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gerrit-public.fairphone.software / platform / external / llvm / 34c4485b7479a12b5ef1cb15d27e96277e8a499a / . / docs / Passes.html
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NAKAMURA Takumib5f74912011-04-21 01:32:19 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2 "http://www.w3.org/TR/html4/strict.dtd">
3<html>
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>$2</td></tr>\n";
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]30 push @y, "$o <a name=\"$1\">-$1: $2</a>\n";
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]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
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]43<h1>LLVM's Analysis and Transform Passes</h1>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]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<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]58<h2><a name="intro">Introduction</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]59<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]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>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]72
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]73<table>
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]74<tr><th colspan="2"><b>ANALYSIS PASSES</b></th></tr>
75<tr><th>Option</th><th>Name</th></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]76<tr><td><a href="#aa-eval">-aa-eval</a></td><td>Exhaustive Alias Analysis Precision Evaluator</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]77<tr><td><a href="#basicaa">-basicaa</a></td><td>Basic Alias Analysis (stateless AA impl)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]78<tr><td><a href="#basiccg">-basiccg</a></td><td>Basic CallGraph Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]79<tr><td><a href="#count-aa">-count-aa</a></td><td>Count Alias Analysis Query Responses</td></tr>
80<tr><td><a href="#debug-aa">-debug-aa</a></td><td>AA use debugger</td></tr>
81<tr><td><a href="#domfrontier">-domfrontier</a></td><td>Dominance Frontier Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]82<tr><td><a href="#domtree">-domtree</a></td><td>Dominator Tree Construction</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]83<tr><td><a href="#dot-callgraph">-dot-callgraph</a></td><td>Print Call Graph to 'dot' file</td></tr>
84<tr><td><a href="#dot-cfg">-dot-cfg</a></td><td>Print CFG of function to 'dot' file</td></tr>
85<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>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]86<tr><td><a href="#dot-dom">-dot-dom</a></td><td>Print dominance tree of function to 'dot' file</td></tr>
87<tr><td><a href="#dot-dom-only">-dot-dom-only</a></td><td>Print dominance tree of function to 'dot' file (with no function bodies)</td></tr>
88<tr><td><a href="#dot-postdom">-dot-postdom</a></td><td>Print postdominance tree of function to 'dot' file</td></tr>
89<tr><td><a href="#dot-postdom-only">-dot-postdom-only</a></td><td>Print postdominance tree of function to 'dot' file (with no function bodies)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]90<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]91<tr><td><a href="#instcount">-instcount</a></td><td>Counts the various types of Instructions</td></tr>
92<tr><td><a href="#intervals">-intervals</a></td><td>Interval Partition Construction</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]93<tr><td><a href="#iv-users">-iv-users</a></td><td>Induction Variable Users</td></tr>
94<tr><td><a href="#lazy-value-info">-lazy-value-info</a></td><td>Lazy Value Information Analysis</td></tr>
95<tr><td><a href="#lda">-lda</a></td><td>Loop Dependence Analysis</td></tr>
96<tr><td><a href="#libcall-aa">-libcall-aa</a></td><td>LibCall Alias Analysis</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]97<tr><td><a href="#lint">-lint</a></td><td>Statically lint-checks LLVM IR</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]98<tr><td><a href="#loops">-loops</a></td><td>Natural Loop Information</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]99<tr><td><a href="#memdep">-memdep</a></td><td>Memory Dependence Analysis</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]100<tr><td><a href="#module-debuginfo">-module-debuginfo</a></td><td>Decodes module-level debug info</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]101<tr><td><a href="#no-aa">-no-aa</a></td><td>No Alias Analysis (always returns 'may' alias)</td></tr>
102<tr><td><a href="#no-profile">-no-profile</a></td><td>No Profile Information</td></tr>
103<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]104<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]105<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]106<tr><td><a href="#print-callgraph">-print-callgraph</a></td><td>Print a call graph</td></tr>
107<tr><td><a href="#print-callgraph-sccs">-print-callgraph-sccs</a></td><td>Print SCCs of the Call Graph</td></tr>
108<tr><td><a href="#print-cfg-sccs">-print-cfg-sccs</a></td><td>Print SCCs of each function CFG</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]109<tr><td><a href="#print-dbginfo">-print-dbginfo</a></td><td>Print debug info in human readable form</td></tr>
110<tr><td><a href="#print-dom-info">-print-dom-info</a></td><td>Dominator Info Printer</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]111<tr><td><a href="#print-externalfnconstants">-print-externalfnconstants</a></td><td>Print external fn callsites passed constants</td></tr>
112<tr><td><a href="#print-function">-print-function</a></td><td>Print function to stderr</td></tr>
113<tr><td><a href="#print-module">-print-module</a></td><td>Print module to stderr</td></tr>
114<tr><td><a href="#print-used-types">-print-used-types</a></td><td>Find Used Types</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]115<tr><td><a href="#profile-estimator">-profile-estimator</a></td><td>Estimate profiling information</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]116<tr><td><a href="#profile-loader">-profile-loader</a></td><td>Load profile information from llvmprof.out</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]117<tr><td><a href="#profile-verifier">-profile-verifier</a></td><td>Verify profiling information</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]118<tr><td><a href="#regions">-regions</a></td><td>Detect single entry single exit regions</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]119<tr><td><a href="#scalar-evolution">-scalar-evolution</a></td><td>Scalar Evolution Analysis</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]120<tr><td><a href="#scev-aa">-scev-aa</a></td><td>ScalarEvolution-based Alias Analysis</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]121<tr><td><a href="#targetdata">-targetdata</a></td><td>Target Data Layout</td></tr>
122
123
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]124<tr><th colspan="2"><b>TRANSFORM PASSES</b></th></tr>
125<tr><th>Option</th><th>Name</th></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]126<tr><td><a href="#adce">-adce</a></td><td>Aggressive Dead Code Elimination</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]127<tr><td><a href="#always-inline">-always-inline</a></td><td>Inliner for always_inline functions</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]128<tr><td><a href="#argpromotion">-argpromotion</a></td><td>Promote 'by reference' arguments to scalars</td></tr>
129<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]130<tr><td><a href="#break-crit-edges">-break-crit-edges</a></td><td>Break critical edges in CFG</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]131<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]132<tr><td><a href="#constmerge">-constmerge</a></td><td>Merge Duplicate Global Constants</td></tr>
133<tr><td><a href="#constprop">-constprop</a></td><td>Simple constant propagation</td></tr>
134<tr><td><a href="#dce">-dce</a></td><td>Dead Code Elimination</td></tr>
135<tr><td><a href="#deadargelim">-deadargelim</a></td><td>Dead Argument Elimination</td></tr>
136<tr><td><a href="#deadtypeelim">-deadtypeelim</a></td><td>Dead Type Elimination</td></tr>
137<tr><td><a href="#die">-die</a></td><td>Dead Instruction Elimination</td></tr>
138<tr><td><a href="#dse">-dse</a></td><td>Dead Store Elimination</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]139<tr><td><a href="#functionattrs">-functionattrs</a></td><td>Deduce function attributes</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]140<tr><td><a href="#globaldce">-globaldce</a></td><td>Dead Global Elimination</td></tr>
141<tr><td><a href="#globalopt">-globalopt</a></td><td>Global Variable Optimizer</td></tr>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]142<tr><td><a href="#gvn">-gvn</a></td><td>Global Value Numbering</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]143<tr><td><a href="#indvars">-indvars</a></td><td>Canonicalize Induction Variables</td></tr>
144<tr><td><a href="#inline">-inline</a></td><td>Function Integration/Inlining</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]145<tr><td><a href="#insert-edge-profiling">-insert-edge-profiling</a></td><td>Insert instrumentation for edge profiling</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]146<tr><td><a href="#insert-optimal-edge-profiling">-insert-optimal-edge-profiling</a></td><td>Insert optimal instrumentation for edge profiling</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]147<tr><td><a href="#instcombine">-instcombine</a></td><td>Combine redundant instructions</td></tr>
148<tr><td><a href="#internalize">-internalize</a></td><td>Internalize Global Symbols</td></tr>
149<tr><td><a href="#ipconstprop">-ipconstprop</a></td><td>Interprocedural constant propagation</td></tr>
150<tr><td><a href="#ipsccp">-ipsccp</a></td><td>Interprocedural Sparse Conditional Constant Propagation</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]151<tr><td><a href="#jump-threading">-jump-threading</a></td><td>Jump Threading</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]152<tr><td><a href="#lcssa">-lcssa</a></td><td>Loop-Closed SSA Form Pass</td></tr>
153<tr><td><a href="#licm">-licm</a></td><td>Loop Invariant Code Motion</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]154<tr><td><a href="#loop-deletion">-loop-deletion</a></td><td>Delete dead loops</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]155<tr><td><a href="#loop-extract">-loop-extract</a></td><td>Extract loops into new functions</td></tr>
156<tr><td><a href="#loop-extract-single">-loop-extract-single</a></td><td>Extract at most one loop into a new function</td></tr>
157<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]158<tr><td><a href="#loop-rotate">-loop-rotate</a></td><td>Rotate Loops</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]159<tr><td><a href="#loop-simplify">-loop-simplify</a></td><td>Canonicalize natural loops</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]160<tr><td><a href="#loop-unroll">-loop-unroll</a></td><td>Unroll loops</td></tr>
161<tr><td><a href="#loop-unswitch">-loop-unswitch</a></td><td>Unswitch loops</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]162<tr><td><a href="#loweratomic">-loweratomic</a></td><td>Lower atomic intrinsics to non-atomic form</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]163<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]164<tr><td><a href="#lowerswitch">-lowerswitch</a></td><td>Lower SwitchInst's to branches</td></tr>
165<tr><td><a href="#mem2reg">-mem2reg</a></td><td>Promote Memory to Register</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]166<tr><td><a href="#memcpyopt">-memcpyopt</a></td><td>MemCpy Optimization</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]167<tr><td><a href="#mergefunc">-mergefunc</a></td><td>Merge Functions</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]168<tr><td><a href="#mergereturn">-mergereturn</a></td><td>Unify function exit nodes</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]169<tr><td><a href="#partial-inliner">-partial-inliner</a></td><td>Partial Inliner</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]170<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]171<tr><td><a href="#reassociate">-reassociate</a></td><td>Reassociate expressions</td></tr>
172<tr><td><a href="#reg2mem">-reg2mem</a></td><td>Demote all values to stack slots</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]173<tr><td><a href="#scalarrepl">-scalarrepl</a></td><td>Scalar Replacement of Aggregates (DT)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]174<tr><td><a href="#sccp">-sccp</a></td><td>Sparse Conditional Constant Propagation</td></tr>
175<tr><td><a href="#simplify-libcalls">-simplify-libcalls</a></td><td>Simplify well-known library calls</td></tr>
176<tr><td><a href="#simplifycfg">-simplifycfg</a></td><td>Simplify the CFG</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]177<tr><td><a href="#sink">-sink</a></td><td>Code sinking</td></tr>
178<tr><td><a href="#sretpromotion">-sretpromotion</a></td><td>Promote sret arguments to multiple ret values</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]179<tr><td><a href="#strip">-strip</a></td><td>Strip all symbols from a module</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]180<tr><td><a href="#strip-dead-debug-info">-strip-dead-debug-info</a></td><td>Strip debug info for unused symbols</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]181<tr><td><a href="#strip-dead-prototypes">-strip-dead-prototypes</a></td><td>Strip Unused Function Prototypes</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]182<tr><td><a href="#strip-debug-declare">-strip-debug-declare</a></td><td>Strip all llvm.dbg.declare intrinsics</td></tr>
183<tr><td><a href="#strip-nondebug">-strip-nondebug</a></td><td>Strip all symbols, except dbg symbols, from a module</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]184<tr><td><a href="#tailcallelim">-tailcallelim</a></td><td>Tail Call Elimination</td></tr>
185<tr><td><a href="#tailduplicate">-tailduplicate</a></td><td>Tail Duplication</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]186
187
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]188<tr><th colspan="2"><b>UTILITY PASSES</b></th></tr>
189<tr><th>Option</th><th>Name</th></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]190<tr><td><a href="#deadarghaX0r">-deadarghaX0r</a></td><td>Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</td></tr>
191<tr><td><a href="#extract-blocks">-extract-blocks</a></td><td>Extract Basic Blocks From Module (for bugpoint use)</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]192<tr><td><a href="#instnamer">-instnamer</a></td><td>Assign names to anonymous instructions</td></tr>
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]193<tr><td><a href="#preverify">-preverify</a></td><td>Preliminary module verification</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]194<tr><td><a href="#verify">-verify</a></td><td>Module Verifier</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]195<tr><td><a href="#view-cfg">-view-cfg</a></td><td>View CFG of function</td></tr>
196<tr><td><a href="#view-cfg-only">-view-cfg-only</a></td><td>View CFG of function (with no function bodies)</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]197<tr><td><a href="#view-dom">-view-dom</a></td><td>View dominance tree of function</td></tr>
198<tr><td><a href="#view-dom-only">-view-dom-only</a></td><td>View dominance tree of function (with no function bodies)</td></tr>
199<tr><td><a href="#view-postdom">-view-postdom</a></td><td>View postdominance tree of function</td></tr>
200<tr><td><a href="#view-postdom-only">-view-postdom-only</a></td><td>View postdominance tree of function (with no function bodies)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]201</table>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]202
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]203</div>
204
205<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]206<h2><a name="analyses">Analysis Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]207<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]208 <p>This section describes the LLVM Analysis Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]209
210<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]211<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]212 <a name="aa-eval">-aa-eval: Exhaustive Alias Analysis Precision Evaluator</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]213</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]214<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]215 <p>This is a simple N^2 alias analysis accuracy evaluator.
216 Basically, for each function in the program, it simply queries to see how the
217 alias analysis implementation answers alias queries between each pair of
218 pointers in the function.</p>
219
220 <p>This is inspired and adapted from code by: Naveen Neelakantam, Francesco
221 Spadini, and Wojciech Stryjewski.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]222</div>
223
224<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]225<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]226 <a name="basicaa">-basicaa: Basic Alias Analysis (stateless AA impl)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]227</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]228<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]229 <p>
230 This is the default implementation of the Alias Analysis interface
231 that simply implements a few identities (two different globals cannot alias,
232 etc), but otherwise does no analysis.
233 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]234</div>
235
236<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]237<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]238 <a name="basiccg">-basiccg: Basic CallGraph Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]239</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]240<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]241 <p>Yet to be written.</p>
242</div>
243
244<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]245<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]246 <a name="count-aa">-count-aa: Count Alias Analysis Query Responses</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]247</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]248<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]249 <p>
250 A pass which can be used to count how many alias queries
251 are being made and how the alias analysis implementation being used responds.
252 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]253</div>
254
255<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]256<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]257 <a name="debug-aa">-debug-aa: AA use debugger</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]258</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]259<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]260 <p>
261 This simple pass checks alias analysis users to ensure that if they
262 create a new value, they do not query AA without informing it of the value.
263 It acts as a shim over any other AA pass you want.
264 </p>
265
266 <p>
267 Yes keeping track of every value in the program is expensive, but this is
268 a debugging pass.
269 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]270</div>
271
272<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]273<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]274 <a name="domfrontier">-domfrontier: Dominance Frontier Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]275</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]276<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]277 <p>
278 This pass is a simple dominator construction algorithm for finding forward
279 dominator frontiers.
280 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]281</div>
282
283<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]284<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]285 <a name="domtree">-domtree: Dominator Tree Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]286</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]287<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]288 <p>
289 This pass is a simple dominator construction algorithm for finding forward
290 dominators.
291 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]292</div>
293
294<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]295<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]296 <a name="dot-callgraph">-dot-callgraph: Print Call Graph to 'dot' file</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]297</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]298<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]299 <p>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]300 This pass, only available in <code>opt</code>, prints the call graph into a
301 <code>.dot</code> graph. This graph can then be processed with the "dot" tool
302 to convert it to postscript or some other suitable format.
303 </p>
304</div>
305
306<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]307<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]308 <a name="dot-cfg">-dot-cfg: Print CFG of function to 'dot' file</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]309</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]310<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]311 <p>
312 This pass, only available in <code>opt</code>, prints the control flow graph
313 into a <code>.dot</code> graph. This graph can then be processed with the
314 "dot" tool to convert it to postscript or some other suitable format.
315 </p>
316</div>
317
318<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]319<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]320 <a name="dot-cfg-only">-dot-cfg-only: Print CFG of function to 'dot' file (with no function bodies)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]321</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]322<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]323 <p>
324 This pass, only available in <code>opt</code>, prints the control flow graph
325 into a <code>.dot</code> graph, omitting the function bodies. This graph can
326 then be processed with the "dot" tool to convert it to postscript or some
327 other suitable format.
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]328 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]329</div>
330
331<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]332<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]333 <a name="dot-dom">-dot-dom: Print dominance tree of function to 'dot' file</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]334</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]335<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]336 <p>
337 This pass, only available in <code>opt</code>, prints the dominator tree
338 into a <code>.dot</code> graph. This graph can then be processed with the
339 "dot" tool to convert it to postscript or some other suitable format.
340 </p>
341</div>
342
343<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]344<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]345 <a name="dot-dom-only">-dot-dom-only: Print dominance tree of function to 'dot' file (with no function bodies)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]346</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]347<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]348 <p>
349 This pass, only available in <code>opt</code>, prints the dominator tree
350 into a <code>.dot</code> graph, omitting the function bodies. This graph can
351 then be processed with the "dot" tool to convert it to postscript or some
352 other suitable format.
353 </p>
354</div>
355
356<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]357<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]358 <a name="dot-postdom">-dot-postdom: Print postdominance tree of function to 'dot' file</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]359</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]360<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]361 <p>
362 This pass, only available in <code>opt</code>, prints the post dominator tree
363 into a <code>.dot</code> graph. This graph can then be processed with the
364 "dot" tool to convert it to postscript or some other suitable format.
365 </p>
366</div>
367
368<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]369<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]370 <a name="dot-postdom-only">-dot-postdom-only: Print postdominance tree of function to 'dot' file (with no function bodies)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]371</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]372<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]373 <p>
374 This pass, only available in <code>opt</code>, prints the post dominator tree
375 into a <code>.dot</code> graph, omitting the function bodies. This graph can
376 then be processed with the "dot" tool to convert it to postscript or some
377 other suitable format.
378 </p>
379</div>
380
381<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]382<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]383 <a name="globalsmodref-aa">-globalsmodref-aa: Simple mod/ref analysis for globals</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]384</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]385<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]386 <p>
387 This simple pass provides alias and mod/ref information for global values
388 that do not have their address taken, and keeps track of whether functions
389 read or write memory (are "pure"). For this simple (but very common) case,
390 we can provide pretty accurate and useful information.
391 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]392</div>
393
394<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]395<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]396 <a name="instcount">-instcount: Counts the various types of Instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]397</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]398<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]399 <p>
400 This pass collects the count of all instructions and reports them
401 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]402</div>
403
404<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]405<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]406 <a name="intervals">-intervals: Interval Partition Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]407</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]408<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]409 <p>
410 This analysis calculates and represents the interval partition of a function,
411 or a preexisting interval partition.
412 </p>
413
414 <p>
415 In this way, the interval partition may be used to reduce a flow graph down
416 to its degenerate single node interval partition (unless it is irreducible).
417 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]418</div>
419
420<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]421<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]422 <a name="iv-users">-iv-users: Induction Variable Users</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]423</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]424<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]425 <p>Bookkeeping for "interesting" users of expressions computed from
426 induction variables.</p>
427</div>
428
429<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]430<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]431 <a name="lazy-value-info">-lazy-value-info: Lazy Value Information Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]432</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]433<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]434 <p>Interface for lazy computation of value constraint information.</p>
435</div>
436
437<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]438<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]439 <a name="lda">-lda: Loop Dependence Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]440</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]441<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]442 <p>Loop dependence analysis framework, which is used to detect dependences in
443 memory accesses in loops.</p>
444</div>
445
446<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]447<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]448 <a name="libcall-aa">-libcall-aa: LibCall Alias Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]449</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]450<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]451 <p>LibCall Alias Analysis.</p>
452</div>
453
454<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]455<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]456 <a name="lint">-lint: Statically lint-checks LLVM IR</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]457</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]458<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]459 <p>This pass statically checks for common and easily-identified constructs
460 which produce undefined or likely unintended behavior in LLVM IR.</p>
461
462 <p>It is not a guarantee of correctness, in two ways. First, it isn't
463 comprehensive. There are checks which could be done statically which are
464 not yet implemented. Some of these are indicated by TODO comments, but
465 those aren't comprehensive either. Second, many conditions cannot be
466 checked statically. This pass does no dynamic instrumentation, so it
467 can't check for all possible problems.</p>
468
469 <p>Another limitation is that it assumes all code will be executed. A store
470 through a null pointer in a basic block which is never reached is harmless,
471 but this pass will warn about it anyway.</p>
472
473 <p>Optimization passes may make conditions that this pass checks for more or
474 less obvious. If an optimization pass appears to be introducing a warning,
475 it may be that the optimization pass is merely exposing an existing
476 condition in the code.</p>
477
478 <p>This code may be run before instcombine. In many cases, instcombine checks
479 for the same kinds of things and turns instructions with undefined behavior
480 into unreachable (or equivalent). Because of this, this pass makes some
481 effort to look through bitcasts and so on.
482 </p>
483</div>
484
485<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]486<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]487 <a name="loops">-loops: Natural Loop Information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]488</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]489<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]490 <p>
491 This analysis is used to identify natural loops and determine the loop depth
492 of various nodes of the CFG. Note that the loops identified may actually be
493 several natural loops that share the same header node... not just a single
494 natural loop.
495 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]496</div>
497
498<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]499<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]500 <a name="memdep">-memdep: Memory Dependence Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]501</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]502<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]503 <p>
504 An analysis that determines, for a given memory operation, what preceding
505 memory operations it depends on. It builds on alias analysis information, and
506 tries to provide a lazy, caching interface to a common kind of alias
507 information query.
508 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]509</div>
510
511<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]512<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]513 <a name="module-debuginfo">-module-debuginfo: Decodes module-level debug info</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]514</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]515<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]516 <p>This pass decodes the debug info metadata in a module and prints in a
517 (sufficiently-prepared-) human-readable form.
518
519 For example, run this pass from opt along with the -analyze option, and
520 it'll print to standard output.
521 </p>
522</div>
523
524<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]525<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]526 <a name="no-aa">-no-aa: No Alias Analysis (always returns 'may' alias)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]527</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]528<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]529 <p>
530 Always returns "I don't know" for alias queries. NoAA is unlike other alias
531 analysis implementations, in that it does not chain to a previous analysis. As
532 such it doesn't follow many of the rules that other alias analyses must.
533 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]534</div>
535
536<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]537<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]538 <a name="no-profile">-no-profile: No Profile Information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]539</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]540<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]541 <p>
542 The default "no profile" implementation of the abstract
543 <code>ProfileInfo</code> interface.
544 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]545</div>
546
547<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]548<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]549 <a name="postdomfrontier">-postdomfrontier: Post-Dominance Frontier Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]550</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]551<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]552 <p>
553 This pass is a simple post-dominator construction algorithm for finding
554 post-dominator frontiers.
555 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]556</div>
557
558<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]559<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]560 <a name="postdomtree">-postdomtree: Post-Dominator Tree Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]561</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]562<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]563 <p>
564 This pass is a simple post-dominator construction algorithm for finding
565 post-dominators.
566 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]567</div>
568
569<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]570<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]571 <a name="print-alias-sets">-print-alias-sets: Alias Set Printer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]572</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]573<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]574 <p>Yet to be written.</p>
575</div>
576
577<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]578<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]579 <a name="print-callgraph">-print-callgraph: Print a call graph</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]580</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]581<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]582 <p>
583 This pass, only available in <code>opt</code>, prints the call graph to
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]584 standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]585 </p>
586</div>
587
588<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]589<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]590 <a name="print-callgraph-sccs">-print-callgraph-sccs: Print SCCs of the Call Graph</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]591</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]592<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]593 <p>
594 This pass, only available in <code>opt</code>, prints the SCCs of the call
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]595 graph to standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]596 </p>
597</div>
598
599<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]600<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]601 <a name="print-cfg-sccs">-print-cfg-sccs: Print SCCs of each function CFG</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]602</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]603<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]604 <p>
605 This pass, only available in <code>opt</code>, prints the SCCs of each
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]606 function CFG to standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]607 </p>
608</div>
609
610<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]611<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]612 <a name="print-dbginfo">-print-dbginfo: Print debug info in human readable form</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]613</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]614<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]615 <p>Pass that prints instructions, and associated debug info:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]616 <ul>
617
618 <li>source/line/col information</li>
619 <li>original variable name</li>
620 <li>original type name</li>
621 </ul>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]622</div>
623
624<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]625<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]626 <a name="print-dom-info">-print-dom-info: Dominator Info Printer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]627</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]628<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]629 <p>Dominator Info Printer.</p>
630</div>
631
632<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]633<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]634 <a name="print-externalfnconstants">-print-externalfnconstants: Print external fn callsites passed constants</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]635</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]636<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]637 <p>
638 This pass, only available in <code>opt</code>, prints out call sites to
639 external functions that are called with constant arguments. This can be
640 useful when looking for standard library functions we should constant fold
641 or handle in alias analyses.
642 </p>
643</div>
644
645<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]646<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]647 <a name="print-function">-print-function: Print function to stderr</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]648</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]649<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]650 <p>
651 The <code>PrintFunctionPass</code> class is designed to be pipelined with
652 other <code>FunctionPass</code>es, and prints out the functions of the module
653 as they are processed.
654 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]655</div>
656
657<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]658<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]659 <a name="print-module">-print-module: Print module to stderr</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]660</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]661<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]662 <p>
663 This pass simply prints out the entire module when it is executed.
664 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]665</div>
666
667<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]668<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]669 <a name="print-used-types">-print-used-types: Find Used Types</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]670</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]671<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]672 <p>
673 This pass is used to seek out all of the types in use by the program. Note
674 that this analysis explicitly does not include types only used by the symbol
675 table.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]676</div>
677
678<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]679<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]680 <a name="profile-estimator">-profile-estimator: Estimate profiling information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]681</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]682<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]683 <p>Profiling information that estimates the profiling information
684 in a very crude and unimaginative way.
685 </p>
686</div>
687
688<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]689<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]690 <a name="profile-loader">-profile-loader: Load profile information from llvmprof.out</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]691</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]692<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]693 <p>
694 A concrete implementation of profiling information that loads the information
695 from a profile dump file.
696 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]697</div>
698
699<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]700<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]701 <a name="profile-verifier">-profile-verifier: Verify profiling information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]702</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]703<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]704 <p>Pass that checks profiling information for plausibility.</p>
705</div>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]706<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]707 <a name="regions">-regions: Detect single entry single exit regions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]708</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]709<div>
Tobias Grosserf96b0062010-07-22 07:46:31 +0000[diff] [blame]710 <p>
711 The <code>RegionInfo</code> pass detects single entry single exit regions in a
712 function, where a region is defined as any subgraph that is connected to the
713 remaining graph at only two spots. Furthermore, an hierarchical region tree is
714 built.
715 </p>
716</div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]717
718<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]719<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]720 <a name="scalar-evolution">-scalar-evolution: Scalar Evolution Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]721</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]722<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]723 <p>
724 The <code>ScalarEvolution</code> analysis can be used to analyze and
725 catagorize scalar expressions in loops. It specializes in recognizing general
726 induction variables, representing them with the abstract and opaque
727 <code>SCEV</code> class. Given this analysis, trip counts of loops and other
728 important properties can be obtained.
729 </p>
730
731 <p>
732 This analysis is primarily useful for induction variable substitution and
733 strength reduction.
734 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]735</div>
736
737<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]738<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]739 <a name="scev-aa">-scev-aa: ScalarEvolution-based Alias Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]740</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]741<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]742 <p>Simple alias analysis implemented in terms of ScalarEvolution queries.
743
744 This differs from traditional loop dependence analysis in that it tests
745 for dependencies within a single iteration of a loop, rather than
746 dependencies between different iterations.
747
748 ScalarEvolution has a more complete understanding of pointer arithmetic
749 than BasicAliasAnalysis' collection of ad-hoc analyses.
750 </p>
751</div>
752
753<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]754<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]755 <a name="targetdata">-targetdata: Target Data Layout</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]756</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]757<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]758 <p>Provides other passes access to information on how the size and alignment
759 required by the the target ABI for various data types.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]760</div>
761
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]762</div>
763
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]764<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]765<h2><a name="transforms">Transform Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]766<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]767 <p>This section describes the LLVM Transform Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]768
769<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]770<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]771 <a name="adce">-adce: Aggressive Dead Code Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]772</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]773<div>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]774 <p>ADCE aggressively tries to eliminate code. This pass is similar to
775 <a href="#dce">DCE</a> but it assumes that values are dead until proven
776 otherwise. This is similar to <a href="#sccp">SCCP</a>, except applied to
777 the liveness of values.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]778</div>
779
780<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]781<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]782 <a name="always-inline">-always-inline: Inliner for always_inline functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]783</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]784<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]785 <p>A custom inliner that handles only functions that are marked as
786 "always inline".</p>
787</div>
788
789<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]790<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]791 <a name="argpromotion">-argpromotion: Promote 'by reference' arguments to scalars</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]792</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]793<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]794 <p>
795 This pass promotes "by reference" arguments to be "by value" arguments. In
796 practice, this means looking for internal functions that have pointer
797 arguments. If it can prove, through the use of alias analysis, that an
798 argument is *only* loaded, then it can pass the value into the function
799 instead of the address of the value. This can cause recursive simplification
800 of code and lead to the elimination of allocas (especially in C++ template
801 code like the STL).
802 </p>
803
804 <p>
805 This pass also handles aggregate arguments that are passed into a function,
806 scalarizing them if the elements of the aggregate are only loaded. Note that
807 it refuses to scalarize aggregates which would require passing in more than
808 three operands to the function, because passing thousands of operands for a
809 large array or structure is unprofitable!
810 </p>
811
812 <p>
813 Note that this transformation could also be done for arguments that are only
814 stored to (returning the value instead), but does not currently. This case
815 would be best handled when and if LLVM starts supporting multiple return
816 values from functions.
817 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]818</div>
819
820<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]821<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]822 <a name="block-placement">-block-placement: Profile Guided Basic Block Placement</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]823</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]824<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]825 <p>This pass is a very simple profile guided basic block placement algorithm.
826 The idea is to put frequently executed blocks together at the start of the
827 function and hopefully increase the number of fall-through conditional
828 branches. If there is no profile information for a particular function, this
829 pass basically orders blocks in depth-first order.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]830</div>
831
832<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]833<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]834 <a name="break-crit-edges">-break-crit-edges: Break critical edges in CFG</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]835</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]836<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]837 <p>
838 Break all of the critical edges in the CFG by inserting a dummy basic block.
839 It may be "required" by passes that cannot deal with critical edges. This
840 transformation obviously invalidates the CFG, but can update forward dominator
841 (set, immediate dominators, tree, and frontier) information.
842 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]843</div>
844
845<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]846<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]847 <a name="codegenprepare">-codegenprepare: Optimize for code generation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]848</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]849<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]850 This pass munges the code in the input function to better prepare it for
851 SelectionDAG-based code generation. This works around limitations in it's
852 basic-block-at-a-time approach. It should eventually be removed.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]853</div>
854
855<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]856<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]857 <a name="constmerge">-constmerge: Merge Duplicate Global Constants</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]858</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]859<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]860 <p>
861 Merges duplicate global constants together into a single constant that is
862 shared. This is useful because some passes (ie TraceValues) insert a lot of
863 string constants into the program, regardless of whether or not an existing
864 string is available.
865 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]866</div>
867
868<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]869<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]870 <a name="constprop">-constprop: Simple constant propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]871</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]872<div>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]873 <p>This file implements constant propagation and merging. It looks for
874 instructions involving only constant operands and replaces them with a
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]875 constant value instead of an instruction. For example:</p>
876 <blockquote><pre>add i32 1, 2</pre></blockquote>
877 <p>becomes</p>
878 <blockquote><pre>i32 3</pre></blockquote>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]879 <p>NOTE: this pass has a habit of making definitions be dead. It is a good
880 idea to to run a <a href="#die">DIE</a> (Dead Instruction Elimination) pass
881 sometime after running this pass.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]882</div>
883
884<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]885<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]886 <a name="dce">-dce: Dead Code Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]887</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]888<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]889 <p>
890 Dead code elimination is similar to <a href="#die">dead instruction
891 elimination</a>, but it rechecks instructions that were used by removed
892 instructions to see if they are newly dead.
893 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]894</div>
895
896<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]897<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]898 <a name="deadargelim">-deadargelim: Dead Argument Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]899</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]900<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]901 <p>
902 This pass deletes dead arguments from internal functions. Dead argument
903 elimination removes arguments which are directly dead, as well as arguments
904 only passed into function calls as dead arguments of other functions. This
905 pass also deletes dead arguments in a similar way.
906 </p>
907
908 <p>
909 This pass is often useful as a cleanup pass to run after aggressive
910 interprocedural passes, which add possibly-dead arguments.
911 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]912</div>
913
914<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]915<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]916 <a name="deadtypeelim">-deadtypeelim: Dead Type Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]917</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]918<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]919 <p>
920 This pass is used to cleanup the output of GCC. It eliminate names for types
921 that are unused in the entire translation unit, using the <a
922 href="#findusedtypes">find used types</a> pass.
923 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]924</div>
925
926<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]927<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]928 <a name="die">-die: Dead Instruction Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]929</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]930<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]931 <p>
932 Dead instruction elimination performs a single pass over the function,
933 removing instructions that are obviously dead.
934 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]935</div>
936
937<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]938<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]939 <a name="dse">-dse: Dead Store Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]940</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]941<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]942 <p>
943 A trivial dead store elimination that only considers basic-block local
944 redundant stores.
945 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]946</div>
947
948<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]949<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]950 <a name="functionattrs">-functionattrs: Deduce function attributes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]951</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]952<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]953 <p>A simple interprocedural pass which walks the call-graph, looking for
954 functions which do not access or only read non-local memory, and marking them
955 readnone/readonly. In addition, it marks function arguments (of pointer type)
956 'nocapture' if a call to the function does not create any copies of the pointer
957 value that outlive the call. This more or less means that the pointer is only
958 dereferenced, and not returned from the function or stored in a global.
959 This pass is implemented as a bottom-up traversal of the call-graph.
960 </p>
961</div>
962
963<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]964<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]965 <a name="globaldce">-globaldce: Dead Global Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]966</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]967<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]968 <p>
969 This transform is designed to eliminate unreachable internal globals from the
970 program. It uses an aggressive algorithm, searching out globals that are
971 known to be alive. After it finds all of the globals which are needed, it
972 deletes whatever is left over. This allows it to delete recursive chunks of
973 the program which are unreachable.
974 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]975</div>
976
977<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]978<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]979 <a name="globalopt">-globalopt: Global Variable Optimizer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]980</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]981<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]982 <p>
983 This pass transforms simple global variables that never have their address
984 taken. If obviously true, it marks read/write globals as constant, deletes
985 variables only stored to, etc.
986 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]987</div>
988
989<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]990<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]991 <a name="gvn">-gvn: Global Value Numbering</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]992</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]993<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]994 <p>
Chris Lattner60f03402009-10-10 18:40:48 +0000[diff] [blame]995 This pass performs global value numbering to eliminate fully and partially
996 redundant instructions. It also performs redundant load elimination.
Matthijs Kooijman845f5242008-06-05 07:55:49 +0000[diff] [blame]997 </p>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]998</div>
999
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1000<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1001<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1002 <a name="indvars">-indvars: Canonicalize Induction Variables</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1003</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1004<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1005 <p>
1006 This transformation analyzes and transforms the induction variables (and
1007 computations derived from them) into simpler forms suitable for subsequent
1008 analysis and transformation.
1009 </p>
1010
1011 <p>
1012 This transformation makes the following changes to each loop with an
1013 identifiable induction variable:
1014 </p>
1015
1016 <ol>
1017 <li>All loops are transformed to have a <em>single</em> canonical
1018 induction variable which starts at zero and steps by one.</li>
1019 <li>The canonical induction variable is guaranteed to be the first PHI node
1020 in the loop header block.</li>
1021 <li>Any pointer arithmetic recurrences are raised to use array
1022 subscripts.</li>
1023 </ol>
1024
1025 <p>
1026 If the trip count of a loop is computable, this pass also makes the following
1027 changes:
1028 </p>
1029
1030 <ol>
1031 <li>The exit condition for the loop is canonicalized to compare the
1032 induction value against the exit value. This turns loops like:
1033 <blockquote><pre>for (i = 7; i*i < 1000; ++i)</pre></blockquote>
1034 into
1035 <blockquote><pre>for (i = 0; i != 25; ++i)</pre></blockquote></li>
1036 <li>Any use outside of the loop of an expression derived from the indvar
1037 is changed to compute the derived value outside of the loop, eliminating
1038 the dependence on the exit value of the induction variable. If the only
1039 purpose of the loop is to compute the exit value of some derived
1040 expression, this transformation will make the loop dead.</li>
Gordon Henriksene626bbe2007-11-04 16:17:00 +0000[diff] [blame]1041 </ol>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1042
1043 <p>
1044 This transformation should be followed by strength reduction after all of the
1045 desired loop transformations have been performed. Additionally, on targets
1046 where it is profitable, the loop could be transformed to count down to zero
1047 (the "do loop" optimization).
1048 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1049</div>
1050
1051<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1052<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1053 <a name="inline">-inline: Function Integration/Inlining</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1054</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1055<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1056 <p>
1057 Bottom-up inlining of functions into callees.
1058 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1059</div>
1060
1061<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1062<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1063 <a name="insert-edge-profiling">-insert-edge-profiling: Insert instrumentation for edge profiling</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1064</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1065<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1066 <p>
1067 This pass instruments the specified program with counters for edge profiling.
1068 Edge profiling can give a reasonable approximation of the hot paths through a
1069 program, and is used for a wide variety of program transformations.
1070 </p>
1071
1072 <p>
1073 Note that this implementation is very naïve. It inserts a counter for
1074 <em>every</em> edge in the program, instead of using control flow information
1075 to prune the number of counters inserted.
1076 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1077</div>
1078
1079<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1080<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1081 <a name="insert-optimal-edge-profiling">-insert-optimal-edge-profiling: Insert optimal instrumentation for edge profiling</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1082</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1083<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1084 <p>This pass instruments the specified program with counters for edge profiling.
1085 Edge profiling can give a reasonable approximation of the hot paths through a
1086 program, and is used for a wide variety of program transformations.
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1087 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1088</div>
1089
1090<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1091<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1092 <a name="instcombine">-instcombine: Combine redundant instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1093</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1094<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1095 <p>
1096 Combine instructions to form fewer, simple
1097 instructions. This pass does not modify the CFG This pass is where algebraic
1098 simplification happens.
1099 </p>
1100
1101 <p>
1102 This pass combines things like:
1103 </p>
1104
1105<blockquote><pre
1106>%Y = add i32 %X, 1
1107%Z = add i32 %Y, 1</pre></blockquote>
1108
1109 <p>
1110 into:
1111 </p>
1112
1113<blockquote><pre
1114>%Z = add i32 %X, 2</pre></blockquote>
1115
1116 <p>
1117 This is a simple worklist driven algorithm.
1118 </p>
1119
1120 <p>
1121 This pass guarantees that the following canonicalizations are performed on
1122 the program:
1123 </p>
1124
1125 <ul>
1126 <li>If a binary operator has a constant operand, it is moved to the right-
1127 hand side.</li>
1128 <li>Bitwise operators with constant operands are always grouped so that
1129 shifts are performed first, then <code>or</code>s, then
1130 <code>and</code>s, then <code>xor</code>s.</li>
1131 <li>Compare instructions are converted from <code>&lt;</code>,
1132 <code>&gt;</code>, <code>≤</code>, or <code>≥</code> to
1133 <code>=</code> or <code>≠</code> if possible.</li>
1134 <li>All <code>cmp</code> instructions on boolean values are replaced with
1135 logical operations.</li>
1136 <li><code>add <var>X</var>, <var>X</var></code> is represented as
1137 <code>mul <var>X</var>, 2</code> ⇒ <code>shl <var>X</var>, 1</code></li>
1138 <li>Multiplies with a constant power-of-two argument are transformed into
1139 shifts.</li>
1140 <li>… etc.</li>
1141 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1142</div>
1143
1144<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1145<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1146 <a name="internalize">-internalize: Internalize Global Symbols</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1147</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1148<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1149 <p>
1150 This pass loops over all of the functions in the input module, looking for a
1151 main function. If a main function is found, all other functions and all
1152 global variables with initializers are marked as internal.
1153 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1154</div>
1155
1156<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1157<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1158 <a name="ipconstprop">-ipconstprop: Interprocedural constant propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1159</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1160<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1161 <p>
1162 This pass implements an <em>extremely</em> simple interprocedural constant
1163 propagation pass. It could certainly be improved in many different ways,
1164 like using a worklist. This pass makes arguments dead, but does not remove
1165 them. The existing dead argument elimination pass should be run after this
1166 to clean up the mess.
1167 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1168</div>
1169
1170<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1171<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1172 <a name="ipsccp">-ipsccp: Interprocedural Sparse Conditional Constant Propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1173</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1174<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1175 <p>
1176 An interprocedural variant of <a href="#sccp">Sparse Conditional Constant
1177 Propagation</a>.
1178 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1179</div>
1180
1181<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1182<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1183 <a name="jump-threading">-jump-threading: Jump Threading</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1184</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1185<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1186 <p>
1187 Jump threading tries to find distinct threads of control flow running through
1188 a basic block. This pass looks at blocks that have multiple predecessors and
1189 multiple successors. If one or more of the predecessors of the block can be
1190 proven to always cause a jump to one of the successors, we forward the edge
1191 from the predecessor to the successor by duplicating the contents of this
1192 block.
1193 </p>
1194 <p>
1195 An example of when this can occur is code like this:
1196 </p>
1197
1198 <pre
1199>if () { ...
1200 X = 4;
1201}
1202if (X &lt; 3) {</pre>
1203
1204 <p>
1205 In this case, the unconditional branch at the end of the first if can be
1206 revectored to the false side of the second if.
1207 </p>
1208</div>
1209
1210<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1211<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1212 <a name="lcssa">-lcssa: Loop-Closed SSA Form Pass</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1213</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1214<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1215 <p>
1216 This pass transforms loops by placing phi nodes at the end of the loops for
1217 all values that are live across the loop boundary. For example, it turns
1218 the left into the right code:
1219 </p>
1220
1221 <pre
1222>for (...) for (...)
1223 if (c) if (c)
1224 X1 = ... X1 = ...
1225 else else
1226 X2 = ... X2 = ...
1227 X3 = phi(X1, X2) X3 = phi(X1, X2)
1228... = X3 + 4 X4 = phi(X3)
1229 ... = X4 + 4</pre>
1230
1231 <p>
1232 This is still valid LLVM; the extra phi nodes are purely redundant, and will
1233 be trivially eliminated by <code>InstCombine</code>. The major benefit of
1234 this transformation is that it makes many other loop optimizations, such as
1235 LoopUnswitching, simpler.
1236 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1237</div>
1238
1239<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1240<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1241 <a name="licm">-licm: Loop Invariant Code Motion</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1242</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1243<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1244 <p>
1245 This pass performs loop invariant code motion, attempting to remove as much
1246 code from the body of a loop as possible. It does this by either hoisting
1247 code into the preheader block, or by sinking code to the exit blocks if it is
1248 safe. This pass also promotes must-aliased memory locations in the loop to
1249 live in registers, thus hoisting and sinking "invariant" loads and stores.
1250 </p>
1251
1252 <p>
1253 This pass uses alias analysis for two purposes:
1254 </p>
1255
1256 <ul>
1257 <li>Moving loop invariant loads and calls out of loops. If we can determine
1258 that a load or call inside of a loop never aliases anything stored to,
1259 we can hoist it or sink it like any other instruction.</li>
1260 <li>Scalar Promotion of Memory - If there is a store instruction inside of
1261 the loop, we try to move the store to happen AFTER the loop instead of
1262 inside of the loop. This can only happen if a few conditions are true:
1263 <ul>
1264 <li>The pointer stored through is loop invariant.</li>
1265 <li>There are no stores or loads in the loop which <em>may</em> alias
1266 the pointer. There are no calls in the loop which mod/ref the
1267 pointer.</li>
1268 </ul>
1269 If these conditions are true, we can promote the loads and stores in the
1270 loop of the pointer to use a temporary alloca'd variable. We then use
1271 the mem2reg functionality to construct the appropriate SSA form for the
1272 variable.</li>
1273 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1274</div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1275
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1276<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1277<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1278 <a name="loop-deletion">-loop-deletion: Delete dead loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1279</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1280<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1281 <p>
1282 This file implements the Dead Loop Deletion Pass. This pass is responsible
1283 for eliminating loops with non-infinite computable trip counts that have no
1284 side effects or volatile instructions, and do not contribute to the
1285 computation of the function's return value.
1286 </p>
1287</div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1288
1289<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1290<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1291 <a name="loop-extract">-loop-extract: Extract loops into new functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1292</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1293<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1294 <p>
1295 A pass wrapper around the <code>ExtractLoop()</code> scalar transformation to
1296 extract each top-level loop into its own new function. If the loop is the
1297 <em>only</em> loop in a given function, it is not touched. This is a pass most
1298 useful for debugging via bugpoint.
1299 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1300</div>
1301
1302<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1303<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1304 <a name="loop-extract-single">-loop-extract-single: Extract at most one loop into a new function</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1305</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1306<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1307 <p>
1308 Similar to <a href="#loop-extract">Extract loops into new functions</a>,
1309 this pass extracts one natural loop from the program into a function if it
1310 can. This is used by bugpoint.
1311 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1312</div>
1313
1314<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1315<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1316 <a name="loop-reduce">-loop-reduce: Loop Strength Reduction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1317</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1318<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1319 <p>
1320 This pass performs a strength reduction on array references inside loops that
1321 have as one or more of their components the loop induction variable. This is
1322 accomplished by creating a new value to hold the initial value of the array
1323 access for the first iteration, and then creating a new GEP instruction in
1324 the loop to increment the value by the appropriate amount.
1325 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1326</div>
1327
1328<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1329<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1330 <a name="loop-rotate">-loop-rotate: Rotate Loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1331</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1332<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1333 <p>A simple loop rotation transformation.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1334</div>
1335
1336<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1337<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1338 <a name="loop-simplify">-loop-simplify: Canonicalize natural loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1339</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1340<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1341 <p>
1342 This pass performs several transformations to transform natural loops into a
1343 simpler form, which makes subsequent analyses and transformations simpler and
1344 more effective.
1345 </p>
1346
1347 <p>
1348 Loop pre-header insertion guarantees that there is a single, non-critical
1349 entry edge from outside of the loop to the loop header. This simplifies a
1350 number of analyses and transformations, such as LICM.
1351 </p>
1352
1353 <p>
1354 Loop exit-block insertion guarantees that all exit blocks from the loop
1355 (blocks which are outside of the loop that have predecessors inside of the
1356 loop) only have predecessors from inside of the loop (and are thus dominated
1357 by the loop header). This simplifies transformations such as store-sinking
1358 that are built into LICM.
1359 </p>
1360
1361 <p>
1362 This pass also guarantees that loops will have exactly one backedge.
1363 </p>
1364
1365 <p>
1366 Note that the simplifycfg pass will clean up blocks which are split out but
1367 end up being unnecessary, so usage of this pass should not pessimize
1368 generated code.
1369 </p>
1370
1371 <p>
1372 This pass obviously modifies the CFG, but updates loop information and
1373 dominator information.
1374 </p>
1375</div>
1376
1377<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1378<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1379 <a name="loop-unroll">-loop-unroll: Unroll loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1380</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1381<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1382 <p>
1383 This pass implements a simple loop unroller. It works best when loops have
1384 been canonicalized by the <a href="#indvars"><tt>-indvars</tt></a> pass,
1385 allowing it to determine the trip counts of loops easily.
1386 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1387</div>
1388
1389<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1390<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1391 <a name="loop-unswitch">-loop-unswitch: Unswitch loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1392</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1393<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1394 <p>
1395 This pass transforms loops that contain branches on loop-invariant conditions
1396 to have multiple loops. For example, it turns the left into the right code:
1397 </p>
1398
1399 <pre
1400>for (...) if (lic)
1401 A for (...)
1402 if (lic) A; B; C
1403 B else
1404 C for (...)
1405 A; C</pre>
1406
1407 <p>
1408 This can increase the size of the code exponentially (doubling it every time
1409 a loop is unswitched) so we only unswitch if the resultant code will be
1410 smaller than a threshold.
1411 </p>
1412
1413 <p>
1414 This pass expects LICM to be run before it to hoist invariant conditions out
1415 of the loop, to make the unswitching opportunity obvious.
1416 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1417</div>
1418
1419<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1420<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]1421 <a name="loweratomic">-loweratomic: Lower atomic intrinsics to non-atomic form</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1422</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1423<div>
Peter Collingbourne3bababf2010-08-03 16:19:16 +0000[diff] [blame]1424 <p>
1425 This pass lowers atomic intrinsics to non-atomic form for use in a known
1426 non-preemptible environment.
1427 </p>
1428
1429 <p>
1430 The pass does not verify that the environment is non-preemptible (in
1431 general this would require knowledge of the entire call graph of the
1432 program including any libraries which may not be available in bitcode form);
1433 it simply lowers every atomic intrinsic.
1434 </p>
1435</div>
1436
1437<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1438<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1439 <a name="lowerinvoke">-lowerinvoke: Lower invoke and unwind, for unwindless code generators</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1440</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1441<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1442 <p>
1443 This transformation is designed for use by code generators which do not yet
1444 support stack unwinding. This pass supports two models of exception handling
1445 lowering, the 'cheap' support and the 'expensive' support.
1446 </p>
1447
1448 <p>
1449 'Cheap' exception handling support gives the program the ability to execute
1450 any program which does not "throw an exception", by turning 'invoke'
1451 instructions into calls and by turning 'unwind' instructions into calls to
1452 abort(). If the program does dynamically use the unwind instruction, the
1453 program will print a message then abort.
1454 </p>
1455
1456 <p>
1457 'Expensive' exception handling support gives the full exception handling
1458 support to the program at the cost of making the 'invoke' instruction
1459 really expensive. It basically inserts setjmp/longjmp calls to emulate the
1460 exception handling as necessary.
1461 </p>
1462
1463 <p>
1464 Because the 'expensive' support slows down programs a lot, and EH is only
1465 used for a subset of the programs, it must be specifically enabled by the
1466 <tt>-enable-correct-eh-support</tt> option.
1467 </p>
1468
1469 <p>
1470 Note that after this pass runs the CFG is not entirely accurate (exceptional
1471 control flow edges are not correct anymore) so only very simple things should
1472 be done after the lowerinvoke pass has run (like generation of native code).
1473 This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't
1474 support the invoke instruction yet" lowering pass.
1475 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1476</div>
1477
1478<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1479<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1480 <a name="lowerswitch">-lowerswitch: Lower SwitchInst's to branches</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1481</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1482<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1483 <p>
1484 Rewrites <tt>switch</tt> instructions with a sequence of branches, which
1485 allows targets to get away with not implementing the switch instruction until
1486 it is convenient.
1487 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1488</div>
1489
1490<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1491<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1492 <a name="mem2reg">-mem2reg: Promote Memory to Register</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1493</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1494<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1495 <p>
1496 This file promotes memory references to be register references. It promotes
1497 <tt>alloca</tt> instructions which only have <tt>load</tt>s and
1498 <tt>store</tt>s as uses. An <tt>alloca</tt> is transformed by using dominator
1499 frontiers to place <tt>phi</tt> nodes, then traversing the function in
1500 depth-first order to rewrite <tt>load</tt>s and <tt>store</tt>s as
1501 appropriate. This is just the standard SSA construction algorithm to construct
1502 "pruned" SSA form.
1503 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1504</div>
1505
1506<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1507<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1508 <a name="memcpyopt">-memcpyopt: MemCpy Optimization</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1509</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1510<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1511 <p>
1512 This pass performs various transformations related to eliminating memcpy
1513 calls, or transforming sets of stores into memset's.
1514 </p>
1515</div>
1516
1517<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1518<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1519 <a name="mergefunc">-mergefunc: Merge Functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1520</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1521<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1522 <p>This pass looks for equivalent functions that are mergable and folds them.
1523
1524 A hash is computed from the function, based on its type and number of
1525 basic blocks.
1526
1527 Once all hashes are computed, we perform an expensive equality comparison
1528 on each function pair. This takes n^2/2 comparisons per bucket, so it's
1529 important that the hash function be high quality. The equality comparison
1530 iterates through each instruction in each basic block.
1531
1532 When a match is found the functions are folded. If both functions are
1533 overridable, we move the functionality into a new internal function and
1534 leave two overridable thunks to it.
1535 </p>
1536</div>
1537
1538<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1539<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1540 <a name="mergereturn">-mergereturn: Unify function exit nodes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1541</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1542<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1543 <p>
1544 Ensure that functions have at most one <tt>ret</tt> instruction in them.
1545 Additionally, it keeps track of which node is the new exit node of the CFG.
1546 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1547</div>
1548
1549<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1550<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1551 <a name="partial-inliner">-partial-inliner: Partial Inliner</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1552</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1553<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1554 <p>This pass performs partial inlining, typically by inlining an if
1555 statement that surrounds the body of the function.
1556 </p>
1557</div>
1558
1559<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1560<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1561 <a name="prune-eh">-prune-eh: Remove unused exception handling info</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1562</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1563<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1564 <p>
1565 This file implements a simple interprocedural pass which walks the call-graph,
1566 turning <tt>invoke</tt> instructions into <tt>call</tt> instructions if and
1567 only if the callee cannot throw an exception. It implements this as a
1568 bottom-up traversal of the call-graph.
1569 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1570</div>
1571
1572<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1573<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1574 <a name="reassociate">-reassociate: Reassociate expressions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1575</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1576<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1577 <p>
1578 This pass reassociates commutative expressions in an order that is designed
1579 to promote better constant propagation, GCSE, LICM, PRE, etc.
1580 </p>
1581
1582 <p>
1583 For example: 4 + (<var>x</var> + 5) ⇒ <var>x</var> + (4 + 5)
1584 </p>
1585
1586 <p>
1587 In the implementation of this algorithm, constants are assigned rank = 0,
1588 function arguments are rank = 1, and other values are assigned ranks
1589 corresponding to the reverse post order traversal of current function
1590 (starting at 2), which effectively gives values in deep loops higher rank
1591 than values not in loops.
1592 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1593</div>
1594
1595<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1596<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1597 <a name="reg2mem">-reg2mem: Demote all values to stack slots</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1598</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1599<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1600 <p>
1601 This file demotes all registers to memory references. It is intented to be
1602 the inverse of <a href="#mem2reg"><tt>-mem2reg</tt></a>. By converting to
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]1603 <tt>load</tt> instructions, the only values live across basic blocks are
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1604 <tt>alloca</tt> instructions and <tt>load</tt> instructions before
1605 <tt>phi</tt> nodes. It is intended that this should make CFG hacking much
1606 easier. To make later hacking easier, the entry block is split into two, such
1607 that all introduced <tt>alloca</tt> instructions (and nothing else) are in the
1608 entry block.
1609 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1610</div>
1611
1612<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1613<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1614 <a name="scalarrepl">-scalarrepl: Scalar Replacement of Aggregates (DT)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1615</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1616<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1617 <p>
1618 The well-known scalar replacement of aggregates transformation. This
1619 transform breaks up <tt>alloca</tt> instructions of aggregate type (structure
1620 or array) into individual <tt>alloca</tt> instructions for each member if
1621 possible. Then, if possible, it transforms the individual <tt>alloca</tt>
1622 instructions into nice clean scalar SSA form.
1623 </p>
1624
1625 <p>
1626 This combines a simple scalar replacement of aggregates algorithm with the <a
1627 href="#mem2reg"><tt>mem2reg</tt></a> algorithm because often interact,
1628 especially for C++ programs. As such, iterating between <tt>scalarrepl</tt>,
1629 then <a href="#mem2reg"><tt>mem2reg</tt></a> until we run out of things to
1630 promote works well.
1631 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1632</div>
1633
1634<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1635<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1636 <a name="sccp">-sccp: Sparse Conditional Constant Propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1637</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1638<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1639 <p>
1640 Sparse conditional constant propagation and merging, which can be summarized
1641 as:
1642 </p>
1643
1644 <ol>
1645 <li>Assumes values are constant unless proven otherwise</li>
1646 <li>Assumes BasicBlocks are dead unless proven otherwise</li>
1647 <li>Proves values to be constant, and replaces them with constants</li>
1648 <li>Proves conditional branches to be unconditional</li>
1649 </ol>
1650
1651 <p>
1652 Note that this pass has a habit of making definitions be dead. It is a good
1653 idea to to run a DCE pass sometime after running this pass.
1654 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1655</div>
1656
1657<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1658<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1659 <a name="simplify-libcalls">-simplify-libcalls: Simplify well-known library calls</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1660</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1661<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1662 <p>
1663 Applies a variety of small optimizations for calls to specific well-known
1664 function calls (e.g. runtime library functions). For example, a call
1665 <tt>exit(3)</tt> that occurs within the <tt>main()</tt> function can be
1666 transformed into simply <tt>return 3</tt>.
1667 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1668</div>
1669
1670<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1671<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1672 <a name="simplifycfg">-simplifycfg: Simplify the CFG</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1673</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1674<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1675 <p>
1676 Performs dead code elimination and basic block merging. Specifically:
1677 </p>
1678
1679 <ol>
1680 <li>Removes basic blocks with no predecessors.</li>
1681 <li>Merges a basic block into its predecessor if there is only one and the
1682 predecessor only has one successor.</li>
1683 <li>Eliminates PHI nodes for basic blocks with a single predecessor.</li>
1684 <li>Eliminates a basic block that only contains an unconditional
1685 branch.</li>
1686 </ol>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1687</div>
1688
1689<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1690<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1691 <a name="sink">-sink: Code sinking</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1692</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1693<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1694 <p>This pass moves instructions into successor blocks, when possible, so that
1695 they aren't executed on paths where their results aren't needed.
1696 </p>
1697</div>
1698
1699<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1700<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1701 <a name="sretpromotion">-sretpromotion: Promote sret arguments to multiple ret values</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1702</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1703<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1704 <p>
1705 This pass finds functions that return a struct (using a pointer to the struct
1706 as the first argument of the function, marked with the '<tt>sret</tt>' attribute) and
1707 replaces them with a new function that simply returns each of the elements of
1708 that struct (using multiple return values).
1709 </p>
1710
1711 <p>
1712 This pass works under a number of conditions:
1713 </p>
1714
1715 <ul>
1716 <li>The returned struct must not contain other structs</li>
1717 <li>The returned struct must only be used to load values from</li>
1718 <li>The placeholder struct passed in is the result of an <tt>alloca</tt></li>
1719 </ul>
1720</div>
1721
1722<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1723<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1724 <a name="strip">-strip: Strip all symbols from a module</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1725</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1726<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1727 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1728 performs code stripping. this transformation can delete:
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1729 </p>
1730
1731 <ol>
1732 <li>names for virtual registers</li>
1733 <li>symbols for internal globals and functions</li>
1734 <li>debug information</li>
1735 </ol>
1736
1737 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1738 note that this transformation makes code much less readable, so it should
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1739 only be used in situations where the <tt>strip</tt> utility would be used,
1740 such as reducing code size or making it harder to reverse engineer code.
1741 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1742</div>
1743
1744<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1745<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1746 <a name="strip-dead-debug-info">-strip-dead-debug-info: Strip debug info for unused symbols</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1747</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1748<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1749 <p>
1750 performs code stripping. this transformation can delete:
1751 </p>
1752
1753 <ol>
1754 <li>names for virtual registers</li>
1755 <li>symbols for internal globals and functions</li>
1756 <li>debug information</li>
1757 </ol>
1758
1759 <p>
1760 note that this transformation makes code much less readable, so it should
1761 only be used in situations where the <tt>strip</tt> utility would be used,
1762 such as reducing code size or making it harder to reverse engineer code.
1763 </p>
1764</div>
1765
1766<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1767<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1768 <a name="strip-dead-prototypes">-strip-dead-prototypes: Strip Unused Function Prototypes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1769</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1770<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1771 <p>
1772 This pass loops over all of the functions in the input module, looking for
1773 dead declarations and removes them. Dead declarations are declarations of
1774 functions for which no implementation is available (i.e., declarations for
1775 unused library functions).
1776 </p>
1777</div>
1778
1779<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1780<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1781 <a name="strip-debug-declare">-strip-debug-declare: Strip all llvm.dbg.declare intrinsics</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1782</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1783<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1784 <p>This pass implements code stripping. Specifically, it can delete:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1785 <ul>
1786 <li>names for virtual registers</li>
1787 <li>symbols for internal globals and functions</li>
1788 <li>debug information</li>
1789 </ul>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1790 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1791 Note that this transformation makes code much less readable, so it should
1792 only be used in situations where the 'strip' utility would be used, such as
1793 reducing code size or making it harder to reverse engineer code.
1794 </p>
1795</div>
1796
1797<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1798<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1799 <a name="strip-nondebug">-strip-nondebug: Strip all symbols, except dbg symbols, from a module</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1800</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1801<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1802 <p>This pass implements code stripping. Specifically, it can delete:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1803 <ul>
1804 <li>names for virtual registers</li>
1805 <li>symbols for internal globals and functions</li>
1806 <li>debug information</li>
1807 </ul>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1808 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1809 Note that this transformation makes code much less readable, so it should
1810 only be used in situations where the 'strip' utility would be used, such as
1811 reducing code size or making it harder to reverse engineer code.
1812 </p>
1813</div>
1814
1815<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1816<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1817 <a name="tailcallelim">-tailcallelim: Tail Call Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1818</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1819<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1820 <p>
1821 This file transforms calls of the current function (self recursion) followed
1822 by a return instruction with a branch to the entry of the function, creating
1823 a loop. This pass also implements the following extensions to the basic
1824 algorithm:
1825 </p>
1826
1827 <ul>
1828 <li>Trivial instructions between the call and return do not prevent the
1829 transformation from taking place, though currently the analysis cannot
1830 support moving any really useful instructions (only dead ones).
1831 <li>This pass transforms functions that are prevented from being tail
1832 recursive by an associative expression to use an accumulator variable,
1833 thus compiling the typical naive factorial or <tt>fib</tt> implementation
1834 into efficient code.
1835 <li>TRE is performed if the function returns void, if the return
1836 returns the result returned by the call, or if the function returns a
1837 run-time constant on all exits from the function. It is possible, though
1838 unlikely, that the return returns something else (like constant 0), and
1839 can still be TRE'd. It can be TRE'd if <em>all other</em> return
1840 instructions in the function return the exact same value.
1841 <li>If it can prove that callees do not access theier caller stack frame,
1842 they are marked as eligible for tail call elimination (by the code
1843 generator).
1844 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1845</div>
1846
1847<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1848<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1849 <a name="tailduplicate">-tailduplicate: Tail Duplication</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1850</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1851<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1852 <p>
1853 This pass performs a limited form of tail duplication, intended to simplify
1854 CFGs by removing some unconditional branches. This pass is necessary to
1855 straighten out loops created by the C front-end, but also is capable of
1856 making other code nicer. After this pass is run, the CFG simplify pass
1857 should be run to clean up the mess.
1858 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1859</div>
1860
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1861</div>
1862
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1863<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1864<h2><a name="utilities">Utility Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1865<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1866 <p>This section describes the LLVM Utility Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1867
1868<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1869<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1870 <a name="deadarghaX0r">-deadarghaX0r: Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1871</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1872<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1873 <p>
1874 Same as dead argument elimination, but deletes arguments to functions which
1875 are external. This is only for use by <a
1876 href="Bugpoint.html">bugpoint</a>.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1877</div>
1878
1879<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1880<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1881 <a name="extract-blocks">-extract-blocks: Extract Basic Blocks From Module (for bugpoint use)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1882</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1883<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1884 <p>
1885 This pass is used by bugpoint to extract all blocks from the module into their
1886 own functions.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1887</div>
1888
1889<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1890<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1891 <a name="instnamer">-instnamer: Assign names to anonymous instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1892</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1893<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1894 <p>This is a little utility pass that gives instructions names, this is mostly
1895 useful when diffing the effect of an optimization because deleting an
1896 unnamed instruction can change all other instruction numbering, making the
1897 diff very noisy.
1898 </p>
1899</div>
1900
1901<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1902<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1903 <a name="preverify">-preverify: Preliminary module verification</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1904</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1905<div>
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]1906 <p>
1907 Ensures that the module is in the form required by the <a
1908 href="#verifier">Module Verifier</a> pass.
1909 </p>
1910
1911 <p>
1912 Running the verifier runs this pass automatically, so there should be no need
1913 to use it directly.
1914 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1915</div>
1916
1917<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1918<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1919 <a name="verify">-verify: Module Verifier</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1920</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1921<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1922 <p>
1923 Verifies an LLVM IR code. This is useful to run after an optimization which is
1924 undergoing testing. Note that <tt>llvm-as</tt> verifies its input before
1925 emitting bitcode, and also that malformed bitcode is likely to make LLVM
1926 crash. All language front-ends are therefore encouraged to verify their output
1927 before performing optimizing transformations.
1928 </p>
1929
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]1930 <ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1931 <li>Both of a binary operator's parameters are of the same type.</li>
1932 <li>Verify that the indices of mem access instructions match other
1933 operands.</li>
1934 <li>Verify that arithmetic and other things are only performed on
1935 first-class types. Verify that shifts and logicals only happen on
1936 integrals f.e.</li>
1937 <li>All of the constants in a switch statement are of the correct type.</li>
1938 <li>The code is in valid SSA form.</li>
Chris Lattner46b3abc2009-10-28 04:47:06 +0000[diff] [blame]1939 <li>It is illegal to put a label into any other type (like a structure) or
1940 to return one.</li>
Nick Lewycky0c78ac12008-03-28 06:46:51 +0000[diff] [blame]1941 <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]1942 invalid.</li>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1943 <li>PHI nodes must have an entry for each predecessor, with no extras.</li>
1944 <li>PHI nodes must be the first thing in a basic block, all grouped
1945 together.</li>
1946 <li>PHI nodes must have at least one entry.</li>
1947 <li>All basic blocks should only end with terminator insts, not contain
1948 them.</li>
1949 <li>The entry node to a function must not have predecessors.</li>
1950 <li>All Instructions must be embedded into a basic block.</li>
1951 <li>Functions cannot take a void-typed parameter.</li>
1952 <li>Verify that a function's argument list agrees with its declared
1953 type.</li>
1954 <li>It is illegal to specify a name for a void value.</li>
1955 <li>It is illegal to have a internal global value with no initializer.</li>
1956 <li>It is illegal to have a ret instruction that returns a value that does
1957 not agree with the function return value type.</li>
1958 <li>Function call argument types match the function prototype.</li>
1959 <li>All other things that are tested by asserts spread about the code.</li>
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]1960 </ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1961
1962 <p>
1963 Note that this does not provide full security verification (like Java), but
1964 instead just tries to ensure that code is well-formed.
1965 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1966</div>
1967
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1968<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1969<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1970 <a name="view-cfg">-view-cfg: View CFG of function</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1971</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1972<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1973 <p>
1974 Displays the control flow graph using the GraphViz tool.
1975 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1976</div>
1977
1978<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1979<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1980 <a name="view-cfg-only">-view-cfg-only: View CFG of function (with no function bodies)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1981</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1982<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1983 <p>
1984 Displays the control flow graph using the GraphViz tool, but omitting function
1985 bodies.
1986 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1987</div>
1988
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]1989<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1990<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1991 <a name="view-dom">-view-dom: View dominance tree of function</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1992</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1993<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]1994 <p>
1995 Displays the dominator tree using the GraphViz tool.
1996 </p>
1997</div>
1998
1999<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2000<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]2001 <a name="view-dom-only">-view-dom-only: View dominance tree of function (with no function bodies)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2002</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2003<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2004 <p>
2005 Displays the dominator tree using the GraphViz tool, but omitting function
2006 bodies.
2007 </p>
2008</div>
2009
2010<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2011<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]2012 <a name="view-postdom">-view-postdom: View postdominance tree of function</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2013</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2014<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2015 <p>
2016 Displays the post dominator tree using the GraphViz tool.
2017 </p>
2018</div>
2019
2020<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2021<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]2022 <a name="view-postdom-only">-view-postdom-only: View postdominance tree of function (with no function bodies)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2023</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2024<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2025 <p>
2026 Displays the post dominator tree using the GraphViz tool, but omitting
2027 function bodies.
2028 </p>
2029</div>
2030
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2031</div>
2032
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2033<!-- *********************************************************************** -->
2034
2035<hr>
2036<address>
2037 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]2038 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2039 <a href="http://validator.w3.org/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]2040 src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2041
2042 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
NAKAMURA Takumib9a33632011-04-09 02:13:37 +0000[diff] [blame]2043 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2044 Last modified: $Date$
2045</address>
2046
2047</body>
2048</html>