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gerrit-public.fairphone.software / fp2-dev / platform / external / llvm / a7645a3c66668da5e2bc772a8e5ab03dc301610c / . / 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>
Daniel Dunbaradea4972012-04-19 20:20:34 +0000[diff] [blame]6 <link rel="stylesheet" href="_static/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>
Benjamin Kramerb8b3f602012-10-26 20:25:01 +0000[diff] [blame]80<tr><td><a href="#da">-da</a></td><td>Dependence Analysis</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]81<tr><td><a href="#debug-aa">-debug-aa</a></td><td>AA use debugger</td></tr>
82<tr><td><a href="#domfrontier">-domfrontier</a></td><td>Dominance Frontier Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]83<tr><td><a href="#domtree">-domtree</a></td><td>Dominator Tree Construction</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]84<tr><td><a href="#dot-callgraph">-dot-callgraph</a></td><td>Print Call Graph to 'dot' file</td></tr>
85<tr><td><a href="#dot-cfg">-dot-cfg</a></td><td>Print CFG of function to 'dot' file</td></tr>
86<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]87<tr><td><a href="#dot-dom">-dot-dom</a></td><td>Print dominance tree of function to 'dot' file</td></tr>
88<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>
89<tr><td><a href="#dot-postdom">-dot-postdom</a></td><td>Print postdominance tree of function to 'dot' file</td></tr>
90<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]91<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]92<tr><td><a href="#instcount">-instcount</a></td><td>Counts the various types of Instructions</td></tr>
93<tr><td><a href="#intervals">-intervals</a></td><td>Interval Partition Construction</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]94<tr><td><a href="#iv-users">-iv-users</a></td><td>Induction Variable Users</td></tr>
95<tr><td><a href="#lazy-value-info">-lazy-value-info</a></td><td>Lazy Value Information Analysis</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]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>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]103<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]104<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]105<tr><td><a href="#print-callgraph">-print-callgraph</a></td><td>Print a call graph</td></tr>
106<tr><td><a href="#print-callgraph-sccs">-print-callgraph-sccs</a></td><td>Print SCCs of the Call Graph</td></tr>
107<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]108<tr><td><a href="#print-dbginfo">-print-dbginfo</a></td><td>Print debug info in human readable form</td></tr>
109<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]110<tr><td><a href="#print-externalfnconstants">-print-externalfnconstants</a></td><td>Print external fn callsites passed constants</td></tr>
111<tr><td><a href="#print-function">-print-function</a></td><td>Print function to stderr</td></tr>
112<tr><td><a href="#print-module">-print-module</a></td><td>Print module to stderr</td></tr>
113<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]114<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]115<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]116<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]117<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]118<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]119<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]120<tr><td><a href="#targetdata">-targetdata</a></td><td>Target Data Layout</td></tr>
121
122
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]123<tr><th colspan="2"><b>TRANSFORM PASSES</b></th></tr>
124<tr><th>Option</th><th>Name</th></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]125<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]126<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]127<tr><td><a href="#argpromotion">-argpromotion</a></td><td>Promote 'by reference' arguments to scalars</td></tr>
Hal Finkelde5e5ec2012-02-01 03:51:43 +0000[diff] [blame]128<tr><td><a href="#bb-vectorize">-bb-vectorize</a></td><td>Combine instructions to form vector instructions within basic blocks</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]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>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]178<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]179<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]180<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]181<tr><td><a href="#strip-debug-declare">-strip-debug-declare</a></td><td>Strip all llvm.dbg.declare intrinsics</td></tr>
182<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]183<tr><td><a href="#tailcallelim">-tailcallelim</a></td><td>Tail Call Elimination</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]184
185
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]186<tr><th colspan="2"><b>UTILITY PASSES</b></th></tr>
187<tr><th>Option</th><th>Name</th></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]188<tr><td><a href="#deadarghaX0r">-deadarghaX0r</a></td><td>Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</td></tr>
189<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]190<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]191<tr><td><a href="#preverify">-preverify</a></td><td>Preliminary module verification</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]192<tr><td><a href="#verify">-verify</a></td><td>Module Verifier</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]193<tr><td><a href="#view-cfg">-view-cfg</a></td><td>View CFG of function</td></tr>
194<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]195<tr><td><a href="#view-dom">-view-dom</a></td><td>View dominance tree of function</td></tr>
196<tr><td><a href="#view-dom-only">-view-dom-only</a></td><td>View dominance tree of function (with no function bodies)</td></tr>
197<tr><td><a href="#view-postdom">-view-postdom</a></td><td>View postdominance tree of function</td></tr>
198<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]199</table>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]200
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]201</div>
202
203<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]204<h2><a name="analyses">Analysis Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]205<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]206 <p>This section describes the LLVM Analysis Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]207
208<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]209<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]210 <a name="aa-eval">-aa-eval: Exhaustive Alias Analysis Precision Evaluator</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]211</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]212<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]213 <p>This is a simple N^2 alias analysis accuracy evaluator.
214 Basically, for each function in the program, it simply queries to see how the
215 alias analysis implementation answers alias queries between each pair of
216 pointers in the function.</p>
217
218 <p>This is inspired and adapted from code by: Naveen Neelakantam, Francesco
219 Spadini, and Wojciech Stryjewski.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]220</div>
221
222<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]223<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]224 <a name="basicaa">-basicaa: Basic Alias Analysis (stateless AA impl)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]225</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]226<div>
Eli Friedman146af5a2011-10-27 22:32:13 +0000[diff] [blame]227 <p>A basic alias analysis pass that implements identities (two different
228 globals cannot alias, etc), but does no stateful analysis.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]229</div>
230
231<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]232<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]233 <a name="basiccg">-basiccg: Basic CallGraph Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]234</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]235<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]236 <p>Yet to be written.</p>
237</div>
238
239<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]240<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]241 <a name="count-aa">-count-aa: Count Alias Analysis Query Responses</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]242</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]243<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]244 <p>
245 A pass which can be used to count how many alias queries
246 are being made and how the alias analysis implementation being used responds.
247 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]248</div>
249
250<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]251<h3>
Benjamin Kramerb8b3f602012-10-26 20:25:01 +0000[diff] [blame]252 <a name="da">-da: Dependence Analysis</a>
253</h3>
254<div>
255 <p>Dependence analysis framework, which is used to detect dependences in
256 memory accesses.</p>
257</div>
258
259<!-------------------------------------------------------------------------- -->
260<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]261 <a name="debug-aa">-debug-aa: AA use debugger</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]262</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]263<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]264 <p>
265 This simple pass checks alias analysis users to ensure that if they
266 create a new value, they do not query AA without informing it of the value.
267 It acts as a shim over any other AA pass you want.
268 </p>
269
270 <p>
271 Yes keeping track of every value in the program is expensive, but this is
272 a debugging pass.
273 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]274</div>
275
276<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]277<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]278 <a name="domfrontier">-domfrontier: Dominance Frontier Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]279</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]280<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]281 <p>
282 This pass is a simple dominator construction algorithm for finding forward
283 dominator frontiers.
284 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]285</div>
286
287<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]288<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]289 <a name="domtree">-domtree: Dominator Tree Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]290</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]291<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]292 <p>
293 This pass is a simple dominator construction algorithm for finding forward
294 dominators.
295 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]296</div>
297
298<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]299<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]300 <a name="dot-callgraph">-dot-callgraph: Print Call Graph to 'dot' file</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]301</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]302<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]303 <p>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]304 This pass, only available in <code>opt</code>, prints the call graph into a
305 <code>.dot</code> graph. This graph can then be processed with the "dot" tool
306 to convert it to postscript or some other suitable format.
307 </p>
308</div>
309
310<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]311<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]312 <a name="dot-cfg">-dot-cfg: Print CFG of function to 'dot' file</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]313</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]314<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]315 <p>
316 This pass, only available in <code>opt</code>, prints the control flow graph
317 into a <code>.dot</code> graph. This graph can then be processed with the
318 "dot" tool to convert it to postscript or some other suitable format.
319 </p>
320</div>
321
322<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]323<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]324 <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]325</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]326<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]327 <p>
328 This pass, only available in <code>opt</code>, prints the control flow graph
329 into a <code>.dot</code> graph, omitting the function bodies. This graph can
330 then be processed with the "dot" tool to convert it to postscript or some
331 other suitable format.
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]332 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]333</div>
334
335<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]336<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]337 <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]338</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]339<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]340 <p>
341 This pass, only available in <code>opt</code>, prints the dominator tree
342 into a <code>.dot</code> graph. This graph can then be processed with the
343 "dot" tool to convert it to postscript or some other suitable format.
344 </p>
345</div>
346
347<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]348<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]349 <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]350</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]351<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]352 <p>
353 This pass, only available in <code>opt</code>, prints the dominator tree
354 into a <code>.dot</code> graph, omitting the function bodies. This graph can
355 then be processed with the "dot" tool to convert it to postscript or some
356 other suitable format.
357 </p>
358</div>
359
360<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]361<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]362 <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]363</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]364<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]365 <p>
366 This pass, only available in <code>opt</code>, prints the post dominator tree
367 into a <code>.dot</code> graph. This graph can then be processed with the
368 "dot" tool to convert it to postscript or some other suitable format.
369 </p>
370</div>
371
372<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]373<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]374 <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]375</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]376<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]377 <p>
378 This pass, only available in <code>opt</code>, prints the post dominator tree
379 into a <code>.dot</code> graph, omitting the function bodies. This graph can
380 then be processed with the "dot" tool to convert it to postscript or some
381 other suitable format.
382 </p>
383</div>
384
385<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]386<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]387 <a name="globalsmodref-aa">-globalsmodref-aa: Simple mod/ref analysis for globals</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]388</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]389<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]390 <p>
391 This simple pass provides alias and mod/ref information for global values
392 that do not have their address taken, and keeps track of whether functions
393 read or write memory (are "pure"). For this simple (but very common) case,
394 we can provide pretty accurate and useful information.
395 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]396</div>
397
398<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]399<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]400 <a name="instcount">-instcount: Counts the various types of Instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]401</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]402<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]403 <p>
404 This pass collects the count of all instructions and reports them
405 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]406</div>
407
408<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]409<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]410 <a name="intervals">-intervals: Interval Partition Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]411</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]412<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]413 <p>
414 This analysis calculates and represents the interval partition of a function,
415 or a preexisting interval partition.
416 </p>
417
418 <p>
419 In this way, the interval partition may be used to reduce a flow graph down
420 to its degenerate single node interval partition (unless it is irreducible).
421 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]422</div>
423
424<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]425<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]426 <a name="iv-users">-iv-users: Induction Variable Users</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]427</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]428<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]429 <p>Bookkeeping for "interesting" users of expressions computed from
430 induction variables.</p>
431</div>
432
433<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]434<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]435 <a name="lazy-value-info">-lazy-value-info: Lazy Value Information Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]436</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]437<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]438 <p>Interface for lazy computation of value constraint information.</p>
439</div>
440
441<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]442<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]443 <a name="libcall-aa">-libcall-aa: LibCall Alias Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]444</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]445<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]446 <p>LibCall Alias Analysis.</p>
447</div>
448
449<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]450<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]451 <a name="lint">-lint: Statically lint-checks LLVM IR</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]452</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]453<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]454 <p>This pass statically checks for common and easily-identified constructs
455 which produce undefined or likely unintended behavior in LLVM IR.</p>
456
457 <p>It is not a guarantee of correctness, in two ways. First, it isn't
458 comprehensive. There are checks which could be done statically which are
459 not yet implemented. Some of these are indicated by TODO comments, but
460 those aren't comprehensive either. Second, many conditions cannot be
461 checked statically. This pass does no dynamic instrumentation, so it
462 can't check for all possible problems.</p>
463
464 <p>Another limitation is that it assumes all code will be executed. A store
465 through a null pointer in a basic block which is never reached is harmless,
466 but this pass will warn about it anyway.</p>
467
468 <p>Optimization passes may make conditions that this pass checks for more or
469 less obvious. If an optimization pass appears to be introducing a warning,
470 it may be that the optimization pass is merely exposing an existing
471 condition in the code.</p>
472
473 <p>This code may be run before instcombine. In many cases, instcombine checks
474 for the same kinds of things and turns instructions with undefined behavior
475 into unreachable (or equivalent). Because of this, this pass makes some
476 effort to look through bitcasts and so on.
477 </p>
478</div>
479
480<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]481<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]482 <a name="loops">-loops: Natural Loop Information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]483</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]484<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]485 <p>
486 This analysis is used to identify natural loops and determine the loop depth
487 of various nodes of the CFG. Note that the loops identified may actually be
488 several natural loops that share the same header node... not just a single
489 natural loop.
490 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]491</div>
492
493<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]494<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]495 <a name="memdep">-memdep: Memory Dependence Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]496</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]497<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]498 <p>
499 An analysis that determines, for a given memory operation, what preceding
500 memory operations it depends on. It builds on alias analysis information, and
501 tries to provide a lazy, caching interface to a common kind of alias
502 information query.
503 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]504</div>
505
506<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]507<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]508 <a name="module-debuginfo">-module-debuginfo: Decodes module-level debug info</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]509</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]510<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]511 <p>This pass decodes the debug info metadata in a module and prints in a
512 (sufficiently-prepared-) human-readable form.
513
514 For example, run this pass from opt along with the -analyze option, and
515 it'll print to standard output.
516 </p>
517</div>
518
519<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]520<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]521 <a name="no-aa">-no-aa: No Alias Analysis (always returns 'may' alias)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]522</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]523<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]524 <p>
Eli Friedman146af5a2011-10-27 22:32:13 +0000[diff] [blame]525 This is the default implementation of the Alias Analysis interface. It always
526 returns "I don't know" for alias queries. NoAA is unlike other alias analysis
527 implementations, in that it does not chain to a previous analysis. As such it
528 doesn't follow many of the rules that other alias analyses must.
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]529 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]530</div>
531
532<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]533<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]534 <a name="no-profile">-no-profile: No Profile Information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]535</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]536<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]537 <p>
538 The default "no profile" implementation of the abstract
539 <code>ProfileInfo</code> interface.
540 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]541</div>
542
543<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]544<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]545 <a name="postdomfrontier">-postdomfrontier: Post-Dominance Frontier Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]546</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]547<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]548 <p>
549 This pass is a simple post-dominator construction algorithm for finding
550 post-dominator frontiers.
551 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]552</div>
553
554<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]555<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]556 <a name="postdomtree">-postdomtree: Post-Dominator Tree Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]557</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]558<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]559 <p>
560 This pass is a simple post-dominator construction algorithm for finding
561 post-dominators.
562 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]563</div>
564
565<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]566<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]567 <a name="print-alias-sets">-print-alias-sets: Alias Set Printer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]568</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]569<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]570 <p>Yet to be written.</p>
571</div>
572
573<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]574<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]575 <a name="print-callgraph">-print-callgraph: Print a call graph</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]576</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]577<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]578 <p>
579 This pass, only available in <code>opt</code>, prints the call graph to
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]580 standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]581 </p>
582</div>
583
584<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]585<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]586 <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]587</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]588<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]589 <p>
590 This pass, only available in <code>opt</code>, prints the SCCs of the call
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]591 graph to standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]592 </p>
593</div>
594
595<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]596<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]597 <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]598</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]599<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]600 <p>
601 This pass, only available in <code>opt</code>, prints the SCCs of each
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]602 function CFG to standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]603 </p>
604</div>
605
606<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]607<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]608 <a name="print-dbginfo">-print-dbginfo: Print debug info in human readable form</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]609</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]610<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]611 <p>Pass that prints instructions, and associated debug info:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]612 <ul>
613
614 <li>source/line/col information</li>
615 <li>original variable name</li>
616 <li>original type name</li>
617 </ul>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]618</div>
619
620<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]621<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]622 <a name="print-dom-info">-print-dom-info: Dominator Info Printer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]623</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]624<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]625 <p>Dominator Info Printer.</p>
626</div>
627
628<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]629<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]630 <a name="print-externalfnconstants">-print-externalfnconstants: Print external fn callsites passed constants</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]631</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]632<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]633 <p>
634 This pass, only available in <code>opt</code>, prints out call sites to
635 external functions that are called with constant arguments. This can be
636 useful when looking for standard library functions we should constant fold
637 or handle in alias analyses.
638 </p>
639</div>
640
641<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]642<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]643 <a name="print-function">-print-function: Print function to stderr</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]644</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]645<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]646 <p>
647 The <code>PrintFunctionPass</code> class is designed to be pipelined with
648 other <code>FunctionPass</code>es, and prints out the functions of the module
649 as they are processed.
650 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]651</div>
652
653<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]654<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]655 <a name="print-module">-print-module: Print module to stderr</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]656</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]657<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]658 <p>
659 This pass simply prints out the entire module when it is executed.
660 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]661</div>
662
663<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]664<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]665 <a name="print-used-types">-print-used-types: Find Used Types</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]666</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]667<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]668 <p>
669 This pass is used to seek out all of the types in use by the program. Note
670 that this analysis explicitly does not include types only used by the symbol
671 table.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]672</div>
673
674<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]675<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]676 <a name="profile-estimator">-profile-estimator: Estimate profiling information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]677</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]678<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]679 <p>Profiling information that estimates the profiling information
680 in a very crude and unimaginative way.
681 </p>
682</div>
683
684<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]685<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]686 <a name="profile-loader">-profile-loader: Load profile information from llvmprof.out</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]687</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]688<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]689 <p>
690 A concrete implementation of profiling information that loads the information
691 from a profile dump file.
692 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]693</div>
694
695<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]696<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]697 <a name="profile-verifier">-profile-verifier: Verify profiling information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]698</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]699<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]700 <p>Pass that checks profiling information for plausibility.</p>
701</div>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]702<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]703 <a name="regions">-regions: Detect single entry single exit regions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]704</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]705<div>
Tobias Grosserf96b0062010-07-22 07:46:31 +0000[diff] [blame]706 <p>
707 The <code>RegionInfo</code> pass detects single entry single exit regions in a
708 function, where a region is defined as any subgraph that is connected to the
709 remaining graph at only two spots. Furthermore, an hierarchical region tree is
710 built.
711 </p>
712</div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]713
714<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]715<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]716 <a name="scalar-evolution">-scalar-evolution: Scalar Evolution Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]717</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]718<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]719 <p>
720 The <code>ScalarEvolution</code> analysis can be used to analyze and
721 catagorize scalar expressions in loops. It specializes in recognizing general
722 induction variables, representing them with the abstract and opaque
723 <code>SCEV</code> class. Given this analysis, trip counts of loops and other
724 important properties can be obtained.
725 </p>
726
727 <p>
728 This analysis is primarily useful for induction variable substitution and
729 strength reduction.
730 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]731</div>
732
733<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]734<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]735 <a name="scev-aa">-scev-aa: ScalarEvolution-based Alias Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]736</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]737<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]738 <p>Simple alias analysis implemented in terms of ScalarEvolution queries.
739
740 This differs from traditional loop dependence analysis in that it tests
741 for dependencies within a single iteration of a loop, rather than
742 dependencies between different iterations.
743
744 ScalarEvolution has a more complete understanding of pointer arithmetic
745 than BasicAliasAnalysis' collection of ad-hoc analyses.
746 </p>
747</div>
748
749<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]750<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]751 <a name="targetdata">-targetdata: Target Data Layout</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]752</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]753<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]754 <p>Provides other passes access to information on how the size and alignment
Sylvestre Ledruc8e41c52012-07-23 08:51:15 +0000[diff] [blame]755 required by the target ABI for various data types.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]756</div>
757
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]758</div>
759
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]760<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]761<h2><a name="transforms">Transform Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]762<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]763 <p>This section describes the LLVM Transform Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]764
765<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]766<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]767 <a name="adce">-adce: Aggressive Dead Code Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]768</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]769<div>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]770 <p>ADCE aggressively tries to eliminate code. This pass is similar to
771 <a href="#dce">DCE</a> but it assumes that values are dead until proven
772 otherwise. This is similar to <a href="#sccp">SCCP</a>, except applied to
773 the liveness of values.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]774</div>
775
776<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]777<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]778 <a name="always-inline">-always-inline: Inliner for always_inline functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]779</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]780<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]781 <p>A custom inliner that handles only functions that are marked as
782 "always inline".</p>
783</div>
784
785<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]786<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]787 <a name="argpromotion">-argpromotion: Promote 'by reference' arguments to scalars</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]788</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]789<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]790 <p>
791 This pass promotes "by reference" arguments to be "by value" arguments. In
792 practice, this means looking for internal functions that have pointer
793 arguments. If it can prove, through the use of alias analysis, that an
794 argument is *only* loaded, then it can pass the value into the function
795 instead of the address of the value. This can cause recursive simplification
796 of code and lead to the elimination of allocas (especially in C++ template
797 code like the STL).
798 </p>
799
800 <p>
801 This pass also handles aggregate arguments that are passed into a function,
802 scalarizing them if the elements of the aggregate are only loaded. Note that
803 it refuses to scalarize aggregates which would require passing in more than
804 three operands to the function, because passing thousands of operands for a
805 large array or structure is unprofitable!
806 </p>
807
808 <p>
809 Note that this transformation could also be done for arguments that are only
810 stored to (returning the value instead), but does not currently. This case
811 would be best handled when and if LLVM starts supporting multiple return
812 values from functions.
813 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]814</div>
815
816<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]817<h3>
Hal Finkelde5e5ec2012-02-01 03:51:43 +0000[diff] [blame]818 <a name="bb-vectorize">-bb-vectorize: Basic-Block Vectorization</a>
819</h3>
820<div>
821 <p>This pass combines instructions inside basic blocks to form vector
822 instructions. It iterates over each basic block, attempting to pair
823 compatible instructions, repeating this process until no additional
824 pairs are selected for vectorization. When the outputs of some pair
825 of compatible instructions are used as inputs by some other pair of
826 compatible instructions, those pairs are part of a potential
827 vectorization chain. Instruction pairs are only fused into vector
828 instructions when they are part of a chain longer than some
829 threshold length. Moreover, the pass attempts to find the best
830 possible chain for each pair of compatible instructions. These
831 heuristics are intended to prevent vectorization in cases where
832 it would not yield a performance increase of the resulting code.
833 </p>
834</div>
835
836<!-------------------------------------------------------------------------- -->
837<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]838 <a name="block-placement">-block-placement: Profile Guided Basic Block Placement</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]839</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]840<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]841 <p>This pass is a very simple profile guided basic block placement algorithm.
842 The idea is to put frequently executed blocks together at the start of the
843 function and hopefully increase the number of fall-through conditional
844 branches. If there is no profile information for a particular function, this
845 pass basically orders blocks in depth-first order.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]846</div>
847
848<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]849<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]850 <a name="break-crit-edges">-break-crit-edges: Break critical edges in CFG</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]851</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]852<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]853 <p>
854 Break all of the critical edges in the CFG by inserting a dummy basic block.
855 It may be "required" by passes that cannot deal with critical edges. This
856 transformation obviously invalidates the CFG, but can update forward dominator
857 (set, immediate dominators, tree, and frontier) information.
858 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]859</div>
860
861<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]862<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]863 <a name="codegenprepare">-codegenprepare: Optimize for code generation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]864</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]865<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]866 This pass munges the code in the input function to better prepare it for
867 SelectionDAG-based code generation. This works around limitations in it's
868 basic-block-at-a-time approach. It should eventually be removed.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]869</div>
870
871<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]872<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]873 <a name="constmerge">-constmerge: Merge Duplicate Global Constants</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]874</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]875<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]876 <p>
877 Merges duplicate global constants together into a single constant that is
878 shared. This is useful because some passes (ie TraceValues) insert a lot of
879 string constants into the program, regardless of whether or not an existing
880 string is available.
881 </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="constprop">-constprop: Simple constant propagation</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>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]889 <p>This file implements constant propagation and merging. It looks for
890 instructions involving only constant operands and replaces them with a
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]891 constant value instead of an instruction. For example:</p>
892 <blockquote><pre>add i32 1, 2</pre></blockquote>
893 <p>becomes</p>
894 <blockquote><pre>i32 3</pre></blockquote>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]895 <p>NOTE: this pass has a habit of making definitions be dead. It is a good
896 idea to to run a <a href="#die">DIE</a> (Dead Instruction Elimination) pass
897 sometime after running this pass.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]898</div>
899
900<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]901<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]902 <a name="dce">-dce: Dead Code Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]903</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]904<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]905 <p>
906 Dead code elimination is similar to <a href="#die">dead instruction
907 elimination</a>, but it rechecks instructions that were used by removed
908 instructions to see if they are newly dead.
909 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]910</div>
911
912<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]913<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]914 <a name="deadargelim">-deadargelim: Dead Argument Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]915</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]916<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]917 <p>
918 This pass deletes dead arguments from internal functions. Dead argument
919 elimination removes arguments which are directly dead, as well as arguments
920 only passed into function calls as dead arguments of other functions. This
921 pass also deletes dead arguments in a similar way.
922 </p>
923
924 <p>
925 This pass is often useful as a cleanup pass to run after aggressive
926 interprocedural passes, which add possibly-dead arguments.
927 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]928</div>
929
930<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]931<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]932 <a name="deadtypeelim">-deadtypeelim: Dead Type Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]933</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]934<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]935 <p>
936 This pass is used to cleanup the output of GCC. It eliminate names for types
937 that are unused in the entire translation unit, using the <a
938 href="#findusedtypes">find used types</a> pass.
939 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]940</div>
941
942<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]943<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]944 <a name="die">-die: Dead Instruction Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]945</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]946<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]947 <p>
948 Dead instruction elimination performs a single pass over the function,
949 removing instructions that are obviously dead.
950 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]951</div>
952
953<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]954<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]955 <a name="dse">-dse: Dead Store Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]956</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]957<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]958 <p>
959 A trivial dead store elimination that only considers basic-block local
960 redundant stores.
961 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]962</div>
963
964<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]965<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]966 <a name="functionattrs">-functionattrs: Deduce function attributes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]967</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]968<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]969 <p>A simple interprocedural pass which walks the call-graph, looking for
970 functions which do not access or only read non-local memory, and marking them
971 readnone/readonly. In addition, it marks function arguments (of pointer type)
972 'nocapture' if a call to the function does not create any copies of the pointer
973 value that outlive the call. This more or less means that the pointer is only
974 dereferenced, and not returned from the function or stored in a global.
975 This pass is implemented as a bottom-up traversal of the call-graph.
976 </p>
977</div>
978
979<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]980<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]981 <a name="globaldce">-globaldce: Dead Global Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]982</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]983<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]984 <p>
985 This transform is designed to eliminate unreachable internal globals from the
986 program. It uses an aggressive algorithm, searching out globals that are
987 known to be alive. After it finds all of the globals which are needed, it
988 deletes whatever is left over. This allows it to delete recursive chunks of
989 the program which are unreachable.
990 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]991</div>
992
993<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]994<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]995 <a name="globalopt">-globalopt: Global Variable Optimizer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]996</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]997<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]998 <p>
999 This pass transforms simple global variables that never have their address
1000 taken. If obviously true, it marks read/write globals as constant, deletes
1001 variables only stored to, etc.
1002 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1003</div>
1004
1005<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1006<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1007 <a name="gvn">-gvn: Global Value Numbering</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1008</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1009<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]1010 <p>
Chris Lattner60f03402009-10-10 18:40:48 +0000[diff] [blame]1011 This pass performs global value numbering to eliminate fully and partially
1012 redundant instructions. It also performs redundant load elimination.
Matthijs Kooijman845f5242008-06-05 07:55:49 +0000[diff] [blame]1013 </p>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]1014</div>
1015
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1016<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1017<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1018 <a name="indvars">-indvars: Canonicalize Induction Variables</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1019</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1020<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1021 <p>
1022 This transformation analyzes and transforms the induction variables (and
1023 computations derived from them) into simpler forms suitable for subsequent
1024 analysis and transformation.
1025 </p>
1026
1027 <p>
1028 This transformation makes the following changes to each loop with an
1029 identifiable induction variable:
1030 </p>
1031
1032 <ol>
1033 <li>All loops are transformed to have a <em>single</em> canonical
1034 induction variable which starts at zero and steps by one.</li>
1035 <li>The canonical induction variable is guaranteed to be the first PHI node
1036 in the loop header block.</li>
1037 <li>Any pointer arithmetic recurrences are raised to use array
1038 subscripts.</li>
1039 </ol>
1040
1041 <p>
1042 If the trip count of a loop is computable, this pass also makes the following
1043 changes:
1044 </p>
1045
1046 <ol>
1047 <li>The exit condition for the loop is canonicalized to compare the
1048 induction value against the exit value. This turns loops like:
1049 <blockquote><pre>for (i = 7; i*i < 1000; ++i)</pre></blockquote>
1050 into
1051 <blockquote><pre>for (i = 0; i != 25; ++i)</pre></blockquote></li>
1052 <li>Any use outside of the loop of an expression derived from the indvar
1053 is changed to compute the derived value outside of the loop, eliminating
1054 the dependence on the exit value of the induction variable. If the only
1055 purpose of the loop is to compute the exit value of some derived
1056 expression, this transformation will make the loop dead.</li>
Gordon Henriksene626bbe2007-11-04 16:17:00 +0000[diff] [blame]1057 </ol>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1058
1059 <p>
1060 This transformation should be followed by strength reduction after all of the
1061 desired loop transformations have been performed. Additionally, on targets
1062 where it is profitable, the loop could be transformed to count down to zero
1063 (the "do loop" optimization).
1064 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1065</div>
1066
1067<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1068<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1069 <a name="inline">-inline: Function Integration/Inlining</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1070</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1071<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1072 <p>
1073 Bottom-up inlining of functions into callees.
1074 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1075</div>
1076
1077<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1078<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1079 <a name="insert-edge-profiling">-insert-edge-profiling: Insert instrumentation for edge profiling</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1080</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1081<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1082 <p>
1083 This pass instruments the specified program with counters for edge profiling.
1084 Edge profiling can give a reasonable approximation of the hot paths through a
1085 program, and is used for a wide variety of program transformations.
1086 </p>
1087
1088 <p>
1089 Note that this implementation is very naïve. It inserts a counter for
1090 <em>every</em> edge in the program, instead of using control flow information
1091 to prune the number of counters inserted.
1092 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1093</div>
1094
1095<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1096<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1097 <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]1098</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1099<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1100 <p>This pass instruments the specified program with counters for edge profiling.
1101 Edge profiling can give a reasonable approximation of the hot paths through a
1102 program, and is used for a wide variety of program transformations.
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1103 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1104</div>
1105
1106<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1107<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1108 <a name="instcombine">-instcombine: Combine redundant instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1109</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1110<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1111 <p>
1112 Combine instructions to form fewer, simple
1113 instructions. This pass does not modify the CFG This pass is where algebraic
1114 simplification happens.
1115 </p>
1116
1117 <p>
1118 This pass combines things like:
1119 </p>
1120
1121<blockquote><pre
1122>%Y = add i32 %X, 1
1123%Z = add i32 %Y, 1</pre></blockquote>
1124
1125 <p>
1126 into:
1127 </p>
1128
1129<blockquote><pre
1130>%Z = add i32 %X, 2</pre></blockquote>
1131
1132 <p>
1133 This is a simple worklist driven algorithm.
1134 </p>
1135
1136 <p>
1137 This pass guarantees that the following canonicalizations are performed on
1138 the program:
1139 </p>
1140
1141 <ul>
1142 <li>If a binary operator has a constant operand, it is moved to the right-
1143 hand side.</li>
1144 <li>Bitwise operators with constant operands are always grouped so that
1145 shifts are performed first, then <code>or</code>s, then
1146 <code>and</code>s, then <code>xor</code>s.</li>
1147 <li>Compare instructions are converted from <code>&lt;</code>,
1148 <code>&gt;</code>, <code>≤</code>, or <code>≥</code> to
1149 <code>=</code> or <code>≠</code> if possible.</li>
1150 <li>All <code>cmp</code> instructions on boolean values are replaced with
1151 logical operations.</li>
1152 <li><code>add <var>X</var>, <var>X</var></code> is represented as
1153 <code>mul <var>X</var>, 2</code> ⇒ <code>shl <var>X</var>, 1</code></li>
1154 <li>Multiplies with a constant power-of-two argument are transformed into
1155 shifts.</li>
1156 <li>… etc.</li>
1157 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1158</div>
1159
1160<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1161<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1162 <a name="internalize">-internalize: Internalize Global Symbols</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1163</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1164<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1165 <p>
1166 This pass loops over all of the functions in the input module, looking for a
1167 main function. If a main function is found, all other functions and all
1168 global variables with initializers are marked as internal.
1169 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1170</div>
1171
1172<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1173<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1174 <a name="ipconstprop">-ipconstprop: Interprocedural constant propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1175</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1176<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1177 <p>
1178 This pass implements an <em>extremely</em> simple interprocedural constant
1179 propagation pass. It could certainly be improved in many different ways,
1180 like using a worklist. This pass makes arguments dead, but does not remove
1181 them. The existing dead argument elimination pass should be run after this
1182 to clean up the mess.
1183 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1184</div>
1185
1186<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1187<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1188 <a name="ipsccp">-ipsccp: Interprocedural Sparse Conditional Constant Propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1189</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1190<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1191 <p>
1192 An interprocedural variant of <a href="#sccp">Sparse Conditional Constant
1193 Propagation</a>.
1194 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1195</div>
1196
1197<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1198<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1199 <a name="jump-threading">-jump-threading: Jump Threading</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1200</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1201<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1202 <p>
1203 Jump threading tries to find distinct threads of control flow running through
1204 a basic block. This pass looks at blocks that have multiple predecessors and
1205 multiple successors. If one or more of the predecessors of the block can be
1206 proven to always cause a jump to one of the successors, we forward the edge
1207 from the predecessor to the successor by duplicating the contents of this
1208 block.
1209 </p>
1210 <p>
1211 An example of when this can occur is code like this:
1212 </p>
1213
1214 <pre
1215>if () { ...
1216 X = 4;
1217}
1218if (X &lt; 3) {</pre>
1219
1220 <p>
1221 In this case, the unconditional branch at the end of the first if can be
1222 revectored to the false side of the second if.
1223 </p>
1224</div>
1225
1226<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1227<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1228 <a name="lcssa">-lcssa: Loop-Closed SSA Form Pass</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1229</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1230<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1231 <p>
1232 This pass transforms loops by placing phi nodes at the end of the loops for
1233 all values that are live across the loop boundary. For example, it turns
1234 the left into the right code:
1235 </p>
1236
1237 <pre
1238>for (...) for (...)
1239 if (c) if (c)
1240 X1 = ... X1 = ...
1241 else else
1242 X2 = ... X2 = ...
1243 X3 = phi(X1, X2) X3 = phi(X1, X2)
1244... = X3 + 4 X4 = phi(X3)
1245 ... = X4 + 4</pre>
1246
1247 <p>
1248 This is still valid LLVM; the extra phi nodes are purely redundant, and will
1249 be trivially eliminated by <code>InstCombine</code>. The major benefit of
1250 this transformation is that it makes many other loop optimizations, such as
1251 LoopUnswitching, simpler.
1252 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1253</div>
1254
1255<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1256<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1257 <a name="licm">-licm: Loop Invariant Code Motion</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1258</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1259<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1260 <p>
1261 This pass performs loop invariant code motion, attempting to remove as much
1262 code from the body of a loop as possible. It does this by either hoisting
1263 code into the preheader block, or by sinking code to the exit blocks if it is
1264 safe. This pass also promotes must-aliased memory locations in the loop to
1265 live in registers, thus hoisting and sinking "invariant" loads and stores.
1266 </p>
1267
1268 <p>
1269 This pass uses alias analysis for two purposes:
1270 </p>
1271
1272 <ul>
1273 <li>Moving loop invariant loads and calls out of loops. If we can determine
1274 that a load or call inside of a loop never aliases anything stored to,
1275 we can hoist it or sink it like any other instruction.</li>
1276 <li>Scalar Promotion of Memory - If there is a store instruction inside of
1277 the loop, we try to move the store to happen AFTER the loop instead of
1278 inside of the loop. This can only happen if a few conditions are true:
1279 <ul>
1280 <li>The pointer stored through is loop invariant.</li>
1281 <li>There are no stores or loads in the loop which <em>may</em> alias
1282 the pointer. There are no calls in the loop which mod/ref the
1283 pointer.</li>
1284 </ul>
1285 If these conditions are true, we can promote the loads and stores in the
1286 loop of the pointer to use a temporary alloca'd variable. We then use
1287 the mem2reg functionality to construct the appropriate SSA form for the
1288 variable.</li>
1289 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1290</div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1291
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1292<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1293<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1294 <a name="loop-deletion">-loop-deletion: Delete dead loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1295</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1296<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1297 <p>
1298 This file implements the Dead Loop Deletion Pass. This pass is responsible
1299 for eliminating loops with non-infinite computable trip counts that have no
1300 side effects or volatile instructions, and do not contribute to the
1301 computation of the function's return value.
1302 </p>
1303</div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1304
1305<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1306<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1307 <a name="loop-extract">-loop-extract: Extract loops into new functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1308</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1309<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1310 <p>
1311 A pass wrapper around the <code>ExtractLoop()</code> scalar transformation to
1312 extract each top-level loop into its own new function. If the loop is the
1313 <em>only</em> loop in a given function, it is not touched. This is a pass most
1314 useful for debugging via bugpoint.
1315 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1316</div>
1317
1318<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1319<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1320 <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]1321</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1322<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1323 <p>
1324 Similar to <a href="#loop-extract">Extract loops into new functions</a>,
1325 this pass extracts one natural loop from the program into a function if it
1326 can. This is used by bugpoint.
1327 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1328</div>
1329
1330<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1331<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1332 <a name="loop-reduce">-loop-reduce: Loop Strength Reduction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1333</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1334<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1335 <p>
1336 This pass performs a strength reduction on array references inside loops that
1337 have as one or more of their components the loop induction variable. This is
1338 accomplished by creating a new value to hold the initial value of the array
1339 access for the first iteration, and then creating a new GEP instruction in
1340 the loop to increment the value by the appropriate amount.
1341 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1342</div>
1343
1344<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1345<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1346 <a name="loop-rotate">-loop-rotate: Rotate Loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1347</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1348<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1349 <p>A simple loop rotation transformation.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1350</div>
1351
1352<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1353<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1354 <a name="loop-simplify">-loop-simplify: Canonicalize natural loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1355</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1356<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1357 <p>
1358 This pass performs several transformations to transform natural loops into a
1359 simpler form, which makes subsequent analyses and transformations simpler and
1360 more effective.
1361 </p>
1362
1363 <p>
1364 Loop pre-header insertion guarantees that there is a single, non-critical
1365 entry edge from outside of the loop to the loop header. This simplifies a
1366 number of analyses and transformations, such as LICM.
1367 </p>
1368
1369 <p>
1370 Loop exit-block insertion guarantees that all exit blocks from the loop
1371 (blocks which are outside of the loop that have predecessors inside of the
1372 loop) only have predecessors from inside of the loop (and are thus dominated
1373 by the loop header). This simplifies transformations such as store-sinking
1374 that are built into LICM.
1375 </p>
1376
1377 <p>
1378 This pass also guarantees that loops will have exactly one backedge.
1379 </p>
1380
1381 <p>
1382 Note that the simplifycfg pass will clean up blocks which are split out but
1383 end up being unnecessary, so usage of this pass should not pessimize
1384 generated code.
1385 </p>
1386
1387 <p>
1388 This pass obviously modifies the CFG, but updates loop information and
1389 dominator information.
1390 </p>
1391</div>
1392
1393<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1394<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1395 <a name="loop-unroll">-loop-unroll: Unroll loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1396</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1397<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1398 <p>
1399 This pass implements a simple loop unroller. It works best when loops have
1400 been canonicalized by the <a href="#indvars"><tt>-indvars</tt></a> pass,
1401 allowing it to determine the trip counts of loops easily.
1402 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1403</div>
1404
1405<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1406<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1407 <a name="loop-unswitch">-loop-unswitch: Unswitch loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1408</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1409<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1410 <p>
1411 This pass transforms loops that contain branches on loop-invariant conditions
1412 to have multiple loops. For example, it turns the left into the right code:
1413 </p>
1414
1415 <pre
1416>for (...) if (lic)
1417 A for (...)
1418 if (lic) A; B; C
1419 B else
1420 C for (...)
1421 A; C</pre>
1422
1423 <p>
1424 This can increase the size of the code exponentially (doubling it every time
1425 a loop is unswitched) so we only unswitch if the resultant code will be
1426 smaller than a threshold.
1427 </p>
1428
1429 <p>
1430 This pass expects LICM to be run before it to hoist invariant conditions out
1431 of the loop, to make the unswitching opportunity obvious.
1432 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1433</div>
1434
1435<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1436<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]1437 <a name="loweratomic">-loweratomic: Lower atomic intrinsics to non-atomic form</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1438</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1439<div>
Peter Collingbourne3bababf2010-08-03 16:19:16 +0000[diff] [blame]1440 <p>
1441 This pass lowers atomic intrinsics to non-atomic form for use in a known
1442 non-preemptible environment.
1443 </p>
1444
1445 <p>
1446 The pass does not verify that the environment is non-preemptible (in
1447 general this would require knowledge of the entire call graph of the
1448 program including any libraries which may not be available in bitcode form);
1449 it simply lowers every atomic intrinsic.
1450 </p>
1451</div>
1452
1453<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1454<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1455 <a name="lowerinvoke">-lowerinvoke: Lower invoke and unwind, for unwindless code generators</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1456</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1457<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1458 <p>
1459 This transformation is designed for use by code generators which do not yet
1460 support stack unwinding. This pass supports two models of exception handling
1461 lowering, the 'cheap' support and the 'expensive' support.
1462 </p>
1463
1464 <p>
1465 'Cheap' exception handling support gives the program the ability to execute
1466 any program which does not "throw an exception", by turning 'invoke'
1467 instructions into calls and by turning 'unwind' instructions into calls to
1468 abort(). If the program does dynamically use the unwind instruction, the
1469 program will print a message then abort.
1470 </p>
1471
1472 <p>
1473 'Expensive' exception handling support gives the full exception handling
1474 support to the program at the cost of making the 'invoke' instruction
1475 really expensive. It basically inserts setjmp/longjmp calls to emulate the
1476 exception handling as necessary.
1477 </p>
1478
1479 <p>
1480 Because the 'expensive' support slows down programs a lot, and EH is only
1481 used for a subset of the programs, it must be specifically enabled by the
1482 <tt>-enable-correct-eh-support</tt> option.
1483 </p>
1484
1485 <p>
1486 Note that after this pass runs the CFG is not entirely accurate (exceptional
1487 control flow edges are not correct anymore) so only very simple things should
1488 be done after the lowerinvoke pass has run (like generation of native code).
1489 This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't
1490 support the invoke instruction yet" lowering pass.
1491 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1492</div>
1493
1494<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1495<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1496 <a name="lowerswitch">-lowerswitch: Lower SwitchInst's to branches</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1497</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1498<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1499 <p>
1500 Rewrites <tt>switch</tt> instructions with a sequence of branches, which
1501 allows targets to get away with not implementing the switch instruction until
1502 it is convenient.
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>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1508 <a name="mem2reg">-mem2reg: Promote Memory to Register</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 Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1511 <p>
1512 This file promotes memory references to be register references. It promotes
1513 <tt>alloca</tt> instructions which only have <tt>load</tt>s and
1514 <tt>store</tt>s as uses. An <tt>alloca</tt> is transformed by using dominator
1515 frontiers to place <tt>phi</tt> nodes, then traversing the function in
1516 depth-first order to rewrite <tt>load</tt>s and <tt>store</tt>s as
1517 appropriate. This is just the standard SSA construction algorithm to construct
1518 "pruned" SSA form.
1519 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1520</div>
1521
1522<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1523<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1524 <a name="memcpyopt">-memcpyopt: MemCpy Optimization</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1525</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1526<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1527 <p>
1528 This pass performs various transformations related to eliminating memcpy
1529 calls, or transforming sets of stores into memset's.
1530 </p>
1531</div>
1532
1533<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1534<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1535 <a name="mergefunc">-mergefunc: Merge Functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1536</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1537<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1538 <p>This pass looks for equivalent functions that are mergable and folds them.
1539
1540 A hash is computed from the function, based on its type and number of
1541 basic blocks.
1542
1543 Once all hashes are computed, we perform an expensive equality comparison
1544 on each function pair. This takes n^2/2 comparisons per bucket, so it's
1545 important that the hash function be high quality. The equality comparison
1546 iterates through each instruction in each basic block.
1547
1548 When a match is found the functions are folded. If both functions are
1549 overridable, we move the functionality into a new internal function and
1550 leave two overridable thunks to it.
1551 </p>
1552</div>
1553
1554<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1555<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1556 <a name="mergereturn">-mergereturn: Unify function exit nodes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1557</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1558<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1559 <p>
1560 Ensure that functions have at most one <tt>ret</tt> instruction in them.
1561 Additionally, it keeps track of which node is the new exit node of the CFG.
1562 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1563</div>
1564
1565<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1566<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1567 <a name="partial-inliner">-partial-inliner: Partial Inliner</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1568</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1569<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1570 <p>This pass performs partial inlining, typically by inlining an if
1571 statement that surrounds the body of the function.
1572 </p>
1573</div>
1574
1575<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1576<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1577 <a name="prune-eh">-prune-eh: Remove unused exception handling info</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1578</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1579<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1580 <p>
1581 This file implements a simple interprocedural pass which walks the call-graph,
1582 turning <tt>invoke</tt> instructions into <tt>call</tt> instructions if and
1583 only if the callee cannot throw an exception. It implements this as a
1584 bottom-up traversal of the call-graph.
1585 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1586</div>
1587
1588<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1589<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1590 <a name="reassociate">-reassociate: Reassociate expressions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1591</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1592<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1593 <p>
1594 This pass reassociates commutative expressions in an order that is designed
1595 to promote better constant propagation, GCSE, LICM, PRE, etc.
1596 </p>
1597
1598 <p>
1599 For example: 4 + (<var>x</var> + 5) ⇒ <var>x</var> + (4 + 5)
1600 </p>
1601
1602 <p>
1603 In the implementation of this algorithm, constants are assigned rank = 0,
1604 function arguments are rank = 1, and other values are assigned ranks
1605 corresponding to the reverse post order traversal of current function
1606 (starting at 2), which effectively gives values in deep loops higher rank
1607 than values not in loops.
1608 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1609</div>
1610
1611<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1612<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1613 <a name="reg2mem">-reg2mem: Demote all values to stack slots</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1614</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1615<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1616 <p>
Benjamin Kramerd9b0b022012-06-02 10:20:22 +0000[diff] [blame]1617 This file demotes all registers to memory references. It is intended to be
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1618 the inverse of <a href="#mem2reg"><tt>-mem2reg</tt></a>. By converting to
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]1619 <tt>load</tt> instructions, the only values live across basic blocks are
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1620 <tt>alloca</tt> instructions and <tt>load</tt> instructions before
1621 <tt>phi</tt> nodes. It is intended that this should make CFG hacking much
1622 easier. To make later hacking easier, the entry block is split into two, such
1623 that all introduced <tt>alloca</tt> instructions (and nothing else) are in the
1624 entry block.
1625 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1626</div>
1627
1628<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1629<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1630 <a name="scalarrepl">-scalarrepl: Scalar Replacement of Aggregates (DT)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1631</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1632<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1633 <p>
1634 The well-known scalar replacement of aggregates transformation. This
1635 transform breaks up <tt>alloca</tt> instructions of aggregate type (structure
1636 or array) into individual <tt>alloca</tt> instructions for each member if
1637 possible. Then, if possible, it transforms the individual <tt>alloca</tt>
1638 instructions into nice clean scalar SSA form.
1639 </p>
1640
1641 <p>
1642 This combines a simple scalar replacement of aggregates algorithm with the <a
1643 href="#mem2reg"><tt>mem2reg</tt></a> algorithm because often interact,
1644 especially for C++ programs. As such, iterating between <tt>scalarrepl</tt>,
1645 then <a href="#mem2reg"><tt>mem2reg</tt></a> until we run out of things to
1646 promote works well.
1647 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1648</div>
1649
1650<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1651<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1652 <a name="sccp">-sccp: Sparse Conditional Constant Propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1653</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1654<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1655 <p>
1656 Sparse conditional constant propagation and merging, which can be summarized
1657 as:
1658 </p>
1659
1660 <ol>
1661 <li>Assumes values are constant unless proven otherwise</li>
1662 <li>Assumes BasicBlocks are dead unless proven otherwise</li>
1663 <li>Proves values to be constant, and replaces them with constants</li>
1664 <li>Proves conditional branches to be unconditional</li>
1665 </ol>
1666
1667 <p>
1668 Note that this pass has a habit of making definitions be dead. It is a good
1669 idea to to run a DCE pass sometime after running this pass.
1670 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1671</div>
1672
1673<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1674<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1675 <a name="simplify-libcalls">-simplify-libcalls: Simplify well-known library calls</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1676</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1677<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1678 <p>
1679 Applies a variety of small optimizations for calls to specific well-known
1680 function calls (e.g. runtime library functions). For example, a call
1681 <tt>exit(3)</tt> that occurs within the <tt>main()</tt> function can be
1682 transformed into simply <tt>return 3</tt>.
1683 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1684</div>
1685
1686<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1687<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1688 <a name="simplifycfg">-simplifycfg: Simplify the CFG</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1689</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1690<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1691 <p>
1692 Performs dead code elimination and basic block merging. Specifically:
1693 </p>
1694
1695 <ol>
1696 <li>Removes basic blocks with no predecessors.</li>
1697 <li>Merges a basic block into its predecessor if there is only one and the
1698 predecessor only has one successor.</li>
1699 <li>Eliminates PHI nodes for basic blocks with a single predecessor.</li>
1700 <li>Eliminates a basic block that only contains an unconditional
1701 branch.</li>
1702 </ol>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1703</div>
1704
1705<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1706<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1707 <a name="sink">-sink: Code sinking</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1708</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1709<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1710 <p>This pass moves instructions into successor blocks, when possible, so that
1711 they aren't executed on paths where their results aren't needed.
1712 </p>
1713</div>
1714
1715<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1716<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1717 <a name="strip">-strip: Strip all symbols from a module</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1718</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1719<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1720 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1721 performs code stripping. this transformation can delete:
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1722 </p>
1723
1724 <ol>
1725 <li>names for virtual registers</li>
1726 <li>symbols for internal globals and functions</li>
1727 <li>debug information</li>
1728 </ol>
1729
1730 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1731 note that this transformation makes code much less readable, so it should
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1732 only be used in situations where the <tt>strip</tt> utility would be used,
1733 such as reducing code size or making it harder to reverse engineer code.
1734 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1735</div>
1736
1737<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1738<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1739 <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]1740</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1741<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1742 <p>
1743 performs code stripping. this transformation can delete:
1744 </p>
1745
1746 <ol>
1747 <li>names for virtual registers</li>
1748 <li>symbols for internal globals and functions</li>
1749 <li>debug information</li>
1750 </ol>
1751
1752 <p>
1753 note that this transformation makes code much less readable, so it should
1754 only be used in situations where the <tt>strip</tt> utility would be used,
1755 such as reducing code size or making it harder to reverse engineer code.
1756 </p>
1757</div>
1758
1759<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1760<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1761 <a name="strip-dead-prototypes">-strip-dead-prototypes: Strip Unused Function Prototypes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1762</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1763<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1764 <p>
1765 This pass loops over all of the functions in the input module, looking for
1766 dead declarations and removes them. Dead declarations are declarations of
1767 functions for which no implementation is available (i.e., declarations for
1768 unused library functions).
1769 </p>
1770</div>
1771
1772<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1773<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1774 <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]1775</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1776<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1777 <p>This pass implements code stripping. Specifically, it can delete:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1778 <ul>
1779 <li>names for virtual registers</li>
1780 <li>symbols for internal globals and functions</li>
1781 <li>debug information</li>
1782 </ul>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1783 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1784 Note that this transformation makes code much less readable, so it should
1785 only be used in situations where the 'strip' utility would be used, such as
1786 reducing code size or making it harder to reverse engineer code.
1787 </p>
1788</div>
1789
1790<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1791<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1792 <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]1793</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1794<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1795 <p>This pass implements code stripping. Specifically, it can delete:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1796 <ul>
1797 <li>names for virtual registers</li>
1798 <li>symbols for internal globals and functions</li>
1799 <li>debug information</li>
1800 </ul>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1801 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1802 Note that this transformation makes code much less readable, so it should
1803 only be used in situations where the 'strip' utility would be used, such as
1804 reducing code size or making it harder to reverse engineer code.
1805 </p>
1806</div>
1807
1808<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1809<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1810 <a name="tailcallelim">-tailcallelim: Tail Call Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1811</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1812<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1813 <p>
1814 This file transforms calls of the current function (self recursion) followed
1815 by a return instruction with a branch to the entry of the function, creating
1816 a loop. This pass also implements the following extensions to the basic
1817 algorithm:
1818 </p>
1819
1820 <ul>
1821 <li>Trivial instructions between the call and return do not prevent the
1822 transformation from taking place, though currently the analysis cannot
1823 support moving any really useful instructions (only dead ones).
1824 <li>This pass transforms functions that are prevented from being tail
1825 recursive by an associative expression to use an accumulator variable,
1826 thus compiling the typical naive factorial or <tt>fib</tt> implementation
1827 into efficient code.
1828 <li>TRE is performed if the function returns void, if the return
1829 returns the result returned by the call, or if the function returns a
1830 run-time constant on all exits from the function. It is possible, though
1831 unlikely, that the return returns something else (like constant 0), and
1832 can still be TRE'd. It can be TRE'd if <em>all other</em> return
1833 instructions in the function return the exact same value.
1834 <li>If it can prove that callees do not access theier caller stack frame,
1835 they are marked as eligible for tail call elimination (by the code
1836 generator).
1837 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1838</div>
1839
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1840<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1841<h2><a name="utilities">Utility Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1842<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1843 <p>This section describes the LLVM Utility Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1844
1845<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1846<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1847 <a name="deadarghaX0r">-deadarghaX0r: Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1848</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1849<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1850 <p>
1851 Same as dead argument elimination, but deletes arguments to functions which
1852 are external. This is only for use by <a
1853 href="Bugpoint.html">bugpoint</a>.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1854</div>
1855
1856<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1857<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1858 <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]1859</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1860<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1861 <p>
1862 This pass is used by bugpoint to extract all blocks from the module into their
1863 own functions.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1864</div>
1865
1866<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1867<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1868 <a name="instnamer">-instnamer: Assign names to anonymous instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1869</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1870<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1871 <p>This is a little utility pass that gives instructions names, this is mostly
1872 useful when diffing the effect of an optimization because deleting an
1873 unnamed instruction can change all other instruction numbering, making the
1874 diff very noisy.
1875 </p>
1876</div>
1877
1878<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1879<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1880 <a name="preverify">-preverify: Preliminary module verification</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1881</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1882<div>
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]1883 <p>
1884 Ensures that the module is in the form required by the <a
1885 href="#verifier">Module Verifier</a> pass.
1886 </p>
1887
1888 <p>
1889 Running the verifier runs this pass automatically, so there should be no need
1890 to use it directly.
1891 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1892</div>
1893
1894<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1895<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1896 <a name="verify">-verify: Module Verifier</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1897</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1898<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1899 <p>
1900 Verifies an LLVM IR code. This is useful to run after an optimization which is
1901 undergoing testing. Note that <tt>llvm-as</tt> verifies its input before
1902 emitting bitcode, and also that malformed bitcode is likely to make LLVM
1903 crash. All language front-ends are therefore encouraged to verify their output
1904 before performing optimizing transformations.
1905 </p>
1906
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]1907 <ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1908 <li>Both of a binary operator's parameters are of the same type.</li>
1909 <li>Verify that the indices of mem access instructions match other
1910 operands.</li>
1911 <li>Verify that arithmetic and other things are only performed on
1912 first-class types. Verify that shifts and logicals only happen on
1913 integrals f.e.</li>
1914 <li>All of the constants in a switch statement are of the correct type.</li>
1915 <li>The code is in valid SSA form.</li>
Chris Lattner46b3abc2009-10-28 04:47:06 +0000[diff] [blame]1916 <li>It is illegal to put a label into any other type (like a structure) or
1917 to return one.</li>
Nick Lewycky0c78ac12008-03-28 06:46:51 +0000[diff] [blame]1918 <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]1919 invalid.</li>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1920 <li>PHI nodes must have an entry for each predecessor, with no extras.</li>
1921 <li>PHI nodes must be the first thing in a basic block, all grouped
1922 together.</li>
1923 <li>PHI nodes must have at least one entry.</li>
1924 <li>All basic blocks should only end with terminator insts, not contain
1925 them.</li>
1926 <li>The entry node to a function must not have predecessors.</li>
1927 <li>All Instructions must be embedded into a basic block.</li>
1928 <li>Functions cannot take a void-typed parameter.</li>
1929 <li>Verify that a function's argument list agrees with its declared
1930 type.</li>
1931 <li>It is illegal to specify a name for a void value.</li>
Sylvestre Ledru7f7390e2012-07-25 22:01:31 +0000[diff] [blame]1932 <li>It is illegal to have an internal global value with no initializer.</li>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1933 <li>It is illegal to have a ret instruction that returns a value that does
1934 not agree with the function return value type.</li>
1935 <li>Function call argument types match the function prototype.</li>
1936 <li>All other things that are tested by asserts spread about the code.</li>
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]1937 </ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1938
1939 <p>
1940 Note that this does not provide full security verification (like Java), but
1941 instead just tries to ensure that code is well-formed.
1942 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1943</div>
1944
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1945<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1946<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1947 <a name="view-cfg">-view-cfg: View CFG of function</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1948</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1949<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1950 <p>
1951 Displays the control flow graph using the GraphViz tool.
1952 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1953</div>
1954
1955<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1956<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1957 <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]1958</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1959<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1960 <p>
1961 Displays the control flow graph using the GraphViz tool, but omitting function
1962 bodies.
1963 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1964</div>
1965
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]1966<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1967<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1968 <a name="view-dom">-view-dom: View dominance tree of function</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1969</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1970<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]1971 <p>
1972 Displays the dominator tree using the GraphViz tool.
1973 </p>
1974</div>
1975
1976<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1977<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1978 <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]1979</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1980<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]1981 <p>
1982 Displays the dominator tree using the GraphViz tool, but omitting function
1983 bodies.
1984 </p>
1985</div>
1986
1987<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1988<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1989 <a name="view-postdom">-view-postdom: View postdominance tree of function</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1990</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1991<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]1992 <p>
1993 Displays the post dominator tree using the GraphViz tool.
1994 </p>
1995</div>
1996
1997<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1998<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1999 <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]2000</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2001<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2002 <p>
2003 Displays the post dominator tree using the GraphViz tool, but omitting
2004 function bodies.
2005 </p>
2006</div>
2007
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2008</div>
2009
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2010<!-- *********************************************************************** -->
2011
2012<hr>
2013<address>
2014 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]2015 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2016 <a href="http://validator.w3.org/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]2017 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]2018
2019 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
NAKAMURA Takumib9a33632011-04-09 02:13:37 +0000[diff] [blame]2020 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2021 Last modified: $Date$
2022</address>
2023
2024</body>
2025</html>