ValueType</tt> register type values
708 that are defined in <tt>include/llvm/CodeGen/ValueTypes.td</tt>. Defined
709 values include integer types (such as <tt>i16</tt>, <tt>i32</tt>,
710 and <tt>i1</tt> for Boolean), floating-point types
711 (<tt>f32</tt>, <tt>f64</tt>), and vector types (for example, <tt>v8i16</tt>
712 for an <tt>8 x i16</tt> vector). All registers in a <tt>RegisterClass</tt>
713 must have the same <tt>ValueType</tt>, but some registers may store vector
714 data in different configurations. For example a register that can process a
715 128-bit vector may be able to handle 16 8-bit integer elements, 8 16-bit
716 integers, 4 32-bit integers, and so on. </li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]717
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]718<li>The third argument of the <tt>RegisterClass</tt> definition specifies the
719 alignment required of the registers when they are stored or loaded to
720 memory.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]721
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]722<li>The final argument, <tt>regList</tt>, specifies which registers are in this
723 class. If an <tt>allocation_order_*</tt> method is not specified,
724 then <tt>regList</tt> also defines the order of allocation used by the
725 register allocator.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]726</ul>
727
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]728<p>
729In <tt>SparcRegisterInfo.td</tt>, three RegisterClass objects are defined:
730<tt>FPRegs</tt>, <tt>DFPRegs</tt>, and <tt>IntRegs</tt>. For all three register
731classes, the first argument defines the namespace with the string
732'<tt>SP</tt>'. <tt>FPRegs</tt> defines a group of 32 single-precision
733floating-point registers (<tt>F0</tt> to <tt>F31</tt>); <tt>DFPRegs</tt> defines
734a group of 16 double-precision registers
735(<tt>D0-D15</tt>). For <tt>IntRegs</tt>, the <tt>MethodProtos</tt>
736and <tt>MethodBodies</tt> methods are used by TableGen to insert the specified
737code into generated output.
738</p>
739
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]740<div class="doc_code">
741<pre>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]742def FPRegs : RegisterClass&lt;"SP", [f32], 32,
743 [F0, F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12, F13, F14, F15,
744 F16, F17, F18, F19, F20, F21, F22, F23, F24, F25, F26, F27, F28, F29, F30, F31]&gt;;
745
746def DFPRegs : RegisterClass&lt;"SP", [f64], 64,
747 [D0, D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, D14, D15]&gt;;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]748&nbsp;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]749def IntRegs : RegisterClass&lt;"SP", [i32], 32,
750 [L0, L1, L2, L3, L4, L5, L6, L7,
751 I0, I1, I2, I3, I4, I5,
752 O0, O1, O2, O3, O4, O5, O7,
753 G1,
754 // Non-allocatable regs:
755 G2, G3, G4,
756 O6, // stack ptr
757 I6, // frame ptr
758 I7, // return address
759 G0, // constant zero
760 G5, G6, G7 // reserved for kernel
761 ]&gt; {
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]762 let MethodProtos = [{
763 iterator allocation_order_end(const MachineFunction &amp;MF) const;
764 }];
765 let MethodBodies = [{
766 IntRegsClass::iterator
767 IntRegsClass::allocation_order_end(const MachineFunction &amp;MF) const {
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]768 return end() - 10 // Don't allocate special registers
769 -1;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]770 }
771 }];
772}
773</pre>
774</div>
775
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]776<p>
777Using <tt>SparcRegisterInfo.td</tt> with TableGen generates several output files
778that are intended for inclusion in other source code that you write.
779<tt>SparcRegisterInfo.td</tt> generates <tt>SparcGenRegisterInfo.h.inc</tt>,
780which should be included in the header file for the implementation of the SPARC
781register implementation that you write (<tt>SparcRegisterInfo.h</tt>). In
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]782<tt>SparcGenRegisterInfo.h.inc</tt> a new structure is defined called
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]783<tt>SparcGenRegisterInfo</tt> that uses <tt>TargetRegisterInfo</tt> as its
784base. It also specifies types, based upon the defined register
785classes: <tt>DFPRegsClass</tt>, <tt>FPRegsClass</tt>, and <tt>IntRegsClass</tt>.
786</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]787
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]788<p>
789<tt>SparcRegisterInfo.td</tt> also generates <tt>SparcGenRegisterInfo.inc</tt>,
790which is included at the bottom of <tt>SparcRegisterInfo.cpp</tt>, the SPARC
791register implementation. The code below shows only the generated integer
792registers and associated register classes. The order of registers
793in <tt>IntRegs</tt> reflects the order in the definition of <tt>IntRegs</tt> in
794the target description file. Take special note of the use
795of <tt>MethodBodies</tt> in <tt>SparcRegisterInfo.td</tt> to create code in
796<tt>SparcGenRegisterInfo.inc</tt>. <tt>MethodProtos</tt> generates similar code
797in <tt>SparcGenRegisterInfo.h.inc</tt>.
798</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]799
800<div class="doc_code">
801<pre> // IntRegs Register Class...
802 static const unsigned IntRegs[] = {
803 SP::L0, SP::L1, SP::L2, SP::L3, SP::L4, SP::L5,
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]804 SP::L6, SP::L7, SP::I0, SP::I1, SP::I2, SP::I3,
805 SP::I4, SP::I5, SP::O0, SP::O1, SP::O2, SP::O3,
806 SP::O4, SP::O5, SP::O7, SP::G1, SP::G2, SP::G3,
807 SP::G4, SP::O6, SP::I6, SP::I7, SP::G0, SP::G5,
808 SP::G6, SP::G7,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]809 };
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]810
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]811 // IntRegsVTs Register Class Value Types...
812 static const MVT::ValueType IntRegsVTs[] = {
813 MVT::i32, MVT::Other
814 };
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]815
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]816namespace SP { // Register class instances
817 DFPRegsClass&nbsp;&nbsp;&nbsp; DFPRegsRegClass;
818 FPRegsClass&nbsp;&nbsp;&nbsp;&nbsp; FPRegsRegClass;
819 IntRegsClass&nbsp;&nbsp;&nbsp; IntRegsRegClass;
820...
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]821 // IntRegs Sub-register Classess...
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]822 static const TargetRegisterClass* const IntRegsSubRegClasses [] = {
823 NULL
824 };
825...
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]826 // IntRegs Super-register Classess...
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]827 static const TargetRegisterClass* const IntRegsSuperRegClasses [] = {
828 NULL
829 };
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]830...
831 // IntRegs Register Class sub-classes...
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]832 static const TargetRegisterClass* const IntRegsSubclasses [] = {
833 NULL
834 };
835...
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]836 // IntRegs Register Class super-classes...
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]837 static const TargetRegisterClass* const IntRegsSuperclasses [] = {
838 NULL
839 };
840...
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]841 IntRegsClass::iterator
842 IntRegsClass::allocation_order_end(const MachineFunction &amp;MF) const {
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]843 return end()-10 // Don't allocate special registers
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]844 -1;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]845 }
846
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]847 IntRegsClass::IntRegsClass() : TargetRegisterClass(IntRegsRegClassID,
848 IntRegsVTs, IntRegsSubclasses, IntRegsSuperclasses, IntRegsSubRegClasses,
849 IntRegsSuperRegClasses, 4, 4, 1, IntRegs, IntRegs + 32) {}
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]850}
851</pre>
852</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]853
854</div>
855
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]856<!-- ======================================================================= -->
857<div class="doc_subsection">
Chris Lattner7d12b4b2008-11-11 19:36:31 +0000[diff] [blame]858 <a name="implementRegister">Implement a subclass of</a>
859 <a href="http://www.llvm.org/docs/CodeGenerator.html#targetregisterinfo">TargetRegisterInfo</a>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]860</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]861
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]862<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]863
864<p>
865The final step is to hand code portions of <tt>XXXRegisterInfo</tt>, which
866implements the interface described in <tt>TargetRegisterInfo.h</tt>. These
867functions return <tt>0</tt>, <tt>NULL</tt>, or <tt>false</tt>, unless
868overridden. Here is a list of functions that are overridden for the SPARC
869implementation in <tt>SparcRegisterInfo.cpp</tt>:
870</p>
871
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]872<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]873<li><tt>getCalleeSavedRegs</tt> &mdash; Returns a list of callee-saved registers
874 in the order of the desired callee-save stack frame offset.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]875
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]876<li><tt>getCalleeSavedRegClasses</tt> &mdash; Returns a list of preferred
877 register classes with which to spill each callee saved register.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]878
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]879<li><tt>getReservedRegs</tt> &mdash; Returns a bitset indexed by physical
880 register numbers, indicating if a particular register is unavailable.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]881
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]882<li><tt>hasFP</tt> &mdash; Return a Boolean indicating if a function should have
883 a dedicated frame pointer register.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]884
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]885<li><tt>eliminateCallFramePseudoInstr</tt> &mdash; If call frame setup or
886 destroy pseudo instructions are used, this can be called to eliminate
887 them.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]888
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]889<li><tt>eliminateFrameIndex</tt> &mdash; Eliminate abstract frame indices from
890 instructions that may use them.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]891
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]892<li><tt>emitPrologue</tt> &mdash; Insert prologue code into the function.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]893
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]894<li><tt>emitEpilogue</tt> &mdash; Insert epilogue code into the function.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]895</ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]896
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]897</div>
898
899<!-- *********************************************************************** -->
900<div class="doc_section">
901 <a name="InstructionSet">Instruction Set</a>
902</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]903
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]904<!-- *********************************************************************** -->
905<div class="doc_text">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]906
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]907<p>
908During the early stages of code generation, the LLVM IR code is converted to a
909<tt>SelectionDAG</tt> with nodes that are instances of the <tt>SDNode</tt> class
910containing target instructions. An <tt>SDNode</tt> has an opcode, operands, type
911requirements, and operation properties. For example, is an operation
912commutative, does an operation load from memory. The various operation node
913types are described in the <tt>include/llvm/CodeGen/SelectionDAGNodes.h</tt>
914file (values of the <tt>NodeType</tt> enum in the <tt>ISD</tt> namespace).
915</p>
916
917<p>
918TableGen uses the following target description (<tt>.td</tt>) input files to
919generate much of the code for instruction definition:
920</p>
921
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]922<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]923<li><tt>Target.td</tt> &mdash; Where the <tt>Instruction</tt>, <tt>Operand</tt>,
924 <tt>InstrInfo</tt>, and other fundamental classes are defined.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]925
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]926<li><tt>TargetSelectionDAG.td</tt>&mdash; Used by <tt>SelectionDAG</tt>
927 instruction selection generators, contains <tt>SDTC*</tt> classes (selection
928 DAG type constraint), definitions of <tt>SelectionDAG</tt> nodes (such as
929 <tt>imm</tt>, <tt>cond</tt>, <tt>bb</tt>, <tt>add</tt>, <tt>fadd</tt>,
930 <tt>sub</tt>), and pattern support (<tt>Pattern</tt>, <tt>Pat</tt>,
931 <tt>PatFrag</tt>, <tt>PatLeaf</tt>, <tt>ComplexPattern</tt>.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]932
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]933<li><tt>XXXInstrFormats.td</tt> &mdash; Patterns for definitions of
934 target-specific instructions.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]935
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]936<li><tt>XXXInstrInfo.td</tt> &mdash; Target-specific definitions of instruction
937 templates, condition codes, and instructions of an instruction set. For
938 architecture modifications, a different file name may be used. For example,
939 for Pentium with SSE instruction, this file is <tt>X86InstrSSE.td</tt>, and
940 for Pentium with MMX, this file is <tt>X86InstrMMX.td</tt>.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]941</ul>
942
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]943<p>
944There is also a target-specific <tt>XXX.td</tt> file, where <tt>XXX</tt> is the
945name of the target. The <tt>XXX.td</tt> file includes the other <tt>.td</tt>
946input files, but its contents are only directly important for subtargets.
947</p>
948
949<p>
950You should describe a concrete target-specific class <tt>XXXInstrInfo</tt> that
951represents machine instructions supported by a target machine.
952<tt>XXXInstrInfo</tt> contains an array of <tt>XXXInstrDescriptor</tt> objects,
953each of which describes one instruction. An instruction descriptor defines:</p>
954
955<ul>
956<li>Opcode mnemonic</li>
957
958<li>Number of operands</li>
959
960<li>List of implicit register definitions and uses</li>
961
962<li>Target-independent properties (such as memory access, is commutable)</li>
963
964<li>Target-specific flags </li>
965</ul>
966
967<p>
968The Instruction class (defined in <tt>Target.td</tt>) is mostly used as a base
969for more complex instruction classes.
970</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]971
972<div class="doc_code">
973<pre>class Instruction {
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]974 string Namespace = "";
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]975 dag OutOperandList; // An dag containing the MI def operand list.
976 dag InOperandList; // An dag containing the MI use operand list.
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]977 string AsmString = ""; // The .s format to print the instruction with.
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]978 list&lt;dag&gt; Pattern; // Set to the DAG pattern for this instruction
979 list&lt;Register&gt; Uses = [];
980 list&lt;Register&gt; Defs = [];
981 list&lt;Predicate&gt; Predicates = []; // predicates turned into isel match code
982 ... remainder not shown for space ...
983}
984</pre>
985</div>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]986
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]987<p>
988A <tt>SelectionDAG</tt> node (<tt>SDNode</tt>) should contain an object
989representing a target-specific instruction that is defined
990in <tt>XXXInstrInfo.td</tt>. The instruction objects should represent
991instructions from the architecture manual of the target machine (such as the
992SPARC Architecture Manual for the SPARC target).
993</p>
994
995<p>
996A single instruction from the architecture manual is often modeled as multiple
997target instructions, depending upon its operands. For example, a manual might
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]998describe an add instruction that takes a register or an immediate operand. An
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]999LLVM target could model this with two instructions named <tt>ADDri</tt> and
1000<tt>ADDrr</tt>.
1001</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1002
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1003<p>
1004You should define a class for each instruction category and define each opcode
1005as a subclass of the category with appropriate parameters such as the fixed
1006binary encoding of opcodes and extended opcodes. You should map the register
1007bits to the bits of the instruction in which they are encoded (for the
1008JIT). Also you should specify how the instruction should be printed when the
1009automatic assembly printer is used.
1010</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1011
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1012<p>
1013As is described in the SPARC Architecture Manual, Version 8, there are three
1014major 32-bit formats for instructions. Format 1 is only for the <tt>CALL</tt>
1015instruction. Format 2 is for branch on condition codes and <tt>SETHI</tt> (set
1016high bits of a register) instructions. Format 3 is for other instructions.
1017</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1018
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1019<p>
1020Each of these formats has corresponding classes in <tt>SparcInstrFormat.td</tt>.
1021<tt>InstSP</tt> is a base class for other instruction classes. Additional base
1022classes are specified for more precise formats: for example
1023in <tt>SparcInstrFormat.td</tt>, <tt>F2_1</tt> is for <tt>SETHI</tt>,
1024and <tt>F2_2</tt> is for branches. There are three other base
1025classes: <tt>F3_1</tt> for register/register operations, <tt>F3_2</tt> for
1026register/immediate operations, and <tt>F3_3</tt> for floating-point
1027operations. <tt>SparcInstrInfo.td</tt> also adds the base class Pseudo for
1028synthetic SPARC instructions.
1029</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1030
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1031<p>
1032<tt>SparcInstrInfo.td</tt> largely consists of operand and instruction
1033definitions for the SPARC target. In <tt>SparcInstrInfo.td</tt>, the following
1034target description file entry, <tt>LDrr</tt>, defines the Load Integer
1035instruction for a Word (the <tt>LD</tt> SPARC opcode) from a memory address to a
1036register. The first parameter, the value 3 (<tt>11<sub>2</sub></tt>), is the
1037operation value for this category of operation. The second parameter
1038(<tt>000000<sub>2</sub></tt>) is the specific operation value
1039for <tt>LD</tt>/Load Word. The third parameter is the output destination, which
1040is a register operand and defined in the <tt>Register</tt> target description
1041file (<tt>IntRegs</tt>).
1042</p>
1043
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1044<div class="doc_code">
1045<pre>def LDrr : F3_1 &lt;3, 0b000000, (outs IntRegs:$dst), (ins MEMrr:$addr),
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1046 "ld [$addr], $dst",
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1047 [(set IntRegs:$dst, (load ADDRrr:$addr))]&gt;;
1048</pre>
1049</div>
1050
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1051<p>
1052The fourth parameter is the input source, which uses the address
1053operand <tt>MEMrr</tt> that is defined earlier in <tt>SparcInstrInfo.td</tt>:
1054</p>
1055
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1056<div class="doc_code">
1057<pre>def MEMrr : Operand&lt;i32&gt; {
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1058 let PrintMethod = "printMemOperand";
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1059 let MIOperandInfo = (ops IntRegs, IntRegs);
1060}
1061</pre>
1062</div>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1063
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1064<p>
1065The fifth parameter is a string that is used by the assembly printer and can be
1066left as an empty string until the assembly printer interface is implemented. The
1067sixth and final parameter is the pattern used to match the instruction during
1068the SelectionDAG Select Phase described in
1069(<a href="http://www.llvm.org/docs/CodeGenerator.html">The LLVM
1070Target-Independent Code Generator</a>). This parameter is detailed in the next
1071section, <a href="#InstructionSelector">Instruction Selector</a>.
1072</p>
1073
1074<p>
1075Instruction class definitions are not overloaded for different operand types, so
1076separate versions of instructions are needed for register, memory, or immediate
1077value operands. For example, to perform a Load Integer instruction for a Word
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1078from an immediate operand to a register, the following instruction class is
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1079defined:
1080</p>
1081
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1082<div class="doc_code">
1083<pre>def LDri : F3_2 &lt;3, 0b000000, (outs IntRegs:$dst), (ins MEMri:$addr),
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1084 "ld [$addr], $dst",
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1085 [(set IntRegs:$dst, (load ADDRri:$addr))]&gt;;
1086</pre>
1087</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1088
1089<p>
1090Writing these definitions for so many similar instructions can involve a lot of
1091cut and paste. In td files, the <tt>multiclass</tt> directive enables the
1092creation of templates to define several instruction classes at once (using
1093the <tt>defm</tt> directive). For example in <tt>SparcInstrInfo.td</tt>, the
1094<tt>multiclass</tt> pattern <tt>F3_12</tt> is defined to create 2 instruction
1095classes each time <tt>F3_12</tt> is invoked:
1096</p>
1097
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1098<div class="doc_code">
1099<pre>multiclass F3_12 &lt;string OpcStr, bits&lt;6&gt; Op3Val, SDNode OpNode&gt; {
1100 def rr : F3_1 &lt;2, Op3Val,
1101 (outs IntRegs:$dst), (ins IntRegs:$b, IntRegs:$c),
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1102 !strconcat(OpcStr, " $b, $c, $dst"),
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1103 [(set IntRegs:$dst, (OpNode IntRegs:$b, IntRegs:$c))]&gt;;
1104 def ri : F3_2 &lt;2, Op3Val,
1105 (outs IntRegs:$dst), (ins IntRegs:$b, i32imm:$c),
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1106 !strconcat(OpcStr, " $b, $c, $dst"),
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1107 [(set IntRegs:$dst, (OpNode IntRegs:$b, simm13:$c))]&gt;;
1108}
1109</pre>
1110</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1111
1112<p>
1113So when the <tt>defm</tt> directive is used for the <tt>XOR</tt>
1114and <tt>ADD</tt> instructions, as seen below, it creates four instruction
1115objects: <tt>XORrr</tt>, <tt>XORri</tt>, <tt>ADDrr</tt>, and <tt>ADDri</tt>.
1116</p>
1117
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1118<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1119<pre>
1120defm XOR : F3_12&lt;"xor", 0b000011, xor&gt;;
1121defm ADD : F3_12&lt;"add", 0b000000, add&gt;;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1122</pre>
1123</div>
1124
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1125<p>
1126<tt>SparcInstrInfo.td</tt> also includes definitions for condition codes that
1127are referenced by branch instructions. The following definitions
1128in <tt>SparcInstrInfo.td</tt> indicate the bit location of the SPARC condition
1129code. For example, the 10<sup>th</sup> bit represents the 'greater than'
1130condition for integers, and the 22<sup>nd</sup> bit represents the 'greater
1131than' condition for floats.
1132</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1133
1134<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1135<pre>
1136def ICC_NE : ICC_VAL&lt; 9&gt;; // Not Equal
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1137def ICC_E : ICC_VAL&lt; 1&gt;; // Equal
1138def ICC_G : ICC_VAL&lt;10&gt;; // Greater
1139...
1140def FCC_U : FCC_VAL&lt;23&gt;; // Unordered
1141def FCC_G : FCC_VAL&lt;22&gt;; // Greater
1142def FCC_UG : FCC_VAL&lt;21&gt;; // Unordered or Greater
1143...
1144</pre>
1145</div>
1146
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1147<p>
1148(Note that <tt>Sparc.h</tt> also defines enums that correspond to the same SPARC
1149condition codes. Care must be taken to ensure the values in <tt>Sparc.h</tt>
1150correspond to the values in <tt>SparcInstrInfo.td</tt>. I.e.,
1151<tt>SPCC::ICC_NE = 9</tt>, <tt>SPCC::FCC_U = 23</tt> and so on.)
1152</p>
1153
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1154</div>
1155
1156<!-- ======================================================================= -->
1157<div class="doc_subsection">
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1158 <a name="operandMapping">Instruction Operand Mapping</a>
1159</div>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1160
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1161<div class="doc_text">
1162
1163<p>
1164The code generator backend maps instruction operands to fields in the
1165instruction. Operands are assigned to unbound fields in the instruction in the
1166order they are defined. Fields are bound when they are assigned a value. For
1167example, the Sparc target defines the <tt>XNORrr</tt> instruction as
1168a <tt>F3_1</tt> format instruction having three operands.
1169</p>
1170
1171<div class="doc_code">
1172<pre>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1173def XNORrr : F3_1&lt;2, 0b000111,
1174 (outs IntRegs:$dst), (ins IntRegs:$b, IntRegs:$c),
1175 "xnor $b, $c, $dst",
1176 [(set IntRegs:$dst, (not (xor IntRegs:$b, IntRegs:$c)))]&gt;;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1177</pre>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1178</div>
1179
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1180<p>
1181The instruction templates in <tt>SparcInstrFormats.td</tt> show the base class
1182for <tt>F3_1</tt> is <tt>InstSP</tt>.
1183</p>
1184
1185<div class="doc_code">
1186<pre>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1187class InstSP&lt;dag outs, dag ins, string asmstr, list&lt;dag&gt; pattern&gt; : Instruction {
1188 field bits&lt;32&gt; Inst;
1189 let Namespace = "SP";
1190 bits&lt;2&gt; op;
1191 let Inst{31-30} = op;
1192 dag OutOperandList = outs;
1193 dag InOperandList = ins;
1194 let AsmString = asmstr;
1195 let Pattern = pattern;
1196}
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1197</pre>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1198</div>
1199
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1200<p><tt>InstSP</tt> leaves the <tt>op</tt> field unbound.</p>
1201
1202<div class="doc_code">
1203<pre>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1204class F3&lt;dag outs, dag ins, string asmstr, list&lt;dag&gt; pattern&gt;
1205 : InstSP&lt;outs, ins, asmstr, pattern&gt; {
1206 bits&lt;5&gt; rd;
1207 bits&lt;6&gt; op3;
1208 bits&lt;5&gt; rs1;
1209 let op{1} = 1; // Op = 2 or 3
1210 let Inst{29-25} = rd;
1211 let Inst{24-19} = op3;
1212 let Inst{18-14} = rs1;
1213}
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1214</pre>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1215</div>
1216
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1217<p>
1218<tt>F3</tt> binds the <tt>op</tt> field and defines the <tt>rd</tt>,
1219<tt>op3</tt>, and <tt>rs1</tt> fields. <tt>F3</tt> format instructions will
1220bind the operands <tt>rd</tt>, <tt>op3</tt>, and <tt>rs1</tt> fields.
1221</p>
1222
1223<div class="doc_code">
1224<pre>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1225class F3_1&lt;bits&lt;2&gt; opVal, bits&lt;6&gt; op3val, dag outs, dag ins,
1226 string asmstr, list&lt;dag&gt; pattern&gt; : F3&lt;outs, ins, asmstr, pattern&gt; {
1227 bits&lt;8&gt; asi = 0; // asi not currently used
1228 bits&lt;5&gt; rs2;
1229 let op = opVal;
1230 let op3 = op3val;
1231 let Inst{13} = 0; // i field = 0
1232 let Inst{12-5} = asi; // address space identifier
1233 let Inst{4-0} = rs2;
1234}
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1235</pre>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1236</div>
1237
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1238<p>
1239<tt>F3_1</tt> binds the <tt>op3</tt> field and defines the <tt>rs2</tt>
1240fields. <tt>F3_1</tt> format instructions will bind the operands to the <tt>rd</tt>,
1241<tt>rs1</tt>, and <tt>rs2</tt> fields. This results in the <tt>XNORrr</tt>
1242instruction binding <tt>$dst</tt>, <tt>$b</tt>, and <tt>$c</tt> operands to
1243the <tt>rd</tt>, <tt>rs1</tt>, and <tt>rs2</tt> fields respectively.
1244</p>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1245
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1246</div>
Chris Lattner7a152732008-11-22 19:10:48 +0000[diff] [blame]1247
1248<!-- ======================================================================= -->
1249<div class="doc_subsection">
Chris Lattner7d12b4b2008-11-11 19:36:31 +0000[diff] [blame]1250 <a name="implementInstr">Implement a subclass of </a>
1251 <a href="http://www.llvm.org/docs/CodeGenerator.html#targetinstrinfo">TargetInstrInfo</a>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1252</div>
1253
1254<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1255
1256<p>
1257The final step is to hand code portions of <tt>XXXInstrInfo</tt>, which
1258implements the interface described in <tt>TargetInstrInfo.h</tt>. These
1259functions return <tt>0</tt> or a Boolean or they assert, unless
1260overridden. Here's a list of functions that are overridden for the SPARC
1261implementation in <tt>SparcInstrInfo.cpp</tt>:
1262</p>
1263
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1264<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1265<li><tt>isMoveInstr</tt> &mdash; Return true if the instruction is a register to
1266 register move; false, otherwise.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1267
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1268<li><tt>isLoadFromStackSlot</tt> &mdash; If the specified machine instruction is
1269 a direct load from a stack slot, return the register number of the
1270 destination and the <tt>FrameIndex</tt> of the stack slot.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1271
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1272<li><tt>isStoreToStackSlot</tt> &mdash; If the specified machine instruction is
1273 a direct store to a stack slot, return the register number of the
1274 destination and the <tt>FrameIndex</tt> of the stack slot.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1275
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1276<li><tt>copyRegToReg</tt> &mdash; Copy values between a pair of registers.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1277
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1278<li><tt>storeRegToStackSlot</tt> &mdash; Store a register value to a stack
1279 slot.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1280
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1281<li><tt>loadRegFromStackSlot</tt> &mdash; Load a register value from a stack
1282 slot.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1283
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1284<li><tt>storeRegToAddr</tt> &mdash; Store a register value to memory.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1285
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1286<li><tt>loadRegFromAddr</tt> &mdash; Load a register value from memory.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1287
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1288<li><tt>foldMemoryOperand</tt> &mdash; Attempt to combine instructions of any
1289 load or store instruction for the specified operand(s).</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1290</ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1291
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1292</div>
1293
1294<!-- ======================================================================= -->
1295<div class="doc_subsection">
1296 <a name="branchFolding">Branch Folding and If Conversion</a>
1297</div>
1298<div class="doc_text">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1299
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1300<p>
1301Performance can be improved by combining instructions or by eliminating
1302instructions that are never reached. The <tt>AnalyzeBranch</tt> method
1303in <tt>XXXInstrInfo</tt> may be implemented to examine conditional instructions
1304and remove unnecessary instructions. <tt>AnalyzeBranch</tt> looks at the end of
1305a machine basic block (MBB) for opportunities for improvement, such as branch
1306folding and if conversion. The <tt>BranchFolder</tt> and <tt>IfConverter</tt>
1307machine function passes (see the source files <tt>BranchFolding.cpp</tt> and
1308<tt>IfConversion.cpp</tt> in the <tt>lib/CodeGen</tt> directory) call
1309<tt>AnalyzeBranch</tt> to improve the control flow graph that represents the
1310instructions.
1311</p>
1312
1313<p>
1314Several implementations of <tt>AnalyzeBranch</tt> (for ARM, Alpha, and X86) can
1315be examined as models for your own <tt>AnalyzeBranch</tt> implementation. Since
1316SPARC does not implement a useful <tt>AnalyzeBranch</tt>, the ARM target
1317implementation is shown below.
1318</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1319
1320<p><tt>AnalyzeBranch</tt> returns a Boolean value and takes four parameters:</p>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1321
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1322<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1323<li><tt>MachineBasicBlock &amp;MBB</tt> &mdash; The incoming block to be
1324 examined.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1325
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1326<li><tt>MachineBasicBlock *&amp;TBB</tt> &mdash; A destination block that is
1327 returned. For a conditional branch that evaluates to true, <tt>TBB</tt> is
1328 the destination.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1329
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1330<li><tt>MachineBasicBlock *&amp;FBB</tt> &mdash; For a conditional branch that
1331 evaluates to false, <tt>FBB</tt> is returned as the destination.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1332
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1333<li><tt>std::vector&lt;MachineOperand&gt; &amp;Cond</tt> &mdash; List of
1334 operands to evaluate a condition for a conditional branch.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1335</ul>
1336
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1337<p>
1338In the simplest case, if a block ends without a branch, then it falls through to
1339the successor block. No destination blocks are specified for either <tt>TBB</tt>
1340or <tt>FBB</tt>, so both parameters return <tt>NULL</tt>. The start of
1341the <tt>AnalyzeBranch</tt> (see code below for the ARM target) shows the
1342function parameters and the code for the simplest case.
1343</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1344
1345<div class="doc_code">
1346<pre>bool ARMInstrInfo::AnalyzeBranch(MachineBasicBlock &amp;MBB,
1347 MachineBasicBlock *&amp;TBB, MachineBasicBlock *&amp;FBB,
1348 std::vector&lt;MachineOperand&gt; &amp;Cond) const
1349{
1350 MachineBasicBlock::iterator I = MBB.end();
1351 if (I == MBB.begin() || !isUnpredicatedTerminator(--I))
1352 return false;
1353</pre>
1354</div>
1355
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1356<p>
1357If a block ends with a single unconditional branch instruction, then
1358<tt>AnalyzeBranch</tt> (shown below) should return the destination of that
1359branch in the <tt>TBB</tt> parameter.
1360</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1361
1362<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1363<pre>
1364 if (LastOpc == ARM::B || LastOpc == ARM::tB) {
1365 TBB = LastInst-&gt;getOperand(0).getMBB();
1366 return false;
1367 }
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1368</pre>
1369</div>
1370
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1371<p>
1372If a block ends with two unconditional branches, then the second branch is never
1373reached. In that situation, as shown below, remove the last branch instruction
1374and return the penultimate branch in the <tt>TBB</tt> parameter.
1375</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1376
1377<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1378<pre>
1379 if ((SecondLastOpc == ARM::B || SecondLastOpc==ARM::tB) &amp;&amp;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1380 (LastOpc == ARM::B || LastOpc == ARM::tB)) {
1381 TBB = SecondLastInst-&gt;getOperand(0).getMBB();
1382 I = LastInst;
1383 I-&gt;eraseFromParent();
1384 return false;
1385 }
1386</pre>
1387</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1388
1389<p>
1390A block may end with a single conditional branch instruction that falls through
1391to successor block if the condition evaluates to false. In that case,
1392<tt>AnalyzeBranch</tt> (shown below) should return the destination of that
1393conditional branch in the <tt>TBB</tt> parameter and a list of operands in
1394the <tt>Cond</tt> parameter to evaluate the condition.
1395</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1396
1397<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1398<pre>
1399 if (LastOpc == ARM::Bcc || LastOpc == ARM::tBcc) {
1400 // Block ends with fall-through condbranch.
1401 TBB = LastInst-&gt;getOperand(0).getMBB();
1402 Cond.push_back(LastInst-&gt;getOperand(1));
1403 Cond.push_back(LastInst-&gt;getOperand(2));
1404 return false;
1405 }
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1406</pre>
1407</div>
1408
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1409<p>
1410If a block ends with both a conditional branch and an ensuing unconditional
1411branch, then <tt>AnalyzeBranch</tt> (shown below) should return the conditional
1412branch destination (assuming it corresponds to a conditional evaluation of
1413'<tt>true</tt>') in the <tt>TBB</tt> parameter and the unconditional branch
1414destination in the <tt>FBB</tt> (corresponding to a conditional evaluation of
1415'<tt>false</tt>'). A list of operands to evaluate the condition should be
1416returned in the <tt>Cond</tt> parameter.
1417</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1418
1419<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1420<pre>
1421 unsigned SecondLastOpc = SecondLastInst-&gt;getOpcode();
1422
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1423 if ((SecondLastOpc == ARM::Bcc &amp;&amp; LastOpc == ARM::B) ||
1424 (SecondLastOpc == ARM::tBcc &amp;&amp; LastOpc == ARM::tB)) {
1425 TBB = SecondLastInst-&gt;getOperand(0).getMBB();
1426 Cond.push_back(SecondLastInst-&gt;getOperand(1));
1427 Cond.push_back(SecondLastInst-&gt;getOperand(2));
1428 FBB = LastInst-&gt;getOperand(0).getMBB();
1429 return false;
1430 }
1431</pre>
1432</div>
1433
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1434<p>
1435For the last two cases (ending with a single conditional branch or ending with
1436one conditional and one unconditional branch), the operands returned in
1437the <tt>Cond</tt> parameter can be passed to methods of other instructions to
1438create new branches or perform other operations. An implementation
1439of <tt>AnalyzeBranch</tt> requires the helper methods <tt>RemoveBranch</tt>
1440and <tt>InsertBranch</tt> to manage subsequent operations.
1441</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1442
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1443<p>
1444<tt>AnalyzeBranch</tt> should return false indicating success in most circumstances.
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1445<tt>AnalyzeBranch</tt> should only return true when the method is stumped about what to
1446do, for example, if a block has three terminating branches. <tt>AnalyzeBranch</tt> may
1447return true if it encounters a terminator it cannot handle, such as an indirect
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1448branch.
1449</p>
1450
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1451</div>
1452
1453<!-- *********************************************************************** -->
1454<div class="doc_section">
1455 <a name="InstructionSelector">Instruction Selector</a>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]1456</div>
1457<!-- *********************************************************************** -->
1458
1459<div class="doc_text">
1460
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1461<p>
1462LLVM uses a <tt>SelectionDAG</tt> to represent LLVM IR instructions, and nodes
1463of the <tt>SelectionDAG</tt> ideally represent native target
1464instructions. During code generation, instruction selection passes are performed
1465to convert non-native DAG instructions into native target-specific
1466instructions. The pass described in <tt>XXXISelDAGToDAG.cpp</tt> is used to
1467match patterns and perform DAG-to-DAG instruction selection. Optionally, a pass
1468may be defined (in <tt>XXXBranchSelector.cpp</tt>) to perform similar DAG-to-DAG
1469operations for branch instructions. Later, the code in
1470<tt>XXXISelLowering.cpp</tt> replaces or removes operations and data types not
1471supported natively (legalizes) in a <tt>SelectionDAG</tt>.
1472</p>
1473
1474<p>
1475TableGen generates code for instruction selection using the following target
1476description input files:
1477</p>
1478
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]1479<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1480<li><tt>XXXInstrInfo.td</tt> &mdash; Contains definitions of instructions in a
1481 target-specific instruction set, generates <tt>XXXGenDAGISel.inc</tt>, which
1482 is included in <tt>XXXISelDAGToDAG.cpp</tt>.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1483
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1484<li><tt>XXXCallingConv.td</tt> &mdash; Contains the calling and return value
1485 conventions for the target architecture, and it generates
1486 <tt>XXXGenCallingConv.inc</tt>, which is included in
1487 <tt>XXXISelLowering.cpp</tt>.</li>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]1488</ul>
1489
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1490<p>
1491The implementation of an instruction selection pass must include a header that
1492declares the <tt>FunctionPass</tt> class or a subclass of <tt>FunctionPass</tt>. In
1493<tt>XXXTargetMachine.cpp</tt>, a Pass Manager (PM) should add each instruction
1494selection pass into the queue of passes to run.
1495</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1496
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1497<p>
1498The LLVM static compiler (<tt>llc</tt>) is an excellent tool for visualizing the
1499contents of DAGs. To display the <tt>SelectionDAG</tt> before or after specific
1500processing phases, use the command line options for <tt>llc</tt>, described
1501at <a href="http://llvm.org/docs/CodeGenerator.html#selectiondag_process">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1502SelectionDAG Instruction Selection Process</a>.
1503</p>
1504
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1505<p>
1506To describe instruction selector behavior, you should add patterns for lowering
1507LLVM code into a <tt>SelectionDAG</tt> as the last parameter of the instruction
1508definitions in <tt>XXXInstrInfo.td</tt>. For example, in
1509<tt>SparcInstrInfo.td</tt>, this entry defines a register store operation, and
1510the last parameter describes a pattern with the store DAG operator.
1511</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1512
1513<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1514<pre>
1515def STrr : F3_1&lt; 3, 0b000100, (outs), (ins MEMrr:$addr, IntRegs:$src),
1516 "st $src, [$addr]", [(store IntRegs:$src, ADDRrr:$addr)]&gt;;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1517</pre>
1518</div>
1519
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1520<p>
1521<tt>ADDRrr</tt> is a memory mode that is also defined in
1522<tt>SparcInstrInfo.td</tt>:
1523</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1524
1525<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1526<pre>
1527def ADDRrr : ComplexPattern&lt;i32, 2, "SelectADDRrr", [], []&gt;;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1528</pre>
1529</div>
1530
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1531<p>
1532The definition of <tt>ADDRrr</tt> refers to <tt>SelectADDRrr</tt>, which is a
1533function defined in an implementation of the Instructor Selector (such
1534as <tt>SparcISelDAGToDAG.cpp</tt>).
1535</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1536
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1537<p>
1538In <tt>lib/Target/TargetSelectionDAG.td</tt>, the DAG operator for store is
1539defined below:
1540</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1541
1542<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1543<pre>
1544def store : PatFrag&lt;(ops node:$val, node:$ptr),
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1545 (st node:$val, node:$ptr), [{
1546 if (StoreSDNode *ST = dyn_cast&lt;StoreSDNode&gt;(N))
1547 return !ST-&gt;isTruncatingStore() &amp;&amp;
1548 ST-&gt;getAddressingMode() == ISD::UNINDEXED;
1549 return false;
1550}]&gt;;
1551</pre>
1552</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1553
1554<p>
1555<tt>XXXInstrInfo.td</tt> also generates (in <tt>XXXGenDAGISel.inc</tt>) the
1556<tt>SelectCode</tt> method that is used to call the appropriate processing
1557method for an instruction. In this example, <tt>SelectCode</tt>
1558calls <tt>Select_ISD_STORE</tt> for the <tt>ISD::STORE</tt> opcode.
1559</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1560
1561<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1562<pre>
1563SDNode *SelectCode(SDValue N) {
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1564 ...
Dan Gohman50ef90d2009-01-28 21:36:46 +0000[diff] [blame]1565 MVT::ValueType NVT = N.getNode()-&gt;getValueType(0);
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1566 switch (N.getOpcode()) {
1567 case ISD::STORE: {
1568 switch (NVT) {
1569 default:
1570 return Select_ISD_STORE(N);
1571 break;
1572 }
1573 break;
1574 }
1575 ...
1576</pre>
1577</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1578
1579<p>
1580The pattern for <tt>STrr</tt> is matched, so elsewhere in
1581<tt>XXXGenDAGISel.inc</tt>, code for <tt>STrr</tt> is created for
1582<tt>Select_ISD_STORE</tt>. The <tt>Emit_22</tt> method is also generated
1583in <tt>XXXGenDAGISel.inc</tt> to complete the processing of this
1584instruction.
1585</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1586
1587<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1588<pre>
1589SDNode *Select_ISD_STORE(const SDValue &amp;N) {
Dan Gohman50ef90d2009-01-28 21:36:46 +0000[diff] [blame]1590 SDValue Chain = N.getOperand(0);
1591 if (Predicate_store(N.getNode())) {
1592 SDValue N1 = N.getOperand(1);
1593 SDValue N2 = N.getOperand(2);
1594 SDValue CPTmp0;
1595 SDValue CPTmp1;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1596
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1597 // Pattern: (st:void IntRegs:i32:$src,
1598 // ADDRrr:i32:$addr)&lt;&lt;P:Predicate_store&gt;&gt;
1599 // Emits: (STrr:void ADDRrr:i32:$addr, IntRegs:i32:$src)
1600 // Pattern complexity = 13 cost = 1 size = 0
1601 if (SelectADDRrr(N, N2, CPTmp0, CPTmp1) &amp;&amp;
Dan Gohman50ef90d2009-01-28 21:36:46 +0000[diff] [blame]1602 N1.getNode()-&gt;getValueType(0) == MVT::i32 &amp;&amp;
1603 N2.getNode()-&gt;getValueType(0) == MVT::i32) {
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1604 return Emit_22(N, SP::STrr, CPTmp0, CPTmp1);
1605 }
1606...
1607</pre>
1608</div>
1609
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1610</div>
1611
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1612<!-- ======================================================================= -->
1613<div class="doc_subsection">
1614 <a name="LegalizePhase">The SelectionDAG Legalize Phase</a>
1615</div>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1616
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1617<div class="doc_text">
1618
1619<p>
1620The Legalize phase converts a DAG to use types and operations that are natively
1621supported by the target. For natively unsupported types and operations, you need
1622to add code to the target-specific XXXTargetLowering implementation to convert
1623unsupported types and operations to supported ones.
1624</p>
1625
1626<p>
1627In the constructor for the <tt>XXXTargetLowering</tt> class, first use the
1628<tt>addRegisterClass</tt> method to specify which types are supports and which
1629register classes are associated with them. The code for the register classes are
1630generated by TableGen from <tt>XXXRegisterInfo.td</tt> and placed
1631in <tt>XXXGenRegisterInfo.h.inc</tt>. For example, the implementation of the
1632constructor for the SparcTargetLowering class (in
1633<tt>SparcISelLowering.cpp</tt>) starts with the following code:
1634</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1635
1636<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1637<pre>
1638addRegisterClass(MVT::i32, SP::IntRegsRegisterClass);
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1639addRegisterClass(MVT::f32, SP::FPRegsRegisterClass);
1640addRegisterClass(MVT::f64, SP::DFPRegsRegisterClass);
1641</pre>
1642</div>
1643
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1644<p>
1645You should examine the node types in the <tt>ISD</tt> namespace
1646(<tt>include/llvm/CodeGen/SelectionDAGNodes.h</tt>) and determine which
1647operations the target natively supports. For operations that do <b>not</b> have
1648native support, add a callback to the constructor for the XXXTargetLowering
1649class, so the instruction selection process knows what to do. The TargetLowering
1650class callback methods (declared in <tt>llvm/Target/TargetLowering.h</tt>) are:
1651</p>
1652
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1653<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1654<li><tt>setOperationAction</tt> &mdash; General operation.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1655
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1656<li><tt>setLoadExtAction</tt> &mdash; Load with extension.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1657
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1658<li><tt>setTruncStoreAction</tt> &mdash; Truncating store.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1659
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1660<li><tt>setIndexedLoadAction</tt> &mdash; Indexed load.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1661
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1662<li><tt>setIndexedStoreAction</tt> &mdash; Indexed store.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1663
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1664<li><tt>setConvertAction</tt> &mdash; Type conversion.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1665
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1666<li><tt>setCondCodeAction</tt> &mdash; Support for a given condition code.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1667</ul>
1668
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1669<p>
1670Note: on older releases, <tt>setLoadXAction</tt> is used instead
1671of <tt>setLoadExtAction</tt>. Also, on older releases,
1672<tt>setCondCodeAction</tt> may not be supported. Examine your release
1673to see what methods are specifically supported.
1674</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1675
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1676<p>
1677These callbacks are used to determine that an operation does or does not work
1678with a specified type (or types). And in all cases, the third parameter is
1679a <tt>LegalAction</tt> type enum value: <tt>Promote</tt>, <tt>Expand</tt>,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1680<tt>Custom</tt>, or <tt>Legal</tt>. <tt>SparcISelLowering.cpp</tt>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1681contains examples of all four <tt>LegalAction</tt> values.
1682</p>
1683
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1684</div>
1685
1686<!-- _______________________________________________________________________ -->
1687<div class="doc_subsubsection">
1688 <a name="promote">Promote</a>
1689</div>
1690
1691<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1692
1693<p>
1694For an operation without native support for a given type, the specified type may
1695be promoted to a larger type that is supported. For example, SPARC does not
1696support a sign-extending load for Boolean values (<tt>i1</tt> type), so
1697in <tt>SparcISelLowering.cpp</tt> the third parameter below, <tt>Promote</tt>,
1698changes <tt>i1</tt> type values to a large type before loading.
1699</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1700
1701<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1702<pre>
1703setLoadExtAction(ISD::SEXTLOAD, MVT::i1, Promote);
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1704</pre>
1705</div>
1706
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1707</div>
1708
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1709<!-- _______________________________________________________________________ -->
1710<div class="doc_subsubsection">
1711 <a name="expand">Expand</a>
1712</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1713
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1714<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1715
1716<p>
1717For a type without native support, a value may need to be broken down further,
1718rather than promoted. For an operation without native support, a combination of
1719other operations may be used to similar effect. In SPARC, the floating-point
1720sine and cosine trig operations are supported by expansion to other operations,
1721as indicated by the third parameter, <tt>Expand</tt>, to
1722<tt>setOperationAction</tt>:
1723</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1724
1725<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1726<pre>
1727setOperationAction(ISD::FSIN, MVT::f32, Expand);
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1728setOperationAction(ISD::FCOS, MVT::f32, Expand);
1729</pre>
1730</div>
1731
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1732</div>
1733
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1734<!-- _______________________________________________________________________ -->
1735<div class="doc_subsubsection">
1736 <a name="custom">Custom</a>
1737</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1738
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1739<div class="doc_text">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1740
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1741<p>
1742For some operations, simple type promotion or operation expansion may be
1743insufficient. In some cases, a special intrinsic function must be implemented.
1744</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1745
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1746<p>
1747For example, a constant value may require special treatment, or an operation may
1748require spilling and restoring registers in the stack and working with register
1749allocators.
1750</p>
1751
1752<p>
1753As seen in <tt>SparcISelLowering.cpp</tt> code below, to perform a type
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1754conversion from a floating point value to a signed integer, first the
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1755<tt>setOperationAction</tt> should be called with <tt>Custom</tt> as the third
1756parameter:
1757</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1758
1759<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1760<pre>
1761setOperationAction(ISD::FP_TO_SINT, MVT::i32, Custom);
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1762</pre>
1763</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1764
1765<p>
1766In the <tt>LowerOperation</tt> method, for each <tt>Custom</tt> operation, a
1767case statement should be added to indicate what function to call. In the
1768following code, an <tt>FP_TO_SINT</tt> opcode will call
1769the <tt>LowerFP_TO_SINT</tt> method:
1770</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1771
1772<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1773<pre>
1774SDValue SparcTargetLowering::LowerOperation(SDValue Op, SelectionDAG &amp;DAG) {
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1775 switch (Op.getOpcode()) {
1776 case ISD::FP_TO_SINT: return LowerFP_TO_SINT(Op, DAG);
1777 ...
1778 }
1779}
1780</pre>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1781</div>
1782
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1783<p>
1784Finally, the <tt>LowerFP_TO_SINT</tt> method is implemented, using an FP
1785register to convert the floating-point value to an integer.
1786</p>
1787
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1788<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1789<pre>
1790static SDValue LowerFP_TO_SINT(SDValue Op, SelectionDAG &amp;DAG) {
1791 assert(Op.getValueType() == MVT::i32);
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1792 Op = DAG.getNode(SPISD::FTOI, MVT::f32, Op.getOperand(0));
1793 return DAG.getNode(ISD::BIT_CONVERT, MVT::i32, Op);
1794}
1795</pre>
1796</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1797
1798</div>
1799
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1800<!-- _______________________________________________________________________ -->
1801<div class="doc_subsubsection">
1802 <a name="legal">Legal</a>
1803</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1804
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1805<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1806
1807<p>
1808The <tt>Legal</tt> LegalizeAction enum value simply indicates that an
1809operation <b>is</b> natively supported. <tt>Legal</tt> represents the default
1810condition, so it is rarely used. In <tt>SparcISelLowering.cpp</tt>, the action
1811for <tt>CTPOP</tt> (an operation to count the bits set in an integer) is
1812natively supported only for SPARC v9. The following code enables
1813the <tt>Expand</tt> conversion technique for non-v9 SPARC implementations.
1814</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1815
1816<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1817<pre>
1818setOperationAction(ISD::CTPOP, MVT::i32, Expand);
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1819...
1820if (TM.getSubtarget&lt;SparcSubtarget&gt;().isV9())
1821 setOperationAction(ISD::CTPOP, MVT::i32, Legal);
1822 case ISD::SETULT: return SPCC::ICC_CS;
1823 case ISD::SETULE: return SPCC::ICC_LEU;
1824 case ISD::SETUGT: return SPCC::ICC_GU;
1825 case ISD::SETUGE: return SPCC::ICC_CC;
1826 }
1827}
1828</pre>
1829</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1830
1831</div>
1832
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1833<!-- ======================================================================= -->
1834<div class="doc_subsection">
1835 <a name="callingConventions">Calling Conventions</a>
1836</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1837
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1838<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1839
1840<p>
1841To support target-specific calling conventions, <tt>XXXGenCallingConv.td</tt>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1842uses interfaces (such as CCIfType and CCAssignToReg) that are defined in
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1843<tt>lib/Target/TargetCallingConv.td</tt>. TableGen can take the target
1844descriptor file <tt>XXXGenCallingConv.td</tt> and generate the header
1845file <tt>XXXGenCallingConv.inc</tt>, which is typically included
1846in <tt>XXXISelLowering.cpp</tt>. You can use the interfaces in
1847<tt>TargetCallingConv.td</tt> to specify:
1848</p>
1849
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1850<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1851<li>The order of parameter allocation.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1852
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1853<li>Where parameters and return values are placed (that is, on the stack or in
1854 registers).</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1855
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1856<li>Which registers may be used.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1857
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1858<li>Whether the caller or callee unwinds the stack.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1859</ul>
1860
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1861<p>
1862The following example demonstrates the use of the <tt>CCIfType</tt> and
1863<tt>CCAssignToReg</tt> interfaces. If the <tt>CCIfType</tt> predicate is true
1864(that is, if the current argument is of type <tt>f32</tt> or <tt>f64</tt>), then
1865the action is performed. In this case, the <tt>CCAssignToReg</tt> action assigns
1866the argument value to the first available register: either <tt>R0</tt>
1867or <tt>R1</tt>.
1868</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1869
1870<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1871<pre>
1872CCIfType&lt;[f32,f64], CCAssignToReg&lt;[R0, R1]&gt;&gt;
1873</pre>
1874</div>
1875
1876<p>
1877<tt>SparcCallingConv.td</tt> contains definitions for a target-specific
1878return-value calling convention (RetCC_Sparc32) and a basic 32-bit C calling
1879convention (<tt>CC_Sparc32</tt>). The definition of <tt>RetCC_Sparc32</tt>
1880(shown below) indicates which registers are used for specified scalar return
1881types. A single-precision float is returned to register <tt>F0</tt>, and a
1882double-precision float goes to register <tt>D0</tt>. A 32-bit integer is
1883returned in register <tt>I0</tt> or <tt>I1</tt>.
1884</p>
1885
1886<div class="doc_code">
1887<pre>
1888def RetCC_Sparc32 : CallingConv&lt;[
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1889 CCIfType&lt;[i32], CCAssignToReg&lt;[I0, I1]&gt;&gt;,
1890 CCIfType&lt;[f32], CCAssignToReg&lt;[F0]&gt;&gt;,
1891 CCIfType&lt;[f64], CCAssignToReg&lt;[D0]&gt;&gt;
1892]&gt;;
1893</pre>
1894</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1895
1896<p>
1897The definition of <tt>CC_Sparc32</tt> in <tt>SparcCallingConv.td</tt> introduces
1898<tt>CCAssignToStack</tt>, which assigns the value to a stack slot with the
1899specified size and alignment. In the example below, the first parameter, 4,
1900indicates the size of the slot, and the second parameter, also 4, indicates the
1901stack alignment along 4-byte units. (Special cases: if size is zero, then the
1902ABI size is used; if alignment is zero, then the ABI alignment is used.)
1903</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1904
1905<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1906<pre>
1907def CC_Sparc32 : CallingConv&lt;[
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1908 // All arguments get passed in integer registers if there is space.
1909 CCIfType&lt;[i32, f32, f64], CCAssignToReg&lt;[I0, I1, I2, I3, I4, I5]&gt;&gt;,
1910 CCAssignToStack&lt;4, 4&gt;
1911]&gt;;
1912</pre>
1913</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1914
1915<p>
1916<tt>CCDelegateTo</tt> is another commonly used interface, which tries to find a
1917specified sub-calling convention, and, if a match is found, it is invoked. In
1918the following example (in <tt>X86CallingConv.td</tt>), the definition of
1919<tt>RetCC_X86_32_C</tt> ends with <tt>CCDelegateTo</tt>. After the current value
1920is assigned to the register <tt>ST0</tt> or <tt>ST1</tt>,
1921the <tt>RetCC_X86Common</tt> is invoked.
1922</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1923
1924<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1925<pre>
1926def RetCC_X86_32_C : CallingConv&lt;[
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1927 CCIfType&lt;[f32], CCAssignToReg&lt;[ST0, ST1]&gt;&gt;,
1928 CCIfType&lt;[f64], CCAssignToReg&lt;[ST0, ST1]&gt;&gt;,
1929 CCDelegateTo&lt;RetCC_X86Common&gt;
1930]&gt;;
1931</pre>
1932</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1933
1934<p>
1935<tt>CCIfCC</tt> is an interface that attempts to match the given name to the
1936current calling convention. If the name identifies the current calling
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1937convention, then a specified action is invoked. In the following example (in
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1938<tt>X86CallingConv.td</tt>), if the <tt>Fast</tt> calling convention is in use,
1939then <tt>RetCC_X86_32_Fast</tt> is invoked. If the <tt>SSECall</tt> calling
1940convention is in use, then <tt>RetCC_X86_32_SSE</tt> is invoked.
1941</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1942
1943<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1944<pre>
1945def RetCC_X86_32 : CallingConv&lt;[
1946 CCIfCC&lt;"CallingConv::Fast", CCDelegateTo&lt;RetCC_X86_32_Fast&gt;&gt;,
1947 CCIfCC&lt;"CallingConv::X86_SSECall", CCDelegateTo&lt;RetCC_X86_32_SSE&gt;&gt;,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1948 CCDelegateTo&lt;RetCC_X86_32_C&gt;
1949]&gt;;
1950</pre>
1951</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1952
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1953<p>Other calling convention interfaces include:</p>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1954
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1955<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1956<li><tt>CCIf &lt;predicate, action&gt;</tt> &mdash; If the predicate matches,
1957 apply the action.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1958
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1959<li><tt>CCIfInReg &lt;action&gt;</tt> &mdash; If the argument is marked with the
1960 '<tt>inreg</tt>' attribute, then apply the action.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1961
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1962<li><tt>CCIfNest &lt;action&gt;</tt> &mdash; Inf the argument is marked with the
1963 '<tt>nest</tt>' attribute, then apply the action.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1964
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1965<li><tt>CCIfNotVarArg &lt;action&gt;</tt> &mdash; If the current function does
1966 not take a variable number of arguments, apply the action.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1967
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1968<li><tt>CCAssignToRegWithShadow &lt;registerList, shadowList&gt;</tt> &mdash;
1969 similar to <tt>CCAssignToReg</tt>, but with a shadow list of registers.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1970
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1971<li><tt>CCPassByVal &lt;size, align&gt;</tt> &mdash; Assign value to a stack
1972 slot with the minimum specified size and alignment.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1973
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1974<li><tt>CCPromoteToType &lt;type&gt;</tt> &mdash; Promote the current value to
1975 the specified type.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1976
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1977<li><tt>CallingConv &lt;[actions]&gt;</tt> &mdash; Define each calling
1978 convention that is supported.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1979</ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1980
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1981</div>
1982
1983<!-- *********************************************************************** -->
1984<div class="doc_section">
1985 <a name="assemblyPrinter">Assembly Printer</a>
1986</div>
1987<!-- *********************************************************************** -->
1988
1989<div class="doc_text">
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]1990
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]1991<p>
1992During the code emission stage, the code generator may utilize an LLVM pass to
1993produce assembly output. To do this, you want to implement the code for a
1994printer that converts LLVM IR to a GAS-format assembly language for your target
1995machine, using the following steps:
1996</p>
1997
1998<ul>
1999<li>Define all the assembly strings for your target, adding them to the
2000 instructions defined in the <tt>XXXInstrInfo.td</tt> file.
2001 (See <a href="#InstructionSet">Instruction Set</a>.) TableGen will produce
2002 an output file (<tt>XXXGenAsmWriter.inc</tt>) with an implementation of
2003 the <tt>printInstruction</tt> method for the XXXAsmPrinter class.</li>
2004
2005<li>Write <tt>XXXTargetAsmInfo.h</tt>, which contains the bare-bones declaration
2006 of the <tt>XXXTargetAsmInfo</tt> class (a subclass
2007 of <tt>TargetAsmInfo</tt>).</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2008
2009<li>Write <tt>XXXTargetAsmInfo.cpp</tt>, which contains target-specific values
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2010 for <tt>TargetAsmInfo</tt> properties and sometimes new implementations for
2011 methods.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2012
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2013<li>Write <tt>XXXAsmPrinter.cpp</tt>, which implements the <tt>AsmPrinter</tt>
2014 class that performs the LLVM-to-assembly conversion.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2015</ul>
2016
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2017<p>
2018The code in <tt>XXXTargetAsmInfo.h</tt> is usually a trivial declaration of the
2019<tt>XXXTargetAsmInfo</tt> class for use in <tt>XXXTargetAsmInfo.cpp</tt>.
2020Similarly, <tt>XXXTargetAsmInfo.cpp</tt> usually has a few declarations of
2021<tt>XXXTargetAsmInfo</tt> replacement values that override the default values
2022in <tt>TargetAsmInfo.cpp</tt>. For example in <tt>SparcTargetAsmInfo.cpp</tt>:
2023</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2024
2025<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2026<pre>
2027SparcTargetAsmInfo::SparcTargetAsmInfo(const SparcTargetMachine &amp;TM) {
2028 Data16bitsDirective = "\t.half\t";
2029 Data32bitsDirective = "\t.word\t";
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2030 Data64bitsDirective = 0; // .xword is only supported by V9.
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2031 ZeroDirective = "\t.skip\t";
2032 CommentString = "!";
2033 ConstantPoolSection = "\t.section \".rodata\",#alloc\n";
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2034}
2035</pre>
2036</div>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2037
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2038<p>
2039The X86 assembly printer implementation (<tt>X86TargetAsmInfo</tt>) is an
2040example where the target specific <tt>TargetAsmInfo</tt> class uses overridden
2041methods: <tt>ExpandInlineAsm</tt> and <tt>PreferredEHDataFormat</tt>.
2042</p>
2043
2044<p>
2045A target-specific implementation of AsmPrinter is written in
2046<tt>XXXAsmPrinter.cpp</tt>, which implements the <tt>AsmPrinter</tt> class that
2047converts the LLVM to printable assembly. The implementation must include the
2048following headers that have declarations for the <tt>AsmPrinter</tt> and
2049<tt>MachineFunctionPass</tt> classes. The <tt>MachineFunctionPass</tt> is a
2050subclass of <tt>FunctionPass</tt>.
2051</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2052
2053<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2054<pre>
2055#include "llvm/CodeGen/AsmPrinter.h"
2056#include "llvm/CodeGen/MachineFunctionPass.h"
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2057</pre>
2058</div>
2059
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2060<p>
2061As a <tt>FunctionPass</tt>, <tt>AsmPrinter</tt> first
2062calls <tt>doInitialization</tt> to set up the <tt>AsmPrinter</tt>. In
2063<tt>SparcAsmPrinter</tt>, a <tt>Mangler</tt> object is instantiated to process
2064variable names.
2065</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2066
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2067<p>
2068In <tt>XXXAsmPrinter.cpp</tt>, the <tt>runOnMachineFunction</tt> method
2069(declared in <tt>MachineFunctionPass</tt>) must be implemented
2070for <tt>XXXAsmPrinter</tt>. In <tt>MachineFunctionPass</tt>,
2071the <tt>runOnFunction</tt> method invokes <tt>runOnMachineFunction</tt>.
2072Target-specific implementations of <tt>runOnMachineFunction</tt> differ, but
2073generally do the following to process each machine function:
2074</p>
2075
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2076<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2077<li>Call <tt>SetupMachineFunction</tt> to perform initialization.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2078
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2079<li>Call <tt>EmitConstantPool</tt> to print out (to the output stream) constants
2080 which have been spilled to memory.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2081
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2082<li>Call <tt>EmitJumpTableInfo</tt> to print out jump tables used by the current
2083 function.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2084
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2085<li>Print out the label for the current function.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2086
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2087<li>Print out the code for the function, including basic block labels and the
2088 assembly for the instruction (using <tt>printInstruction</tt>)</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2089</ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2090
2091<p>
2092The <tt>XXXAsmPrinter</tt> implementation must also include the code generated
2093by TableGen that is output in the <tt>XXXGenAsmWriter.inc</tt> file. The code
2094in <tt>XXXGenAsmWriter.inc</tt> contains an implementation of the
2095<tt>printInstruction</tt> method that may call these methods:
2096</p>
2097
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2098<ul>
2099<li><tt>printOperand</tt></li>
2100
2101<li><tt>printMemOperand</tt></li>
2102
2103<li><tt>printCCOperand (for conditional statements)</tt></li>
2104
2105<li><tt>printDataDirective</tt></li>
2106
2107<li><tt>printDeclare</tt></li>
2108
2109<li><tt>printImplicitDef</tt></li>
2110
2111<li><tt>printInlineAsm</tt></li>
2112
2113<li><tt>printLabel</tt></li>
2114
2115<li><tt>printPICJumpTableEntry</tt></li>
2116
2117<li><tt>printPICJumpTableSetLabel</tt></li>
2118</ul>
2119
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2120<p>
2121The implementations of <tt>printDeclare</tt>, <tt>printImplicitDef</tt>,
2122<tt>printInlineAsm</tt>, and <tt>printLabel</tt> in <tt>AsmPrinter.cpp</tt> are
2123generally adequate for printing assembly and do not need to be
2124overridden. (<tt>printBasicBlockLabel</tt> is another method that is implemented
2125in <tt>AsmPrinter.cpp</tt> that may be directly used in an implementation of
2126<tt>XXXAsmPrinter</tt>.)
2127</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2128
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2129<p>
2130The <tt>printOperand</tt> method is implemented with a long switch/case
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2131statement for the type of operand: register, immediate, basic block, external
2132symbol, global address, constant pool index, or jump table index. For an
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2133instruction with a memory address operand, the <tt>printMemOperand</tt> method
2134should be implemented to generate the proper output. Similarly,
2135<tt>printCCOperand</tt> should be used to print a conditional operand.
2136</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2137
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2138<p><tt>doFinalization</tt> should be overridden in <tt>XXXAsmPrinter</tt>, and
2139it should be called to shut down the assembly printer. During
2140<tt>doFinalization</tt>, global variables and constants are printed to
2141output.
2142</p>
2143
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2144</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2145
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2146<!-- *********************************************************************** -->
2147<div class="doc_section">
2148 <a name="subtargetSupport">Subtarget Support</a>
2149</div>
2150<!-- *********************************************************************** -->
2151
2152<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2153
2154<p>
2155Subtarget support is used to inform the code generation process of instruction
2156set variations for a given chip set. For example, the LLVM SPARC implementation
2157provided covers three major versions of the SPARC microprocessor architecture:
2158Version 8 (V8, which is a 32-bit architecture), Version 9 (V9, a 64-bit
2159architecture), and the UltraSPARC architecture. V8 has 16 double-precision
2160floating-point registers that are also usable as either 32 single-precision or 8
2161quad-precision registers. V8 is also purely big-endian. V9 has 32
2162double-precision floating-point registers that are also usable as 16
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2163quad-precision registers, but cannot be used as single-precision registers. The
2164UltraSPARC architecture combines V9 with UltraSPARC Visual Instruction Set
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2165extensions.
2166</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2167
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2168<p>
2169If subtarget support is needed, you should implement a target-specific
2170XXXSubtarget class for your architecture. This class should process the
2171command-line options <tt>-mcpu=</tt> and <tt>-mattr=</tt>.
2172</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2173
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2174<p>
2175TableGen uses definitions in the <tt>Target.td</tt> and <tt>Sparc.td</tt> files
2176to generate code in <tt>SparcGenSubtarget.inc</tt>. In <tt>Target.td</tt>, shown
2177below, the <tt>SubtargetFeature</tt> interface is defined. The first 4 string
2178parameters of the <tt>SubtargetFeature</tt> interface are a feature name, an
2179attribute set by the feature, the value of the attribute, and a description of
2180the feature. (The fifth parameter is a list of features whose presence is
2181implied, and its default value is an empty array.)
2182</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2183
2184<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2185<pre>
2186class SubtargetFeature&lt;string n, string a, string v, string d,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2187 list&lt;SubtargetFeature&gt; i = []&gt; {
2188 string Name = n;
2189 string Attribute = a;
2190 string Value = v;
2191 string Desc = d;
2192 list&lt;SubtargetFeature&gt; Implies = i;
2193}
2194</pre>
2195</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2196
2197<p>
2198In the <tt>Sparc.td</tt> file, the SubtargetFeature is used to define the
2199following features.
2200</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2201
2202<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2203<pre>
2204def FeatureV9 : SubtargetFeature&lt;"v9", "IsV9", "true",
2205 "Enable SPARC-V9 instructions"&gt;;
2206def FeatureV8Deprecated : SubtargetFeature&lt;"deprecated-v8",
2207 "V8DeprecatedInsts", "true",
2208 "Enable deprecated V8 instructions in V9 mode"&gt;;
2209def FeatureVIS : SubtargetFeature&lt;"vis", "IsVIS", "true",
2210 "Enable UltraSPARC Visual Instruction Set extensions"&gt;;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2211</pre>
2212</div>
2213
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2214<p>
2215Elsewhere in <tt>Sparc.td</tt>, the Proc class is defined and then is used to
2216define particular SPARC processor subtypes that may have the previously
2217described features.
2218</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2219
2220<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2221<pre>
2222class Proc&lt;string Name, list&lt;SubtargetFeature&gt; Features&gt;
2223 : Processor&lt;Name, NoItineraries, Features&gt;;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2224&nbsp;
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2225def : Proc&lt;"generic", []&gt;;
2226def : Proc&lt;"v8", []&gt;;
2227def : Proc&lt;"supersparc", []&gt;;
2228def : Proc&lt;"sparclite", []&gt;;
2229def : Proc&lt;"f934", []&gt;;
2230def : Proc&lt;"hypersparc", []&gt;;
2231def : Proc&lt;"sparclite86x", []&gt;;
2232def : Proc&lt;"sparclet", []&gt;;
2233def : Proc&lt;"tsc701", []&gt;;
2234def : Proc&lt;"v9", [FeatureV9]&gt;;
2235def : Proc&lt;"ultrasparc", [FeatureV9, FeatureV8Deprecated]&gt;;
2236def : Proc&lt;"ultrasparc3", [FeatureV9, FeatureV8Deprecated]&gt;;
2237def : Proc&lt;"ultrasparc3-vis", [FeatureV9, FeatureV8Deprecated, FeatureVIS]&gt;;
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2238</pre>
2239</div>
2240
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2241<p>
2242From <tt>Target.td</tt> and <tt>Sparc.td</tt> files, the resulting
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2243SparcGenSubtarget.inc specifies enum values to identify the features, arrays of
2244constants to represent the CPU features and CPU subtypes, and the
2245ParseSubtargetFeatures method that parses the features string that sets
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2246specified subtarget options. The generated <tt>SparcGenSubtarget.inc</tt> file
2247should be included in the <tt>SparcSubtarget.cpp</tt>. The target-specific
2248implementation of the XXXSubtarget method should follow this pseudocode:
2249</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2250
2251<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2252<pre>
2253XXXSubtarget::XXXSubtarget(const Module &amp;M, const std::string &amp;FS) {
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2254 // Set the default features
2255 // Determine default and user specified characteristics of the CPU
2256 // Call ParseSubtargetFeatures(FS, CPU) to parse the features string
2257 // Perform any additional operations
2258}
2259</pre>
2260</div>
2261
2262<!-- *********************************************************************** -->
2263<div class="doc_section">
2264 <a name="jitSupport">JIT Support</a>
2265</div>
2266<!-- *********************************************************************** -->
2267
2268<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2269
2270<p>
2271The implementation of a target machine optionally includes a Just-In-Time (JIT)
2272code generator that emits machine code and auxiliary structures as binary output
2273that can be written directly to memory. To do this, implement JIT code
2274generation by performing the following steps:
2275</p>
2276
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2277<ul>
2278<li>Write an <tt>XXXCodeEmitter.cpp</tt> file that contains a machine function
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2279 pass that transforms target-machine instructions into relocatable machine
2280 code.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2281
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2282<li>Write an <tt>XXXJITInfo.cpp</tt> file that implements the JIT interfaces for
2283 target-specific code-generation activities, such as emitting machine code
2284 and stubs.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2285
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2286<li>Modify <tt>XXXTargetMachine</tt> so that it provides a
2287 <tt>TargetJITInfo</tt> object through its <tt>getJITInfo</tt> method.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2288</ul>
2289
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2290<p>
2291There are several different approaches to writing the JIT support code. For
2292instance, TableGen and target descriptor files may be used for creating a JIT
2293code generator, but are not mandatory. For the Alpha and PowerPC target
2294machines, TableGen is used to generate <tt>XXXGenCodeEmitter.inc</tt>, which
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2295contains the binary coding of machine instructions and the
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2296<tt>getBinaryCodeForInstr</tt> method to access those codes. Other JIT
2297implementations do not.
2298</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2299
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2300<p>
2301Both <tt>XXXJITInfo.cpp</tt> and <tt>XXXCodeEmitter.cpp</tt> must include the
2302<tt>llvm/CodeGen/MachineCodeEmitter.h</tt> header file that defines the
2303<tt>MachineCodeEmitter</tt> class containing code for several callback functions
2304that write data (in bytes, words, strings, etc.) to the output stream.
2305</p>
2306
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2307</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2308
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2309<!-- ======================================================================= -->
2310<div class="doc_subsection">
2311 <a name="mce">Machine Code Emitter</a>
2312</div>
2313
2314<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2315
2316<p>
2317In <tt>XXXCodeEmitter.cpp</tt>, a target-specific of the <tt>Emitter</tt> class
2318is implemented as a function pass (subclass
2319of <tt>MachineFunctionPass</tt>). The target-specific implementation
2320of <tt>runOnMachineFunction</tt> (invoked by
2321<tt>runOnFunction</tt> in <tt>MachineFunctionPass</tt>) iterates through the
2322<tt>MachineBasicBlock</tt> calls <tt>emitInstruction</tt> to process each
2323instruction and emit binary code. <tt>emitInstruction</tt> is largely
2324implemented with case statements on the instruction types defined in
2325<tt>XXXInstrInfo.h</tt>. For example, in <tt>X86CodeEmitter.cpp</tt>,
2326the <tt>emitInstruction</tt> method is built around the following switch/case
2327statements:
2328</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2329
2330<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2331<pre>
2332switch (Desc-&gt;TSFlags &amp; X86::FormMask) {
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2333case X86II::Pseudo: // for not yet implemented instructions
2334 ... // or pseudo-instructions
2335 break;
2336case X86II::RawFrm: // for instructions with a fixed opcode value
2337 ...
2338 break;
2339case X86II::AddRegFrm: // for instructions that have one register operand
2340 ... // added to their opcode
2341 break;
2342case X86II::MRMDestReg:// for instructions that use the Mod/RM byte
2343 ... // to specify a destination (register)
2344 break;
2345case X86II::MRMDestMem:// for instructions that use the Mod/RM byte
2346 ... // to specify a destination (memory)
2347 break;
2348case X86II::MRMSrcReg: // for instructions that use the Mod/RM byte
2349 ... // to specify a source (register)
2350 break;
2351case X86II::MRMSrcMem: // for instructions that use the Mod/RM byte
2352 ... // to specify a source (memory)
2353 break;
2354case X86II::MRM0r: case X86II::MRM1r: // for instructions that operate on
2355case X86II::MRM2r: case X86II::MRM3r: // a REGISTER r/m operand and
2356case X86II::MRM4r: case X86II::MRM5r: // use the Mod/RM byte and a field
2357case X86II::MRM6r: case X86II::MRM7r: // to hold extended opcode data
2358 ...
2359 break;
2360case X86II::MRM0m: case X86II::MRM1m: // for instructions that operate on
2361case X86II::MRM2m: case X86II::MRM3m: // a MEMORY r/m operand and
2362case X86II::MRM4m: case X86II::MRM5m: // use the Mod/RM byte and a field
2363case X86II::MRM6m: case X86II::MRM7m: // to hold extended opcode data
2364 ...
2365 break;
2366case X86II::MRMInitReg: // for instructions whose source and
2367 ... // destination are the same register
2368 break;
2369}
2370</pre>
2371</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2372
2373<p>
2374The implementations of these case statements often first emit the opcode and
2375then get the operand(s). Then depending upon the operand, helper methods may be
2376called to process the operand(s). For example, in <tt>X86CodeEmitter.cpp</tt>,
2377for the <tt>X86II::AddRegFrm</tt> case, the first data emitted
2378(by <tt>emitByte</tt>) is the opcode added to the register operand. Then an
2379object representing the machine operand, <tt>MO1</tt>, is extracted. The helper
2380methods such as <tt>isImmediate</tt>,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2381<tt>isGlobalAddress</tt>, <tt>isExternalSymbol</tt>, <tt>isConstantPoolIndex</tt>, and
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2382<tt>isJumpTableIndex</tt> determine the operand
2383type. (<tt>X86CodeEmitter.cpp</tt> also has private methods such
2384as <tt>emitConstant</tt>, <tt>emitGlobalAddress</tt>,
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2385<tt>emitExternalSymbolAddress</tt>, <tt>emitConstPoolAddress</tt>,
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2386and <tt>emitJumpTableAddress</tt> that emit the data into the output stream.)
2387</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2388
2389<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2390<pre>
2391case X86II::AddRegFrm:
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2392 MCE.emitByte(BaseOpcode + getX86RegNum(MI.getOperand(CurOp++).getReg()));
2393
2394 if (CurOp != NumOps) {
2395 const MachineOperand &amp;MO1 = MI.getOperand(CurOp++);
2396 unsigned Size = X86InstrInfo::sizeOfImm(Desc);
2397 if (MO1.isImmediate())
2398 emitConstant(MO1.getImm(), Size);
2399 else {
2400 unsigned rt = Is64BitMode ? X86::reloc_pcrel_word
2401 : (IsPIC ? X86::reloc_picrel_word : X86::reloc_absolute_word);
2402 if (Opcode == X86::MOV64ri)
2403 rt = X86::reloc_absolute_dword; // FIXME: add X86II flag?
2404 if (MO1.isGlobalAddress()) {
2405 bool NeedStub = isa&lt;Function&gt;(MO1.getGlobal());
2406 bool isLazy = gvNeedsLazyPtr(MO1.getGlobal());
2407 emitGlobalAddress(MO1.getGlobal(), rt, MO1.getOffset(), 0,
2408 NeedStub, isLazy);
2409 } else if (MO1.isExternalSymbol())
2410 emitExternalSymbolAddress(MO1.getSymbolName(), rt);
2411 else if (MO1.isConstantPoolIndex())
2412 emitConstPoolAddress(MO1.getIndex(), rt);
2413 else if (MO1.isJumpTableIndex())
2414 emitJumpTableAddress(MO1.getIndex(), rt);
2415 }
2416 }
2417 break;
2418</pre>
2419</div>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2420
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2421<p>
2422In the previous example, <tt>XXXCodeEmitter.cpp</tt> uses the
2423variable <tt>rt</tt>, which is a RelocationType enum that may be used to
2424relocate addresses (for example, a global address with a PIC base offset). The
2425<tt>RelocationType</tt> enum for that target is defined in the short
2426target-specific <tt>XXXRelocations.h</tt> file. The <tt>RelocationType</tt> is used by
2427the <tt>relocate</tt> method defined in <tt>XXXJITInfo.cpp</tt> to rewrite
2428addresses for referenced global symbols.
2429</p>
2430
2431<p>
2432For example, <tt>X86Relocations.h</tt> specifies the following relocation types
2433for the X86 addresses. In all four cases, the relocated value is added to the
2434value already in memory. For <tt>reloc_pcrel_word</tt>
2435and <tt>reloc_picrel_word</tt>, there is an additional initial adjustment.
2436</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2437
2438<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2439<pre>
2440enum RelocationType {
2441 reloc_pcrel_word = 0, // add reloc value after adjusting for the PC loc
2442 reloc_picrel_word = 1, // add reloc value after adjusting for the PIC base
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2443 reloc_absolute_word = 2, // absolute relocation; no additional adjustment
2444 reloc_absolute_dword = 3 // absolute relocation; no additional adjustment
2445};
2446</pre>
2447</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2448
2449</div>
2450
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2451<!-- ======================================================================= -->
2452<div class="doc_subsection">
2453 <a name="targetJITInfo">Target JIT Info</a>
2454</div>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2455
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2456<div class="doc_text">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2457
2458<p>
2459<tt>XXXJITInfo.cpp</tt> implements the JIT interfaces for target-specific
2460code-generation activities, such as emitting machine code and stubs. At minimum,
2461a target-specific version of <tt>XXXJITInfo</tt> implements the following:
2462</p>
2463
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2464<ul>
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2465<li><tt>getLazyResolverFunction</tt> &mdash; Initializes the JIT, gives the
2466 target a function that is used for compilation.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2467
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2468<li><tt>emitFunctionStub</tt> &mdash; Returns a native function with a specified
2469 address for a callback function.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2470
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2471<li><tt>relocate</tt> &mdash; Changes the addresses of referenced globals, based
2472 on relocation types.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2473
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2474<li>Callback function that are wrappers to a function stub that is used when the
2475 real target is not initially known.</li>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2476</ul>
2477
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2478<p>
2479<tt>getLazyResolverFunction</tt> is generally trivial to implement. It makes the
2480incoming parameter as the global <tt>JITCompilerFunction</tt> and returns the
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2481callback function that will be used a function wrapper. For the Alpha target
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2482(in <tt>AlphaJITInfo.cpp</tt>), the <tt>getLazyResolverFunction</tt>
2483implementation is simply:
2484</p>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2485
2486<div class="doc_code">
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2487<pre>
2488TargetJITInfo::LazyResolverFn AlphaJITInfo::getLazyResolverFunction(
2489 JITCompilerFn F) {
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2490 JITCompilerFunction = F;
2491 return AlphaCompilationCallback;
2492}
2493</pre>
2494</div>
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2495
Bill Wendling4a2bca82009-04-05 00:41:19 +0000[diff] [blame^]2496<p>
2497For the X86 target, the <tt>getLazyResolverFunction</tt> implementation is a
2498little more complication, because it returns a different callback function for
2499processors with SSE instructions and XMM registers.
2500</p>
2501
2502<p>
2503The callback function initially saves and later restores the callee register
2504values, incoming arguments, and frame and return address. The callback function
2505needs low-level access to the registers or stack, so it is typically implemented
2506with assembler.
2507</p>
2508
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]2509</div>
2510
2511<!-- *********************************************************************** -->
2512
2513<hr>
2514<address>
2515 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]2516 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]2517 <a href="http://validator.w3.org/check/referer"><img
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Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]2519
Chris Lattner78975382008-11-11 19:30:41 +0000[diff] [blame]2520 <a href="http://www.woo.com">Mason Woo</a> and <a href="http://misha.brukman.net">Misha Brukman</a><br>
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]2521 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a>
Misha Brukman8eb67192004-09-06 22:58:13 +0000[diff] [blame]2522 <br>
2523 Last modified: $Date$
2524</address>
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2526</body>
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