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gerrit-public.fairphone.software / fp2-dev / platform / external / llvm / 258c58cc6257cf61c9bdbb9c4cea67ba2691adf0 / . / docs / Passes.html
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Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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4<head>
5 <title>LLVM's Analysis and Transform Passes</title>
6 <link rel="stylesheet" href="llvm.css" type="text/css">
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]8</head>
9<body>
10
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]11<!--
12
13If Passes.html is up to date, the following "one-liner" should print
14an empty diff.
15
16egrep -e '^<tr><td><a href="#.*">-.*</a></td><td>.*</td></tr>$' \
17 -e '^ <a name=".*">.*</a>$' < Passes.html >html; \
18perl >help <<'EOT' && diff -u help html; rm -f help html
19open HTML, "<Passes.html" or die "open: Passes.html: $!\n";
20while (<HTML>) {
21 m:^<tr><td><a href="#(.*)">-.*</a></td><td>.*</td></tr>$: or next;
22 $order{$1} = sprintf("%03d", 1 + int %order);
23}
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]24open HELP, "../Release/bin/opt -help|" or die "open: opt -help: $!\n";
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]25while (<HELP>) {
26 m:^ -([^ ]+) +- (.*)$: or next;
27 my $o = $order{$1};
28 $o = "000" unless defined $o;
29 push @x, "$o<tr><td><a href=\"#$1\">-$1</a></td><td>$2</td></tr>\n";
30 push @y, "$o <a name=\"$1\">$2</a>\n";
31}
32@x = map { s/^\d\d\d//; $_ } sort @x;
33@y = map { s/^\d\d\d//; $_ } sort @y;
34print @x, @y;
35EOT
36
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]37This (real) one-liner can also be helpful when converting comments to HTML:
38
39perl -e '$/ = undef; for (split(/\n/, <>)) { s:^ *///? ?::; print " <p>\n" if !$on && $_ =~ /\S/; print " </p>\n" if $on && $_ =~ /^\s*$/; print " $_\n"; $on = ($_ =~ /\S/); } print " </p>\n" if $on'
40
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]41 -->
42
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]43<div class="doc_title">LLVM's Analysis and Transform Passes</div>
44
45<ol>
46 <li><a href="#intro">Introduction</a></li>
47 <li><a href="#analyses">Analysis Passes</a>
48 <li><a href="#transforms">Transform Passes</a></li>
49 <li><a href="#utilities">Utility Passes</a></li>
50</ol>
51
52<div class="doc_author">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]53 <p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a>
54 and Gordon Henriksen</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]55</div>
56
57<!-- ======================================================================= -->
58<div class="doc_section"> <a name="intro">Introduction</a> </div>
59<div class="doc_text">
60 <p>This document serves as a high level summary of the optimization features
61 that LLVM provides. Optimizations are implemented as Passes that traverse some
62 portion of a program to either collect information or transform the program.
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]63 The table below divides the passes that LLVM provides into three categories.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]64 Analysis passes compute information that other passes can use or for debugging
65 or program visualization purposes. Transform passes can use (or invalidate)
66 the analysis passes. Transform passes all mutate the program in some way.
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]67 Utility passes provides some utility but don't otherwise fit categorization.
Gabor Greif04367bf2007-07-06 22:07:22 +0000[diff] [blame]68 For example passes to extract functions to bitcode or write a module to
69 bitcode are neither analysis nor transform passes.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]70 <p>The table below provides a quick summary of each pass and links to the more
71 complete pass description later in the document.</p>
72</div>
73<div class="doc_text" >
74<table>
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]75<tr><th colspan="2"><b>ANALYSIS PASSES</b></th></tr>
76<tr><th>Option</th><th>Name</th></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]77<tr><td><a href="#aa-eval">-aa-eval</a></td><td>Exhaustive Alias Analysis Precision Evaluator</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]78<tr><td><a href="#basicaa">-basicaa</a></td><td>Basic Alias Analysis (default AA impl)</td></tr>
79<tr><td><a href="#basiccg">-basiccg</a></td><td>Basic CallGraph Construction</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]80<tr><td><a href="#codegenprepare">-codegenprepare</a></td><td>Optimize for code generation</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]81<tr><td><a href="#count-aa">-count-aa</a></td><td>Count Alias Analysis Query Responses</td></tr>
82<tr><td><a href="#debug-aa">-debug-aa</a></td><td>AA use debugger</td></tr>
83<tr><td><a href="#domfrontier">-domfrontier</a></td><td>Dominance Frontier Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]84<tr><td><a href="#domtree">-domtree</a></td><td>Dominator Tree Construction</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]85<tr><td><a href="#dot-callgraph">-dot-callgraph</a></td><td>Print Call Graph to 'dot' file</td></tr>
86<tr><td><a href="#dot-cfg">-dot-cfg</a></td><td>Print CFG of function to 'dot' file</td></tr>
87<tr><td><a href="#dot-cfg-only">-dot-cfg-only</a></td><td>Print CFG of function to 'dot' file (with no function bodies)</td></tr>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]88<tr><td><a href="#dot-dom">-dot-dom</a></td><td>Print dominator tree of function to 'dot' file</td></tr>
89<tr><td><a href="#dot-dom-only">-dot-dom-only</a></td><td>Print dominator tree of function to 'dot' file (with no function bodies)</td></tr>
90<tr><td><a href="#dot-postdom">-dot-postdom</a></td><td>Print post dominator tree of function to 'dot' file</td></tr>
91<tr><td><a href="#dot-postdom-only">-dot-postdom-only</a></td><td>Print post dominator tree of function to 'dot' file (with no function bodies)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]92<tr><td><a href="#globalsmodref-aa">-globalsmodref-aa</a></td><td>Simple mod/ref analysis for globals</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]93<tr><td><a href="#instcount">-instcount</a></td><td>Counts the various types of Instructions</td></tr>
94<tr><td><a href="#intervals">-intervals</a></td><td>Interval Partition Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]95<tr><td><a href="#loops">-loops</a></td><td>Natural Loop Construction</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]96<tr><td><a href="#memdep">-memdep</a></td><td>Memory Dependence Analysis</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]97<tr><td><a href="#no-aa">-no-aa</a></td><td>No Alias Analysis (always returns 'may' alias)</td></tr>
98<tr><td><a href="#no-profile">-no-profile</a></td><td>No Profile Information</td></tr>
99<tr><td><a href="#postdomfrontier">-postdomfrontier</a></td><td>Post-Dominance Frontier Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]100<tr><td><a href="#postdomtree">-postdomtree</a></td><td>Post-Dominator Tree Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]101<tr><td><a href="#print-alias-sets">-print-alias-sets</a></td><td>Alias Set Printer</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]102<tr><td><a href="#print-callgraph">-print-callgraph</a></td><td>Print a call graph</td></tr>
103<tr><td><a href="#print-callgraph-sccs">-print-callgraph-sccs</a></td><td>Print SCCs of the Call Graph</td></tr>
104<tr><td><a href="#print-cfg-sccs">-print-cfg-sccs</a></td><td>Print SCCs of each function CFG</td></tr>
105<tr><td><a href="#print-externalfnconstants">-print-externalfnconstants</a></td><td>Print external fn callsites passed constants</td></tr>
106<tr><td><a href="#print-function">-print-function</a></td><td>Print function to stderr</td></tr>
107<tr><td><a href="#print-module">-print-module</a></td><td>Print module to stderr</td></tr>
108<tr><td><a href="#print-used-types">-print-used-types</a></td><td>Find Used Types</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]109<tr><td><a href="#profile-loader">-profile-loader</a></td><td>Load profile information from llvmprof.out</td></tr>
110<tr><td><a href="#scalar-evolution">-scalar-evolution</a></td><td>Scalar Evolution Analysis</td></tr>
111<tr><td><a href="#targetdata">-targetdata</a></td><td>Target Data Layout</td></tr>
112
113
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]114<tr><th colspan="2"><b>TRANSFORM PASSES</b></th></tr>
115<tr><th>Option</th><th>Name</th></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]116<tr><td><a href="#adce">-adce</a></td><td>Aggressive Dead Code Elimination</td></tr>
117<tr><td><a href="#argpromotion">-argpromotion</a></td><td>Promote 'by reference' arguments to scalars</td></tr>
118<tr><td><a href="#block-placement">-block-placement</a></td><td>Profile Guided Basic Block Placement</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]119<tr><td><a href="#break-crit-edges">-break-crit-edges</a></td><td>Break critical edges in CFG</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]120<tr><td><a href="#codegenprepare">-codegenprepare</a></td><td>Prepare a function for code generation </td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]121<tr><td><a href="#constmerge">-constmerge</a></td><td>Merge Duplicate Global Constants</td></tr>
122<tr><td><a href="#constprop">-constprop</a></td><td>Simple constant propagation</td></tr>
123<tr><td><a href="#dce">-dce</a></td><td>Dead Code Elimination</td></tr>
124<tr><td><a href="#deadargelim">-deadargelim</a></td><td>Dead Argument Elimination</td></tr>
125<tr><td><a href="#deadtypeelim">-deadtypeelim</a></td><td>Dead Type Elimination</td></tr>
126<tr><td><a href="#die">-die</a></td><td>Dead Instruction Elimination</td></tr>
127<tr><td><a href="#dse">-dse</a></td><td>Dead Store Elimination</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]128<tr><td><a href="#globaldce">-globaldce</a></td><td>Dead Global Elimination</td></tr>
129<tr><td><a href="#globalopt">-globalopt</a></td><td>Global Variable Optimizer</td></tr>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]130<tr><td><a href="#gvn">-gvn</a></td><td>Global Value Numbering</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]131<tr><td><a href="#indvars">-indvars</a></td><td>Canonicalize Induction Variables</td></tr>
132<tr><td><a href="#inline">-inline</a></td><td>Function Integration/Inlining</td></tr>
133<tr><td><a href="#insert-block-profiling">-insert-block-profiling</a></td><td>Insert instrumentation for block profiling</td></tr>
134<tr><td><a href="#insert-edge-profiling">-insert-edge-profiling</a></td><td>Insert instrumentation for edge profiling</td></tr>
135<tr><td><a href="#insert-function-profiling">-insert-function-profiling</a></td><td>Insert instrumentation for function profiling</td></tr>
136<tr><td><a href="#insert-null-profiling-rs">-insert-null-profiling-rs</a></td><td>Measure profiling framework overhead</td></tr>
137<tr><td><a href="#insert-rs-profiling-framework">-insert-rs-profiling-framework</a></td><td>Insert random sampling instrumentation framework</td></tr>
138<tr><td><a href="#instcombine">-instcombine</a></td><td>Combine redundant instructions</td></tr>
139<tr><td><a href="#internalize">-internalize</a></td><td>Internalize Global Symbols</td></tr>
140<tr><td><a href="#ipconstprop">-ipconstprop</a></td><td>Interprocedural constant propagation</td></tr>
141<tr><td><a href="#ipsccp">-ipsccp</a></td><td>Interprocedural Sparse Conditional Constant Propagation</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]142<tr><td><a href="#jump-threading">-jump-threading</a></td><td>Thread control through conditional blocks </td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]143<tr><td><a href="#lcssa">-lcssa</a></td><td>Loop-Closed SSA Form Pass</td></tr>
144<tr><td><a href="#licm">-licm</a></td><td>Loop Invariant Code Motion</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]145<tr><td><a href="#loop-deletion">-loop-deletion</a></td><td>Dead Loop Deletion Pass </td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]146<tr><td><a href="#loop-extract">-loop-extract</a></td><td>Extract loops into new functions</td></tr>
147<tr><td><a href="#loop-extract-single">-loop-extract-single</a></td><td>Extract at most one loop into a new function</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]148<tr><td><a href="#loop-index-split">-loop-index-split</a></td><td>Index Split Loops</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]149<tr><td><a href="#loop-reduce">-loop-reduce</a></td><td>Loop Strength Reduction</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]150<tr><td><a href="#loop-rotate">-loop-rotate</a></td><td>Rotate Loops</td></tr>
151<tr><td><a href="#loop-unroll">-loop-unroll</a></td><td>Unroll loops</td></tr>
152<tr><td><a href="#loop-unswitch">-loop-unswitch</a></td><td>Unswitch loops</td></tr>
153<tr><td><a href="#loopsimplify">-loopsimplify</a></td><td>Canonicalize natural loops</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]154<tr><td><a href="#lowerinvoke">-lowerinvoke</a></td><td>Lower invoke and unwind, for unwindless code generators</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]155<tr><td><a href="#lowersetjmp">-lowersetjmp</a></td><td>Lower Set Jump</td></tr>
156<tr><td><a href="#lowerswitch">-lowerswitch</a></td><td>Lower SwitchInst's to branches</td></tr>
157<tr><td><a href="#mem2reg">-mem2reg</a></td><td>Promote Memory to Register</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]158<tr><td><a href="#memcpyopt">-memcpyopt</a></td><td>Optimize use of memcpy and friends</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]159<tr><td><a href="#mergereturn">-mergereturn</a></td><td>Unify function exit nodes</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]160<tr><td><a href="#prune-eh">-prune-eh</a></td><td>Remove unused exception handling info</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]161<tr><td><a href="#reassociate">-reassociate</a></td><td>Reassociate expressions</td></tr>
162<tr><td><a href="#reg2mem">-reg2mem</a></td><td>Demote all values to stack slots</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]163<tr><td><a href="#scalarrepl">-scalarrepl</a></td><td>Scalar Replacement of Aggregates</td></tr>
164<tr><td><a href="#sccp">-sccp</a></td><td>Sparse Conditional Constant Propagation</td></tr>
165<tr><td><a href="#simplify-libcalls">-simplify-libcalls</a></td><td>Simplify well-known library calls</td></tr>
166<tr><td><a href="#simplifycfg">-simplifycfg</a></td><td>Simplify the CFG</td></tr>
167<tr><td><a href="#strip">-strip</a></td><td>Strip all symbols from a module</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]168<tr><td><a href="#strip-dead-prototypes">-strip-dead-prototypes</a></td><td>Remove unused function declarations</td></tr>
169<tr><td><a href="#sretpromotion">-sretpromotion</a></td><td>Promote sret arguments</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]170<tr><td><a href="#tailcallelim">-tailcallelim</a></td><td>Tail Call Elimination</td></tr>
171<tr><td><a href="#tailduplicate">-tailduplicate</a></td><td>Tail Duplication</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]172
173
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]174<tr><th colspan="2"><b>UTILITY PASSES</b></th></tr>
175<tr><th>Option</th><th>Name</th></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]176<tr><td><a href="#deadarghaX0r">-deadarghaX0r</a></td><td>Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</td></tr>
177<tr><td><a href="#extract-blocks">-extract-blocks</a></td><td>Extract Basic Blocks From Module (for bugpoint use)</td></tr>
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]178<tr><td><a href="#preverify">-preverify</a></td><td>Preliminary module verification</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]179<tr><td><a href="#verify">-verify</a></td><td>Module Verifier</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]180<tr><td><a href="#view-cfg">-view-cfg</a></td><td>View CFG of function</td></tr>
181<tr><td><a href="#view-cfg-only">-view-cfg-only</a></td><td>View CFG of function (with no function bodies)</td></tr>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]182<tr><td><a href="#view-dom">-view-dom</a></td><td>View dominator tree of function</td></tr>
183<tr><td><a href="#view-dom-only">-view-dom-only</a></td><td>View dominator tree of function (with no function bodies)</td></tr>
184<tr><td><a href="#view-postdom">-view-postdom</a></td><td>View post dominator tree of function</td></tr>
185<tr><td><a href="#view-postdom-only">-view-postdom-only</a></td><td>View post dominator tree of function (with no function bodies)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]186</table>
187</div>
188
189<!-- ======================================================================= -->
190<div class="doc_section"> <a name="example">Analysis Passes</a></div>
191<div class="doc_text">
192 <p>This section describes the LLVM Analysis Passes.</p>
193</div>
194
195<!-------------------------------------------------------------------------- -->
196<div class="doc_subsection">
197 <a name="aa-eval">Exhaustive Alias Analysis Precision Evaluator</a>
198</div>
199<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]200 <p>This is a simple N^2 alias analysis accuracy evaluator.
201 Basically, for each function in the program, it simply queries to see how the
202 alias analysis implementation answers alias queries between each pair of
203 pointers in the function.</p>
204
205 <p>This is inspired and adapted from code by: Naveen Neelakantam, Francesco
206 Spadini, and Wojciech Stryjewski.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]207</div>
208
209<!-------------------------------------------------------------------------- -->
210<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]211 <a name="basicaa">Basic Alias Analysis (default AA impl)</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]212</div>
213<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]214 <p>
215 This is the default implementation of the Alias Analysis interface
216 that simply implements a few identities (two different globals cannot alias,
217 etc), but otherwise does no analysis.
218 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]219</div>
220
221<!-------------------------------------------------------------------------- -->
222<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]223 <a name="basiccg">Basic CallGraph Construction</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]224</div>
225<div class="doc_text">
226 <p>Yet to be written.</p>
227</div>
228
229<!-------------------------------------------------------------------------- -->
230<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]231 <a name="codegenprepare">Optimize for code generation</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]232</div>
233<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]234 <p>
235 This pass munges the code in the input function to better prepare it for
236 SelectionDAG-based code generation. This works around limitations in it's
237 basic-block-at-a-time approach. It should eventually be removed.
238 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]239</div>
240
241<!-------------------------------------------------------------------------- -->
242<div class="doc_subsection">
243 <a name="count-aa">Count Alias Analysis Query Responses</a>
244</div>
245<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]246 <p>
247 A pass which can be used to count how many alias queries
248 are being made and how the alias analysis implementation being used responds.
249 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]250</div>
251
252<!-------------------------------------------------------------------------- -->
253<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]254 <a name="debug-aa">AA use debugger</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]255</div>
256<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]257 <p>
258 This simple pass checks alias analysis users to ensure that if they
259 create a new value, they do not query AA without informing it of the value.
260 It acts as a shim over any other AA pass you want.
261 </p>
262
263 <p>
264 Yes keeping track of every value in the program is expensive, but this is
265 a debugging pass.
266 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]267</div>
268
269<!-------------------------------------------------------------------------- -->
270<div class="doc_subsection">
271 <a name="domfrontier">Dominance Frontier Construction</a>
272</div>
273<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]274 <p>
275 This pass is a simple dominator construction algorithm for finding forward
276 dominator frontiers.
277 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]278</div>
279
280<!-------------------------------------------------------------------------- -->
281<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]282 <a name="domtree">Dominator Tree Construction</a>
283</div>
284<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]285 <p>
286 This pass is a simple dominator construction algorithm for finding forward
287 dominators.
288 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]289</div>
290
291<!-------------------------------------------------------------------------- -->
292<div class="doc_subsection">
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]293 <a name="dot-callgraph">Print Call Graph to 'dot' file</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]294</div>
295<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]296 <p>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]297 This pass, only available in <code>opt</code>, prints the call graph into a
298 <code>.dot</code> graph. This graph can then be processed with the "dot" tool
299 to convert it to postscript or some other suitable format.
300 </p>
301</div>
302
303<!-------------------------------------------------------------------------- -->
304<div class="doc_subsection">
305 <a name="dot-cfg">Print CFG of function to 'dot' file</a>
306</div>
307<div class="doc_text">
308 <p>
309 This pass, only available in <code>opt</code>, prints the control flow graph
310 into a <code>.dot</code> graph. This graph can then be processed with the
311 "dot" tool to convert it to postscript or some other suitable format.
312 </p>
313</div>
314
315<!-------------------------------------------------------------------------- -->
316<div class="doc_subsection">
317 <a name="dot-cfg-only">Print CFG of function to 'dot' file (with no function bodies)</a>
318</div>
319<div class="doc_text">
320 <p>
321 This pass, only available in <code>opt</code>, prints the control flow graph
322 into a <code>.dot</code> graph, omitting the function bodies. This graph can
323 then be processed with the "dot" tool to convert it to postscript or some
324 other suitable format.
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]325 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]326</div>
327
328<!-------------------------------------------------------------------------- -->
329<div class="doc_subsection">
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]330 <a name="dot-dom">Print dominator tree of function to 'dot' file</a>
331</div>
332<div class="doc_text">
333 <p>
334 This pass, only available in <code>opt</code>, prints the dominator tree
335 into a <code>.dot</code> graph. This graph can then be processed with the
336 "dot" tool to convert it to postscript or some other suitable format.
337 </p>
338</div>
339
340<!-------------------------------------------------------------------------- -->
341<div class="doc_subsection">
342 <a name="dot-dom-only">Print dominator tree of function to 'dot' file (with no
343 function bodies)</a>
344</div>
345<div class="doc_text">
346 <p>
347 This pass, only available in <code>opt</code>, prints the dominator tree
348 into a <code>.dot</code> graph, omitting the function bodies. This graph can
349 then be processed with the "dot" tool to convert it to postscript or some
350 other suitable format.
351 </p>
352</div>
353
354<!-------------------------------------------------------------------------- -->
355<div class="doc_subsection">
356 <a name="dot-postdom">Print post dominator tree of function to 'dot' file</a>
357</div>
358<div class="doc_text">
359 <p>
360 This pass, only available in <code>opt</code>, prints the post dominator tree
361 into a <code>.dot</code> graph. This graph can then be processed with the
362 "dot" tool to convert it to postscript or some other suitable format.
363 </p>
364</div>
365
366<!-------------------------------------------------------------------------- -->
367<div class="doc_subsection">
368 <a name="dot-postdom-only">Print post dominator tree of function to 'dot' file
369 (with no function bodies)</a>
370</div>
371<div class="doc_text">
372 <p>
373 This pass, only available in <code>opt</code>, prints the post dominator tree
374 into a <code>.dot</code> graph, omitting the function bodies. This graph can
375 then be processed with the "dot" tool to convert it to postscript or some
376 other suitable format.
377 </p>
378</div>
379
380<!-------------------------------------------------------------------------- -->
381<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]382 <a name="globalsmodref-aa">Simple mod/ref analysis for globals</a>
383</div>
384<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]385 <p>
386 This simple pass provides alias and mod/ref information for global values
387 that do not have their address taken, and keeps track of whether functions
388 read or write memory (are "pure"). For this simple (but very common) case,
389 we can provide pretty accurate and useful information.
390 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]391</div>
392
393<!-------------------------------------------------------------------------- -->
394<div class="doc_subsection">
395 <a name="instcount">Counts the various types of Instructions</a>
396</div>
397<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]398 <p>
399 This pass collects the count of all instructions and reports them
400 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]401</div>
402
403<!-------------------------------------------------------------------------- -->
404<div class="doc_subsection">
405 <a name="intervals">Interval Partition Construction</a>
406</div>
407<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]408 <p>
409 This analysis calculates and represents the interval partition of a function,
410 or a preexisting interval partition.
411 </p>
412
413 <p>
414 In this way, the interval partition may be used to reduce a flow graph down
415 to its degenerate single node interval partition (unless it is irreducible).
416 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]417</div>
418
419<!-------------------------------------------------------------------------- -->
420<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]421 <a name="loops">Natural Loop Construction</a>
422</div>
423<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]424 <p>
425 This analysis is used to identify natural loops and determine the loop depth
426 of various nodes of the CFG. Note that the loops identified may actually be
427 several natural loops that share the same header node... not just a single
428 natural loop.
429 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]430</div>
431
432<!-------------------------------------------------------------------------- -->
433<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]434 <a name="memdep">Memory Dependence Analysis</a>
435</div>
436<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]437 <p>
438 An analysis that determines, for a given memory operation, what preceding
439 memory operations it depends on. It builds on alias analysis information, and
440 tries to provide a lazy, caching interface to a common kind of alias
441 information query.
442 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]443</div>
444
445<!-------------------------------------------------------------------------- -->
446<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]447 <a name="no-aa">No Alias Analysis (always returns 'may' alias)</a>
448</div>
449<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]450 <p>
451 Always returns "I don't know" for alias queries. NoAA is unlike other alias
452 analysis implementations, in that it does not chain to a previous analysis. As
453 such it doesn't follow many of the rules that other alias analyses must.
454 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]455</div>
456
457<!-------------------------------------------------------------------------- -->
458<div class="doc_subsection">
459 <a name="no-profile">No Profile Information</a>
460</div>
461<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]462 <p>
463 The default "no profile" implementation of the abstract
464 <code>ProfileInfo</code> interface.
465 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]466</div>
467
468<!-------------------------------------------------------------------------- -->
469<div class="doc_subsection">
470 <a name="postdomfrontier">Post-Dominance Frontier Construction</a>
471</div>
472<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]473 <p>
474 This pass is a simple post-dominator construction algorithm for finding
475 post-dominator frontiers.
476 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]477</div>
478
479<!-------------------------------------------------------------------------- -->
480<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]481 <a name="postdomtree">Post-Dominator Tree Construction</a>
482</div>
483<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]484 <p>
485 This pass is a simple post-dominator construction algorithm for finding
486 post-dominators.
487 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]488</div>
489
490<!-------------------------------------------------------------------------- -->
491<div class="doc_subsection">
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]492 <a name="print-alias-sets">Alias Set Printer</a>
493</div>
494<div class="doc_text">
495 <p>Yet to be written.</p>
496</div>
497
498<!-------------------------------------------------------------------------- -->
499<div class="doc_subsection">
500 <a name="print-callgraph">Print a call graph</a>
501</div>
502<div class="doc_text">
503 <p>
504 This pass, only available in <code>opt</code>, prints the call graph to
505 standard output in a human-readable form.
506 </p>
507</div>
508
509<!-------------------------------------------------------------------------- -->
510<div class="doc_subsection">
511 <a name="print-callgraph-sccs">Print SCCs of the Call Graph</a>
512</div>
513<div class="doc_text">
514 <p>
515 This pass, only available in <code>opt</code>, prints the SCCs of the call
516 graph to standard output in a human-readable form.
517 </p>
518</div>
519
520<!-------------------------------------------------------------------------- -->
521<div class="doc_subsection">
522 <a name="print-cfg-sccs">Print SCCs of each function CFG</a>
523</div>
524<div class="doc_text">
525 <p>
526 This pass, only available in <code>opt</code>, prints the SCCs of each
527 function CFG to standard output in a human-readable form.
528 </p>
529</div>
530
531<!-------------------------------------------------------------------------- -->
532<div class="doc_subsection">
533 <a name="print-externalfnconstants">Print external fn callsites passed constants</a>
534</div>
535<div class="doc_text">
536 <p>
537 This pass, only available in <code>opt</code>, prints out call sites to
538 external functions that are called with constant arguments. This can be
539 useful when looking for standard library functions we should constant fold
540 or handle in alias analyses.
541 </p>
542</div>
543
544<!-------------------------------------------------------------------------- -->
545<div class="doc_subsection">
546 <a name="print-function">Print function to stderr</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]547</div>
548<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]549 <p>
550 The <code>PrintFunctionPass</code> class is designed to be pipelined with
551 other <code>FunctionPass</code>es, and prints out the functions of the module
552 as they are processed.
553 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]554</div>
555
556<!-------------------------------------------------------------------------- -->
557<div class="doc_subsection">
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]558 <a name="print-module">Print module to stderr</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]559</div>
560<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]561 <p>
562 This pass simply prints out the entire module when it is executed.
563 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]564</div>
565
566<!-------------------------------------------------------------------------- -->
567<div class="doc_subsection">
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]568 <a name="print-used-types">Find Used Types</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]569</div>
570<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]571 <p>
572 This pass is used to seek out all of the types in use by the program. Note
573 that this analysis explicitly does not include types only used by the symbol
574 table.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]575</div>
576
577<!-------------------------------------------------------------------------- -->
578<div class="doc_subsection">
579 <a name="profile-loader">Load profile information from llvmprof.out</a>
580</div>
581<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]582 <p>
583 A concrete implementation of profiling information that loads the information
584 from a profile dump file.
585 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]586</div>
587
588<!-------------------------------------------------------------------------- -->
589<div class="doc_subsection">
590 <a name="scalar-evolution">Scalar Evolution Analysis</a>
591</div>
592<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]593 <p>
594 The <code>ScalarEvolution</code> analysis can be used to analyze and
595 catagorize scalar expressions in loops. It specializes in recognizing general
596 induction variables, representing them with the abstract and opaque
597 <code>SCEV</code> class. Given this analysis, trip counts of loops and other
598 important properties can be obtained.
599 </p>
600
601 <p>
602 This analysis is primarily useful for induction variable substitution and
603 strength reduction.
604 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]605</div>
606
607<!-------------------------------------------------------------------------- -->
608<div class="doc_subsection">
609 <a name="targetdata">Target Data Layout</a>
610</div>
611<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]612 <p>Provides other passes access to information on how the size and alignment
613 required by the the target ABI for various data types.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]614</div>
615
616<!-- ======================================================================= -->
617<div class="doc_section"> <a name="transform">Transform Passes</a></div>
618<div class="doc_text">
619 <p>This section describes the LLVM Transform Passes.</p>
620</div>
621
622<!-------------------------------------------------------------------------- -->
623<div class="doc_subsection">
624 <a name="adce">Aggressive Dead Code Elimination</a>
625</div>
626<div class="doc_text">
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]627 <p>ADCE aggressively tries to eliminate code. This pass is similar to
628 <a href="#dce">DCE</a> but it assumes that values are dead until proven
629 otherwise. This is similar to <a href="#sccp">SCCP</a>, except applied to
630 the liveness of values.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]631</div>
632
633<!-------------------------------------------------------------------------- -->
634<div class="doc_subsection">
635 <a name="argpromotion">Promote 'by reference' arguments to scalars</a>
636</div>
637<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]638 <p>
639 This pass promotes "by reference" arguments to be "by value" arguments. In
640 practice, this means looking for internal functions that have pointer
641 arguments. If it can prove, through the use of alias analysis, that an
642 argument is *only* loaded, then it can pass the value into the function
643 instead of the address of the value. This can cause recursive simplification
644 of code and lead to the elimination of allocas (especially in C++ template
645 code like the STL).
646 </p>
647
648 <p>
649 This pass also handles aggregate arguments that are passed into a function,
650 scalarizing them if the elements of the aggregate are only loaded. Note that
651 it refuses to scalarize aggregates which would require passing in more than
652 three operands to the function, because passing thousands of operands for a
653 large array or structure is unprofitable!
654 </p>
655
656 <p>
657 Note that this transformation could also be done for arguments that are only
658 stored to (returning the value instead), but does not currently. This case
659 would be best handled when and if LLVM starts supporting multiple return
660 values from functions.
661 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]662</div>
663
664<!-------------------------------------------------------------------------- -->
665<div class="doc_subsection">
666 <a name="block-placement">Profile Guided Basic Block Placement</a>
667</div>
668<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]669 <p>This pass is a very simple profile guided basic block placement algorithm.
670 The idea is to put frequently executed blocks together at the start of the
671 function and hopefully increase the number of fall-through conditional
672 branches. If there is no profile information for a particular function, this
673 pass basically orders blocks in depth-first order.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]674</div>
675
676<!-------------------------------------------------------------------------- -->
677<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]678 <a name="break-crit-edges">Break critical edges in CFG</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]679</div>
680<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]681 <p>
682 Break all of the critical edges in the CFG by inserting a dummy basic block.
683 It may be "required" by passes that cannot deal with critical edges. This
684 transformation obviously invalidates the CFG, but can update forward dominator
685 (set, immediate dominators, tree, and frontier) information.
686 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]687</div>
688
689<!-------------------------------------------------------------------------- -->
690<div class="doc_subsection">
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]691 <a name="codegenprepare">Prepare a function for code generation</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]692</div>
693<div class="doc_text">
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]694 This pass munges the code in the input function to better prepare it for
695 SelectionDAG-based code generation. This works around limitations in it's
696 basic-block-at-a-time approach. It should eventually be removed.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]697</div>
698
699<!-------------------------------------------------------------------------- -->
700<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]701 <a name="constmerge">Merge Duplicate Global Constants</a>
702</div>
703<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]704 <p>
705 Merges duplicate global constants together into a single constant that is
706 shared. This is useful because some passes (ie TraceValues) insert a lot of
707 string constants into the program, regardless of whether or not an existing
708 string is available.
709 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]710</div>
711
712<!-------------------------------------------------------------------------- -->
713<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]714 <a name="constprop">Simple constant propagation</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]715</div>
716<div class="doc_text">
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]717 <p>This file implements constant propagation and merging. It looks for
718 instructions involving only constant operands and replaces them with a
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]719 constant value instead of an instruction. For example:</p>
720 <blockquote><pre>add i32 1, 2</pre></blockquote>
721 <p>becomes</p>
722 <blockquote><pre>i32 3</pre></blockquote>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]723 <p>NOTE: this pass has a habit of making definitions be dead. It is a good
724 idea to to run a <a href="#die">DIE</a> (Dead Instruction Elimination) pass
725 sometime after running this pass.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]726</div>
727
728<!-------------------------------------------------------------------------- -->
729<div class="doc_subsection">
730 <a name="dce">Dead Code Elimination</a>
731</div>
732<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]733 <p>
734 Dead code elimination is similar to <a href="#die">dead instruction
735 elimination</a>, but it rechecks instructions that were used by removed
736 instructions to see if they are newly dead.
737 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]738</div>
739
740<!-------------------------------------------------------------------------- -->
741<div class="doc_subsection">
742 <a name="deadargelim">Dead Argument Elimination</a>
743</div>
744<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]745 <p>
746 This pass deletes dead arguments from internal functions. Dead argument
747 elimination removes arguments which are directly dead, as well as arguments
748 only passed into function calls as dead arguments of other functions. This
749 pass also deletes dead arguments in a similar way.
750 </p>
751
752 <p>
753 This pass is often useful as a cleanup pass to run after aggressive
754 interprocedural passes, which add possibly-dead arguments.
755 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]756</div>
757
758<!-------------------------------------------------------------------------- -->
759<div class="doc_subsection">
760 <a name="deadtypeelim">Dead Type Elimination</a>
761</div>
762<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]763 <p>
764 This pass is used to cleanup the output of GCC. It eliminate names for types
765 that are unused in the entire translation unit, using the <a
766 href="#findusedtypes">find used types</a> pass.
767 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]768</div>
769
770<!-------------------------------------------------------------------------- -->
771<div class="doc_subsection">
772 <a name="die">Dead Instruction Elimination</a>
773</div>
774<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]775 <p>
776 Dead instruction elimination performs a single pass over the function,
777 removing instructions that are obviously dead.
778 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]779</div>
780
781<!-------------------------------------------------------------------------- -->
782<div class="doc_subsection">
783 <a name="dse">Dead Store Elimination</a>
784</div>
785<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]786 <p>
787 A trivial dead store elimination that only considers basic-block local
788 redundant stores.
789 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]790</div>
791
792<!-------------------------------------------------------------------------- -->
793<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]794 <a name="globaldce">Dead Global Elimination</a>
795</div>
796<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]797 <p>
798 This transform is designed to eliminate unreachable internal globals from the
799 program. It uses an aggressive algorithm, searching out globals that are
800 known to be alive. After it finds all of the globals which are needed, it
801 deletes whatever is left over. This allows it to delete recursive chunks of
802 the program which are unreachable.
803 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]804</div>
805
806<!-------------------------------------------------------------------------- -->
807<div class="doc_subsection">
808 <a name="globalopt">Global Variable Optimizer</a>
809</div>
810<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]811 <p>
812 This pass transforms simple global variables that never have their address
813 taken. If obviously true, it marks read/write globals as constant, deletes
814 variables only stored to, etc.
815 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]816</div>
817
818<!-------------------------------------------------------------------------- -->
819<div class="doc_subsection">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]820 <a name="gvn">Global Value Numbering</a>
821</div>
822<div class="doc_text">
823 <p>
Chris Lattner60f03402009-10-10 18:40:48 +0000[diff] [blame]824 This pass performs global value numbering to eliminate fully and partially
825 redundant instructions. It also performs redundant load elimination.
Matthijs Kooijman845f5242008-06-05 07:55:49 +0000[diff] [blame]826 </p>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]827</div>
828
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]829
830<!-------------------------------------------------------------------------- -->
831<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]832 <a name="indvars">Canonicalize Induction Variables</a>
833</div>
834<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]835 <p>
836 This transformation analyzes and transforms the induction variables (and
837 computations derived from them) into simpler forms suitable for subsequent
838 analysis and transformation.
839 </p>
840
841 <p>
842 This transformation makes the following changes to each loop with an
843 identifiable induction variable:
844 </p>
845
846 <ol>
847 <li>All loops are transformed to have a <em>single</em> canonical
848 induction variable which starts at zero and steps by one.</li>
849 <li>The canonical induction variable is guaranteed to be the first PHI node
850 in the loop header block.</li>
851 <li>Any pointer arithmetic recurrences are raised to use array
852 subscripts.</li>
853 </ol>
854
855 <p>
856 If the trip count of a loop is computable, this pass also makes the following
857 changes:
858 </p>
859
860 <ol>
861 <li>The exit condition for the loop is canonicalized to compare the
862 induction value against the exit value. This turns loops like:
863 <blockquote><pre>for (i = 7; i*i < 1000; ++i)</pre></blockquote>
864 into
865 <blockquote><pre>for (i = 0; i != 25; ++i)</pre></blockquote></li>
866 <li>Any use outside of the loop of an expression derived from the indvar
867 is changed to compute the derived value outside of the loop, eliminating
868 the dependence on the exit value of the induction variable. If the only
869 purpose of the loop is to compute the exit value of some derived
870 expression, this transformation will make the loop dead.</li>
Gordon Henriksene626bbe2007-11-04 16:17:00 +0000[diff] [blame]871 </ol>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]872
873 <p>
874 This transformation should be followed by strength reduction after all of the
875 desired loop transformations have been performed. Additionally, on targets
876 where it is profitable, the loop could be transformed to count down to zero
877 (the "do loop" optimization).
878 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]879</div>
880
881<!-------------------------------------------------------------------------- -->
882<div class="doc_subsection">
883 <a name="inline">Function Integration/Inlining</a>
884</div>
885<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]886 <p>
887 Bottom-up inlining of functions into callees.
888 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]889</div>
890
891<!-------------------------------------------------------------------------- -->
892<div class="doc_subsection">
893 <a name="insert-block-profiling">Insert instrumentation for block profiling</a>
894</div>
895<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]896 <p>
897 This pass instruments the specified program with counters for basic block
898 profiling, which counts the number of times each basic block executes. This
899 is the most basic form of profiling, which can tell which blocks are hot, but
900 cannot reliably detect hot paths through the CFG.
901 </p>
902
903 <p>
904 Note that this implementation is very naïve. Control equivalent regions of
905 the CFG should not require duplicate counters, but it does put duplicate
906 counters in.
907 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]908</div>
909
910<!-------------------------------------------------------------------------- -->
911<div class="doc_subsection">
912 <a name="insert-edge-profiling">Insert instrumentation for edge profiling</a>
913</div>
914<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]915 <p>
916 This pass instruments the specified program with counters for edge profiling.
917 Edge profiling can give a reasonable approximation of the hot paths through a
918 program, and is used for a wide variety of program transformations.
919 </p>
920
921 <p>
922 Note that this implementation is very naïve. It inserts a counter for
923 <em>every</em> edge in the program, instead of using control flow information
924 to prune the number of counters inserted.
925 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]926</div>
927
928<!-------------------------------------------------------------------------- -->
929<div class="doc_subsection">
930 <a name="insert-function-profiling">Insert instrumentation for function profiling</a>
931</div>
932<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]933 <p>
934 This pass instruments the specified program with counters for function
935 profiling, which counts the number of times each function is called.
936 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]937</div>
938
939<!-------------------------------------------------------------------------- -->
940<div class="doc_subsection">
941 <a name="insert-null-profiling-rs">Measure profiling framework overhead</a>
942</div>
943<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]944 <p>
945 The basic profiler that does nothing. It is the default profiler and thus
946 terminates <code>RSProfiler</code> chains. It is useful for measuring
947 framework overhead.
948 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]949</div>
950
951<!-------------------------------------------------------------------------- -->
952<div class="doc_subsection">
953 <a name="insert-rs-profiling-framework">Insert random sampling instrumentation framework</a>
954</div>
955<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]956 <p>
957 The second stage of the random-sampling instrumentation framework, duplicates
958 all instructions in a function, ignoring the profiling code, then connects the
959 two versions together at the entry and at backedges. At each connection point
960 a choice is made as to whether to jump to the profiled code (take a sample) or
961 execute the unprofiled code.
962 </p>
963
964 <p>
965 After this pass, it is highly recommended to run<a href="#mem2reg">mem2reg</a>
966 and <a href="#adce">adce</a>. <a href="#instcombine">instcombine</a>,
967 <a href="#load-vn">load-vn</a>, <a href="#gdce">gdce</a>, and
968 <a href="#dse">dse</a> also are good to run afterwards.
969 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]970</div>
971
972<!-------------------------------------------------------------------------- -->
973<div class="doc_subsection">
974 <a name="instcombine">Combine redundant instructions</a>
975</div>
976<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]977 <p>
978 Combine instructions to form fewer, simple
979 instructions. This pass does not modify the CFG This pass is where algebraic
980 simplification happens.
981 </p>
982
983 <p>
984 This pass combines things like:
985 </p>
986
987<blockquote><pre
988>%Y = add i32 %X, 1
989%Z = add i32 %Y, 1</pre></blockquote>
990
991 <p>
992 into:
993 </p>
994
995<blockquote><pre
996>%Z = add i32 %X, 2</pre></blockquote>
997
998 <p>
999 This is a simple worklist driven algorithm.
1000 </p>
1001
1002 <p>
1003 This pass guarantees that the following canonicalizations are performed on
1004 the program:
1005 </p>
1006
1007 <ul>
1008 <li>If a binary operator has a constant operand, it is moved to the right-
1009 hand side.</li>
1010 <li>Bitwise operators with constant operands are always grouped so that
1011 shifts are performed first, then <code>or</code>s, then
1012 <code>and</code>s, then <code>xor</code>s.</li>
1013 <li>Compare instructions are converted from <code>&lt;</code>,
1014 <code>&gt;</code>, <code>≤</code>, or <code>≥</code> to
1015 <code>=</code> or <code>≠</code> if possible.</li>
1016 <li>All <code>cmp</code> instructions on boolean values are replaced with
1017 logical operations.</li>
1018 <li><code>add <var>X</var>, <var>X</var></code> is represented as
1019 <code>mul <var>X</var>, 2</code> ⇒ <code>shl <var>X</var>, 1</code></li>
1020 <li>Multiplies with a constant power-of-two argument are transformed into
1021 shifts.</li>
1022 <li>… etc.</li>
1023 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1024</div>
1025
1026<!-------------------------------------------------------------------------- -->
1027<div class="doc_subsection">
1028 <a name="internalize">Internalize Global Symbols</a>
1029</div>
1030<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1031 <p>
1032 This pass loops over all of the functions in the input module, looking for a
1033 main function. If a main function is found, all other functions and all
1034 global variables with initializers are marked as internal.
1035 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1036</div>
1037
1038<!-------------------------------------------------------------------------- -->
1039<div class="doc_subsection">
1040 <a name="ipconstprop">Interprocedural constant propagation</a>
1041</div>
1042<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1043 <p>
1044 This pass implements an <em>extremely</em> simple interprocedural constant
1045 propagation pass. It could certainly be improved in many different ways,
1046 like using a worklist. This pass makes arguments dead, but does not remove
1047 them. The existing dead argument elimination pass should be run after this
1048 to clean up the mess.
1049 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1050</div>
1051
1052<!-------------------------------------------------------------------------- -->
1053<div class="doc_subsection">
1054 <a name="ipsccp">Interprocedural Sparse Conditional Constant Propagation</a>
1055</div>
1056<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1057 <p>
1058 An interprocedural variant of <a href="#sccp">Sparse Conditional Constant
1059 Propagation</a>.
1060 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1061</div>
1062
1063<!-------------------------------------------------------------------------- -->
1064<div class="doc_subsection">
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1065 <a name="jump-threading">Thread control through conditional blocks</a>
1066</div>
1067<div class="doc_text">
1068 <p>
1069 Jump threading tries to find distinct threads of control flow running through
1070 a basic block. This pass looks at blocks that have multiple predecessors and
1071 multiple successors. If one or more of the predecessors of the block can be
1072 proven to always cause a jump to one of the successors, we forward the edge
1073 from the predecessor to the successor by duplicating the contents of this
1074 block.
1075 </p>
1076 <p>
1077 An example of when this can occur is code like this:
1078 </p>
1079
1080 <pre
1081>if () { ...
1082 X = 4;
1083}
1084if (X &lt; 3) {</pre>
1085
1086 <p>
1087 In this case, the unconditional branch at the end of the first if can be
1088 revectored to the false side of the second if.
1089 </p>
1090</div>
1091
1092<!-------------------------------------------------------------------------- -->
1093<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1094 <a name="lcssa">Loop-Closed SSA Form Pass</a>
1095</div>
1096<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1097 <p>
1098 This pass transforms loops by placing phi nodes at the end of the loops for
1099 all values that are live across the loop boundary. For example, it turns
1100 the left into the right code:
1101 </p>
1102
1103 <pre
1104>for (...) for (...)
1105 if (c) if (c)
1106 X1 = ... X1 = ...
1107 else else
1108 X2 = ... X2 = ...
1109 X3 = phi(X1, X2) X3 = phi(X1, X2)
1110... = X3 + 4 X4 = phi(X3)
1111 ... = X4 + 4</pre>
1112
1113 <p>
1114 This is still valid LLVM; the extra phi nodes are purely redundant, and will
1115 be trivially eliminated by <code>InstCombine</code>. The major benefit of
1116 this transformation is that it makes many other loop optimizations, such as
1117 LoopUnswitching, simpler.
1118 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1119</div>
1120
1121<!-------------------------------------------------------------------------- -->
1122<div class="doc_subsection">
1123 <a name="licm">Loop Invariant Code Motion</a>
1124</div>
1125<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1126 <p>
1127 This pass performs loop invariant code motion, attempting to remove as much
1128 code from the body of a loop as possible. It does this by either hoisting
1129 code into the preheader block, or by sinking code to the exit blocks if it is
1130 safe. This pass also promotes must-aliased memory locations in the loop to
1131 live in registers, thus hoisting and sinking "invariant" loads and stores.
1132 </p>
1133
1134 <p>
1135 This pass uses alias analysis for two purposes:
1136 </p>
1137
1138 <ul>
1139 <li>Moving loop invariant loads and calls out of loops. If we can determine
1140 that a load or call inside of a loop never aliases anything stored to,
1141 we can hoist it or sink it like any other instruction.</li>
1142 <li>Scalar Promotion of Memory - If there is a store instruction inside of
1143 the loop, we try to move the store to happen AFTER the loop instead of
1144 inside of the loop. This can only happen if a few conditions are true:
1145 <ul>
1146 <li>The pointer stored through is loop invariant.</li>
1147 <li>There are no stores or loads in the loop which <em>may</em> alias
1148 the pointer. There are no calls in the loop which mod/ref the
1149 pointer.</li>
1150 </ul>
1151 If these conditions are true, we can promote the loads and stores in the
1152 loop of the pointer to use a temporary alloca'd variable. We then use
1153 the mem2reg functionality to construct the appropriate SSA form for the
1154 variable.</li>
1155 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1156</div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1157<!-------------------------------------------------------------------------- -->
1158<div class="doc_subsection">
1159 <a name="loop-deletion">Dead Loop Deletion Pass</a>
1160</div>
1161<div class="doc_text">
1162 <p>
1163 This file implements the Dead Loop Deletion Pass. This pass is responsible
1164 for eliminating loops with non-infinite computable trip counts that have no
1165 side effects or volatile instructions, and do not contribute to the
1166 computation of the function's return value.
1167 </p>
1168</div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1169
1170<!-------------------------------------------------------------------------- -->
1171<div class="doc_subsection">
1172 <a name="loop-extract">Extract loops into new functions</a>
1173</div>
1174<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1175 <p>
1176 A pass wrapper around the <code>ExtractLoop()</code> scalar transformation to
1177 extract each top-level loop into its own new function. If the loop is the
1178 <em>only</em> loop in a given function, it is not touched. This is a pass most
1179 useful for debugging via bugpoint.
1180 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1181</div>
1182
1183<!-------------------------------------------------------------------------- -->
1184<div class="doc_subsection">
1185 <a name="loop-extract-single">Extract at most one loop into a new function</a>
1186</div>
1187<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1188 <p>
1189 Similar to <a href="#loop-extract">Extract loops into new functions</a>,
1190 this pass extracts one natural loop from the program into a function if it
1191 can. This is used by bugpoint.
1192 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1193</div>
1194
1195<!-------------------------------------------------------------------------- -->
1196<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1197 <a name="loop-index-split">Index Split Loops</a>
1198</div>
1199<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1200 <p>
1201 This pass divides loop's iteration range by spliting loop such that each
1202 individual loop is executed efficiently.
1203 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1204</div>
1205
1206<!-------------------------------------------------------------------------- -->
1207<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1208 <a name="loop-reduce">Loop Strength Reduction</a>
1209</div>
1210<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1211 <p>
1212 This pass performs a strength reduction on array references inside loops that
1213 have as one or more of their components the loop induction variable. This is
1214 accomplished by creating a new value to hold the initial value of the array
1215 access for the first iteration, and then creating a new GEP instruction in
1216 the loop to increment the value by the appropriate amount.
1217 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1218</div>
1219
1220<!-------------------------------------------------------------------------- -->
1221<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1222 <a name="loop-rotate">Rotate Loops</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1223</div>
1224<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1225 <p>A simple loop rotation transformation.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1226</div>
1227
1228<!-------------------------------------------------------------------------- -->
1229<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1230 <a name="loop-unroll">Unroll loops</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1231</div>
1232<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1233 <p>
1234 This pass implements a simple loop unroller. It works best when loops have
1235 been canonicalized by the <a href="#indvars"><tt>-indvars</tt></a> pass,
1236 allowing it to determine the trip counts of loops easily.
1237 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1238</div>
1239
1240<!-------------------------------------------------------------------------- -->
1241<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1242 <a name="loop-unswitch">Unswitch loops</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1243</div>
1244<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1245 <p>
1246 This pass transforms loops that contain branches on loop-invariant conditions
1247 to have multiple loops. For example, it turns the left into the right code:
1248 </p>
1249
1250 <pre
1251>for (...) if (lic)
1252 A for (...)
1253 if (lic) A; B; C
1254 B else
1255 C for (...)
1256 A; C</pre>
1257
1258 <p>
1259 This can increase the size of the code exponentially (doubling it every time
1260 a loop is unswitched) so we only unswitch if the resultant code will be
1261 smaller than a threshold.
1262 </p>
1263
1264 <p>
1265 This pass expects LICM to be run before it to hoist invariant conditions out
1266 of the loop, to make the unswitching opportunity obvious.
1267 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1268</div>
1269
1270<!-------------------------------------------------------------------------- -->
1271<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1272 <a name="loopsimplify">Canonicalize natural loops</a>
1273</div>
1274<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1275 <p>
1276 This pass performs several transformations to transform natural loops into a
1277 simpler form, which makes subsequent analyses and transformations simpler and
1278 more effective.
1279 </p>
1280
1281 <p>
1282 Loop pre-header insertion guarantees that there is a single, non-critical
1283 entry edge from outside of the loop to the loop header. This simplifies a
1284 number of analyses and transformations, such as LICM.
1285 </p>
1286
1287 <p>
1288 Loop exit-block insertion guarantees that all exit blocks from the loop
1289 (blocks which are outside of the loop that have predecessors inside of the
1290 loop) only have predecessors from inside of the loop (and are thus dominated
1291 by the loop header). This simplifies transformations such as store-sinking
1292 that are built into LICM.
1293 </p>
1294
1295 <p>
1296 This pass also guarantees that loops will have exactly one backedge.
1297 </p>
1298
1299 <p>
1300 Note that the simplifycfg pass will clean up blocks which are split out but
1301 end up being unnecessary, so usage of this pass should not pessimize
1302 generated code.
1303 </p>
1304
1305 <p>
1306 This pass obviously modifies the CFG, but updates loop information and
1307 dominator information.
1308 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1309</div>
1310
1311<!-------------------------------------------------------------------------- -->
1312<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1313 <a name="lowerinvoke">Lower invoke and unwind, for unwindless code generators</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1314</div>
1315<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1316 <p>
1317 This transformation is designed for use by code generators which do not yet
1318 support stack unwinding. This pass supports two models of exception handling
1319 lowering, the 'cheap' support and the 'expensive' support.
1320 </p>
1321
1322 <p>
1323 'Cheap' exception handling support gives the program the ability to execute
1324 any program which does not "throw an exception", by turning 'invoke'
1325 instructions into calls and by turning 'unwind' instructions into calls to
1326 abort(). If the program does dynamically use the unwind instruction, the
1327 program will print a message then abort.
1328 </p>
1329
1330 <p>
1331 'Expensive' exception handling support gives the full exception handling
1332 support to the program at the cost of making the 'invoke' instruction
1333 really expensive. It basically inserts setjmp/longjmp calls to emulate the
1334 exception handling as necessary.
1335 </p>
1336
1337 <p>
1338 Because the 'expensive' support slows down programs a lot, and EH is only
1339 used for a subset of the programs, it must be specifically enabled by the
1340 <tt>-enable-correct-eh-support</tt> option.
1341 </p>
1342
1343 <p>
1344 Note that after this pass runs the CFG is not entirely accurate (exceptional
1345 control flow edges are not correct anymore) so only very simple things should
1346 be done after the lowerinvoke pass has run (like generation of native code).
1347 This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't
1348 support the invoke instruction yet" lowering pass.
1349 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1350</div>
1351
1352<!-------------------------------------------------------------------------- -->
1353<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1354 <a name="lowersetjmp">Lower Set Jump</a>
1355</div>
1356<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1357 <p>
1358 Lowers <tt>setjmp</tt> and <tt>longjmp</tt> to use the LLVM invoke and unwind
1359 instructions as necessary.
1360 </p>
1361
1362 <p>
1363 Lowering of <tt>longjmp</tt> is fairly trivial. We replace the call with a
1364 call to the LLVM library function <tt>__llvm_sjljeh_throw_longjmp()</tt>.
1365 This unwinds the stack for us calling all of the destructors for
1366 objects allocated on the stack.
1367 </p>
1368
1369 <p>
1370 At a <tt>setjmp</tt> call, the basic block is split and the <tt>setjmp</tt>
1371 removed. The calls in a function that have a <tt>setjmp</tt> are converted to
1372 invoke where the except part checks to see if it's a <tt>longjmp</tt>
1373 exception and, if so, if it's handled in the function. If it is, then it gets
1374 the value returned by the <tt>longjmp</tt> and goes to where the basic block
1375 was split. <tt>invoke</tt> instructions are handled in a similar fashion with
1376 the original except block being executed if it isn't a <tt>longjmp</tt>
1377 except that is handled by that function.
1378 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1379</div>
1380
1381<!-------------------------------------------------------------------------- -->
1382<div class="doc_subsection">
1383 <a name="lowerswitch">Lower SwitchInst's to branches</a>
1384</div>
1385<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1386 <p>
1387 Rewrites <tt>switch</tt> instructions with a sequence of branches, which
1388 allows targets to get away with not implementing the switch instruction until
1389 it is convenient.
1390 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1391</div>
1392
1393<!-------------------------------------------------------------------------- -->
1394<div class="doc_subsection">
1395 <a name="mem2reg">Promote Memory to Register</a>
1396</div>
1397<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1398 <p>
1399 This file promotes memory references to be register references. It promotes
1400 <tt>alloca</tt> instructions which only have <tt>load</tt>s and
1401 <tt>store</tt>s as uses. An <tt>alloca</tt> is transformed by using dominator
1402 frontiers to place <tt>phi</tt> nodes, then traversing the function in
1403 depth-first order to rewrite <tt>load</tt>s and <tt>store</tt>s as
1404 appropriate. This is just the standard SSA construction algorithm to construct
1405 "pruned" SSA form.
1406 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1407</div>
1408
1409<!-------------------------------------------------------------------------- -->
1410<div class="doc_subsection">
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1411 <a name="memcpyopt">Optimize use of memcpy and friend</a>
1412</div>
1413<div class="doc_text">
1414 <p>
1415 This pass performs various transformations related to eliminating memcpy
1416 calls, or transforming sets of stores into memset's.
1417 </p>
1418</div>
1419
1420<!-------------------------------------------------------------------------- -->
1421<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1422 <a name="mergereturn">Unify function exit nodes</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1423</div>
1424<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1425 <p>
1426 Ensure that functions have at most one <tt>ret</tt> instruction in them.
1427 Additionally, it keeps track of which node is the new exit node of the CFG.
1428 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1429</div>
1430
1431<!-------------------------------------------------------------------------- -->
1432<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1433 <a name="prune-eh">Remove unused exception handling info</a>
1434</div>
1435<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1436 <p>
1437 This file implements a simple interprocedural pass which walks the call-graph,
1438 turning <tt>invoke</tt> instructions into <tt>call</tt> instructions if and
1439 only if the callee cannot throw an exception. It implements this as a
1440 bottom-up traversal of the call-graph.
1441 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1442</div>
1443
1444<!-------------------------------------------------------------------------- -->
1445<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1446 <a name="reassociate">Reassociate expressions</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1447</div>
1448<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1449 <p>
1450 This pass reassociates commutative expressions in an order that is designed
1451 to promote better constant propagation, GCSE, LICM, PRE, etc.
1452 </p>
1453
1454 <p>
1455 For example: 4 + (<var>x</var> + 5) ⇒ <var>x</var> + (4 + 5)
1456 </p>
1457
1458 <p>
1459 In the implementation of this algorithm, constants are assigned rank = 0,
1460 function arguments are rank = 1, and other values are assigned ranks
1461 corresponding to the reverse post order traversal of current function
1462 (starting at 2), which effectively gives values in deep loops higher rank
1463 than values not in loops.
1464 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1465</div>
1466
1467<!-------------------------------------------------------------------------- -->
1468<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1469 <a name="reg2mem">Demote all values to stack slots</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1470</div>
1471<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1472 <p>
1473 This file demotes all registers to memory references. It is intented to be
1474 the inverse of <a href="#mem2reg"><tt>-mem2reg</tt></a>. By converting to
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]1475 <tt>load</tt> instructions, the only values live across basic blocks are
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1476 <tt>alloca</tt> instructions and <tt>load</tt> instructions before
1477 <tt>phi</tt> nodes. It is intended that this should make CFG hacking much
1478 easier. To make later hacking easier, the entry block is split into two, such
1479 that all introduced <tt>alloca</tt> instructions (and nothing else) are in the
1480 entry block.
1481 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1482</div>
1483
1484<!-------------------------------------------------------------------------- -->
1485<div class="doc_subsection">
1486 <a name="scalarrepl">Scalar Replacement of Aggregates</a>
1487</div>
1488<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1489 <p>
1490 The well-known scalar replacement of aggregates transformation. This
1491 transform breaks up <tt>alloca</tt> instructions of aggregate type (structure
1492 or array) into individual <tt>alloca</tt> instructions for each member if
1493 possible. Then, if possible, it transforms the individual <tt>alloca</tt>
1494 instructions into nice clean scalar SSA form.
1495 </p>
1496
1497 <p>
1498 This combines a simple scalar replacement of aggregates algorithm with the <a
1499 href="#mem2reg"><tt>mem2reg</tt></a> algorithm because often interact,
1500 especially for C++ programs. As such, iterating between <tt>scalarrepl</tt>,
1501 then <a href="#mem2reg"><tt>mem2reg</tt></a> until we run out of things to
1502 promote works well.
1503 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1504</div>
1505
1506<!-------------------------------------------------------------------------- -->
1507<div class="doc_subsection">
1508 <a name="sccp">Sparse Conditional Constant Propagation</a>
1509</div>
1510<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1511 <p>
1512 Sparse conditional constant propagation and merging, which can be summarized
1513 as:
1514 </p>
1515
1516 <ol>
1517 <li>Assumes values are constant unless proven otherwise</li>
1518 <li>Assumes BasicBlocks are dead unless proven otherwise</li>
1519 <li>Proves values to be constant, and replaces them with constants</li>
1520 <li>Proves conditional branches to be unconditional</li>
1521 </ol>
1522
1523 <p>
1524 Note that this pass has a habit of making definitions be dead. It is a good
1525 idea to to run a DCE pass sometime after running this pass.
1526 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1527</div>
1528
1529<!-------------------------------------------------------------------------- -->
1530<div class="doc_subsection">
1531 <a name="simplify-libcalls">Simplify well-known library calls</a>
1532</div>
1533<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1534 <p>
1535 Applies a variety of small optimizations for calls to specific well-known
1536 function calls (e.g. runtime library functions). For example, a call
1537 <tt>exit(3)</tt> that occurs within the <tt>main()</tt> function can be
1538 transformed into simply <tt>return 3</tt>.
1539 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1540</div>
1541
1542<!-------------------------------------------------------------------------- -->
1543<div class="doc_subsection">
1544 <a name="simplifycfg">Simplify the CFG</a>
1545</div>
1546<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1547 <p>
1548 Performs dead code elimination and basic block merging. Specifically:
1549 </p>
1550
1551 <ol>
1552 <li>Removes basic blocks with no predecessors.</li>
1553 <li>Merges a basic block into its predecessor if there is only one and the
1554 predecessor only has one successor.</li>
1555 <li>Eliminates PHI nodes for basic blocks with a single predecessor.</li>
1556 <li>Eliminates a basic block that only contains an unconditional
1557 branch.</li>
1558 </ol>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1559</div>
1560
1561<!-------------------------------------------------------------------------- -->
1562<div class="doc_subsection">
1563 <a name="strip">Strip all symbols from a module</a>
1564</div>
1565<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1566 <p>
1567 Performs code stripping. This transformation can delete:
1568 </p>
1569
1570 <ol>
1571 <li>names for virtual registers</li>
1572 <li>symbols for internal globals and functions</li>
1573 <li>debug information</li>
1574 </ol>
1575
1576 <p>
1577 Note that this transformation makes code much less readable, so it should
1578 only be used in situations where the <tt>strip</tt> utility would be used,
1579 such as reducing code size or making it harder to reverse engineer code.
1580 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1581</div>
1582
1583<!-------------------------------------------------------------------------- -->
1584<div class="doc_subsection">
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1585 <a name="strip-dead-prototypes">Remove unused function declarations</a>
1586</div>
1587<div class="doc_text">
1588 <p>
1589 This pass loops over all of the functions in the input module, looking for
1590 dead declarations and removes them. Dead declarations are declarations of
1591 functions for which no implementation is available (i.e., declarations for
1592 unused library functions).
1593 </p>
1594</div>
1595
1596<!-------------------------------------------------------------------------- -->
1597<div class="doc_subsection">
1598 <a name="sretpromotion">Promote sret arguments</a>
1599</div>
1600<div class="doc_text">
1601 <p>
1602 This pass finds functions that return a struct (using a pointer to the struct
1603 as the first argument of the function, marked with the '<tt>sret</tt>' attribute) and
1604 replaces them with a new function that simply returns each of the elements of
1605 that struct (using multiple return values).
1606 </p>
1607
1608 <p>
1609 This pass works under a number of conditions:
1610 </p>
1611
1612 <ul>
1613 <li>The returned struct must not contain other structs</li>
1614 <li>The returned struct must only be used to load values from</li>
1615 <li>The placeholder struct passed in is the result of an <tt>alloca</tt></li>
1616 </ul>
1617</div>
1618
1619<!-------------------------------------------------------------------------- -->
1620<div class="doc_subsection">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1621 <a name="tailcallelim">Tail Call Elimination</a>
1622</div>
1623<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1624 <p>
1625 This file transforms calls of the current function (self recursion) followed
1626 by a return instruction with a branch to the entry of the function, creating
1627 a loop. This pass also implements the following extensions to the basic
1628 algorithm:
1629 </p>
1630
1631 <ul>
1632 <li>Trivial instructions between the call and return do not prevent the
1633 transformation from taking place, though currently the analysis cannot
1634 support moving any really useful instructions (only dead ones).
1635 <li>This pass transforms functions that are prevented from being tail
1636 recursive by an associative expression to use an accumulator variable,
1637 thus compiling the typical naive factorial or <tt>fib</tt> implementation
1638 into efficient code.
1639 <li>TRE is performed if the function returns void, if the return
1640 returns the result returned by the call, or if the function returns a
1641 run-time constant on all exits from the function. It is possible, though
1642 unlikely, that the return returns something else (like constant 0), and
1643 can still be TRE'd. It can be TRE'd if <em>all other</em> return
1644 instructions in the function return the exact same value.
1645 <li>If it can prove that callees do not access theier caller stack frame,
1646 they are marked as eligible for tail call elimination (by the code
1647 generator).
1648 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1649</div>
1650
1651<!-------------------------------------------------------------------------- -->
1652<div class="doc_subsection">
1653 <a name="tailduplicate">Tail Duplication</a>
1654</div>
1655<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1656 <p>
1657 This pass performs a limited form of tail duplication, intended to simplify
1658 CFGs by removing some unconditional branches. This pass is necessary to
1659 straighten out loops created by the C front-end, but also is capable of
1660 making other code nicer. After this pass is run, the CFG simplify pass
1661 should be run to clean up the mess.
1662 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1663</div>
1664
1665<!-- ======================================================================= -->
1666<div class="doc_section"> <a name="transform">Utility Passes</a></div>
1667<div class="doc_text">
1668 <p>This section describes the LLVM Utility Passes.</p>
1669</div>
1670
1671<!-------------------------------------------------------------------------- -->
1672<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1673 <a name="deadarghaX0r">Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1674</div>
1675<div class="doc_text">
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1676 <p>
1677 Same as dead argument elimination, but deletes arguments to functions which
1678 are external. This is only for use by <a
1679 href="Bugpoint.html">bugpoint</a>.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1680</div>
1681
1682<!-------------------------------------------------------------------------- -->
1683<div class="doc_subsection">
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1684 <a name="extract-blocks">Extract Basic Blocks From Module (for bugpoint use)</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1685</div>
1686<div class="doc_text">
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1687 <p>
1688 This pass is used by bugpoint to extract all blocks from the module into their
1689 own functions.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1690</div>
1691
1692<!-------------------------------------------------------------------------- -->
1693<div class="doc_subsection">
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]1694 <a name="preverify">Preliminary module verification</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1695</div>
1696<div class="doc_text">
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]1697 <p>
1698 Ensures that the module is in the form required by the <a
1699 href="#verifier">Module Verifier</a> pass.
1700 </p>
1701
1702 <p>
1703 Running the verifier runs this pass automatically, so there should be no need
1704 to use it directly.
1705 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1706</div>
1707
1708<!-------------------------------------------------------------------------- -->
1709<div class="doc_subsection">
1710 <a name="verify">Module Verifier</a>
1711</div>
1712<div class="doc_text">
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1713 <p>
1714 Verifies an LLVM IR code. This is useful to run after an optimization which is
1715 undergoing testing. Note that <tt>llvm-as</tt> verifies its input before
1716 emitting bitcode, and also that malformed bitcode is likely to make LLVM
1717 crash. All language front-ends are therefore encouraged to verify their output
1718 before performing optimizing transformations.
1719 </p>
1720
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]1721 <ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1722 <li>Both of a binary operator's parameters are of the same type.</li>
1723 <li>Verify that the indices of mem access instructions match other
1724 operands.</li>
1725 <li>Verify that arithmetic and other things are only performed on
1726 first-class types. Verify that shifts and logicals only happen on
1727 integrals f.e.</li>
1728 <li>All of the constants in a switch statement are of the correct type.</li>
1729 <li>The code is in valid SSA form.</li>
Chris Lattner46b3abc2009-10-28 04:47:06 +0000[diff] [blame]1730 <li>It is illegal to put a label into any other type (like a structure) or
1731 to return one.</li>
Nick Lewycky0c78ac12008-03-28 06:46:51 +0000[diff] [blame]1732 <li>Only phi nodes can be self referential: <tt>%x = add i32 %x, %x</tt> is
Gordon Henriksen873390e2007-11-04 18:17:58 +0000[diff] [blame]1733 invalid.</li>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1734 <li>PHI nodes must have an entry for each predecessor, with no extras.</li>
1735 <li>PHI nodes must be the first thing in a basic block, all grouped
1736 together.</li>
1737 <li>PHI nodes must have at least one entry.</li>
1738 <li>All basic blocks should only end with terminator insts, not contain
1739 them.</li>
1740 <li>The entry node to a function must not have predecessors.</li>
1741 <li>All Instructions must be embedded into a basic block.</li>
1742 <li>Functions cannot take a void-typed parameter.</li>
1743 <li>Verify that a function's argument list agrees with its declared
1744 type.</li>
1745 <li>It is illegal to specify a name for a void value.</li>
1746 <li>It is illegal to have a internal global value with no initializer.</li>
1747 <li>It is illegal to have a ret instruction that returns a value that does
1748 not agree with the function return value type.</li>
1749 <li>Function call argument types match the function prototype.</li>
1750 <li>All other things that are tested by asserts spread about the code.</li>
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]1751 </ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1752
1753 <p>
1754 Note that this does not provide full security verification (like Java), but
1755 instead just tries to ensure that code is well-formed.
1756 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1757</div>
1758
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1759<!-------------------------------------------------------------------------- -->
1760<div class="doc_subsection">
1761 <a name="view-cfg">View CFG of function</a>
1762</div>
1763<div class="doc_text">
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1764 <p>
1765 Displays the control flow graph using the GraphViz tool.
1766 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1767</div>
1768
1769<!-------------------------------------------------------------------------- -->
1770<div class="doc_subsection">
1771 <a name="view-cfg-only">View CFG of function (with no function bodies)</a>
1772</div>
1773<div class="doc_text">
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1774 <p>
1775 Displays the control flow graph using the GraphViz tool, but omitting function
1776 bodies.
1777 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1778</div>
1779
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]1780<!-------------------------------------------------------------------------- -->
1781<div class="doc_subsection">
1782 <a name="view-dom">View dominator tree of function</a>
1783</div>
1784<div class="doc_text">
1785 <p>
1786 Displays the dominator tree using the GraphViz tool.
1787 </p>
1788</div>
1789
1790<!-------------------------------------------------------------------------- -->
1791<div class="doc_subsection">
1792 <a name="view-dom-only">View dominator tree of function (with no function
1793 bodies)
1794 </a>
1795</div>
1796<div class="doc_text">
1797 <p>
1798 Displays the dominator tree using the GraphViz tool, but omitting function
1799 bodies.
1800 </p>
1801</div>
1802
1803<!-------------------------------------------------------------------------- -->
1804<div class="doc_subsection">
1805 <a name="view-postdom">View post dominator tree of function</a>
1806</div>
1807<div class="doc_text">
1808 <p>
1809 Displays the post dominator tree using the GraphViz tool.
1810 </p>
1811</div>
1812
1813<!-------------------------------------------------------------------------- -->
1814<div class="doc_subsection">
1815 <a name="view-postdom-only">View post dominator tree of function (with no
1816 function bodies)
1817 </a>
1818</div>
1819<div class="doc_text">
1820 <p>
1821 Displays the post dominator tree using the GraphViz tool, but omitting
1822 function bodies.
1823 </p>
1824</div>
1825
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1826<!-- *********************************************************************** -->
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