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gerrit-public.fairphone.software / fp2-dev / platform / external / llvm / 3020c964408e369a81a61013111b9185e6884331 / . / 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>
Hal Finkelde5e5ec2012-02-01 03:51:43 +0000[diff] [blame]129<tr><td><a href="#bb-vectorize">-bb-vectorize</a></td><td>Combine instructions to form vector instructions within basic blocks</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]130<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]131<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]132<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]133<tr><td><a href="#constmerge">-constmerge</a></td><td>Merge Duplicate Global Constants</td></tr>
134<tr><td><a href="#constprop">-constprop</a></td><td>Simple constant propagation</td></tr>
135<tr><td><a href="#dce">-dce</a></td><td>Dead Code Elimination</td></tr>
136<tr><td><a href="#deadargelim">-deadargelim</a></td><td>Dead Argument Elimination</td></tr>
137<tr><td><a href="#deadtypeelim">-deadtypeelim</a></td><td>Dead Type Elimination</td></tr>
138<tr><td><a href="#die">-die</a></td><td>Dead Instruction Elimination</td></tr>
139<tr><td><a href="#dse">-dse</a></td><td>Dead Store Elimination</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]140<tr><td><a href="#functionattrs">-functionattrs</a></td><td>Deduce function attributes</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]141<tr><td><a href="#globaldce">-globaldce</a></td><td>Dead Global Elimination</td></tr>
142<tr><td><a href="#globalopt">-globalopt</a></td><td>Global Variable Optimizer</td></tr>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]143<tr><td><a href="#gvn">-gvn</a></td><td>Global Value Numbering</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]144<tr><td><a href="#indvars">-indvars</a></td><td>Canonicalize Induction Variables</td></tr>
145<tr><td><a href="#inline">-inline</a></td><td>Function Integration/Inlining</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]146<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]147<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]148<tr><td><a href="#instcombine">-instcombine</a></td><td>Combine redundant instructions</td></tr>
149<tr><td><a href="#internalize">-internalize</a></td><td>Internalize Global Symbols</td></tr>
150<tr><td><a href="#ipconstprop">-ipconstprop</a></td><td>Interprocedural constant propagation</td></tr>
151<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]152<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]153<tr><td><a href="#lcssa">-lcssa</a></td><td>Loop-Closed SSA Form Pass</td></tr>
154<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]155<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]156<tr><td><a href="#loop-extract">-loop-extract</a></td><td>Extract loops into new functions</td></tr>
157<tr><td><a href="#loop-extract-single">-loop-extract-single</a></td><td>Extract at most one loop into a new function</td></tr>
158<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]159<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]160<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]161<tr><td><a href="#loop-unroll">-loop-unroll</a></td><td>Unroll loops</td></tr>
162<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]163<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]164<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]165<tr><td><a href="#lowerswitch">-lowerswitch</a></td><td>Lower SwitchInst's to branches</td></tr>
166<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]167<tr><td><a href="#memcpyopt">-memcpyopt</a></td><td>MemCpy Optimization</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]168<tr><td><a href="#mergefunc">-mergefunc</a></td><td>Merge Functions</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]169<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]170<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]171<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]172<tr><td><a href="#reassociate">-reassociate</a></td><td>Reassociate expressions</td></tr>
173<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]174<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]175<tr><td><a href="#sccp">-sccp</a></td><td>Sparse Conditional Constant Propagation</td></tr>
176<tr><td><a href="#simplify-libcalls">-simplify-libcalls</a></td><td>Simplify well-known library calls</td></tr>
177<tr><td><a href="#simplifycfg">-simplifycfg</a></td><td>Simplify the CFG</td></tr>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]178<tr><td><a href="#sink">-sink</a></td><td>Code sinking</td></tr>
179<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]180<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]181<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]182<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]183<tr><td><a href="#strip-debug-declare">-strip-debug-declare</a></td><td>Strip all llvm.dbg.declare intrinsics</td></tr>
184<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]185<tr><td><a href="#tailcallelim">-tailcallelim</a></td><td>Tail Call Elimination</td></tr>
186<tr><td><a href="#tailduplicate">-tailduplicate</a></td><td>Tail Duplication</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]187
188
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]189<tr><th colspan="2"><b>UTILITY PASSES</b></th></tr>
190<tr><th>Option</th><th>Name</th></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]191<tr><td><a href="#deadarghaX0r">-deadarghaX0r</a></td><td>Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</td></tr>
192<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]193<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]194<tr><td><a href="#preverify">-preverify</a></td><td>Preliminary module verification</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]195<tr><td><a href="#verify">-verify</a></td><td>Module Verifier</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]196<tr><td><a href="#view-cfg">-view-cfg</a></td><td>View CFG of function</td></tr>
197<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]198<tr><td><a href="#view-dom">-view-dom</a></td><td>View dominance tree of function</td></tr>
199<tr><td><a href="#view-dom-only">-view-dom-only</a></td><td>View dominance tree of function (with no function bodies)</td></tr>
200<tr><td><a href="#view-postdom">-view-postdom</a></td><td>View postdominance tree of function</td></tr>
201<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]202</table>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]203
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]204</div>
205
206<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]207<h2><a name="analyses">Analysis Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]208<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]209 <p>This section describes the LLVM Analysis Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]210
211<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]212<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]213 <a name="aa-eval">-aa-eval: Exhaustive Alias Analysis Precision Evaluator</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]214</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]215<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]216 <p>This is a simple N^2 alias analysis accuracy evaluator.
217 Basically, for each function in the program, it simply queries to see how the
218 alias analysis implementation answers alias queries between each pair of
219 pointers in the function.</p>
220
221 <p>This is inspired and adapted from code by: Naveen Neelakantam, Francesco
222 Spadini, and Wojciech Stryjewski.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]223</div>
224
225<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]226<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]227 <a name="basicaa">-basicaa: Basic Alias Analysis (stateless AA impl)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]228</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]229<div>
Eli Friedman146af5a2011-10-27 22:32:13 +0000[diff] [blame]230 <p>A basic alias analysis pass that implements identities (two different
231 globals cannot alias, etc), but does no stateful analysis.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]232</div>
233
234<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]235<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]236 <a name="basiccg">-basiccg: Basic CallGraph Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]237</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]238<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]239 <p>Yet to be written.</p>
240</div>
241
242<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]243<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]244 <a name="count-aa">-count-aa: Count Alias Analysis Query Responses</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]245</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]246<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]247 <p>
248 A pass which can be used to count how many alias queries
249 are being made and how the alias analysis implementation being used responds.
250 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]251</div>
252
253<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]254<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]255 <a name="debug-aa">-debug-aa: AA use debugger</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]256</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]257<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]258 <p>
259 This simple pass checks alias analysis users to ensure that if they
260 create a new value, they do not query AA without informing it of the value.
261 It acts as a shim over any other AA pass you want.
262 </p>
263
264 <p>
265 Yes keeping track of every value in the program is expensive, but this is
266 a debugging pass.
267 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]268</div>
269
270<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]271<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]272 <a name="domfrontier">-domfrontier: Dominance Frontier Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]273</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]274<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]275 <p>
276 This pass is a simple dominator construction algorithm for finding forward
277 dominator frontiers.
278 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]279</div>
280
281<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]282<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]283 <a name="domtree">-domtree: Dominator Tree Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]284</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]285<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]286 <p>
287 This pass is a simple dominator construction algorithm for finding forward
288 dominators.
289 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]290</div>
291
292<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]293<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]294 <a name="dot-callgraph">-dot-callgraph: Print Call Graph to 'dot' file</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]295</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]296<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]297 <p>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]298 This pass, only available in <code>opt</code>, prints the call graph into a
299 <code>.dot</code> graph. This graph can then be processed with the "dot" tool
300 to convert it to postscript or some other suitable format.
301 </p>
302</div>
303
304<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]305<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]306 <a name="dot-cfg">-dot-cfg: Print CFG of function to 'dot' file</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]307</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]308<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]309 <p>
310 This pass, only available in <code>opt</code>, prints the control flow graph
311 into a <code>.dot</code> graph. This graph can then be processed with the
312 "dot" tool to convert it to postscript or some other suitable format.
313 </p>
314</div>
315
316<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]317<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]318 <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]319</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]320<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]321 <p>
322 This pass, only available in <code>opt</code>, prints the control flow graph
323 into a <code>.dot</code> graph, omitting the function bodies. This graph can
324 then be processed with the "dot" tool to convert it to postscript or some
325 other suitable format.
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]326 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]327</div>
328
329<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]330<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]331 <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]332</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]333<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]334 <p>
335 This pass, only available in <code>opt</code>, prints the dominator tree
336 into a <code>.dot</code> graph. This graph can then be processed with the
337 "dot" tool to convert it to postscript or some other suitable format.
338 </p>
339</div>
340
341<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]342<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]343 <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]344</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]345<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]346 <p>
347 This pass, only available in <code>opt</code>, prints the dominator tree
348 into a <code>.dot</code> graph, omitting the function bodies. This graph can
349 then be processed with the "dot" tool to convert it to postscript or some
350 other suitable format.
351 </p>
352</div>
353
354<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]355<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]356 <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]357</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]358<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]359 <p>
360 This pass, only available in <code>opt</code>, prints the post dominator tree
361 into a <code>.dot</code> graph. This graph can then be processed with the
362 "dot" tool to convert it to postscript or some other suitable format.
363 </p>
364</div>
365
366<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]367<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]368 <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]369</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]370<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]371 <p>
372 This pass, only available in <code>opt</code>, prints the post dominator tree
373 into a <code>.dot</code> graph, omitting the function bodies. This graph can
374 then be processed with the "dot" tool to convert it to postscript or some
375 other suitable format.
376 </p>
377</div>
378
379<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]380<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]381 <a name="globalsmodref-aa">-globalsmodref-aa: Simple mod/ref analysis for globals</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]382</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]383<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]384 <p>
385 This simple pass provides alias and mod/ref information for global values
386 that do not have their address taken, and keeps track of whether functions
387 read or write memory (are "pure"). For this simple (but very common) case,
388 we can provide pretty accurate and useful information.
389 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]390</div>
391
392<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]393<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]394 <a name="instcount">-instcount: Counts the various types of Instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]395</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]396<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]397 <p>
398 This pass collects the count of all instructions and reports them
399 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]400</div>
401
402<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]403<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]404 <a name="intervals">-intervals: Interval Partition Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]405</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]406<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]407 <p>
408 This analysis calculates and represents the interval partition of a function,
409 or a preexisting interval partition.
410 </p>
411
412 <p>
413 In this way, the interval partition may be used to reduce a flow graph down
414 to its degenerate single node interval partition (unless it is irreducible).
415 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]416</div>
417
418<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]419<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]420 <a name="iv-users">-iv-users: Induction Variable Users</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]421</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]422<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]423 <p>Bookkeeping for "interesting" users of expressions computed from
424 induction variables.</p>
425</div>
426
427<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]428<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]429 <a name="lazy-value-info">-lazy-value-info: Lazy Value Information Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]430</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]431<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]432 <p>Interface for lazy computation of value constraint information.</p>
433</div>
434
435<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]436<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]437 <a name="lda">-lda: Loop Dependence Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]438</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]439<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]440 <p>Loop dependence analysis framework, which is used to detect dependences in
441 memory accesses in loops.</p>
442</div>
443
444<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]445<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]446 <a name="libcall-aa">-libcall-aa: LibCall Alias Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]447</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]448<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]449 <p>LibCall Alias Analysis.</p>
450</div>
451
452<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]453<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]454 <a name="lint">-lint: Statically lint-checks LLVM IR</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]455</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]456<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]457 <p>This pass statically checks for common and easily-identified constructs
458 which produce undefined or likely unintended behavior in LLVM IR.</p>
459
460 <p>It is not a guarantee of correctness, in two ways. First, it isn't
461 comprehensive. There are checks which could be done statically which are
462 not yet implemented. Some of these are indicated by TODO comments, but
463 those aren't comprehensive either. Second, many conditions cannot be
464 checked statically. This pass does no dynamic instrumentation, so it
465 can't check for all possible problems.</p>
466
467 <p>Another limitation is that it assumes all code will be executed. A store
468 through a null pointer in a basic block which is never reached is harmless,
469 but this pass will warn about it anyway.</p>
470
471 <p>Optimization passes may make conditions that this pass checks for more or
472 less obvious. If an optimization pass appears to be introducing a warning,
473 it may be that the optimization pass is merely exposing an existing
474 condition in the code.</p>
475
476 <p>This code may be run before instcombine. In many cases, instcombine checks
477 for the same kinds of things and turns instructions with undefined behavior
478 into unreachable (or equivalent). Because of this, this pass makes some
479 effort to look through bitcasts and so on.
480 </p>
481</div>
482
483<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]484<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]485 <a name="loops">-loops: Natural Loop Information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]486</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]487<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]488 <p>
489 This analysis is used to identify natural loops and determine the loop depth
490 of various nodes of the CFG. Note that the loops identified may actually be
491 several natural loops that share the same header node... not just a single
492 natural loop.
493 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]494</div>
495
496<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]497<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]498 <a name="memdep">-memdep: Memory Dependence Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]499</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]500<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]501 <p>
502 An analysis that determines, for a given memory operation, what preceding
503 memory operations it depends on. It builds on alias analysis information, and
504 tries to provide a lazy, caching interface to a common kind of alias
505 information query.
506 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]507</div>
508
509<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]510<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]511 <a name="module-debuginfo">-module-debuginfo: Decodes module-level debug info</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]512</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]513<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]514 <p>This pass decodes the debug info metadata in a module and prints in a
515 (sufficiently-prepared-) human-readable form.
516
517 For example, run this pass from opt along with the -analyze option, and
518 it'll print to standard output.
519 </p>
520</div>
521
522<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]523<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]524 <a name="no-aa">-no-aa: No Alias Analysis (always returns 'may' alias)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]525</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]526<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]527 <p>
Eli Friedman146af5a2011-10-27 22:32:13 +0000[diff] [blame]528 This is the default implementation of the Alias Analysis interface. It always
529 returns "I don't know" for alias queries. NoAA is unlike other alias analysis
530 implementations, in that it does not chain to a previous analysis. As such it
531 doesn't follow many of the rules that other alias analyses must.
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]532 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]533</div>
534
535<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]536<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]537 <a name="no-profile">-no-profile: No Profile Information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]538</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]539<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]540 <p>
541 The default "no profile" implementation of the abstract
542 <code>ProfileInfo</code> interface.
543 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]544</div>
545
546<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]547<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]548 <a name="postdomfrontier">-postdomfrontier: Post-Dominance Frontier Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]549</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]550<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]551 <p>
552 This pass is a simple post-dominator construction algorithm for finding
553 post-dominator frontiers.
554 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]555</div>
556
557<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]558<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]559 <a name="postdomtree">-postdomtree: Post-Dominator Tree Construction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]560</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]561<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]562 <p>
563 This pass is a simple post-dominator construction algorithm for finding
564 post-dominators.
565 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]566</div>
567
568<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]569<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]570 <a name="print-alias-sets">-print-alias-sets: Alias Set Printer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]571</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]572<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]573 <p>Yet to be written.</p>
574</div>
575
576<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]577<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]578 <a name="print-callgraph">-print-callgraph: Print a call graph</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]579</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]580<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]581 <p>
582 This pass, only available in <code>opt</code>, prints the call graph to
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]583 standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]584 </p>
585</div>
586
587<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]588<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]589 <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]590</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]591<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]592 <p>
593 This pass, only available in <code>opt</code>, prints the SCCs of the call
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]594 graph to standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]595 </p>
596</div>
597
598<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]599<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]600 <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]601</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]602<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]603 <p>
604 This pass, only available in <code>opt</code>, prints the SCCs of each
Dan Gohman52fdaed2010-08-20 01:03:44 +0000[diff] [blame]605 function CFG to standard error in a human-readable form.
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]606 </p>
607</div>
608
609<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]610<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]611 <a name="print-dbginfo">-print-dbginfo: Print debug info in human readable form</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]612</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]613<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]614 <p>Pass that prints instructions, and associated debug info:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]615 <ul>
616
617 <li>source/line/col information</li>
618 <li>original variable name</li>
619 <li>original type name</li>
620 </ul>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]621</div>
622
623<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]624<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]625 <a name="print-dom-info">-print-dom-info: Dominator Info Printer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]626</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]627<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]628 <p>Dominator Info Printer.</p>
629</div>
630
631<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]632<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]633 <a name="print-externalfnconstants">-print-externalfnconstants: Print external fn callsites passed constants</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]634</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]635<div>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]636 <p>
637 This pass, only available in <code>opt</code>, prints out call sites to
638 external functions that are called with constant arguments. This can be
639 useful when looking for standard library functions we should constant fold
640 or handle in alias analyses.
641 </p>
642</div>
643
644<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]645<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]646 <a name="print-function">-print-function: Print function to stderr</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]647</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]648<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]649 <p>
650 The <code>PrintFunctionPass</code> class is designed to be pipelined with
651 other <code>FunctionPass</code>es, and prints out the functions of the module
652 as they are processed.
653 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]654</div>
655
656<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]657<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]658 <a name="print-module">-print-module: Print module to stderr</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]659</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]660<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]661 <p>
662 This pass simply prints out the entire module when it is executed.
663 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]664</div>
665
666<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]667<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]668 <a name="print-used-types">-print-used-types: Find Used Types</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]669</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]670<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]671 <p>
672 This pass is used to seek out all of the types in use by the program. Note
673 that this analysis explicitly does not include types only used by the symbol
674 table.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]675</div>
676
677<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]678<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]679 <a name="profile-estimator">-profile-estimator: Estimate profiling information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]680</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]681<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]682 <p>Profiling information that estimates the profiling information
683 in a very crude and unimaginative way.
684 </p>
685</div>
686
687<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]688<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]689 <a name="profile-loader">-profile-loader: Load profile information from llvmprof.out</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]690</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]691<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]692 <p>
693 A concrete implementation of profiling information that loads the information
694 from a profile dump file.
695 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]696</div>
697
698<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]699<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]700 <a name="profile-verifier">-profile-verifier: Verify profiling information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]701</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]702<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]703 <p>Pass that checks profiling information for plausibility.</p>
704</div>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]705<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]706 <a name="regions">-regions: Detect single entry single exit regions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]707</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]708<div>
Tobias Grosserf96b0062010-07-22 07:46:31 +0000[diff] [blame]709 <p>
710 The <code>RegionInfo</code> pass detects single entry single exit regions in a
711 function, where a region is defined as any subgraph that is connected to the
712 remaining graph at only two spots. Furthermore, an hierarchical region tree is
713 built.
714 </p>
715</div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]716
717<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]718<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]719 <a name="scalar-evolution">-scalar-evolution: Scalar Evolution Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]720</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]721<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]722 <p>
723 The <code>ScalarEvolution</code> analysis can be used to analyze and
724 catagorize scalar expressions in loops. It specializes in recognizing general
725 induction variables, representing them with the abstract and opaque
726 <code>SCEV</code> class. Given this analysis, trip counts of loops and other
727 important properties can be obtained.
728 </p>
729
730 <p>
731 This analysis is primarily useful for induction variable substitution and
732 strength reduction.
733 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]734</div>
735
736<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]737<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]738 <a name="scev-aa">-scev-aa: ScalarEvolution-based Alias Analysis</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]739</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]740<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]741 <p>Simple alias analysis implemented in terms of ScalarEvolution queries.
742
743 This differs from traditional loop dependence analysis in that it tests
744 for dependencies within a single iteration of a loop, rather than
745 dependencies between different iterations.
746
747 ScalarEvolution has a more complete understanding of pointer arithmetic
748 than BasicAliasAnalysis' collection of ad-hoc analyses.
749 </p>
750</div>
751
752<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]753<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]754 <a name="targetdata">-targetdata: Target Data Layout</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]755</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]756<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]757 <p>Provides other passes access to information on how the size and alignment
758 required by the the target ABI for various data types.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]759</div>
760
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]761</div>
762
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]763<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]764<h2><a name="transforms">Transform Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]765<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]766 <p>This section describes the LLVM Transform Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]767
768<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]769<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]770 <a name="adce">-adce: Aggressive Dead Code Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]771</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]772<div>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]773 <p>ADCE aggressively tries to eliminate code. This pass is similar to
774 <a href="#dce">DCE</a> but it assumes that values are dead until proven
775 otherwise. This is similar to <a href="#sccp">SCCP</a>, except applied to
776 the liveness of values.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]777</div>
778
779<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]780<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]781 <a name="always-inline">-always-inline: Inliner for always_inline functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]782</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]783<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]784 <p>A custom inliner that handles only functions that are marked as
785 "always inline".</p>
786</div>
787
788<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]789<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]790 <a name="argpromotion">-argpromotion: Promote 'by reference' arguments to scalars</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]791</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]792<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]793 <p>
794 This pass promotes "by reference" arguments to be "by value" arguments. In
795 practice, this means looking for internal functions that have pointer
796 arguments. If it can prove, through the use of alias analysis, that an
797 argument is *only* loaded, then it can pass the value into the function
798 instead of the address of the value. This can cause recursive simplification
799 of code and lead to the elimination of allocas (especially in C++ template
800 code like the STL).
801 </p>
802
803 <p>
804 This pass also handles aggregate arguments that are passed into a function,
805 scalarizing them if the elements of the aggregate are only loaded. Note that
806 it refuses to scalarize aggregates which would require passing in more than
807 three operands to the function, because passing thousands of operands for a
808 large array or structure is unprofitable!
809 </p>
810
811 <p>
812 Note that this transformation could also be done for arguments that are only
813 stored to (returning the value instead), but does not currently. This case
814 would be best handled when and if LLVM starts supporting multiple return
815 values from functions.
816 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]817</div>
818
819<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]820<h3>
Hal Finkelde5e5ec2012-02-01 03:51:43 +0000[diff] [blame]821 <a name="bb-vectorize">-bb-vectorize: Basic-Block Vectorization</a>
822</h3>
823<div>
824 <p>This pass combines instructions inside basic blocks to form vector
825 instructions. It iterates over each basic block, attempting to pair
826 compatible instructions, repeating this process until no additional
827 pairs are selected for vectorization. When the outputs of some pair
828 of compatible instructions are used as inputs by some other pair of
829 compatible instructions, those pairs are part of a potential
830 vectorization chain. Instruction pairs are only fused into vector
831 instructions when they are part of a chain longer than some
832 threshold length. Moreover, the pass attempts to find the best
833 possible chain for each pair of compatible instructions. These
834 heuristics are intended to prevent vectorization in cases where
835 it would not yield a performance increase of the resulting code.
836 </p>
837</div>
838
839<!-------------------------------------------------------------------------- -->
840<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]841 <a name="block-placement">-block-placement: Profile Guided Basic Block Placement</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]842</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]843<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]844 <p>This pass is a very simple profile guided basic block placement algorithm.
845 The idea is to put frequently executed blocks together at the start of the
846 function and hopefully increase the number of fall-through conditional
847 branches. If there is no profile information for a particular function, this
848 pass basically orders blocks in depth-first order.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]849</div>
850
851<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]852<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]853 <a name="break-crit-edges">-break-crit-edges: Break critical edges in CFG</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]854</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]855<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]856 <p>
857 Break all of the critical edges in the CFG by inserting a dummy basic block.
858 It may be "required" by passes that cannot deal with critical edges. This
859 transformation obviously invalidates the CFG, but can update forward dominator
860 (set, immediate dominators, tree, and frontier) information.
861 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]862</div>
863
864<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]865<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]866 <a name="codegenprepare">-codegenprepare: Optimize for code generation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]867</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]868<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]869 This pass munges the code in the input function to better prepare it for
870 SelectionDAG-based code generation. This works around limitations in it's
871 basic-block-at-a-time approach. It should eventually be removed.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]872</div>
873
874<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]875<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]876 <a name="constmerge">-constmerge: Merge Duplicate Global Constants</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]877</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]878<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]879 <p>
880 Merges duplicate global constants together into a single constant that is
881 shared. This is useful because some passes (ie TraceValues) insert a lot of
882 string constants into the program, regardless of whether or not an existing
883 string is available.
884 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]885</div>
886
887<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]888<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]889 <a name="constprop">-constprop: Simple constant propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]890</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]891<div>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]892 <p>This file implements constant propagation and merging. It looks for
893 instructions involving only constant operands and replaces them with a
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]894 constant value instead of an instruction. For example:</p>
895 <blockquote><pre>add i32 1, 2</pre></blockquote>
896 <p>becomes</p>
897 <blockquote><pre>i32 3</pre></blockquote>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]898 <p>NOTE: this pass has a habit of making definitions be dead. It is a good
899 idea to to run a <a href="#die">DIE</a> (Dead Instruction Elimination) pass
900 sometime after running this pass.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]901</div>
902
903<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]904<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]905 <a name="dce">-dce: Dead Code Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]906</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]907<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]908 <p>
909 Dead code elimination is similar to <a href="#die">dead instruction
910 elimination</a>, but it rechecks instructions that were used by removed
911 instructions to see if they are newly dead.
912 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]913</div>
914
915<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]916<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]917 <a name="deadargelim">-deadargelim: Dead Argument Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]918</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]919<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]920 <p>
921 This pass deletes dead arguments from internal functions. Dead argument
922 elimination removes arguments which are directly dead, as well as arguments
923 only passed into function calls as dead arguments of other functions. This
924 pass also deletes dead arguments in a similar way.
925 </p>
926
927 <p>
928 This pass is often useful as a cleanup pass to run after aggressive
929 interprocedural passes, which add possibly-dead arguments.
930 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]931</div>
932
933<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]934<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]935 <a name="deadtypeelim">-deadtypeelim: Dead Type Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]936</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]937<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]938 <p>
939 This pass is used to cleanup the output of GCC. It eliminate names for types
940 that are unused in the entire translation unit, using the <a
941 href="#findusedtypes">find used types</a> pass.
942 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]943</div>
944
945<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]946<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]947 <a name="die">-die: Dead Instruction Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]948</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]949<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]950 <p>
951 Dead instruction elimination performs a single pass over the function,
952 removing instructions that are obviously dead.
953 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]954</div>
955
956<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]957<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]958 <a name="dse">-dse: Dead Store Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]959</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]960<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]961 <p>
962 A trivial dead store elimination that only considers basic-block local
963 redundant stores.
964 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]965</div>
966
967<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]968<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]969 <a name="functionattrs">-functionattrs: Deduce function attributes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]970</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]971<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]972 <p>A simple interprocedural pass which walks the call-graph, looking for
973 functions which do not access or only read non-local memory, and marking them
974 readnone/readonly. In addition, it marks function arguments (of pointer type)
975 'nocapture' if a call to the function does not create any copies of the pointer
976 value that outlive the call. This more or less means that the pointer is only
977 dereferenced, and not returned from the function or stored in a global.
978 This pass is implemented as a bottom-up traversal of the call-graph.
979 </p>
980</div>
981
982<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]983<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]984 <a name="globaldce">-globaldce: Dead Global Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]985</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]986<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]987 <p>
988 This transform is designed to eliminate unreachable internal globals from the
989 program. It uses an aggressive algorithm, searching out globals that are
990 known to be alive. After it finds all of the globals which are needed, it
991 deletes whatever is left over. This allows it to delete recursive chunks of
992 the program which are unreachable.
993 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]994</div>
995
996<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]997<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]998 <a name="globalopt">-globalopt: Global Variable Optimizer</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]999</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1000<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1001 <p>
1002 This pass transforms simple global variables that never have their address
1003 taken. If obviously true, it marks read/write globals as constant, deletes
1004 variables only stored to, etc.
1005 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1006</div>
1007
1008<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1009<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1010 <a name="gvn">-gvn: Global Value Numbering</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1011</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1012<div>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]1013 <p>
Chris Lattner60f03402009-10-10 18:40:48 +0000[diff] [blame]1014 This pass performs global value numbering to eliminate fully and partially
1015 redundant instructions. It also performs redundant load elimination.
Matthijs Kooijman845f5242008-06-05 07:55:49 +0000[diff] [blame]1016 </p>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]1017</div>
1018
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1019<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1020<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1021 <a name="indvars">-indvars: Canonicalize Induction Variables</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1022</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1023<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1024 <p>
1025 This transformation analyzes and transforms the induction variables (and
1026 computations derived from them) into simpler forms suitable for subsequent
1027 analysis and transformation.
1028 </p>
1029
1030 <p>
1031 This transformation makes the following changes to each loop with an
1032 identifiable induction variable:
1033 </p>
1034
1035 <ol>
1036 <li>All loops are transformed to have a <em>single</em> canonical
1037 induction variable which starts at zero and steps by one.</li>
1038 <li>The canonical induction variable is guaranteed to be the first PHI node
1039 in the loop header block.</li>
1040 <li>Any pointer arithmetic recurrences are raised to use array
1041 subscripts.</li>
1042 </ol>
1043
1044 <p>
1045 If the trip count of a loop is computable, this pass also makes the following
1046 changes:
1047 </p>
1048
1049 <ol>
1050 <li>The exit condition for the loop is canonicalized to compare the
1051 induction value against the exit value. This turns loops like:
1052 <blockquote><pre>for (i = 7; i*i < 1000; ++i)</pre></blockquote>
1053 into
1054 <blockquote><pre>for (i = 0; i != 25; ++i)</pre></blockquote></li>
1055 <li>Any use outside of the loop of an expression derived from the indvar
1056 is changed to compute the derived value outside of the loop, eliminating
1057 the dependence on the exit value of the induction variable. If the only
1058 purpose of the loop is to compute the exit value of some derived
1059 expression, this transformation will make the loop dead.</li>
Gordon Henriksene626bbe2007-11-04 16:17:00 +0000[diff] [blame]1060 </ol>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1061
1062 <p>
1063 This transformation should be followed by strength reduction after all of the
1064 desired loop transformations have been performed. Additionally, on targets
1065 where it is profitable, the loop could be transformed to count down to zero
1066 (the "do loop" optimization).
1067 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1068</div>
1069
1070<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1071<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1072 <a name="inline">-inline: Function Integration/Inlining</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1073</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1074<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1075 <p>
1076 Bottom-up inlining of functions into callees.
1077 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1078</div>
1079
1080<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1081<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1082 <a name="insert-edge-profiling">-insert-edge-profiling: Insert instrumentation for edge profiling</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1083</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1084<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1085 <p>
1086 This pass instruments the specified program with counters for edge profiling.
1087 Edge profiling can give a reasonable approximation of the hot paths through a
1088 program, and is used for a wide variety of program transformations.
1089 </p>
1090
1091 <p>
1092 Note that this implementation is very naïve. It inserts a counter for
1093 <em>every</em> edge in the program, instead of using control flow information
1094 to prune the number of counters inserted.
1095 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1096</div>
1097
1098<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1099<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1100 <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]1101</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1102<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1103 <p>This pass instruments the specified program with counters for edge profiling.
1104 Edge profiling can give a reasonable approximation of the hot paths through a
1105 program, and is used for a wide variety of program transformations.
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1106 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1107</div>
1108
1109<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1110<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1111 <a name="instcombine">-instcombine: Combine redundant instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1112</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1113<div>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1114 <p>
1115 Combine instructions to form fewer, simple
1116 instructions. This pass does not modify the CFG This pass is where algebraic
1117 simplification happens.
1118 </p>
1119
1120 <p>
1121 This pass combines things like:
1122 </p>
1123
1124<blockquote><pre
1125>%Y = add i32 %X, 1
1126%Z = add i32 %Y, 1</pre></blockquote>
1127
1128 <p>
1129 into:
1130 </p>
1131
1132<blockquote><pre
1133>%Z = add i32 %X, 2</pre></blockquote>
1134
1135 <p>
1136 This is a simple worklist driven algorithm.
1137 </p>
1138
1139 <p>
1140 This pass guarantees that the following canonicalizations are performed on
1141 the program:
1142 </p>
1143
1144 <ul>
1145 <li>If a binary operator has a constant operand, it is moved to the right-
1146 hand side.</li>
1147 <li>Bitwise operators with constant operands are always grouped so that
1148 shifts are performed first, then <code>or</code>s, then
1149 <code>and</code>s, then <code>xor</code>s.</li>
1150 <li>Compare instructions are converted from <code>&lt;</code>,
1151 <code>&gt;</code>, <code>≤</code>, or <code>≥</code> to
1152 <code>=</code> or <code>≠</code> if possible.</li>
1153 <li>All <code>cmp</code> instructions on boolean values are replaced with
1154 logical operations.</li>
1155 <li><code>add <var>X</var>, <var>X</var></code> is represented as
1156 <code>mul <var>X</var>, 2</code> ⇒ <code>shl <var>X</var>, 1</code></li>
1157 <li>Multiplies with a constant power-of-two argument are transformed into
1158 shifts.</li>
1159 <li>… etc.</li>
1160 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1161</div>
1162
1163<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1164<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1165 <a name="internalize">-internalize: Internalize Global Symbols</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1166</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1167<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1168 <p>
1169 This pass loops over all of the functions in the input module, looking for a
1170 main function. If a main function is found, all other functions and all
1171 global variables with initializers are marked as internal.
1172 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1173</div>
1174
1175<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1176<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1177 <a name="ipconstprop">-ipconstprop: Interprocedural constant propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1178</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1179<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1180 <p>
1181 This pass implements an <em>extremely</em> simple interprocedural constant
1182 propagation pass. It could certainly be improved in many different ways,
1183 like using a worklist. This pass makes arguments dead, but does not remove
1184 them. The existing dead argument elimination pass should be run after this
1185 to clean up the mess.
1186 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1187</div>
1188
1189<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1190<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1191 <a name="ipsccp">-ipsccp: Interprocedural Sparse Conditional Constant Propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1192</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1193<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1194 <p>
1195 An interprocedural variant of <a href="#sccp">Sparse Conditional Constant
1196 Propagation</a>.
1197 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1198</div>
1199
1200<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1201<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1202 <a name="jump-threading">-jump-threading: Jump Threading</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1203</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1204<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1205 <p>
1206 Jump threading tries to find distinct threads of control flow running through
1207 a basic block. This pass looks at blocks that have multiple predecessors and
1208 multiple successors. If one or more of the predecessors of the block can be
1209 proven to always cause a jump to one of the successors, we forward the edge
1210 from the predecessor to the successor by duplicating the contents of this
1211 block.
1212 </p>
1213 <p>
1214 An example of when this can occur is code like this:
1215 </p>
1216
1217 <pre
1218>if () { ...
1219 X = 4;
1220}
1221if (X &lt; 3) {</pre>
1222
1223 <p>
1224 In this case, the unconditional branch at the end of the first if can be
1225 revectored to the false side of the second if.
1226 </p>
1227</div>
1228
1229<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1230<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1231 <a name="lcssa">-lcssa: Loop-Closed SSA Form Pass</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1232</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1233<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1234 <p>
1235 This pass transforms loops by placing phi nodes at the end of the loops for
1236 all values that are live across the loop boundary. For example, it turns
1237 the left into the right code:
1238 </p>
1239
1240 <pre
1241>for (...) for (...)
1242 if (c) if (c)
1243 X1 = ... X1 = ...
1244 else else
1245 X2 = ... X2 = ...
1246 X3 = phi(X1, X2) X3 = phi(X1, X2)
1247... = X3 + 4 X4 = phi(X3)
1248 ... = X4 + 4</pre>
1249
1250 <p>
1251 This is still valid LLVM; the extra phi nodes are purely redundant, and will
1252 be trivially eliminated by <code>InstCombine</code>. The major benefit of
1253 this transformation is that it makes many other loop optimizations, such as
1254 LoopUnswitching, simpler.
1255 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1256</div>
1257
1258<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1259<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1260 <a name="licm">-licm: Loop Invariant Code Motion</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1261</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1262<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1263 <p>
1264 This pass performs loop invariant code motion, attempting to remove as much
1265 code from the body of a loop as possible. It does this by either hoisting
1266 code into the preheader block, or by sinking code to the exit blocks if it is
1267 safe. This pass also promotes must-aliased memory locations in the loop to
1268 live in registers, thus hoisting and sinking "invariant" loads and stores.
1269 </p>
1270
1271 <p>
1272 This pass uses alias analysis for two purposes:
1273 </p>
1274
1275 <ul>
1276 <li>Moving loop invariant loads and calls out of loops. If we can determine
1277 that a load or call inside of a loop never aliases anything stored to,
1278 we can hoist it or sink it like any other instruction.</li>
1279 <li>Scalar Promotion of Memory - If there is a store instruction inside of
1280 the loop, we try to move the store to happen AFTER the loop instead of
1281 inside of the loop. This can only happen if a few conditions are true:
1282 <ul>
1283 <li>The pointer stored through is loop invariant.</li>
1284 <li>There are no stores or loads in the loop which <em>may</em> alias
1285 the pointer. There are no calls in the loop which mod/ref the
1286 pointer.</li>
1287 </ul>
1288 If these conditions are true, we can promote the loads and stores in the
1289 loop of the pointer to use a temporary alloca'd variable. We then use
1290 the mem2reg functionality to construct the appropriate SSA form for the
1291 variable.</li>
1292 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1293</div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1294
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1295<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1296<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1297 <a name="loop-deletion">-loop-deletion: Delete dead loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1298</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1299<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1300 <p>
1301 This file implements the Dead Loop Deletion Pass. This pass is responsible
1302 for eliminating loops with non-infinite computable trip counts that have no
1303 side effects or volatile instructions, and do not contribute to the
1304 computation of the function's return value.
1305 </p>
1306</div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1307
1308<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1309<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1310 <a name="loop-extract">-loop-extract: Extract loops into new functions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1311</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1312<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1313 <p>
1314 A pass wrapper around the <code>ExtractLoop()</code> scalar transformation to
1315 extract each top-level loop into its own new function. If the loop is the
1316 <em>only</em> loop in a given function, it is not touched. This is a pass most
1317 useful for debugging via bugpoint.
1318 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1319</div>
1320
1321<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1322<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1323 <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]1324</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1325<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1326 <p>
1327 Similar to <a href="#loop-extract">Extract loops into new functions</a>,
1328 this pass extracts one natural loop from the program into a function if it
1329 can. This is used by bugpoint.
1330 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1331</div>
1332
1333<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1334<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1335 <a name="loop-reduce">-loop-reduce: Loop Strength Reduction</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1336</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1337<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1338 <p>
1339 This pass performs a strength reduction on array references inside loops that
1340 have as one or more of their components the loop induction variable. This is
1341 accomplished by creating a new value to hold the initial value of the array
1342 access for the first iteration, and then creating a new GEP instruction in
1343 the loop to increment the value by the appropriate amount.
1344 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1345</div>
1346
1347<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1348<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1349 <a name="loop-rotate">-loop-rotate: Rotate Loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1350</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1351<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1352 <p>A simple loop rotation transformation.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1353</div>
1354
1355<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1356<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1357 <a name="loop-simplify">-loop-simplify: Canonicalize natural loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1358</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1359<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1360 <p>
1361 This pass performs several transformations to transform natural loops into a
1362 simpler form, which makes subsequent analyses and transformations simpler and
1363 more effective.
1364 </p>
1365
1366 <p>
1367 Loop pre-header insertion guarantees that there is a single, non-critical
1368 entry edge from outside of the loop to the loop header. This simplifies a
1369 number of analyses and transformations, such as LICM.
1370 </p>
1371
1372 <p>
1373 Loop exit-block insertion guarantees that all exit blocks from the loop
1374 (blocks which are outside of the loop that have predecessors inside of the
1375 loop) only have predecessors from inside of the loop (and are thus dominated
1376 by the loop header). This simplifies transformations such as store-sinking
1377 that are built into LICM.
1378 </p>
1379
1380 <p>
1381 This pass also guarantees that loops will have exactly one backedge.
1382 </p>
1383
1384 <p>
1385 Note that the simplifycfg pass will clean up blocks which are split out but
1386 end up being unnecessary, so usage of this pass should not pessimize
1387 generated code.
1388 </p>
1389
1390 <p>
1391 This pass obviously modifies the CFG, but updates loop information and
1392 dominator information.
1393 </p>
1394</div>
1395
1396<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1397<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1398 <a name="loop-unroll">-loop-unroll: Unroll loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1399</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1400<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1401 <p>
1402 This pass implements a simple loop unroller. It works best when loops have
1403 been canonicalized by the <a href="#indvars"><tt>-indvars</tt></a> pass,
1404 allowing it to determine the trip counts of loops easily.
1405 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1406</div>
1407
1408<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1409<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1410 <a name="loop-unswitch">-loop-unswitch: Unswitch loops</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1411</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1412<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1413 <p>
1414 This pass transforms loops that contain branches on loop-invariant conditions
1415 to have multiple loops. For example, it turns the left into the right code:
1416 </p>
1417
1418 <pre
1419>for (...) if (lic)
1420 A for (...)
1421 if (lic) A; B; C
1422 B else
1423 C for (...)
1424 A; C</pre>
1425
1426 <p>
1427 This can increase the size of the code exponentially (doubling it every time
1428 a loop is unswitched) so we only unswitch if the resultant code will be
1429 smaller than a threshold.
1430 </p>
1431
1432 <p>
1433 This pass expects LICM to be run before it to hoist invariant conditions out
1434 of the loop, to make the unswitching opportunity obvious.
1435 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1436</div>
1437
1438<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1439<h3>
Eli Friedmande8ec5b2011-03-19 04:55:29 +0000[diff] [blame]1440 <a name="loweratomic">-loweratomic: Lower atomic intrinsics to non-atomic form</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1441</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1442<div>
Peter Collingbourne3bababf2010-08-03 16:19:16 +0000[diff] [blame]1443 <p>
1444 This pass lowers atomic intrinsics to non-atomic form for use in a known
1445 non-preemptible environment.
1446 </p>
1447
1448 <p>
1449 The pass does not verify that the environment is non-preemptible (in
1450 general this would require knowledge of the entire call graph of the
1451 program including any libraries which may not be available in bitcode form);
1452 it simply lowers every atomic intrinsic.
1453 </p>
1454</div>
1455
1456<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1457<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1458 <a name="lowerinvoke">-lowerinvoke: Lower invoke and unwind, for unwindless code generators</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1459</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1460<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1461 <p>
1462 This transformation is designed for use by code generators which do not yet
1463 support stack unwinding. This pass supports two models of exception handling
1464 lowering, the 'cheap' support and the 'expensive' support.
1465 </p>
1466
1467 <p>
1468 'Cheap' exception handling support gives the program the ability to execute
1469 any program which does not "throw an exception", by turning 'invoke'
1470 instructions into calls and by turning 'unwind' instructions into calls to
1471 abort(). If the program does dynamically use the unwind instruction, the
1472 program will print a message then abort.
1473 </p>
1474
1475 <p>
1476 'Expensive' exception handling support gives the full exception handling
1477 support to the program at the cost of making the 'invoke' instruction
1478 really expensive. It basically inserts setjmp/longjmp calls to emulate the
1479 exception handling as necessary.
1480 </p>
1481
1482 <p>
1483 Because the 'expensive' support slows down programs a lot, and EH is only
1484 used for a subset of the programs, it must be specifically enabled by the
1485 <tt>-enable-correct-eh-support</tt> option.
1486 </p>
1487
1488 <p>
1489 Note that after this pass runs the CFG is not entirely accurate (exceptional
1490 control flow edges are not correct anymore) so only very simple things should
1491 be done after the lowerinvoke pass has run (like generation of native code).
1492 This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't
1493 support the invoke instruction yet" lowering pass.
1494 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1495</div>
1496
1497<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1498<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1499 <a name="lowerswitch">-lowerswitch: Lower SwitchInst's to branches</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1500</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1501<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1502 <p>
1503 Rewrites <tt>switch</tt> instructions with a sequence of branches, which
1504 allows targets to get away with not implementing the switch instruction until
1505 it is convenient.
1506 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1507</div>
1508
1509<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1510<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1511 <a name="mem2reg">-mem2reg: Promote Memory to Register</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1512</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1513<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1514 <p>
1515 This file promotes memory references to be register references. It promotes
1516 <tt>alloca</tt> instructions which only have <tt>load</tt>s and
1517 <tt>store</tt>s as uses. An <tt>alloca</tt> is transformed by using dominator
1518 frontiers to place <tt>phi</tt> nodes, then traversing the function in
1519 depth-first order to rewrite <tt>load</tt>s and <tt>store</tt>s as
1520 appropriate. This is just the standard SSA construction algorithm to construct
1521 "pruned" SSA form.
1522 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1523</div>
1524
1525<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1526<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1527 <a name="memcpyopt">-memcpyopt: MemCpy Optimization</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1528</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1529<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1530 <p>
1531 This pass performs various transformations related to eliminating memcpy
1532 calls, or transforming sets of stores into memset's.
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="mergefunc">-mergefunc: Merge Functions</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>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1541 <p>This pass looks for equivalent functions that are mergable and folds them.
1542
1543 A hash is computed from the function, based on its type and number of
1544 basic blocks.
1545
1546 Once all hashes are computed, we perform an expensive equality comparison
1547 on each function pair. This takes n^2/2 comparisons per bucket, so it's
1548 important that the hash function be high quality. The equality comparison
1549 iterates through each instruction in each basic block.
1550
1551 When a match is found the functions are folded. If both functions are
1552 overridable, we move the functionality into a new internal function and
1553 leave two overridable thunks to it.
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="mergereturn">-mergereturn: Unify function exit nodes</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 Ensure that functions have at most one <tt>ret</tt> instruction in them.
1564 Additionally, it keeps track of which node is the new exit node of the CFG.
1565 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1566</div>
1567
1568<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1569<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1570 <a name="partial-inliner">-partial-inliner: Partial Inliner</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1571</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1572<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1573 <p>This pass performs partial inlining, typically by inlining an if
1574 statement that surrounds the body of the function.
1575 </p>
1576</div>
1577
1578<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1579<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1580 <a name="prune-eh">-prune-eh: Remove unused exception handling info</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1581</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1582<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1583 <p>
1584 This file implements a simple interprocedural pass which walks the call-graph,
1585 turning <tt>invoke</tt> instructions into <tt>call</tt> instructions if and
1586 only if the callee cannot throw an exception. It implements this as a
1587 bottom-up traversal of the call-graph.
1588 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1589</div>
1590
1591<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1592<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1593 <a name="reassociate">-reassociate: Reassociate expressions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1594</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1595<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1596 <p>
1597 This pass reassociates commutative expressions in an order that is designed
1598 to promote better constant propagation, GCSE, LICM, PRE, etc.
1599 </p>
1600
1601 <p>
1602 For example: 4 + (<var>x</var> + 5) ⇒ <var>x</var> + (4 + 5)
1603 </p>
1604
1605 <p>
1606 In the implementation of this algorithm, constants are assigned rank = 0,
1607 function arguments are rank = 1, and other values are assigned ranks
1608 corresponding to the reverse post order traversal of current function
1609 (starting at 2), which effectively gives values in deep loops higher rank
1610 than values not in loops.
1611 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1612</div>
1613
1614<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1615<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1616 <a name="reg2mem">-reg2mem: Demote all values to stack slots</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1617</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1618<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1619 <p>
1620 This file demotes all registers to memory references. It is intented to be
1621 the inverse of <a href="#mem2reg"><tt>-mem2reg</tt></a>. By converting to
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]1622 <tt>load</tt> instructions, the only values live across basic blocks are
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1623 <tt>alloca</tt> instructions and <tt>load</tt> instructions before
1624 <tt>phi</tt> nodes. It is intended that this should make CFG hacking much
1625 easier. To make later hacking easier, the entry block is split into two, such
1626 that all introduced <tt>alloca</tt> instructions (and nothing else) are in the
1627 entry block.
1628 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1629</div>
1630
1631<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1632<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1633 <a name="scalarrepl">-scalarrepl: Scalar Replacement of Aggregates (DT)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1634</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1635<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1636 <p>
1637 The well-known scalar replacement of aggregates transformation. This
1638 transform breaks up <tt>alloca</tt> instructions of aggregate type (structure
1639 or array) into individual <tt>alloca</tt> instructions for each member if
1640 possible. Then, if possible, it transforms the individual <tt>alloca</tt>
1641 instructions into nice clean scalar SSA form.
1642 </p>
1643
1644 <p>
1645 This combines a simple scalar replacement of aggregates algorithm with the <a
1646 href="#mem2reg"><tt>mem2reg</tt></a> algorithm because often interact,
1647 especially for C++ programs. As such, iterating between <tt>scalarrepl</tt>,
1648 then <a href="#mem2reg"><tt>mem2reg</tt></a> until we run out of things to
1649 promote works well.
1650 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1651</div>
1652
1653<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1654<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1655 <a name="sccp">-sccp: Sparse Conditional Constant Propagation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1656</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1657<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1658 <p>
1659 Sparse conditional constant propagation and merging, which can be summarized
1660 as:
1661 </p>
1662
1663 <ol>
1664 <li>Assumes values are constant unless proven otherwise</li>
1665 <li>Assumes BasicBlocks are dead unless proven otherwise</li>
1666 <li>Proves values to be constant, and replaces them with constants</li>
1667 <li>Proves conditional branches to be unconditional</li>
1668 </ol>
1669
1670 <p>
1671 Note that this pass has a habit of making definitions be dead. It is a good
1672 idea to to run a DCE pass sometime after running this pass.
1673 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1674</div>
1675
1676<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1677<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1678 <a name="simplify-libcalls">-simplify-libcalls: Simplify well-known library calls</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1679</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1680<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1681 <p>
1682 Applies a variety of small optimizations for calls to specific well-known
1683 function calls (e.g. runtime library functions). For example, a call
1684 <tt>exit(3)</tt> that occurs within the <tt>main()</tt> function can be
1685 transformed into simply <tt>return 3</tt>.
1686 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1687</div>
1688
1689<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1690<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1691 <a name="simplifycfg">-simplifycfg: Simplify the CFG</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1692</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1693<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1694 <p>
1695 Performs dead code elimination and basic block merging. Specifically:
1696 </p>
1697
1698 <ol>
1699 <li>Removes basic blocks with no predecessors.</li>
1700 <li>Merges a basic block into its predecessor if there is only one and the
1701 predecessor only has one successor.</li>
1702 <li>Eliminates PHI nodes for basic blocks with a single predecessor.</li>
1703 <li>Eliminates a basic block that only contains an unconditional
1704 branch.</li>
1705 </ol>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1706</div>
1707
1708<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1709<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1710 <a name="sink">-sink: Code sinking</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1711</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1712<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1713 <p>This pass moves instructions into successor blocks, when possible, so that
1714 they aren't executed on paths where their results aren't needed.
1715 </p>
1716</div>
1717
1718<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1719<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1720 <a name="sretpromotion">-sretpromotion: Promote sret arguments to multiple ret values</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1721</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1722<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1723 <p>
1724 This pass finds functions that return a struct (using a pointer to the struct
1725 as the first argument of the function, marked with the '<tt>sret</tt>' attribute) and
1726 replaces them with a new function that simply returns each of the elements of
1727 that struct (using multiple return values).
1728 </p>
1729
1730 <p>
1731 This pass works under a number of conditions:
1732 </p>
1733
1734 <ul>
1735 <li>The returned struct must not contain other structs</li>
1736 <li>The returned struct must only be used to load values from</li>
1737 <li>The placeholder struct passed in is the result of an <tt>alloca</tt></li>
1738 </ul>
1739</div>
1740
1741<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1742<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1743 <a name="strip">-strip: Strip all symbols from a module</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1744</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1745<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1746 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1747 performs code stripping. this transformation can delete:
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1748 </p>
1749
1750 <ol>
1751 <li>names for virtual registers</li>
1752 <li>symbols for internal globals and functions</li>
1753 <li>debug information</li>
1754 </ol>
1755
1756 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1757 note that this transformation makes code much less readable, so it should
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1758 only be used in situations where the <tt>strip</tt> utility would be used,
1759 such as reducing code size or making it harder to reverse engineer code.
1760 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1761</div>
1762
1763<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1764<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1765 <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]1766</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1767<div>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]1768 <p>
1769 performs code stripping. this transformation can delete:
1770 </p>
1771
1772 <ol>
1773 <li>names for virtual registers</li>
1774 <li>symbols for internal globals and functions</li>
1775 <li>debug information</li>
1776 </ol>
1777
1778 <p>
1779 note that this transformation makes code much less readable, so it should
1780 only be used in situations where the <tt>strip</tt> utility would be used,
1781 such as reducing code size or making it harder to reverse engineer code.
1782 </p>
1783</div>
1784
1785<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1786<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]1787 <a name="strip-dead-prototypes">-strip-dead-prototypes: Strip Unused Function Prototypes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1788</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1789<div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1790 <p>
1791 This pass loops over all of the functions in the input module, looking for
1792 dead declarations and removes them. Dead declarations are declarations of
1793 functions for which no implementation is available (i.e., declarations for
1794 unused library functions).
1795 </p>
1796</div>
1797
1798<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1799<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1800 <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]1801</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1802<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1803 <p>This pass implements code stripping. Specifically, it can delete:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1804 <ul>
1805 <li>names for virtual registers</li>
1806 <li>symbols for internal globals and functions</li>
1807 <li>debug information</li>
1808 </ul>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1809 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1810 Note that this transformation makes code much less readable, so it should
1811 only be used in situations where the 'strip' utility would be used, such as
1812 reducing code size or making it harder to reverse engineer code.
1813 </p>
1814</div>
1815
1816<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1817<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1818 <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]1819</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1820<div>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1821 <p>This pass implements code stripping. Specifically, it can delete:</p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1822 <ul>
1823 <li>names for virtual registers</li>
1824 <li>symbols for internal globals and functions</li>
1825 <li>debug information</li>
1826 </ul>
Peter Collingbournec3086ba2010-08-06 02:13:25 +0000[diff] [blame]1827 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1828 Note that this transformation makes code much less readable, so it should
1829 only be used in situations where the 'strip' utility would be used, such as
1830 reducing code size or making it harder to reverse engineer code.
1831 </p>
1832</div>
1833
1834<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1835<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1836 <a name="tailcallelim">-tailcallelim: Tail Call Elimination</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1837</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1838<div>
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1839 <p>
1840 This file transforms calls of the current function (self recursion) followed
1841 by a return instruction with a branch to the entry of the function, creating
1842 a loop. This pass also implements the following extensions to the basic
1843 algorithm:
1844 </p>
1845
1846 <ul>
1847 <li>Trivial instructions between the call and return do not prevent the
1848 transformation from taking place, though currently the analysis cannot
1849 support moving any really useful instructions (only dead ones).
1850 <li>This pass transforms functions that are prevented from being tail
1851 recursive by an associative expression to use an accumulator variable,
1852 thus compiling the typical naive factorial or <tt>fib</tt> implementation
1853 into efficient code.
1854 <li>TRE is performed if the function returns void, if the return
1855 returns the result returned by the call, or if the function returns a
1856 run-time constant on all exits from the function. It is possible, though
1857 unlikely, that the return returns something else (like constant 0), and
1858 can still be TRE'd. It can be TRE'd if <em>all other</em> return
1859 instructions in the function return the exact same value.
1860 <li>If it can prove that callees do not access theier caller stack frame,
1861 they are marked as eligible for tail call elimination (by the code
1862 generator).
1863 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1864</div>
1865
1866<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1867<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1868 <a name="tailduplicate">-tailduplicate: Tail Duplication</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 Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1871 <p>
1872 This pass performs a limited form of tail duplication, intended to simplify
1873 CFGs by removing some unconditional branches. This pass is necessary to
1874 straighten out loops created by the C front-end, but also is capable of
1875 making other code nicer. After this pass is run, the CFG simplify pass
1876 should be run to clean up the mess.
1877 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1878</div>
1879
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1880</div>
1881
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1882<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1883<h2><a name="utilities">Utility Passes</a></h2>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1884<div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1885 <p>This section describes the LLVM Utility Passes.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]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="deadarghaX0r">-deadarghaX0r: Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</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>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1892 <p>
1893 Same as dead argument elimination, but deletes arguments to functions which
1894 are external. This is only for use by <a
1895 href="Bugpoint.html">bugpoint</a>.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1896</div>
1897
1898<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1899<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1900 <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]1901</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1902<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1903 <p>
1904 This pass is used by bugpoint to extract all blocks from the module into their
1905 own functions.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1906</div>
1907
1908<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1909<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1910 <a name="instnamer">-instnamer: Assign names to anonymous instructions</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1911</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1912<div>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1913 <p>This is a little utility pass that gives instructions names, this is mostly
1914 useful when diffing the effect of an optimization because deleting an
1915 unnamed instruction can change all other instruction numbering, making the
1916 diff very noisy.
1917 </p>
1918</div>
1919
1920<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1921<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1922 <a name="preverify">-preverify: Preliminary module verification</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1923</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1924<div>
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]1925 <p>
1926 Ensures that the module is in the form required by the <a
1927 href="#verifier">Module Verifier</a> pass.
1928 </p>
1929
1930 <p>
1931 Running the verifier runs this pass automatically, so there should be no need
1932 to use it directly.
1933 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1934</div>
1935
1936<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1937<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1938 <a name="verify">-verify: Module Verifier</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1939</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1940<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1941 <p>
1942 Verifies an LLVM IR code. This is useful to run after an optimization which is
1943 undergoing testing. Note that <tt>llvm-as</tt> verifies its input before
1944 emitting bitcode, and also that malformed bitcode is likely to make LLVM
1945 crash. All language front-ends are therefore encouraged to verify their output
1946 before performing optimizing transformations.
1947 </p>
1948
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]1949 <ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1950 <li>Both of a binary operator's parameters are of the same type.</li>
1951 <li>Verify that the indices of mem access instructions match other
1952 operands.</li>
1953 <li>Verify that arithmetic and other things are only performed on
1954 first-class types. Verify that shifts and logicals only happen on
1955 integrals f.e.</li>
1956 <li>All of the constants in a switch statement are of the correct type.</li>
1957 <li>The code is in valid SSA form.</li>
Chris Lattner46b3abc2009-10-28 04:47:06 +0000[diff] [blame]1958 <li>It is illegal to put a label into any other type (like a structure) or
1959 to return one.</li>
Nick Lewycky0c78ac12008-03-28 06:46:51 +0000[diff] [blame]1960 <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]1961 invalid.</li>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1962 <li>PHI nodes must have an entry for each predecessor, with no extras.</li>
1963 <li>PHI nodes must be the first thing in a basic block, all grouped
1964 together.</li>
1965 <li>PHI nodes must have at least one entry.</li>
1966 <li>All basic blocks should only end with terminator insts, not contain
1967 them.</li>
1968 <li>The entry node to a function must not have predecessors.</li>
1969 <li>All Instructions must be embedded into a basic block.</li>
1970 <li>Functions cannot take a void-typed parameter.</li>
1971 <li>Verify that a function's argument list agrees with its declared
1972 type.</li>
1973 <li>It is illegal to specify a name for a void value.</li>
1974 <li>It is illegal to have a internal global value with no initializer.</li>
1975 <li>It is illegal to have a ret instruction that returns a value that does
1976 not agree with the function return value type.</li>
1977 <li>Function call argument types match the function prototype.</li>
1978 <li>All other things that are tested by asserts spread about the code.</li>
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]1979 </ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1980
1981 <p>
1982 Note that this does not provide full security verification (like Java), but
1983 instead just tries to ensure that code is well-formed.
1984 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1985</div>
1986
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1987<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1988<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1989 <a name="view-cfg">-view-cfg: View CFG 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>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]1992 <p>
1993 Displays the control flow graph using the GraphViz tool.
1994 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1995</div>
1996
1997<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1998<h3>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame]1999 <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]2000</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2001<div>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]2002 <p>
2003 Displays the control flow graph using the GraphViz tool, but omitting function
2004 bodies.
2005 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]2006</div>
2007
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]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-dom">-view-dom: View dominance 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 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-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]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 dominator tree using the GraphViz tool, but omitting function
2025 bodies.
2026 </p>
2027</div>
2028
2029<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2030<h3>
Eli Friedmane6ed15b2011-03-19 04:47:52 +0000[diff] [blame]2031 <a name="view-postdom">-view-postdom: View postdominance tree of function</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2032</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2033<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2034 <p>
2035 Displays the post dominator tree using the GraphViz tool.
2036 </p>
2037</div>
2038
2039<!-------------------------------------------------------------------------- -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2040<h3>
Eli Friedman415247d2011-03-19 05:02:14 +0000[diff] [blame]2041 <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]2042</h3>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2043<div>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2044 <p>
2045 Displays the post dominator tree using the GraphViz tool, but omitting
2046 function bodies.
2047 </p>
2048</div>
2049
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2050</div>
2051
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2052<!-- *********************************************************************** -->
2053
2054<hr>
2055<address>
2056 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]2057 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2058 <a href="http://validator.w3.org/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]2059 src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2060
2061 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
NAKAMURA Takumib9a33632011-04-09 02:13:37 +0000[diff] [blame]2062 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2063 Last modified: $Date$
2064</address>
2065
2066</body>
2067</html>