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gerrit-public.fairphone.software / fp2-dev / platform / external / llvm / 21e1b7a13c0b1201b51304c9801a66a9f7dd7871 / . / docs / Passes.html
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NAKAMURA Takumib5f74912011-04-21 01:32:19 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2 "http://www.w3.org/TR/html4/strict.dtd">
3<html>
4<head>
5 <title>LLVM's Analysis and Transform Passes</title>
6 <link rel="stylesheet" href="llvm.css" type="text/css">
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]8</head>
9<body>
10
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]11<!--
12
13If Passes.html is up to date, the following "one-liner" should print
14an empty diff.
15
16egrep -e '^<tr><td><a href="#.*">-.*</a></td><td>.*</td></tr>$' \
17 -e '^ <a name=".*">.*</a>$' < Passes.html >html; \
18perl >help <<'EOT' && diff -u help html; rm -f help html
19open HTML, "<Passes.html" or die "open: Passes.html: $!\n";
20while (<HTML>) {
21 m:^<tr><td><a href="#(.*)">-.*</a></td><td>.*</td></tr>$: or next;
22 $order{$1} = sprintf("%03d", 1 + int %order);
23}
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]24open HELP, "../Release/bin/opt -help|" or die "open: opt -help: $!\n";
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]25while (<HELP>) {
26 m:^ -([^ ]+) +- (.*)$: or next;
27 my $o = $order{$1};
28 $o = "000" unless defined $o;
29 push @x, "$o<tr><td><a href=\"#$1\">-$1</a></td><td>$2</td></tr>\n";
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]30 push @y, "$o <a name=\"$1\">-$1: $2</a>\n";
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]31}
32@x = map { s/^\d\d\d//; $_ } sort @x;
33@y = map { s/^\d\d\d//; $_ } sort @y;
34print @x, @y;
35EOT
36
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]37This (real) one-liner can also be helpful when converting comments to HTML:
38
39perl -e '$/ = undef; for (split(/\n/, <>)) { s:^ *///? ?::; print " <p>\n" if !$on && $_ =~ /\S/; print " </p>\n" if $on && $_ =~ /^\s*$/; print " $_\n"; $on = ($_ =~ /\S/); } print " </p>\n" if $on'
40
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]41 -->
42
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]43<h1>LLVM's Analysis and Transform Passes</h1>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]44
45<ol>
46 <li><a href="#intro">Introduction</a></li>
47 <li><a href="#analyses">Analysis Passes</a>
48 <li><a href="#transforms">Transform Passes</a></li>
49 <li><a href="#utilities">Utility Passes</a></li>
50</ol>
51
52<div class="doc_author">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]53 <p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a>
54 and Gordon Henriksen</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]55</div>
56
57<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]58<h2><a name="intro">Introduction</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]59<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]60 <p>This document serves as a high level summary of the optimization features
61 that LLVM provides. Optimizations are implemented as Passes that traverse some
62 portion of a program to either collect information or transform the program.
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]63 The table below divides the passes that LLVM provides into three categories.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]64 Analysis passes compute information that other passes can use or for debugging
65 or program visualization purposes. Transform passes can use (or invalidate)
66 the analysis passes. Transform passes all mutate the program in some way.
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]67 Utility passes provides some utility but don't otherwise fit categorization.
Gabor Greif04367bf2007-07-06 22:07:22 +0000[diff] [blame]68 For example passes to extract functions to bitcode or write a module to
69 bitcode are neither analysis nor transform passes.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]70 <p>The table below provides a quick summary of each pass and links to the more
71 complete pass description later in the document.</p>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]72
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]73<table>
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]74<tr><th colspan="2"><b>ANALYSIS PASSES</b></th></tr>
75<tr><th>Option</th><th>Name</th></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]76<tr><td><a href="#aa-eval">-aa-eval</a></td><td>Exhaustive Alias Analysis Precision Evaluator</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]77<tr><td><a href="#basicaa">-basicaa</a></td><td>Basic Alias Analysis (stateless AA impl)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]78<tr><td><a href="#basiccg">-basiccg</a></td><td>Basic CallGraph Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]79<tr><td><a href="#count-aa">-count-aa</a></td><td>Count Alias Analysis Query Responses</td></tr>
80<tr><td><a href="#debug-aa">-debug-aa</a></td><td>AA use debugger</td></tr>
81<tr><td><a href="#domfrontier">-domfrontier</a></td><td>Dominance Frontier Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]82<tr><td><a href="#domtree">-domtree</a></td><td>Dominator Tree Construction</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]83<tr><td><a href="#dot-callgraph">-dot-callgraph</a></td><td>Print Call Graph to 'dot' file</td></tr>
84<tr><td><a href="#dot-cfg">-dot-cfg</a></td><td>Print CFG of function to 'dot' file</td></tr>
85<tr><td><a href="#dot-cfg-only">-dot-cfg-only</a></td><td>Print CFG of function to 'dot' file (with no function bodies)</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]86<tr><td><a href="#dot-dom">-dot-dom</a></td><td>Print dominance tree of function to 'dot' file</td></tr>
87<tr><td><a href="#dot-dom-only">-dot-dom-only</a></td><td>Print dominance tree of function to 'dot' file (with no function bodies)</td></tr>
88<tr><td><a href="#dot-postdom">-dot-postdom</a></td><td>Print postdominance tree of function to 'dot' file</td></tr>
89<tr><td><a href="#dot-postdom-only">-dot-postdom-only</a></td><td>Print postdominance tree of function to 'dot' file (with no function bodies)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]90<tr><td><a href="#globalsmodref-aa">-globalsmodref-aa</a></td><td>Simple mod/ref analysis for globals</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]91<tr><td><a href="#instcount">-instcount</a></td><td>Counts the various types of Instructions</td></tr>
92<tr><td><a href="#intervals">-intervals</a></td><td>Interval Partition Construction</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]93<tr><td><a href="#iv-users">-iv-users</a></td><td>Induction Variable Users</td></tr>
94<tr><td><a href="#lazy-value-info">-lazy-value-info</a></td><td>Lazy Value Information Analysis</td></tr>
95<tr><td><a href="#lda">-lda</a></td><td>Loop Dependence Analysis</td></tr>
96<tr><td><a href="#libcall-aa">-libcall-aa</a></td><td>LibCall Alias Analysis</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]97<tr><td><a href="#lint">-lint</a></td><td>Statically lint-checks LLVM IR</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]98<tr><td><a href="#loops">-loops</a></td><td>Natural Loop Information</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]99<tr><td><a href="#memdep">-memdep</a></td><td>Memory Dependence Analysis</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]100<tr><td><a href="#module-debuginfo">-module-debuginfo</a></td><td>Decodes module-level debug info</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]101<tr><td><a href="#no-aa">-no-aa</a></td><td>No Alias Analysis (always returns 'may' alias)</td></tr>
102<tr><td><a href="#no-profile">-no-profile</a></td><td>No Profile Information</td></tr>
103<tr><td><a href="#postdomfrontier">-postdomfrontier</a></td><td>Post-Dominance Frontier Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]104<tr><td><a href="#postdomtree">-postdomtree</a></td><td>Post-Dominator Tree Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]105<tr><td><a href="#print-alias-sets">-print-alias-sets</a></td><td>Alias Set Printer</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]106<tr><td><a href="#print-callgraph">-print-callgraph</a></td><td>Print a call graph</td></tr>
107<tr><td><a href="#print-callgraph-sccs">-print-callgraph-sccs</a></td><td>Print SCCs of the Call Graph</td></tr>
108<tr><td><a href="#print-cfg-sccs">-print-cfg-sccs</a></td><td>Print SCCs of each function CFG</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]109<tr><td><a href="#print-dbginfo">-print-dbginfo</a></td><td>Print debug info in human readable form</td></tr>
110<tr><td><a href="#print-dom-info">-print-dom-info</a></td><td>Dominator Info Printer</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]111<tr><td><a href="#print-externalfnconstants">-print-externalfnconstants</a></td><td>Print external fn callsites passed constants</td></tr>
112<tr><td><a href="#print-function">-print-function</a></td><td>Print function to stderr</td></tr>
113<tr><td><a href="#print-module">-print-module</a></td><td>Print module to stderr</td></tr>
114<tr><td><a href="#print-used-types">-print-used-types</a></td><td>Find Used Types</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]115<tr><td><a href="#profile-estimator">-profile-estimator</a></td><td>Estimate profiling information</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]116<tr><td><a href="#profile-loader">-profile-loader</a></td><td>Load profile information from llvmprof.out</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]117<tr><td><a href="#profile-verifier">-profile-verifier</a></td><td>Verify profiling information</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]118<tr><td><a href="#regions">-regions</a></td><td>Detect single entry single exit regions</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]119<tr><td><a href="#scalar-evolution">-scalar-evolution</a></td><td>Scalar Evolution Analysis</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]120<tr><td><a href="#scev-aa">-scev-aa</a></td><td>ScalarEvolution-based Alias Analysis</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]121<tr><td><a href="#targetdata">-targetdata</a></td><td>Target Data Layout</td></tr>
122
123
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]124<tr><th colspan="2"><b>TRANSFORM PASSES</b></th></tr>
125<tr><th>Option</th><th>Name</th></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]126<tr><td><a href="#adce">-adce</a></td><td>Aggressive Dead Code Elimination</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]127<tr><td><a href="#always-inline">-always-inline</a></td><td>Inliner for always_inline functions</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]128<tr><td><a href="#argpromotion">-argpromotion</a></td><td>Promote 'by reference' arguments to scalars</td></tr>
129<tr><td><a href="#block-placement">-block-placement</a></td><td>Profile Guided Basic Block Placement</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]130<tr><td><a href="#break-crit-edges">-break-crit-edges</a></td><td>Break critical edges in CFG</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]131<tr><td><a href="#codegenprepare">-codegenprepare</a></td><td>Optimize for code generation</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]132<tr><td><a href="#constmerge">-constmerge</a></td><td>Merge Duplicate Global Constants</td></tr>
133<tr><td><a href="#constprop">-constprop</a></td><td>Simple constant propagation</td></tr>
134<tr><td><a href="#dce">-dce</a></td><td>Dead Code Elimination</td></tr>
135<tr><td><a href="#deadargelim">-deadargelim</a></td><td>Dead Argument Elimination</td></tr>
136<tr><td><a href="#deadtypeelim">-deadtypeelim</a></td><td>Dead Type Elimination</td></tr>
137<tr><td><a href="#die">-die</a></td><td>Dead Instruction Elimination</td></tr>
138<tr><td><a href="#dse">-dse</a></td><td>Dead Store Elimination</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]139<tr><td><a href="#functionattrs">-functionattrs</a></td><td>Deduce function attributes</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]140<tr><td><a href="#globaldce">-globaldce</a></td><td>Dead Global Elimination</td></tr>
141<tr><td><a href="#globalopt">-globalopt</a></td><td>Global Variable Optimizer</td></tr>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]142<tr><td><a href="#gvn">-gvn</a></td><td>Global Value Numbering</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]143<tr><td><a href="#indvars">-indvars</a></td><td>Canonicalize Induction Variables</td></tr>
144<tr><td><a href="#inline">-inline</a></td><td>Function Integration/Inlining</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]145<tr><td><a href="#insert-edge-profiling">-insert-edge-profiling</a></td><td>Insert instrumentation for edge profiling</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]146<tr><td><a href="#insert-optimal-edge-profiling">-insert-optimal-edge-profiling</a></td><td>Insert optimal instrumentation for edge profiling</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]147<tr><td><a href="#instcombine">-instcombine</a></td><td>Combine redundant instructions</td></tr>
148<tr><td><a href="#internalize">-internalize</a></td><td>Internalize Global Symbols</td></tr>
149<tr><td><a href="#ipconstprop">-ipconstprop</a></td><td>Interprocedural constant propagation</td></tr>
150<tr><td><a href="#ipsccp">-ipsccp</a></td><td>Interprocedural Sparse Conditional Constant Propagation</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]151<tr><td><a href="#jump-threading">-jump-threading</a></td><td>Jump Threading</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]152<tr><td><a href="#lcssa">-lcssa</a></td><td>Loop-Closed SSA Form Pass</td></tr>
153<tr><td><a href="#licm">-licm</a></td><td>Loop Invariant Code Motion</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]154<tr><td><a href="#loop-deletion">-loop-deletion</a></td><td>Delete dead loops</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]155<tr><td><a href="#loop-extract">-loop-extract</a></td><td>Extract loops into new functions</td></tr>
156<tr><td><a href="#loop-extract-single">-loop-extract-single</a></td><td>Extract at most one loop into a new function</td></tr>
157<tr><td><a href="#loop-reduce">-loop-reduce</a></td><td>Loop Strength Reduction</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]158<tr><td><a href="#loop-rotate">-loop-rotate</a></td><td>Rotate Loops</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]159<tr><td><a href="#loop-simplify">-loop-simplify</a></td><td>Canonicalize natural loops</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]160<tr><td><a href="#loop-unroll">-loop-unroll</a></td><td>Unroll loops</td></tr>
161<tr><td><a href="#loop-unswitch">-loop-unswitch</a></td><td>Unswitch loops</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]162<tr><td><a href="#loweratomic">-loweratomic</a></td><td>Lower atomic intrinsics to non-atomic form</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]163<tr><td><a href="#lowerinvoke">-lowerinvoke</a></td><td>Lower invoke and unwind, for unwindless code generators</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]164<tr><td><a href="#lowerswitch">-lowerswitch</a></td><td>Lower SwitchInst's to branches</td></tr>
165<tr><td><a href="#mem2reg">-mem2reg</a></td><td>Promote Memory to Register</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]166<tr><td><a href="#memcpyopt">-memcpyopt</a></td><td>MemCpy Optimization</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]167<tr><td><a href="#mergefunc">-mergefunc</a></td><td>Merge Functions</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]168<tr><td><a href="#mergereturn">-mergereturn</a></td><td>Unify function exit nodes</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]169<tr><td><a href="#partial-inliner">-partial-inliner</a></td><td>Partial Inliner</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]170<tr><td><a href="#prune-eh">-prune-eh</a></td><td>Remove unused exception handling info</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]171<tr><td><a href="#reassociate">-reassociate</a></td><td>Reassociate expressions</td></tr>
172<tr><td><a href="#reg2mem">-reg2mem</a></td><td>Demote all values to stack slots</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]173<tr><td><a href="#scalarrepl">-scalarrepl</a></td><td>Scalar Replacement of Aggregates (DT)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]174<tr><td><a href="#sccp">-sccp</a></td><td>Sparse Conditional Constant Propagation</td></tr>
175<tr><td><a href="#simplify-libcalls">-simplify-libcalls</a></td><td>Simplify well-known library calls</td></tr>
176<tr><td><a href="#simplifycfg">-simplifycfg</a></td><td>Simplify the CFG</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]177<tr><td><a href="#sink">-sink</a></td><td>Code sinking</td></tr>
178<tr><td><a href="#sretpromotion">-sretpromotion</a></td><td>Promote sret arguments to multiple ret values</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]179<tr><td><a href="#strip">-strip</a></td><td>Strip all symbols from a module</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]180<tr><td><a href="#strip-dead-debug-info">-strip-dead-debug-info</a></td><td>Strip debug info for unused symbols</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]181<tr><td><a href="#strip-dead-prototypes">-strip-dead-prototypes</a></td><td>Strip Unused Function Prototypes</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]182<tr><td><a href="#strip-debug-declare">-strip-debug-declare</a></td><td>Strip all llvm.dbg.declare intrinsics</td></tr>
183<tr><td><a href="#strip-nondebug">-strip-nondebug</a></td><td>Strip all symbols, except dbg symbols, from a module</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]184<tr><td><a href="#tailcallelim">-tailcallelim</a></td><td>Tail Call Elimination</td></tr>
185<tr><td><a href="#tailduplicate">-tailduplicate</a></td><td>Tail Duplication</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]186
187
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]188<tr><th colspan="2"><b>UTILITY PASSES</b></th></tr>
189<tr><th>Option</th><th>Name</th></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]190<tr><td><a href="#deadarghaX0r">-deadarghaX0r</a></td><td>Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</td></tr>
191<tr><td><a href="#extract-blocks">-extract-blocks</a></td><td>Extract Basic Blocks From Module (for bugpoint use)</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]192<tr><td><a href="#instnamer">-instnamer</a></td><td>Assign names to anonymous instructions</td></tr>
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]193<tr><td><a href="#preverify">-preverify</a></td><td>Preliminary module verification</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]194<tr><td><a href="#verify">-verify</a></td><td>Module Verifier</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]195<tr><td><a href="#view-cfg">-view-cfg</a></td><td>View CFG of function</td></tr>
196<tr><td><a href="#view-cfg-only">-view-cfg-only</a></td><td>View CFG of function (with no function bodies)</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]197<tr><td><a href="#view-dom">-view-dom</a></td><td>View dominance tree of function</td></tr>
198<tr><td><a href="#view-dom-only">-view-dom-only</a></td><td>View dominance tree of function (with no function bodies)</td></tr>
199<tr><td><a href="#view-postdom">-view-postdom</a></td><td>View postdominance tree of function</td></tr>
200<tr><td><a href="#view-postdom-only">-view-postdom-only</a></td><td>View postdominance tree of function (with no function bodies)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]201</table>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]202
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]203</div>
204
205<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]206<h2><a name="analyses">Analysis Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]207<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]208 <p>This section describes the LLVM Analysis Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]209
210<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]211<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]212 <a name="aa-eval">-aa-eval: Exhaustive Alias Analysis Precision Evaluator</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]213</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]214<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]215 <p>This is a simple N^2 alias analysis accuracy evaluator.
216 Basically, for each function in the program, it simply queries to see how the
217 alias analysis implementation answers alias queries between each pair of
218 pointers in the function.</p>
219
220 <p>This is inspired and adapted from code by: Naveen Neelakantam, Francesco
221 Spadini, and Wojciech Stryjewski.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]222</div>
223
224<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]225<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]226 <a name="basicaa">-basicaa: Basic Alias Analysis (stateless AA impl)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]227</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]228<div>
Eli Friedman146af5a2011-10-27 22:32:13 +0000[diff] [blame]229 <p>A basic alias analysis pass that implements identities (two different
230 globals cannot alias, etc), but does no stateful analysis.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]231</div>
232
233<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]234<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]235 <a name="basiccg">-basiccg: Basic CallGraph Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]236</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]237<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]238 <p>Yet to be written.</p>
239</div>
240
241<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]242<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]243 <a name="count-aa">-count-aa: Count Alias Analysis Query Responses</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]244</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]245<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]246 <p>
247 A pass which can be used to count how many alias queries
248 are being made and how the alias analysis implementation being used responds.
249 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]250</div>
251
252<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]253<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]254 <a name="debug-aa">-debug-aa: AA use debugger</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]255</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]256<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]257 <p>
258 This simple pass checks alias analysis users to ensure that if they
259 create a new value, they do not query AA without informing it of the value.
260 It acts as a shim over any other AA pass you want.
261 </p>
262
263 <p>
264 Yes keeping track of every value in the program is expensive, but this is
265 a debugging pass.
266 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]267</div>
268
269<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]270<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]271 <a name="domfrontier">-domfrontier: Dominance Frontier Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]272</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]273<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]274 <p>
275 This pass is a simple dominator construction algorithm for finding forward
276 dominator frontiers.
277 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]278</div>
279
280<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]281<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]282 <a name="domtree">-domtree: Dominator Tree Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]283</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]284<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]285 <p>
286 This pass is a simple dominator construction algorithm for finding forward
287 dominators.
288 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]289</div>
290
291<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]292<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]293 <a name="dot-callgraph">-dot-callgraph: Print Call Graph to 'dot' file</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]294</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]295<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]296 <p>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]297 This pass, only available in <code>opt</code>, prints the call graph into a
298 <code>.dot</code> graph. This graph can then be processed with the "dot" tool
299 to convert it to postscript or some other suitable format.
300 </p>
301</div>
302
303<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]304<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]305 <a name="dot-cfg">-dot-cfg: Print CFG of function to 'dot' file</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]306</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]307<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]308 <p>
309 This pass, only available in <code>opt</code>, prints the control flow graph
310 into a <code>.dot</code> graph. This graph can then be processed with the
311 "dot" tool to convert it to postscript or some other suitable format.
312 </p>
313</div>
314
315<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]316<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]317 <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]318</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]319<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]320 <p>
321 This pass, only available in <code>opt</code>, prints the control flow graph
322 into a <code>.dot</code> graph, omitting the function bodies. This graph can
323 then be processed with the "dot" tool to convert it to postscript or some
324 other suitable format.
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]325 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]326</div>
327
328<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]329<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]330 <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]331</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]332<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]333 <p>
334 This pass, only available in <code>opt</code>, prints the dominator tree
335 into a <code>.dot</code> graph. This graph can then be processed with the
336 "dot" tool to convert it to postscript or some other suitable format.
337 </p>
338</div>
339
340<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]341<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]342 <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]343</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]344<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]345 <p>
346 This pass, only available in <code>opt</code>, prints the dominator tree
347 into a <code>.dot</code> graph, omitting the function bodies. This graph can
348 then be processed with the "dot" tool to convert it to postscript or some
349 other suitable format.
350 </p>
351</div>
352
353<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]354<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]355 <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]356</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]357<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]358 <p>
359 This pass, only available in <code>opt</code>, prints the post dominator tree
360 into a <code>.dot</code> graph. This graph can then be processed with the
361 "dot" tool to convert it to postscript or some other suitable format.
362 </p>
363</div>
364
365<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]366<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]367 <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]368</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]369<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]370 <p>
371 This pass, only available in <code>opt</code>, prints the post dominator tree
372 into a <code>.dot</code> graph, omitting the function bodies. This graph can
373 then be processed with the "dot" tool to convert it to postscript or some
374 other suitable format.
375 </p>
376</div>
377
378<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]379<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]380 <a name="globalsmodref-aa">-globalsmodref-aa: Simple mod/ref analysis for globals</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]381</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]382<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]383 <p>
384 This simple pass provides alias and mod/ref information for global values
385 that do not have their address taken, and keeps track of whether functions
386 read or write memory (are "pure"). For this simple (but very common) case,
387 we can provide pretty accurate and useful information.
388 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]389</div>
390
391<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]392<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]393 <a name="instcount">-instcount: Counts the various types of Instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]394</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]395<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]396 <p>
397 This pass collects the count of all instructions and reports them
398 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]399</div>
400
401<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]402<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]403 <a name="intervals">-intervals: Interval Partition Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]404</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]405<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]406 <p>
407 This analysis calculates and represents the interval partition of a function,
408 or a preexisting interval partition.
409 </p>
410
411 <p>
412 In this way, the interval partition may be used to reduce a flow graph down
413 to its degenerate single node interval partition (unless it is irreducible).
414 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]415</div>
416
417<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]418<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]419 <a name="iv-users">-iv-users: Induction Variable Users</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]420</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]421<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]422 <p>Bookkeeping for "interesting" users of expressions computed from
423 induction variables.</p>
424</div>
425
426<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]427<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]428 <a name="lazy-value-info">-lazy-value-info: Lazy Value Information Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]429</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]430<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]431 <p>Interface for lazy computation of value constraint information.</p>
432</div>
433
434<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]435<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]436 <a name="lda">-lda: Loop Dependence Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]437</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]438<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]439 <p>Loop dependence analysis framework, which is used to detect dependences in
440 memory accesses in loops.</p>
441</div>
442
443<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]444<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]445 <a name="libcall-aa">-libcall-aa: LibCall Alias Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]446</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]447<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]448 <p>LibCall Alias Analysis.</p>
449</div>
450
451<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]452<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]453 <a name="lint">-lint: Statically lint-checks LLVM IR</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]454</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]455<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]456 <p>This pass statically checks for common and easily-identified constructs
457 which produce undefined or likely unintended behavior in LLVM IR.</p>
458
459 <p>It is not a guarantee of correctness, in two ways. First, it isn't
460 comprehensive. There are checks which could be done statically which are
461 not yet implemented. Some of these are indicated by TODO comments, but
462 those aren't comprehensive either. Second, many conditions cannot be
463 checked statically. This pass does no dynamic instrumentation, so it
464 can't check for all possible problems.</p>
465
466 <p>Another limitation is that it assumes all code will be executed. A store
467 through a null pointer in a basic block which is never reached is harmless,
468 but this pass will warn about it anyway.</p>
469
470 <p>Optimization passes may make conditions that this pass checks for more or
471 less obvious. If an optimization pass appears to be introducing a warning,
472 it may be that the optimization pass is merely exposing an existing
473 condition in the code.</p>
474
475 <p>This code may be run before instcombine. In many cases, instcombine checks
476 for the same kinds of things and turns instructions with undefined behavior
477 into unreachable (or equivalent). Because of this, this pass makes some
478 effort to look through bitcasts and so on.
479 </p>
480</div>
481
482<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]483<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]484 <a name="loops">-loops: Natural Loop Information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]485</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]486<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]487 <p>
488 This analysis is used to identify natural loops and determine the loop depth
489 of various nodes of the CFG. Note that the loops identified may actually be
490 several natural loops that share the same header node... not just a single
491 natural loop.
492 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]493</div>
494
495<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]496<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]497 <a name="memdep">-memdep: Memory Dependence Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]498</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]499<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]500 <p>
501 An analysis that determines, for a given memory operation, what preceding
502 memory operations it depends on. It builds on alias analysis information, and
503 tries to provide a lazy, caching interface to a common kind of alias
504 information query.
505 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]506</div>
507
508<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]509<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]510 <a name="module-debuginfo">-module-debuginfo: Decodes module-level debug info</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]511</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]512<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]513 <p>This pass decodes the debug info metadata in a module and prints in a
514 (sufficiently-prepared-) human-readable form.
515
516 For example, run this pass from opt along with the -analyze option, and
517 it'll print to standard output.
518 </p>
519</div>
520
521<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]522<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]523 <a name="no-aa">-no-aa: No Alias Analysis (always returns 'may' alias)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]524</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]525<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]526 <p>
Eli Friedman146af5a2011-10-27 22:32:13 +0000[diff] [blame]527 This is the default implementation of the Alias Analysis interface. It always
528 returns "I don't know" for alias queries. NoAA is unlike other alias analysis
529 implementations, in that it does not chain to a previous analysis. As such it
530 doesn't follow many of the rules that other alias analyses must.
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]531 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]532</div>
533
534<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]535<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]536 <a name="no-profile">-no-profile: No Profile Information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]537</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]538<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]539 <p>
540 The default "no profile" implementation of the abstract
541 <code>ProfileInfo</code> interface.
542 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]543</div>
544
545<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]546<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]547 <a name="postdomfrontier">-postdomfrontier: Post-Dominance Frontier Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]548</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]549<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]550 <p>
551 This pass is a simple post-dominator construction algorithm for finding
552 post-dominator frontiers.
553 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]554</div>
555
556<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]557<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]558 <a name="postdomtree">-postdomtree: Post-Dominator Tree Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]559</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]560<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]561 <p>
562 This pass is a simple post-dominator construction algorithm for finding
563 post-dominators.
564 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]565</div>
566
567<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]568<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]569 <a name="print-alias-sets">-print-alias-sets: Alias Set Printer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]570</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]571<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]572 <p>Yet to be written.</p>
573</div>
574
575<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]576<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]577 <a name="print-callgraph">-print-callgraph: Print a call graph</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]578</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]579<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]580 <p>
581 This pass, only available in <code>opt</code>, prints the call graph to
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]582 standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]583 </p>
584</div>
585
586<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]587<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]588 <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]589</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]590<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]591 <p>
592 This pass, only available in <code>opt</code>, prints the SCCs of the call
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]593 graph to standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]594 </p>
595</div>
596
597<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]598<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]599 <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]600</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]601<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]602 <p>
603 This pass, only available in <code>opt</code>, prints the SCCs of each
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]604 function CFG to standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]605 </p>
606</div>
607
608<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]609<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]610 <a name="print-dbginfo">-print-dbginfo: Print debug info in human readable form</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]611</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]612<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]613 <p>Pass that prints instructions, and associated debug info:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]614 <ul>
615
616 <li>source/line/col information</li>
617 <li>original variable name</li>
618 <li>original type name</li>
619 </ul>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]620</div>
621
622<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]623<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]624 <a name="print-dom-info">-print-dom-info: Dominator Info Printer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]625</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]626<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]627 <p>Dominator Info Printer.</p>
628</div>
629
630<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]631<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]632 <a name="print-externalfnconstants">-print-externalfnconstants: Print external fn callsites passed constants</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]633</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]634<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]635 <p>
636 This pass, only available in <code>opt</code>, prints out call sites to
637 external functions that are called with constant arguments. This can be
638 useful when looking for standard library functions we should constant fold
639 or handle in alias analyses.
640 </p>
641</div>
642
643<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]644<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]645 <a name="print-function">-print-function: Print function to stderr</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]646</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]647<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]648 <p>
649 The <code>PrintFunctionPass</code> class is designed to be pipelined with
650 other <code>FunctionPass</code>es, and prints out the functions of the module
651 as they are processed.
652 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]653</div>
654
655<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]656<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]657 <a name="print-module">-print-module: Print module to stderr</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]658</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]659<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]660 <p>
661 This pass simply prints out the entire module when it is executed.
662 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]663</div>
664
665<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]666<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]667 <a name="print-used-types">-print-used-types: Find Used Types</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]668</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]669<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]670 <p>
671 This pass is used to seek out all of the types in use by the program. Note
672 that this analysis explicitly does not include types only used by the symbol
673 table.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]674</div>
675
676<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]677<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]678 <a name="profile-estimator">-profile-estimator: Estimate profiling information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]679</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]680<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]681 <p>Profiling information that estimates the profiling information
682 in a very crude and unimaginative way.
683 </p>
684</div>
685
686<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]687<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]688 <a name="profile-loader">-profile-loader: Load profile information from llvmprof.out</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]689</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]690<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]691 <p>
692 A concrete implementation of profiling information that loads the information
693 from a profile dump file.
694 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]695</div>
696
697<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]698<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]699 <a name="profile-verifier">-profile-verifier: Verify profiling information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]700</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]701<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]702 <p>Pass that checks profiling information for plausibility.</p>
703</div>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]704<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]705 <a name="regions">-regions: Detect single entry single exit regions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]706</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]707<div>
Tobias Grosserf96b0062010-07-22 07:46:31 +0000[diff] [blame]708 <p>
709 The <code>RegionInfo</code> pass detects single entry single exit regions in a
710 function, where a region is defined as any subgraph that is connected to the
711 remaining graph at only two spots. Furthermore, an hierarchical region tree is
712 built.
713 </p>
714</div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]715
716<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]717<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]718 <a name="scalar-evolution">-scalar-evolution: Scalar Evolution Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]719</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]720<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]721 <p>
722 The <code>ScalarEvolution</code> analysis can be used to analyze and
723 catagorize scalar expressions in loops. It specializes in recognizing general
724 induction variables, representing them with the abstract and opaque
725 <code>SCEV</code> class. Given this analysis, trip counts of loops and other
726 important properties can be obtained.
727 </p>
728
729 <p>
730 This analysis is primarily useful for induction variable substitution and
731 strength reduction.
732 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]733</div>
734
735<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]736<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]737 <a name="scev-aa">-scev-aa: ScalarEvolution-based Alias Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]738</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]739<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]740 <p>Simple alias analysis implemented in terms of ScalarEvolution queries.
741
742 This differs from traditional loop dependence analysis in that it tests
743 for dependencies within a single iteration of a loop, rather than
744 dependencies between different iterations.
745
746 ScalarEvolution has a more complete understanding of pointer arithmetic
747 than BasicAliasAnalysis' collection of ad-hoc analyses.
748 </p>
749</div>
750
751<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]752<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]753 <a name="targetdata">-targetdata: Target Data Layout</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]754</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]755<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]756 <p>Provides other passes access to information on how the size and alignment
757 required by the the target ABI for various data types.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]758</div>
759
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]760</div>
761
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]762<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]763<h2><a name="transforms">Transform Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]764<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]765 <p>This section describes the LLVM Transform Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]766
767<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]768<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]769 <a name="adce">-adce: Aggressive Dead Code Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]770</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]771<div>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]772 <p>ADCE aggressively tries to eliminate code. This pass is similar to
773 <a href="#dce">DCE</a> but it assumes that values are dead until proven
774 otherwise. This is similar to <a href="#sccp">SCCP</a>, except applied to
775 the liveness of values.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]776</div>
777
778<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]779<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]780 <a name="always-inline">-always-inline: Inliner for always_inline functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]781</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]782<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]783 <p>A custom inliner that handles only functions that are marked as
784 "always inline".</p>
785</div>
786
787<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]788<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]789 <a name="argpromotion">-argpromotion: Promote 'by reference' arguments to scalars</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]790</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]791<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]792 <p>
793 This pass promotes "by reference" arguments to be "by value" arguments. In
794 practice, this means looking for internal functions that have pointer
795 arguments. If it can prove, through the use of alias analysis, that an
796 argument is *only* loaded, then it can pass the value into the function
797 instead of the address of the value. This can cause recursive simplification
798 of code and lead to the elimination of allocas (especially in C++ template
799 code like the STL).
800 </p>
801
802 <p>
803 This pass also handles aggregate arguments that are passed into a function,
804 scalarizing them if the elements of the aggregate are only loaded. Note that
805 it refuses to scalarize aggregates which would require passing in more than
806 three operands to the function, because passing thousands of operands for a
807 large array or structure is unprofitable!
808 </p>
809
810 <p>
811 Note that this transformation could also be done for arguments that are only
812 stored to (returning the value instead), but does not currently. This case
813 would be best handled when and if LLVM starts supporting multiple return
814 values from functions.
815 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]816</div>
817
818<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]819<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]820 <a name="block-placement">-block-placement: Profile Guided Basic Block Placement</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]821</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]822<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]823 <p>This pass is a very simple profile guided basic block placement algorithm.
824 The idea is to put frequently executed blocks together at the start of the
825 function and hopefully increase the number of fall-through conditional
826 branches. If there is no profile information for a particular function, this
827 pass basically orders blocks in depth-first order.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]828</div>
829
830<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]831<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]832 <a name="break-crit-edges">-break-crit-edges: Break critical edges in CFG</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]833</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]834<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]835 <p>
836 Break all of the critical edges in the CFG by inserting a dummy basic block.
837 It may be "required" by passes that cannot deal with critical edges. This
838 transformation obviously invalidates the CFG, but can update forward dominator
839 (set, immediate dominators, tree, and frontier) information.
840 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]841</div>
842
843<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]844<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]845 <a name="codegenprepare">-codegenprepare: Optimize for code generation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]846</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]847<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]848 This pass munges the code in the input function to better prepare it for
849 SelectionDAG-based code generation. This works around limitations in it's
850 basic-block-at-a-time approach. It should eventually be removed.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]851</div>
852
853<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]854<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]855 <a name="constmerge">-constmerge: Merge Duplicate Global Constants</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]856</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]857<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]858 <p>
859 Merges duplicate global constants together into a single constant that is
860 shared. This is useful because some passes (ie TraceValues) insert a lot of
861 string constants into the program, regardless of whether or not an existing
862 string is available.
863 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]864</div>
865
866<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]867<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]868 <a name="constprop">-constprop: Simple constant propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]869</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]870<div>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]871 <p>This file implements constant propagation and merging. It looks for
872 instructions involving only constant operands and replaces them with a
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]873 constant value instead of an instruction. For example:</p>
874 <blockquote><pre>add i32 1, 2</pre></blockquote>
875 <p>becomes</p>
876 <blockquote><pre>i32 3</pre></blockquote>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]877 <p>NOTE: this pass has a habit of making definitions be dead. It is a good
878 idea to to run a <a href="#die">DIE</a> (Dead Instruction Elimination) pass
879 sometime after running this pass.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]880</div>
881
882<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]883<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]884 <a name="dce">-dce: Dead Code Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]885</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]886<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]887 <p>
888 Dead code elimination is similar to <a href="#die">dead instruction
889 elimination</a>, but it rechecks instructions that were used by removed
890 instructions to see if they are newly dead.
891 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]892</div>
893
894<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]895<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]896 <a name="deadargelim">-deadargelim: Dead Argument Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]897</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]898<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]899 <p>
900 This pass deletes dead arguments from internal functions. Dead argument
901 elimination removes arguments which are directly dead, as well as arguments
902 only passed into function calls as dead arguments of other functions. This
903 pass also deletes dead arguments in a similar way.
904 </p>
905
906 <p>
907 This pass is often useful as a cleanup pass to run after aggressive
908 interprocedural passes, which add possibly-dead arguments.
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="deadtypeelim">-deadtypeelim: Dead Type 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 is used to cleanup the output of GCC. It eliminate names for types
919 that are unused in the entire translation unit, using the <a
920 href="#findusedtypes">find used types</a> pass.
921 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]922</div>
923
924<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]925<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]926 <a name="die">-die: Dead Instruction Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]927</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]928<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]929 <p>
930 Dead instruction elimination performs a single pass over the function,
931 removing instructions that are obviously dead.
932 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]933</div>
934
935<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]936<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]937 <a name="dse">-dse: Dead Store Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]938</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]939<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]940 <p>
941 A trivial dead store elimination that only considers basic-block local
942 redundant stores.
943 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]944</div>
945
946<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]947<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]948 <a name="functionattrs">-functionattrs: Deduce function attributes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]949</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]950<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]951 <p>A simple interprocedural pass which walks the call-graph, looking for
952 functions which do not access or only read non-local memory, and marking them
953 readnone/readonly. In addition, it marks function arguments (of pointer type)
954 'nocapture' if a call to the function does not create any copies of the pointer
955 value that outlive the call. This more or less means that the pointer is only
956 dereferenced, and not returned from the function or stored in a global.
957 This pass is implemented as a bottom-up traversal of the call-graph.
958 </p>
959</div>
960
961<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]962<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]963 <a name="globaldce">-globaldce: Dead Global Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]964</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]965<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]966 <p>
967 This transform is designed to eliminate unreachable internal globals from the
968 program. It uses an aggressive algorithm, searching out globals that are
969 known to be alive. After it finds all of the globals which are needed, it
970 deletes whatever is left over. This allows it to delete recursive chunks of
971 the program which are unreachable.
972 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]973</div>
974
975<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]976<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]977 <a name="globalopt">-globalopt: Global Variable Optimizer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]978</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]979<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]980 <p>
981 This pass transforms simple global variables that never have their address
982 taken. If obviously true, it marks read/write globals as constant, deletes
983 variables only stored to, etc.
984 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]985</div>
986
987<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]988<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]989 <a name="gvn">-gvn: Global Value Numbering</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]990</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]991<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]992 <p>
Chris Lattner60f03402009-10-10 18:40:48 +0000[diff] [blame]993 This pass performs global value numbering to eliminate fully and partially
994 redundant instructions. It also performs redundant load elimination.
Matthijs Kooijman845f5242008-06-05 07:55:49 +0000[diff] [blame]995 </p>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]996</div>
997
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]998<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]999<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1000 <a name="indvars">-indvars: Canonicalize Induction Variables</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1001</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1002<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1003 <p>
1004 This transformation analyzes and transforms the induction variables (and
1005 computations derived from them) into simpler forms suitable for subsequent
1006 analysis and transformation.
1007 </p>
1008
1009 <p>
1010 This transformation makes the following changes to each loop with an
1011 identifiable induction variable:
1012 </p>
1013
1014 <ol>
1015 <li>All loops are transformed to have a <em>single</em> canonical
1016 induction variable which starts at zero and steps by one.</li>
1017 <li>The canonical induction variable is guaranteed to be the first PHI node
1018 in the loop header block.</li>
1019 <li>Any pointer arithmetic recurrences are raised to use array
1020 subscripts.</li>
1021 </ol>
1022
1023 <p>
1024 If the trip count of a loop is computable, this pass also makes the following
1025 changes:
1026 </p>
1027
1028 <ol>
1029 <li>The exit condition for the loop is canonicalized to compare the
1030 induction value against the exit value. This turns loops like:
1031 <blockquote><pre>for (i = 7; i*i < 1000; ++i)</pre></blockquote>
1032 into
1033 <blockquote><pre>for (i = 0; i != 25; ++i)</pre></blockquote></li>
1034 <li>Any use outside of the loop of an expression derived from the indvar
1035 is changed to compute the derived value outside of the loop, eliminating
1036 the dependence on the exit value of the induction variable. If the only
1037 purpose of the loop is to compute the exit value of some derived
1038 expression, this transformation will make the loop dead.</li>
Gordon Henriksene626bbe2007-11-04 16:17:00 +0000[diff] [blame]1039 </ol>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1040
1041 <p>
1042 This transformation should be followed by strength reduction after all of the
1043 desired loop transformations have been performed. Additionally, on targets
1044 where it is profitable, the loop could be transformed to count down to zero
1045 (the "do loop" optimization).
1046 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1047</div>
1048
1049<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1050<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1051 <a name="inline">-inline: Function Integration/Inlining</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1052</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1053<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1054 <p>
1055 Bottom-up inlining of functions into callees.
1056 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1057</div>
1058
1059<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1060<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1061 <a name="insert-edge-profiling">-insert-edge-profiling: Insert instrumentation for edge profiling</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1062</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1063<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1064 <p>
1065 This pass instruments the specified program with counters for edge profiling.
1066 Edge profiling can give a reasonable approximation of the hot paths through a
1067 program, and is used for a wide variety of program transformations.
1068 </p>
1069
1070 <p>
1071 Note that this implementation is very naïve. It inserts a counter for
1072 <em>every</em> edge in the program, instead of using control flow information
1073 to prune the number of counters inserted.
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-optimal-edge-profiling">-insert-optimal-edge-profiling: Insert optimal 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>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1082 <p>This pass instruments the specified program with counters for edge profiling.
1083 Edge profiling can give a reasonable approximation of the hot paths through a
1084 program, and is used for a wide variety of program transformations.
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1085 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1086</div>
1087
1088<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1089<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1090 <a name="instcombine">-instcombine: Combine redundant instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1091</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1092<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1093 <p>
1094 Combine instructions to form fewer, simple
1095 instructions. This pass does not modify the CFG This pass is where algebraic
1096 simplification happens.
1097 </p>
1098
1099 <p>
1100 This pass combines things like:
1101 </p>
1102
1103<blockquote><pre
1104>%Y = add i32 %X, 1
1105%Z = add i32 %Y, 1</pre></blockquote>
1106
1107 <p>
1108 into:
1109 </p>
1110
1111<blockquote><pre
1112>%Z = add i32 %X, 2</pre></blockquote>
1113
1114 <p>
1115 This is a simple worklist driven algorithm.
1116 </p>
1117
1118 <p>
1119 This pass guarantees that the following canonicalizations are performed on
1120 the program:
1121 </p>
1122
1123 <ul>
1124 <li>If a binary operator has a constant operand, it is moved to the right-
1125 hand side.</li>
1126 <li>Bitwise operators with constant operands are always grouped so that
1127 shifts are performed first, then <code>or</code>s, then
1128 <code>and</code>s, then <code>xor</code>s.</li>
1129 <li>Compare instructions are converted from <code>&lt;</code>,
1130 <code>&gt;</code>, <code>≤</code>, or <code>≥</code> to
1131 <code>=</code> or <code>≠</code> if possible.</li>
1132 <li>All <code>cmp</code> instructions on boolean values are replaced with
1133 logical operations.</li>
1134 <li><code>add <var>X</var>, <var>X</var></code> is represented as
1135 <code>mul <var>X</var>, 2</code> ⇒ <code>shl <var>X</var>, 1</code></li>
1136 <li>Multiplies with a constant power-of-two argument are transformed into
1137 shifts.</li>
1138 <li>… etc.</li>
1139 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1140</div>
1141
1142<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1143<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1144 <a name="internalize">-internalize: Internalize Global Symbols</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1145</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1146<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1147 <p>
1148 This pass loops over all of the functions in the input module, looking for a
1149 main function. If a main function is found, all other functions and all
1150 global variables with initializers are marked as internal.
1151 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1152</div>
1153
1154<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1155<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1156 <a name="ipconstprop">-ipconstprop: Interprocedural constant propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1157</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1158<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1159 <p>
1160 This pass implements an <em>extremely</em> simple interprocedural constant
1161 propagation pass. It could certainly be improved in many different ways,
1162 like using a worklist. This pass makes arguments dead, but does not remove
1163 them. The existing dead argument elimination pass should be run after this
1164 to clean up the mess.
1165 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1166</div>
1167
1168<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1169<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1170 <a name="ipsccp">-ipsccp: Interprocedural Sparse Conditional Constant Propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1171</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1172<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1173 <p>
1174 An interprocedural variant of <a href="#sccp">Sparse Conditional Constant
1175 Propagation</a>.
1176 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1177</div>
1178
1179<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1180<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1181 <a name="jump-threading">-jump-threading: Jump Threading</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1182</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1183<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1184 <p>
1185 Jump threading tries to find distinct threads of control flow running through
1186 a basic block. This pass looks at blocks that have multiple predecessors and
1187 multiple successors. If one or more of the predecessors of the block can be
1188 proven to always cause a jump to one of the successors, we forward the edge
1189 from the predecessor to the successor by duplicating the contents of this
1190 block.
1191 </p>
1192 <p>
1193 An example of when this can occur is code like this:
1194 </p>
1195
1196 <pre
1197>if () { ...
1198 X = 4;
1199}
1200if (X &lt; 3) {</pre>
1201
1202 <p>
1203 In this case, the unconditional branch at the end of the first if can be
1204 revectored to the false side of the second if.
1205 </p>
1206</div>
1207
1208<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1209<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1210 <a name="lcssa">-lcssa: Loop-Closed SSA Form Pass</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1211</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1212<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1213 <p>
1214 This pass transforms loops by placing phi nodes at the end of the loops for
1215 all values that are live across the loop boundary. For example, it turns
1216 the left into the right code:
1217 </p>
1218
1219 <pre
1220>for (...) for (...)
1221 if (c) if (c)
1222 X1 = ... X1 = ...
1223 else else
1224 X2 = ... X2 = ...
1225 X3 = phi(X1, X2) X3 = phi(X1, X2)
1226... = X3 + 4 X4 = phi(X3)
1227 ... = X4 + 4</pre>
1228
1229 <p>
1230 This is still valid LLVM; the extra phi nodes are purely redundant, and will
1231 be trivially eliminated by <code>InstCombine</code>. The major benefit of
1232 this transformation is that it makes many other loop optimizations, such as
1233 LoopUnswitching, simpler.
1234 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1235</div>
1236
1237<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1238<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1239 <a name="licm">-licm: Loop Invariant Code Motion</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1240</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1241<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1242 <p>
1243 This pass performs loop invariant code motion, attempting to remove as much
1244 code from the body of a loop as possible. It does this by either hoisting
1245 code into the preheader block, or by sinking code to the exit blocks if it is
1246 safe. This pass also promotes must-aliased memory locations in the loop to
1247 live in registers, thus hoisting and sinking "invariant" loads and stores.
1248 </p>
1249
1250 <p>
1251 This pass uses alias analysis for two purposes:
1252 </p>
1253
1254 <ul>
1255 <li>Moving loop invariant loads and calls out of loops. If we can determine
1256 that a load or call inside of a loop never aliases anything stored to,
1257 we can hoist it or sink it like any other instruction.</li>
1258 <li>Scalar Promotion of Memory - If there is a store instruction inside of
1259 the loop, we try to move the store to happen AFTER the loop instead of
1260 inside of the loop. This can only happen if a few conditions are true:
1261 <ul>
1262 <li>The pointer stored through is loop invariant.</li>
1263 <li>There are no stores or loads in the loop which <em>may</em> alias
1264 the pointer. There are no calls in the loop which mod/ref the
1265 pointer.</li>
1266 </ul>
1267 If these conditions are true, we can promote the loads and stores in the
1268 loop of the pointer to use a temporary alloca'd variable. We then use
1269 the mem2reg functionality to construct the appropriate SSA form for the
1270 variable.</li>
1271 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1272</div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1273
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1274<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1275<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1276 <a name="loop-deletion">-loop-deletion: Delete dead loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1277</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1278<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1279 <p>
1280 This file implements the Dead Loop Deletion Pass. This pass is responsible
1281 for eliminating loops with non-infinite computable trip counts that have no
1282 side effects or volatile instructions, and do not contribute to the
1283 computation of the function's return value.
1284 </p>
1285</div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1286
1287<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1288<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1289 <a name="loop-extract">-loop-extract: Extract loops into new functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1290</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1291<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1292 <p>
1293 A pass wrapper around the <code>ExtractLoop()</code> scalar transformation to
1294 extract each top-level loop into its own new function. If the loop is the
1295 <em>only</em> loop in a given function, it is not touched. This is a pass most
1296 useful for debugging via bugpoint.
1297 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1298</div>
1299
1300<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1301<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1302 <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]1303</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1304<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1305 <p>
1306 Similar to <a href="#loop-extract">Extract loops into new functions</a>,
1307 this pass extracts one natural loop from the program into a function if it
1308 can. This is used by bugpoint.
1309 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1310</div>
1311
1312<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1313<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1314 <a name="loop-reduce">-loop-reduce: Loop Strength Reduction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1315</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1316<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1317 <p>
1318 This pass performs a strength reduction on array references inside loops that
1319 have as one or more of their components the loop induction variable. This is
1320 accomplished by creating a new value to hold the initial value of the array
1321 access for the first iteration, and then creating a new GEP instruction in
1322 the loop to increment the value by the appropriate amount.
1323 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1324</div>
1325
1326<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1327<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1328 <a name="loop-rotate">-loop-rotate: Rotate Loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1329</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1330<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1331 <p>A simple loop rotation transformation.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1332</div>
1333
1334<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1335<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1336 <a name="loop-simplify">-loop-simplify: Canonicalize natural loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1337</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1338<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1339 <p>
1340 This pass performs several transformations to transform natural loops into a
1341 simpler form, which makes subsequent analyses and transformations simpler and
1342 more effective.
1343 </p>
1344
1345 <p>
1346 Loop pre-header insertion guarantees that there is a single, non-critical
1347 entry edge from outside of the loop to the loop header. This simplifies a
1348 number of analyses and transformations, such as LICM.
1349 </p>
1350
1351 <p>
1352 Loop exit-block insertion guarantees that all exit blocks from the loop
1353 (blocks which are outside of the loop that have predecessors inside of the
1354 loop) only have predecessors from inside of the loop (and are thus dominated
1355 by the loop header). This simplifies transformations such as store-sinking
1356 that are built into LICM.
1357 </p>
1358
1359 <p>
1360 This pass also guarantees that loops will have exactly one backedge.
1361 </p>
1362
1363 <p>
1364 Note that the simplifycfg pass will clean up blocks which are split out but
1365 end up being unnecessary, so usage of this pass should not pessimize
1366 generated code.
1367 </p>
1368
1369 <p>
1370 This pass obviously modifies the CFG, but updates loop information and
1371 dominator information.
1372 </p>
1373</div>
1374
1375<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1376<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1377 <a name="loop-unroll">-loop-unroll: Unroll loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1378</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1379<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1380 <p>
1381 This pass implements a simple loop unroller. It works best when loops have
1382 been canonicalized by the <a href="#indvars"><tt>-indvars</tt></a> pass,
1383 allowing it to determine the trip counts of loops easily.
1384 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1385</div>
1386
1387<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1388<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1389 <a name="loop-unswitch">-loop-unswitch: Unswitch loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1390</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1391<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1392 <p>
1393 This pass transforms loops that contain branches on loop-invariant conditions
1394 to have multiple loops. For example, it turns the left into the right code:
1395 </p>
1396
1397 <pre
1398>for (...) if (lic)
1399 A for (...)
1400 if (lic) A; B; C
1401 B else
1402 C for (...)
1403 A; C</pre>
1404
1405 <p>
1406 This can increase the size of the code exponentially (doubling it every time
1407 a loop is unswitched) so we only unswitch if the resultant code will be
1408 smaller than a threshold.
1409 </p>
1410
1411 <p>
1412 This pass expects LICM to be run before it to hoist invariant conditions out
1413 of the loop, to make the unswitching opportunity obvious.
1414 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1415</div>
1416
1417<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1418<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]1419 <a name="loweratomic">-loweratomic: Lower atomic intrinsics to non-atomic form</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1420</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1421<div>
Peter Collingbourne3bababf2010-08-03 16:19:16 +0000[diff] [blame]1422 <p>
1423 This pass lowers atomic intrinsics to non-atomic form for use in a known
1424 non-preemptible environment.
1425 </p>
1426
1427 <p>
1428 The pass does not verify that the environment is non-preemptible (in
1429 general this would require knowledge of the entire call graph of the
1430 program including any libraries which may not be available in bitcode form);
1431 it simply lowers every atomic intrinsic.
1432 </p>
1433</div>
1434
1435<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1436<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1437 <a name="lowerinvoke">-lowerinvoke: Lower invoke and unwind, for unwindless code generators</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>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1440 <p>
1441 This transformation is designed for use by code generators which do not yet
1442 support stack unwinding. This pass supports two models of exception handling
1443 lowering, the 'cheap' support and the 'expensive' support.
1444 </p>
1445
1446 <p>
1447 'Cheap' exception handling support gives the program the ability to execute
1448 any program which does not "throw an exception", by turning 'invoke'
1449 instructions into calls and by turning 'unwind' instructions into calls to
1450 abort(). If the program does dynamically use the unwind instruction, the
1451 program will print a message then abort.
1452 </p>
1453
1454 <p>
1455 'Expensive' exception handling support gives the full exception handling
1456 support to the program at the cost of making the 'invoke' instruction
1457 really expensive. It basically inserts setjmp/longjmp calls to emulate the
1458 exception handling as necessary.
1459 </p>
1460
1461 <p>
1462 Because the 'expensive' support slows down programs a lot, and EH is only
1463 used for a subset of the programs, it must be specifically enabled by the
1464 <tt>-enable-correct-eh-support</tt> option.
1465 </p>
1466
1467 <p>
1468 Note that after this pass runs the CFG is not entirely accurate (exceptional
1469 control flow edges are not correct anymore) so only very simple things should
1470 be done after the lowerinvoke pass has run (like generation of native code).
1471 This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't
1472 support the invoke instruction yet" lowering pass.
1473 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1474</div>
1475
1476<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1477<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1478 <a name="lowerswitch">-lowerswitch: Lower SwitchInst's to branches</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1479</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1480<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1481 <p>
1482 Rewrites <tt>switch</tt> instructions with a sequence of branches, which
1483 allows targets to get away with not implementing the switch instruction until
1484 it is convenient.
1485 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1486</div>
1487
1488<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1489<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1490 <a name="mem2reg">-mem2reg: Promote Memory to Register</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1491</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1492<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1493 <p>
1494 This file promotes memory references to be register references. It promotes
1495 <tt>alloca</tt> instructions which only have <tt>load</tt>s and
1496 <tt>store</tt>s as uses. An <tt>alloca</tt> is transformed by using dominator
1497 frontiers to place <tt>phi</tt> nodes, then traversing the function in
1498 depth-first order to rewrite <tt>load</tt>s and <tt>store</tt>s as
1499 appropriate. This is just the standard SSA construction algorithm to construct
1500 "pruned" SSA form.
1501 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1502</div>
1503
1504<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1505<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1506 <a name="memcpyopt">-memcpyopt: MemCpy Optimization</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1507</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1508<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1509 <p>
1510 This pass performs various transformations related to eliminating memcpy
1511 calls, or transforming sets of stores into memset's.
1512 </p>
1513</div>
1514
1515<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1516<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1517 <a name="mergefunc">-mergefunc: Merge Functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1518</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1519<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1520 <p>This pass looks for equivalent functions that are mergable and folds them.
1521
1522 A hash is computed from the function, based on its type and number of
1523 basic blocks.
1524
1525 Once all hashes are computed, we perform an expensive equality comparison
1526 on each function pair. This takes n^2/2 comparisons per bucket, so it's
1527 important that the hash function be high quality. The equality comparison
1528 iterates through each instruction in each basic block.
1529
1530 When a match is found the functions are folded. If both functions are
1531 overridable, we move the functionality into a new internal function and
1532 leave two overridable thunks to it.
1533 </p>
1534</div>
1535
1536<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1537<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1538 <a name="mergereturn">-mergereturn: Unify function exit nodes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1539</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1540<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1541 <p>
1542 Ensure that functions have at most one <tt>ret</tt> instruction in them.
1543 Additionally, it keeps track of which node is the new exit node of the CFG.
1544 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1545</div>
1546
1547<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1548<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1549 <a name="partial-inliner">-partial-inliner: Partial Inliner</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1550</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1551<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1552 <p>This pass performs partial inlining, typically by inlining an if
1553 statement that surrounds the body of the function.
1554 </p>
1555</div>
1556
1557<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1558<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1559 <a name="prune-eh">-prune-eh: Remove unused exception handling info</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1560</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1561<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1562 <p>
1563 This file implements a simple interprocedural pass which walks the call-graph,
1564 turning <tt>invoke</tt> instructions into <tt>call</tt> instructions if and
1565 only if the callee cannot throw an exception. It implements this as a
1566 bottom-up traversal of the call-graph.
1567 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1568</div>
1569
1570<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1571<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1572 <a name="reassociate">-reassociate: Reassociate expressions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1573</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1574<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1575 <p>
1576 This pass reassociates commutative expressions in an order that is designed
1577 to promote better constant propagation, GCSE, LICM, PRE, etc.
1578 </p>
1579
1580 <p>
1581 For example: 4 + (<var>x</var> + 5) ⇒ <var>x</var> + (4 + 5)
1582 </p>
1583
1584 <p>
1585 In the implementation of this algorithm, constants are assigned rank = 0,
1586 function arguments are rank = 1, and other values are assigned ranks
1587 corresponding to the reverse post order traversal of current function
1588 (starting at 2), which effectively gives values in deep loops higher rank
1589 than values not in loops.
1590 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1591</div>
1592
1593<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1594<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1595 <a name="reg2mem">-reg2mem: Demote all values to stack slots</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1596</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1597<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1598 <p>
1599 This file demotes all registers to memory references. It is intented to be
1600 the inverse of <a href="#mem2reg"><tt>-mem2reg</tt></a>. By converting to
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]1601 <tt>load</tt> instructions, the only values live across basic blocks are
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1602 <tt>alloca</tt> instructions and <tt>load</tt> instructions before
1603 <tt>phi</tt> nodes. It is intended that this should make CFG hacking much
1604 easier. To make later hacking easier, the entry block is split into two, such
1605 that all introduced <tt>alloca</tt> instructions (and nothing else) are in the
1606 entry block.
1607 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1608</div>
1609
1610<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1611<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1612 <a name="scalarrepl">-scalarrepl: Scalar Replacement of Aggregates (DT)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1613</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1614<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1615 <p>
1616 The well-known scalar replacement of aggregates transformation. This
1617 transform breaks up <tt>alloca</tt> instructions of aggregate type (structure
1618 or array) into individual <tt>alloca</tt> instructions for each member if
1619 possible. Then, if possible, it transforms the individual <tt>alloca</tt>
1620 instructions into nice clean scalar SSA form.
1621 </p>
1622
1623 <p>
1624 This combines a simple scalar replacement of aggregates algorithm with the <a
1625 href="#mem2reg"><tt>mem2reg</tt></a> algorithm because often interact,
1626 especially for C++ programs. As such, iterating between <tt>scalarrepl</tt>,
1627 then <a href="#mem2reg"><tt>mem2reg</tt></a> until we run out of things to
1628 promote works well.
1629 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1630</div>
1631
1632<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1633<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1634 <a name="sccp">-sccp: Sparse Conditional Constant Propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1635</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1636<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1637 <p>
1638 Sparse conditional constant propagation and merging, which can be summarized
1639 as:
1640 </p>
1641
1642 <ol>
1643 <li>Assumes values are constant unless proven otherwise</li>
1644 <li>Assumes BasicBlocks are dead unless proven otherwise</li>
1645 <li>Proves values to be constant, and replaces them with constants</li>
1646 <li>Proves conditional branches to be unconditional</li>
1647 </ol>
1648
1649 <p>
1650 Note that this pass has a habit of making definitions be dead. It is a good
1651 idea to to run a DCE pass sometime after running this pass.
1652 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1653</div>
1654
1655<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1656<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1657 <a name="simplify-libcalls">-simplify-libcalls: Simplify well-known library calls</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1658</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1659<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1660 <p>
1661 Applies a variety of small optimizations for calls to specific well-known
1662 function calls (e.g. runtime library functions). For example, a call
1663 <tt>exit(3)</tt> that occurs within the <tt>main()</tt> function can be
1664 transformed into simply <tt>return 3</tt>.
1665 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1666</div>
1667
1668<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1669<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1670 <a name="simplifycfg">-simplifycfg: Simplify the CFG</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1671</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1672<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1673 <p>
1674 Performs dead code elimination and basic block merging. Specifically:
1675 </p>
1676
1677 <ol>
1678 <li>Removes basic blocks with no predecessors.</li>
1679 <li>Merges a basic block into its predecessor if there is only one and the
1680 predecessor only has one successor.</li>
1681 <li>Eliminates PHI nodes for basic blocks with a single predecessor.</li>
1682 <li>Eliminates a basic block that only contains an unconditional
1683 branch.</li>
1684 </ol>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1685</div>
1686
1687<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1688<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1689 <a name="sink">-sink: Code sinking</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1690</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1691<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1692 <p>This pass moves instructions into successor blocks, when possible, so that
1693 they aren't executed on paths where their results aren't needed.
1694 </p>
1695</div>
1696
1697<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1698<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1699 <a name="sretpromotion">-sretpromotion: Promote sret arguments to multiple ret values</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1700</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1701<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1702 <p>
1703 This pass finds functions that return a struct (using a pointer to the struct
1704 as the first argument of the function, marked with the '<tt>sret</tt>' attribute) and
1705 replaces them with a new function that simply returns each of the elements of
1706 that struct (using multiple return values).
1707 </p>
1708
1709 <p>
1710 This pass works under a number of conditions:
1711 </p>
1712
1713 <ul>
1714 <li>The returned struct must not contain other structs</li>
1715 <li>The returned struct must only be used to load values from</li>
1716 <li>The placeholder struct passed in is the result of an <tt>alloca</tt></li>
1717 </ul>
1718</div>
1719
1720<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1721<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1722 <a name="strip">-strip: Strip all symbols from a module</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1723</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1724<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1725 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1726 performs code stripping. this transformation can delete:
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1727 </p>
1728
1729 <ol>
1730 <li>names for virtual registers</li>
1731 <li>symbols for internal globals and functions</li>
1732 <li>debug information</li>
1733 </ol>
1734
1735 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1736 note that this transformation makes code much less readable, so it should
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1737 only be used in situations where the <tt>strip</tt> utility would be used,
1738 such as reducing code size or making it harder to reverse engineer code.
1739 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1740</div>
1741
1742<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1743<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1744 <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]1745</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1746<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1747 <p>
1748 performs code stripping. this transformation can delete:
1749 </p>
1750
1751 <ol>
1752 <li>names for virtual registers</li>
1753 <li>symbols for internal globals and functions</li>
1754 <li>debug information</li>
1755 </ol>
1756
1757 <p>
1758 note that this transformation makes code much less readable, so it should
1759 only be used in situations where the <tt>strip</tt> utility would be used,
1760 such as reducing code size or making it harder to reverse engineer code.
1761 </p>
1762</div>
1763
1764<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1765<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1766 <a name="strip-dead-prototypes">-strip-dead-prototypes: Strip Unused Function Prototypes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1767</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1768<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1769 <p>
1770 This pass loops over all of the functions in the input module, looking for
1771 dead declarations and removes them. Dead declarations are declarations of
1772 functions for which no implementation is available (i.e., declarations for
1773 unused library functions).
1774 </p>
1775</div>
1776
1777<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1778<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1779 <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]1780</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1781<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1782 <p>This pass implements code stripping. Specifically, it can delete:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1783 <ul>
1784 <li>names for virtual registers</li>
1785 <li>symbols for internal globals and functions</li>
1786 <li>debug information</li>
1787 </ul>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1788 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1789 Note that this transformation makes code much less readable, so it should
1790 only be used in situations where the 'strip' utility would be used, such as
1791 reducing code size or making it harder to reverse engineer code.
1792 </p>
1793</div>
1794
1795<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1796<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1797 <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]1798</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1799<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1800 <p>This pass implements code stripping. Specifically, it can delete:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1801 <ul>
1802 <li>names for virtual registers</li>
1803 <li>symbols for internal globals and functions</li>
1804 <li>debug information</li>
1805 </ul>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1806 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1807 Note that this transformation makes code much less readable, so it should
1808 only be used in situations where the 'strip' utility would be used, such as
1809 reducing code size or making it harder to reverse engineer code.
1810 </p>
1811</div>
1812
1813<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1814<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1815 <a name="tailcallelim">-tailcallelim: Tail Call Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1816</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1817<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1818 <p>
1819 This file transforms calls of the current function (self recursion) followed
1820 by a return instruction with a branch to the entry of the function, creating
1821 a loop. This pass also implements the following extensions to the basic
1822 algorithm:
1823 </p>
1824
1825 <ul>
1826 <li>Trivial instructions between the call and return do not prevent the
1827 transformation from taking place, though currently the analysis cannot
1828 support moving any really useful instructions (only dead ones).
1829 <li>This pass transforms functions that are prevented from being tail
1830 recursive by an associative expression to use an accumulator variable,
1831 thus compiling the typical naive factorial or <tt>fib</tt> implementation
1832 into efficient code.
1833 <li>TRE is performed if the function returns void, if the return
1834 returns the result returned by the call, or if the function returns a
1835 run-time constant on all exits from the function. It is possible, though
1836 unlikely, that the return returns something else (like constant 0), and
1837 can still be TRE'd. It can be TRE'd if <em>all other</em> return
1838 instructions in the function return the exact same value.
1839 <li>If it can prove that callees do not access theier caller stack frame,
1840 they are marked as eligible for tail call elimination (by the code
1841 generator).
1842 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1843</div>
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="tailduplicate">-tailduplicate: Tail Duplication</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 Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1850 <p>
1851 This pass performs a limited form of tail duplication, intended to simplify
1852 CFGs by removing some unconditional branches. This pass is necessary to
1853 straighten out loops created by the C front-end, but also is capable of
1854 making other code nicer. After this pass is run, the CFG simplify pass
1855 should be run to clean up the mess.
1856 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1857</div>
1858
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1859</div>
1860
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1861<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1862<h2><a name="utilities">Utility Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1863<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1864 <p>This section describes the LLVM Utility Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]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="deadarghaX0r">-deadarghaX0r: Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</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>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1871 <p>
1872 Same as dead argument elimination, but deletes arguments to functions which
1873 are external. This is only for use by <a
1874 href="Bugpoint.html">bugpoint</a>.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1875</div>
1876
1877<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1878<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1879 <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]1880</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1881<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1882 <p>
1883 This pass is used by bugpoint to extract all blocks from the module into their
1884 own functions.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1885</div>
1886
1887<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1888<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1889 <a name="instnamer">-instnamer: Assign names to anonymous instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1890</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1891<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1892 <p>This is a little utility pass that gives instructions names, this is mostly
1893 useful when diffing the effect of an optimization because deleting an
1894 unnamed instruction can change all other instruction numbering, making the
1895 diff very noisy.
1896 </p>
1897</div>
1898
1899<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1900<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1901 <a name="preverify">-preverify: Preliminary module verification</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1902</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1903<div>
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]1904 <p>
1905 Ensures that the module is in the form required by the <a
1906 href="#verifier">Module Verifier</a> pass.
1907 </p>
1908
1909 <p>
1910 Running the verifier runs this pass automatically, so there should be no need
1911 to use it directly.
1912 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1913</div>
1914
1915<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1916<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1917 <a name="verify">-verify: Module Verifier</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1918</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1919<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1920 <p>
1921 Verifies an LLVM IR code. This is useful to run after an optimization which is
1922 undergoing testing. Note that <tt>llvm-as</tt> verifies its input before
1923 emitting bitcode, and also that malformed bitcode is likely to make LLVM
1924 crash. All language front-ends are therefore encouraged to verify their output
1925 before performing optimizing transformations.
1926 </p>
1927
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]1928 <ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1929 <li>Both of a binary operator's parameters are of the same type.</li>
1930 <li>Verify that the indices of mem access instructions match other
1931 operands.</li>
1932 <li>Verify that arithmetic and other things are only performed on
1933 first-class types. Verify that shifts and logicals only happen on
1934 integrals f.e.</li>
1935 <li>All of the constants in a switch statement are of the correct type.</li>
1936 <li>The code is in valid SSA form.</li>
Chris Lattner46b3abc2009-10-28 04:47:06 +0000[diff] [blame]1937 <li>It is illegal to put a label into any other type (like a structure) or
1938 to return one.</li>
Nick Lewycky0c78ac12008-03-28 06:46:51 +0000[diff] [blame]1939 <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]1940 invalid.</li>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1941 <li>PHI nodes must have an entry for each predecessor, with no extras.</li>
1942 <li>PHI nodes must be the first thing in a basic block, all grouped
1943 together.</li>
1944 <li>PHI nodes must have at least one entry.</li>
1945 <li>All basic blocks should only end with terminator insts, not contain
1946 them.</li>
1947 <li>The entry node to a function must not have predecessors.</li>
1948 <li>All Instructions must be embedded into a basic block.</li>
1949 <li>Functions cannot take a void-typed parameter.</li>
1950 <li>Verify that a function's argument list agrees with its declared
1951 type.</li>
1952 <li>It is illegal to specify a name for a void value.</li>
1953 <li>It is illegal to have a internal global value with no initializer.</li>
1954 <li>It is illegal to have a ret instruction that returns a value that does
1955 not agree with the function return value type.</li>
1956 <li>Function call argument types match the function prototype.</li>
1957 <li>All other things that are tested by asserts spread about the code.</li>
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]1958 </ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1959
1960 <p>
1961 Note that this does not provide full security verification (like Java), but
1962 instead just tries to ensure that code is well-formed.
1963 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1964</div>
1965
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1966<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1967<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1968 <a name="view-cfg">-view-cfg: View CFG 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>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1971 <p>
1972 Displays the control flow graph using the GraphViz tool.
1973 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1974</div>
1975
1976<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1977<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1978 <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]1979</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1980<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1981 <p>
1982 Displays the control flow graph using the GraphViz tool, but omitting function
1983 bodies.
1984 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1985</div>
1986
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]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-dom">-view-dom: View dominance 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 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-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]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 dominator tree using the GraphViz tool, but omitting function
2004 bodies.
2005 </p>
2006</div>
2007
2008<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2009<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]2010 <a name="view-postdom">-view-postdom: View postdominance tree of function</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2011</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2012<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2013 <p>
2014 Displays the post dominator tree using the GraphViz tool.
2015 </p>
2016</div>
2017
2018<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2019<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]2020 <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]2021</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2022<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2023 <p>
2024 Displays the post dominator tree using the GraphViz tool, but omitting
2025 function bodies.
2026 </p>
2027</div>
2028
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2029</div>
2030
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2031<!-- *********************************************************************** -->
2032
2033<hr>
2034<address>
2035 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]2036 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2037 <a href="http://validator.w3.org/check/referer"><img
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Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2039
2040 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
NAKAMURA Takumib9a33632011-04-09 02:13:37 +0000[diff] [blame]2041 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2042 Last modified: $Date$
2043</address>
2044
2045</body>
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