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gerrit-public.fairphone.software / toolchain / llvm-project / bde917666307faf3c9e2d290c38a0018f54d7a68 / . / llvm / docs / Passes.html
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NAKAMURA Takumi590ba612011-04-21 01:32:19 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]2 "http://www.w3.org/TR/html4/strict.dtd">
3<html>
4<head>
5 <title>LLVM's Analysis and Transform Passes</title>
Daniel Dunbar46d611a2012-04-19 20:20:34 +0000[diff] [blame]6 <link rel="stylesheet" href="_static/llvm.css" type="text/css">
Gordon Henriksenac72db52007-10-25 08:58:56 +0000[diff] [blame]7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]8</head>
9<body>
10
Gordon Henriksen50768f82007-10-25 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 Henriksenac72db52007-10-25 08:58:56 +0000[diff] [blame]24open HELP, "../Release/bin/opt -help|" or die "open: opt -help: $!\n";
Gordon Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]25while (<HELP>) {
26 m:^ -([^ ]+) +- (.*)$: 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>$2</td></tr>\n";
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]30 push @y, "$o <a name=\"$1\">-$1: $2</a>\n";
Gordon Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]31}
32@x = map { s/^\d\d\d//; $_ } sort @x;
33@y = map { s/^\d\d\d//; $_ } sort @y;
34print @x, @y;
35EOT
36
Gordon Henriksen77d27522007-10-25 10:18:27 +0000[diff] [blame]37This (real) one-liner can also be helpful when converting comments to HTML:
38
39perl -e '$/ = 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 Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]41 -->
42
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]43<h1>LLVM's Analysis and Transform Passes</h1>
Reid Spencer2853e602007-03-26 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 Henriksen77d27522007-10-25 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]55</div>
56
57<!-- ======================================================================= -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]58<h2><a name="intro">Introduction</a></h2>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]59<div>
Reid Spencer2853e602007-03-26 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 Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]63 The table below divides the passes that LLVM provides into three categories.
Reid Spencer2853e602007-03-26 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 Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]67 Utility passes provides some utility but don't otherwise fit categorization.
Gabor Greifa54634a2007-07-06 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 Spencer2853e602007-03-26 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 Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]72
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]73<table>
Gordon Henriksenac72db52007-10-25 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 Spencer2853e602007-03-26 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 Friedmane513e872011-03-19 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]78<tr><td><a href="#basiccg">-basiccg</a></td><td>Basic CallGraph Construction</td></tr>
Reid Spencer2853e602007-03-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]82<tr><td><a href="#domtree">-domtree</a></td><td>Dominator Tree Construction</td></tr>
Duncan Sands9c40c282008-09-23 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 Friedmane513e872011-03-19 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 Spencer2853e602007-03-26 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 Spencer2853e602007-03-26 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 Sands83cec972010-07-06 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 Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]97<tr><td><a href="#lint">-lint</a></td><td>Statically lint-checks LLVM IR</td></tr>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]98<tr><td><a href="#loops">-loops</a></td><td>Natural Loop Information</td></tr>
Gordon Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]99<tr><td><a href="#memdep">-memdep</a></td><td>Memory Dependence Analysis</td></tr>
Eli Friedmane513e872011-03-19 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 Spencer2853e602007-03-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]104<tr><td><a href="#postdomtree">-postdomtree</a></td><td>Post-Dominator Tree Construction</td></tr>
Reid Spencer2853e602007-03-26 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 Sands9c40c282008-09-23 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 Sands83cec972010-07-06 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 Sands9c40c282008-09-23 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 Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]115<tr><td><a href="#profile-estimator">-profile-estimator</a></td><td>Estimate profiling information</td></tr>
Reid Spencer2853e602007-03-26 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 Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]117<tr><td><a href="#profile-verifier">-profile-verifier</a></td><td>Verify profiling information</td></tr>
Eli Friedmane513e872011-03-19 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]119<tr><td><a href="#scalar-evolution">-scalar-evolution</a></td><td>Scalar Evolution Analysis</td></tr>
Duncan Sands83cec972010-07-06 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]121<tr><td><a href="#targetdata">-targetdata</a></td><td>Target Data Layout</td></tr>
122
123
Gordon Henriksenac72db52007-10-25 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]126<tr><td><a href="#adce">-adce</a></td><td>Aggressive Dead Code Elimination</td></tr>
Duncan Sands83cec972010-07-06 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 Spencer2853e602007-03-26 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 Finkelc34e5112012-02-01 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 Spencer2853e602007-03-26 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 Henriksen50768f82007-10-25 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 Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]132<tr><td><a href="#codegenprepare">-codegenprepare</a></td><td>Optimize for code generation</td></tr>
Reid Spencer2853e602007-03-26 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 Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]140<tr><td><a href="#functionattrs">-functionattrs</a></td><td>Deduce function attributes</td></tr>
Reid Spencer2853e602007-03-26 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 Henriksen77d27522007-10-25 10:18:27 +0000[diff] [blame]143<tr><td><a href="#gvn">-gvn</a></td><td>Global Value Numbering</td></tr>
Reid Spencer2853e602007-03-26 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 Spencer2853e602007-03-26 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 Sands83cec972010-07-06 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 Spencer2853e602007-03-26 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 Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]152<tr><td><a href="#jump-threading">-jump-threading</a></td><td>Jump Threading</td></tr>
Reid Spencer2853e602007-03-26 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 Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]155<tr><td><a href="#loop-deletion">-loop-deletion</a></td><td>Delete dead loops</td></tr>
Reid Spencer2853e602007-03-26 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 Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]159<tr><td><a href="#loop-rotate">-loop-rotate</a></td><td>Rotate Loops</td></tr>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]160<tr><td><a href="#loop-simplify">-loop-simplify</a></td><td>Canonicalize natural loops</td></tr>
Gordon Henriksen50768f82007-10-25 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 Friedmane513e872011-03-19 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 Henriksen50768f82007-10-25 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 Spencer2853e602007-03-26 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 Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]167<tr><td><a href="#memcpyopt">-memcpyopt</a></td><td>MemCpy Optimization</td></tr>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]168<tr><td><a href="#mergefunc">-mergefunc</a></td><td>Merge Functions</td></tr>
Gordon Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]169<tr><td><a href="#mergereturn">-mergereturn</a></td><td>Unify function exit nodes</td></tr>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]170<tr><td><a href="#partial-inliner">-partial-inliner</a></td><td>Partial Inliner</td></tr>
Reid Spencer2853e602007-03-26 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 Henriksen50768f82007-10-25 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 Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]174<tr><td><a href="#scalarrepl">-scalarrepl</a></td><td>Scalar Replacement of Aggregates (DT)</td></tr>
Reid Spencer2853e602007-03-26 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 Friedmane513e872011-03-19 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 Spencer2853e602007-03-26 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 Sands83cec972010-07-06 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 Friedmane513e872011-03-19 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 Sands83cec972010-07-06 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 Spencer2853e602007-03-26 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 Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]187
188
Gordon Henriksenac72db52007-10-25 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 Henriksen50768f82007-10-25 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 Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]193<tr><td><a href="#instnamer">-instnamer</a></td><td>Assign names to anonymous instructions</td></tr>
Gordon Henriksen2657b212007-11-05 02:05:35 +0000[diff] [blame]194<tr><td><a href="#preverify">-preverify</a></td><td>Preliminary module verification</td></tr>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]195<tr><td><a href="#verify">-verify</a></td><td>Module Verifier</td></tr>
Gordon Henriksen50768f82007-10-25 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 Friedmane513e872011-03-19 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]202</table>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]203
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]204</div>
205
206<!-- ======================================================================= -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]207<h2><a name="analyses">Analysis Passes</a></h2>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]208<div>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]209 <p>This section describes the LLVM Analysis Passes.</p>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]210
211<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]212<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]213 <a name="aa-eval">-aa-eval: Exhaustive Alias Analysis Precision Evaluator</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]214</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]215<div>
Gordon Henriksen77d27522007-10-25 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]223</div>
224
225<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]226<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]227 <a name="basicaa">-basicaa: Basic Alias Analysis (stateless AA impl)</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]228</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]229<div>
Eli Friedman54873562011-10-27 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]232</div>
233
234<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]235<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]236 <a name="basiccg">-basiccg: Basic CallGraph Construction</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]237</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]238<div>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]239 <p>Yet to be written.</p>
240</div>
241
242<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]243<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]244 <a name="count-aa">-count-aa: Count Alias Analysis Query Responses</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]245</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]246<div>
Gordon Henriksen77d27522007-10-25 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]251</div>
252
253<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]254<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]255 <a name="debug-aa">-debug-aa: AA use debugger</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]256</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]257<div>
Gordon Henriksen77d27522007-10-25 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]268</div>
269
270<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]271<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]272 <a name="domfrontier">-domfrontier: Dominance Frontier Construction</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]273</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]274<div>
Gordon Henriksen77d27522007-10-25 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]279</div>
280
281<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]282<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]283 <a name="domtree">-domtree: Dominator Tree Construction</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]284</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]285<div>
Gordon Henriksen77d27522007-10-25 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]290</div>
291
292<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]293<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]294 <a name="dot-callgraph">-dot-callgraph: Print Call Graph to 'dot' file</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]295</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]296<div>
Gordon Henriksen77d27522007-10-25 10:18:27 +0000[diff] [blame]297 <p>
Duncan Sands9c40c282008-09-23 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]305<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]306 <a name="dot-cfg">-dot-cfg: Print CFG of function to 'dot' file</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]307</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]308<div>
Duncan Sands9c40c282008-09-23 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]317<h3>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]319</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]320<div>
Duncan Sands9c40c282008-09-23 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 Henriksen77d27522007-10-25 10:18:27 +0000[diff] [blame]326 </p>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]327</div>
328
329<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]330<h3>
Eli Friedmane04761c2011-03-19 04:55:29 +0000[diff] [blame]331 <a name="dot-dom">-dot-dom: Print dominance tree of function to 'dot' file</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]332</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]333<div>
Tobias Grosser4c91c522010-05-07 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]342<h3>
Eli Friedmane04761c2011-03-19 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]344</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]345<div>
Tobias Grosser4c91c522010-05-07 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]355<h3>
Eli Friedmane04761c2011-03-19 04:55:29 +0000[diff] [blame]356 <a name="dot-postdom">-dot-postdom: Print postdominance tree of function to 'dot' file</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]357</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]358<div>
Tobias Grosser4c91c522010-05-07 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]367<h3>
Eli Friedmane04761c2011-03-19 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]369</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]370<div>
Tobias Grosser4c91c522010-05-07 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]380<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]381 <a name="globalsmodref-aa">-globalsmodref-aa: Simple mod/ref analysis for globals</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]382</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]383<div>
Gordon Henriksen77d27522007-10-25 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]390</div>
391
392<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]393<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]394 <a name="instcount">-instcount: Counts the various types of Instructions</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]395</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]396<div>
Gordon Henriksen77d27522007-10-25 10:18:27 +0000[diff] [blame]397 <p>
398 This pass collects the count of all instructions and reports them
399 </p>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]400</div>
401
402<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]403<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]404 <a name="intervals">-intervals: Interval Partition Construction</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]405</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]406<div>
Gordon Henriksen77d27522007-10-25 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]416</div>
417
418<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]419<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]420 <a name="iv-users">-iv-users: Induction Variable Users</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]421</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]422<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]428<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]429 <a name="lazy-value-info">-lazy-value-info: Lazy Value Information Analysis</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]430</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]431<div>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]432 <p>Interface for lazy computation of value constraint information.</p>
433</div>
434
435<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]436<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]437 <a name="lda">-lda: Loop Dependence Analysis</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]438</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]439<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]445<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]446 <a name="libcall-aa">-libcall-aa: LibCall Alias Analysis</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]447</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]448<div>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]449 <p>LibCall Alias Analysis.</p>
450</div>
451
452<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]453<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]454 <a name="lint">-lint: Statically lint-checks LLVM IR</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]455</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]456<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]484<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]485 <a name="loops">-loops: Natural Loop Information</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]486</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]487<div>
Gordon Henriksen77d27522007-10-25 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]494</div>
495
496<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]497<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]498 <a name="memdep">-memdep: Memory Dependence Analysis</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]499</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]500<div>
Gordon Henriksen78c63ac2007-10-26 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 Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]507</div>
508
509<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]510<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]511 <a name="module-debuginfo">-module-debuginfo: Decodes module-level debug info</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]512</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]513<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]523<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]524 <a name="no-aa">-no-aa: No Alias Analysis (always returns 'may' alias)</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]525</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]526<div>
Gordon Henriksen78c63ac2007-10-26 03:03:51 +0000[diff] [blame]527 <p>
Eli Friedman54873562011-10-27 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 Henriksen78c63ac2007-10-26 03:03:51 +0000[diff] [blame]532 </p>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]533</div>
534
535<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]536<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]537 <a name="no-profile">-no-profile: No Profile Information</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]538</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]539<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]544</div>
545
546<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]547<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]548 <a name="postdomfrontier">-postdomfrontier: Post-Dominance Frontier Construction</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]549</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]550<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]555</div>
556
557<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]558<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]559 <a name="postdomtree">-postdomtree: Post-Dominator Tree Construction</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]560</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]561<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]566</div>
567
568<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]569<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]570 <a name="print-alias-sets">-print-alias-sets: Alias Set Printer</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]571</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]572<div>
Duncan Sands9c40c282008-09-23 12:47:39 +0000[diff] [blame]573 <p>Yet to be written.</p>
574</div>
575
576<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]577<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]578 <a name="print-callgraph">-print-callgraph: Print a call graph</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]579</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]580<div>
Duncan Sands9c40c282008-09-23 12:47:39 +0000[diff] [blame]581 <p>
582 This pass, only available in <code>opt</code>, prints the call graph to
Dan Gohmand3ee4232010-08-20 01:03:44 +0000[diff] [blame]583 standard error in a human-readable form.
Duncan Sands9c40c282008-09-23 12:47:39 +0000[diff] [blame]584 </p>
585</div>
586
587<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]588<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]589 <a name="print-callgraph-sccs">-print-callgraph-sccs: Print SCCs of the Call Graph</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]590</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]591<div>
Duncan Sands9c40c282008-09-23 12:47:39 +0000[diff] [blame]592 <p>
593 This pass, only available in <code>opt</code>, prints the SCCs of the call
Dan Gohmand3ee4232010-08-20 01:03:44 +0000[diff] [blame]594 graph to standard error in a human-readable form.
Duncan Sands9c40c282008-09-23 12:47:39 +0000[diff] [blame]595 </p>
596</div>
597
598<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]599<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]600 <a name="print-cfg-sccs">-print-cfg-sccs: Print SCCs of each function CFG</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]601</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]602<div>
Duncan Sands9c40c282008-09-23 12:47:39 +0000[diff] [blame]603 <p>
604 This pass, only available in <code>opt</code>, prints the SCCs of each
Dan Gohmand3ee4232010-08-20 01:03:44 +0000[diff] [blame]605 function CFG to standard error in a human-readable form.
Duncan Sands9c40c282008-09-23 12:47:39 +0000[diff] [blame]606 </p>
607</div>
608
609<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]610<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]611 <a name="print-dbginfo">-print-dbginfo: Print debug info in human readable form</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]612</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]613<div>
Peter Collingbourne099c4e32010-08-06 02:13:25 +0000[diff] [blame]614 <p>Pass that prints instructions, and associated debug info:</p>
Duncan Sands83cec972010-07-06 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 Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]621</div>
622
623<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]624<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]625 <a name="print-dom-info">-print-dom-info: Dominator Info Printer</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]626</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]627<div>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]628 <p>Dominator Info Printer.</p>
629</div>
630
631<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]632<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]633 <a name="print-externalfnconstants">-print-externalfnconstants: Print external fn callsites passed constants</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]634</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]635<div>
Duncan Sands9c40c282008-09-23 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]645<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]646 <a name="print-function">-print-function: Print function to stderr</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]647</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]648<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]654</div>
655
656<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]657<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]658 <a name="print-module">-print-module: Print module to stderr</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]659</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]660<div>
Gordon Henriksen78c63ac2007-10-26 03:03:51 +0000[diff] [blame]661 <p>
662 This pass simply prints out the entire module when it is executed.
663 </p>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]664</div>
665
666<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]667<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]668 <a name="print-used-types">-print-used-types: Find Used Types</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]669</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]670<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]675</div>
676
677<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]678<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]679 <a name="profile-estimator">-profile-estimator: Estimate profiling information</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]680</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]681<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]688<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]689 <a name="profile-loader">-profile-loader: Load profile information from llvmprof.out</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]690</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]691<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]696</div>
697
698<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]699<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]700 <a name="profile-verifier">-profile-verifier: Verify profiling information</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]701</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]702<div>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]703 <p>Pass that checks profiling information for plausibility.</p>
704</div>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]705<h3>
Eli Friedmane04761c2011-03-19 04:55:29 +0000[diff] [blame]706 <a name="regions">-regions: Detect single entry single exit regions</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]707</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]708<div>
Tobias Grosser336734a2010-07-22 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 Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]716
717<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]718<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]719 <a name="scalar-evolution">-scalar-evolution: Scalar Evolution Analysis</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]720</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]721<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]734</div>
735
736<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]737<h3>
Eli Friedmane04761c2011-03-19 04:55:29 +0000[diff] [blame]738 <a name="scev-aa">-scev-aa: ScalarEvolution-based Alias Analysis</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]739</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]740<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]753<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]754 <a name="targetdata">-targetdata: Target Data Layout</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]755</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]756<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]759</div>
760
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]761</div>
762
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]763<!-- ======================================================================= -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]764<h2><a name="transforms">Transform Passes</a></h2>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]765<div>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]766 <p>This section describes the LLVM Transform Passes.</p>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]767
768<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]769<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]770 <a name="adce">-adce: Aggressive Dead Code Elimination</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]771</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]772<div>
Reid Spencer81ffa092007-03-27 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]777</div>
778
779<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]780<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]781 <a name="always-inline">-always-inline: Inliner for always_inline functions</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]782</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]783<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]789<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]790 <a name="argpromotion">-argpromotion: Promote 'by reference' arguments to scalars</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]791</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]792<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]817</div>
818
819<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]820<h3>
Hal Finkelc34e5112012-02-01 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 Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]841 <a name="block-placement">-block-placement: Profile Guided Basic Block Placement</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]842</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]843<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]849</div>
850
851<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]852<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]853 <a name="break-crit-edges">-break-crit-edges: Break critical edges in CFG</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]854</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]855<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]862</div>
863
864<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]865<h3>
Eli Friedmane04761c2011-03-19 04:55:29 +0000[diff] [blame]866 <a name="codegenprepare">-codegenprepare: Optimize for code generation</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]867</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]868<div>
Gordon Henriksen829046b2008-05-08 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]872</div>
873
874<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]875<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]876 <a name="constmerge">-constmerge: Merge Duplicate Global Constants</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]877</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]878<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]885</div>
886
887<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]888<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]889 <a name="constprop">-constprop: Simple constant propagation</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]890</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]891<div>
Reid Spencer81ffa092007-03-27 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 Henriksenac72db52007-10-25 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 Spencer81ffa092007-03-27 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]901</div>
902
903<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]904<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]905 <a name="dce">-dce: Dead Code Elimination</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]906</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]907<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]913</div>
914
915<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]916<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]917 <a name="deadargelim">-deadargelim: Dead Argument Elimination</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]918</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]919<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]931</div>
932
933<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]934<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]935 <a name="deadtypeelim">-deadtypeelim: Dead Type Elimination</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]936</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]937<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]943</div>
944
945<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]946<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]947 <a name="die">-die: Dead Instruction Elimination</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]948</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]949<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]954</div>
955
956<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]957<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]958 <a name="dse">-dse: Dead Store Elimination</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]959</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]960<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]965</div>
966
967<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]968<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]969 <a name="functionattrs">-functionattrs: Deduce function attributes</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]970</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]971<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]983<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]984 <a name="globaldce">-globaldce: Dead Global Elimination</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]985</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]986<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]994</div>
995
996<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]997<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]998 <a name="globalopt">-globalopt: Global Variable Optimizer</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]999</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1000<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1006</div>
1007
1008<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1009<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1010 <a name="gvn">-gvn: Global Value Numbering</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1011</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1012<div>
Gordon Henriksen77d27522007-10-25 10:18:27 +0000[diff] [blame]1013 <p>
Chris Lattnera0846272009-10-10 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 Kooijman5afc2742008-06-05 07:55:49 +0000[diff] [blame]1016 </p>
Gordon Henriksen77d27522007-10-25 10:18:27 +0000[diff] [blame]1017</div>
1018
Gordon Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]1019<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1020<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1021 <a name="indvars">-indvars: Canonicalize Induction Variables</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1022</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1023<div>
Gordon Henriksen78c63ac2007-10-26 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 Henriksena18a2762007-11-04 16:17:00 +0000[diff] [blame]1060 </ol>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1068</div>
1069
1070<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1071<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1072 <a name="inline">-inline: Function Integration/Inlining</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1073</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1074<div>
Gordon Henriksen78c63ac2007-10-26 03:03:51 +0000[diff] [blame]1075 <p>
1076 Bottom-up inlining of functions into callees.
1077 </p>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1078</div>
1079
1080<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1081<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1082 <a name="insert-edge-profiling">-insert-edge-profiling: Insert instrumentation for edge profiling</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1083</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1084<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1096</div>
1097
1098<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1099<h3>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1101</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1102<div>
Duncan Sands83cec972010-07-06 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 Henriksen78c63ac2007-10-26 03:03:51 +0000[diff] [blame]1106 </p>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1107</div>
1108
1109<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1110<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1111 <a name="instcombine">-instcombine: Combine redundant instructions</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1112</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1113<div>
Gordon Henriksen78c63ac2007-10-26 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1161</div>
1162
1163<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1164<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1165 <a name="internalize">-internalize: Internalize Global Symbols</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1166</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1167<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1173</div>
1174
1175<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1176<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1177 <a name="ipconstprop">-ipconstprop: Interprocedural constant propagation</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1178</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1179<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1187</div>
1188
1189<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1190<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1191 <a name="ipsccp">-ipsccp: Interprocedural Sparse Conditional Constant Propagation</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1192</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1193<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1198</div>
1199
1200<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1201<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]1202 <a name="jump-threading">-jump-threading: Jump Threading</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1203</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1204<div>
Gordon Henriksen829046b2008-05-08 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1230<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1231 <a name="lcssa">-lcssa: Loop-Closed SSA Form Pass</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1232</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1233<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1256</div>
1257
1258<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1259<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1260 <a name="licm">-licm: Loop Invariant Code Motion</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1261</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1262<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1293</div>
Eli Friedmanecdb00e2011-03-19 05:02:14 +0000[diff] [blame]1294
Gordon Henriksen829046b2008-05-08 17:46:35 +0000[diff] [blame]1295<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1296<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]1297 <a name="loop-deletion">-loop-deletion: Delete dead loops</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1298</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1299<div>
Gordon Henriksen829046b2008-05-08 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1307
1308<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1309<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1310 <a name="loop-extract">-loop-extract: Extract loops into new functions</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1311</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1312<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1319</div>
1320
1321<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1322<h3>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1324</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1325<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1331</div>
1332
1333<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1334<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1335 <a name="loop-reduce">-loop-reduce: Loop Strength Reduction</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1336</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1337<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1345</div>
1346
1347<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1348<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1349 <a name="loop-rotate">-loop-rotate: Rotate Loops</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1350</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1351<div>
Gordon Henriksend5687672007-11-04 16:15:04 +0000[diff] [blame]1352 <p>A simple loop rotation transformation.</p>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1353</div>
1354
1355<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1356<h3>
Eli Friedmanecdb00e2011-03-19 05:02:14 +0000[diff] [blame]1357 <a name="loop-simplify">-loop-simplify: Canonicalize natural loops</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1358</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1359<div>
Eli Friedmanecdb00e2011-03-19 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1397<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1398 <a name="loop-unroll">-loop-unroll: Unroll loops</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1399</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1400<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1406</div>
1407
1408<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1409<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1410 <a name="loop-unswitch">-loop-unswitch: Unswitch loops</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1411</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1412<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1436</div>
1437
1438<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1439<h3>
Eli Friedmane04761c2011-03-19 04:55:29 +0000[diff] [blame]1440 <a name="loweratomic">-loweratomic: Lower atomic intrinsics to non-atomic form</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1441</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1442<div>
Peter Collingbourneddaaf402010-08-03 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1457<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1458 <a name="lowerinvoke">-lowerinvoke: Lower invoke and unwind, for unwindless code generators</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1459</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1460<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1495</div>
1496
1497<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1498<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1499 <a name="lowerswitch">-lowerswitch: Lower SwitchInst's to branches</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1500</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1501<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1507</div>
1508
1509<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1510<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1511 <a name="mem2reg">-mem2reg: Promote Memory to Register</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1512</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1513<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1523</div>
1524
1525<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1526<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]1527 <a name="memcpyopt">-memcpyopt: MemCpy Optimization</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1528</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1529<div>
Gordon Henriksen829046b2008-05-08 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1537<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1538 <a name="mergefunc">-mergefunc: Merge Functions</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1539</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1540<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1558<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1559 <a name="mergereturn">-mergereturn: Unify function exit nodes</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1560</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1561<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1566</div>
1567
1568<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1569<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1570 <a name="partial-inliner">-partial-inliner: Partial Inliner</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1571</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1572<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1579<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1580 <a name="prune-eh">-prune-eh: Remove unused exception handling info</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1581</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1582<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1589</div>
1590
1591<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1592<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1593 <a name="reassociate">-reassociate: Reassociate expressions</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1594</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1595<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1612</div>
1613
1614<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1615<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1616 <a name="reg2mem">-reg2mem: Demote all values to stack slots</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1617</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1618<div>
Gordon Henriksend5687672007-11-04 16:15:04 +0000[diff] [blame]1619 <p>
Benjamin Kramerbde91762012-06-02 10:20:22 +0000[diff] [blame^]1620 This file demotes all registers to memory references. It is intended to be
Gordon Henriksend5687672007-11-04 16:15:04 +0000[diff] [blame]1621 the inverse of <a href="#mem2reg"><tt>-mem2reg</tt></a>. By converting to
Benjamin Kramer0f420382009-10-12 14:46:08 +0000[diff] [blame]1622 <tt>load</tt> instructions, the only values live across basic blocks are
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1629</div>
1630
1631<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1632<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]1633 <a name="scalarrepl">-scalarrepl: Scalar Replacement of Aggregates (DT)</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1634</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1635<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1651</div>
1652
1653<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1654<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1655 <a name="sccp">-sccp: Sparse Conditional Constant Propagation</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1656</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1657<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1674</div>
1675
1676<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1677<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1678 <a name="simplify-libcalls">-simplify-libcalls: Simplify well-known library calls</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1679</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1680<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1687</div>
1688
1689<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1690<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1691 <a name="simplifycfg">-simplifycfg: Simplify the CFG</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1692</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1693<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1706</div>
1707
1708<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1709<h3>
Eli Friedmanecdb00e2011-03-19 05:02:14 +0000[diff] [blame]1710 <a name="sink">-sink: Code sinking</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1711</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1712<div>
Eli Friedmanecdb00e2011-03-19 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1719<h3>
Eli Friedmanecdb00e2011-03-19 05:02:14 +0000[diff] [blame]1720 <a name="sretpromotion">-sretpromotion: Promote sret arguments to multiple ret values</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1721</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1722<div>
Eli Friedmanecdb00e2011-03-19 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1742<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1743 <a name="strip">-strip: Strip all symbols from a module</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1744</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1745<div>
Gordon Henriksend5687672007-11-04 16:15:04 +0000[diff] [blame]1746 <p>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1747 performs code stripping. this transformation can delete:
Gordon Henriksend5687672007-11-04 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 Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1757 note that this transformation makes code much less readable, so it should
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1761</div>
1762
1763<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1764<h3>
Eli Friedmanecdb00e2011-03-19 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1766</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1767<div>
Eli Friedmanecdb00e2011-03-19 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1786<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]1787 <a name="strip-dead-prototypes">-strip-dead-prototypes: Strip Unused Function Prototypes</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1788</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1789<div>
Gordon Henriksen829046b2008-05-08 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1799<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1800 <a name="strip-debug-declare">-strip-debug-declare: Strip all llvm.dbg.declare intrinsics</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1801</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1802<div>
Peter Collingbourne099c4e32010-08-06 02:13:25 +0000[diff] [blame]1803 <p>This pass implements code stripping. Specifically, it can delete:</p>
Duncan Sands83cec972010-07-06 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 Collingbourne099c4e32010-08-06 02:13:25 +0000[diff] [blame]1809 <p>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1817<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1818 <a name="strip-nondebug">-strip-nondebug: Strip all symbols, except dbg symbols, from a module</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1819</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1820<div>
Peter Collingbourne099c4e32010-08-06 02:13:25 +0000[diff] [blame]1821 <p>This pass implements code stripping. Specifically, it can delete:</p>
Duncan Sands83cec972010-07-06 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 Collingbourne099c4e32010-08-06 02:13:25 +0000[diff] [blame]1827 <p>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1835<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1836 <a name="tailcallelim">-tailcallelim: Tail Call Elimination</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1837</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1838<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1864</div>
1865
1866<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1867<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1868 <a name="tailduplicate">-tailduplicate: Tail Duplication</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1869</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1870<div>
Gordon Henriksend5687672007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1878</div>
1879
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1880</div>
1881
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1882<!-- ======================================================================= -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1883<h2><a name="utilities">Utility Passes</a></h2>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1884<div>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1885 <p>This section describes the LLVM Utility Passes.</p>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1886
1887<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1888<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1889 <a name="deadarghaX0r">-deadarghaX0r: Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1890</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1891<div>
Gordon Henriksen9f6c4c42007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1896</div>
1897
1898<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1899<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1900 <a name="extract-blocks">-extract-blocks: Extract Basic Blocks From Module (for bugpoint use)</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1901</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1902<div>
Gordon Henriksen9f6c4c42007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1906</div>
1907
1908<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1909<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1910 <a name="instnamer">-instnamer: Assign names to anonymous instructions</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1911</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1912<div>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1921<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1922 <a name="preverify">-preverify: Preliminary module verification</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1923</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1924<div>
Gordon Henriksen2657b212007-11-05 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1934</div>
1935
1936<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1937<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1938 <a name="verify">-verify: Module Verifier</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1939</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1940<div>
Gordon Henriksen9f6c4c42007-11-04 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 Henriksenc55d1f62007-11-04 18:14:08 +0000[diff] [blame]1949 <ul>
Gordon Henriksen9f6c4c42007-11-04 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 Lattnerc750bb62009-10-28 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 Lewyckyf88c84f2008-03-28 06:46:51 +0000[diff] [blame]1960 <li>Only phi nodes can be self referential: <tt>%x = add i32 %x, %x</tt> is
Gordon Henriksenad459912007-11-04 18:17:58 +0000[diff] [blame]1961 invalid.</li>
Gordon Henriksen9f6c4c42007-11-04 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 Henriksenc55d1f62007-11-04 18:14:08 +0000[diff] [blame]1979 </ul>
Gordon Henriksen9f6c4c42007-11-04 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 Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]1985</div>
1986
Gordon Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]1987<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1988<h3>
Duncan Sands83cec972010-07-06 15:52:15 +0000[diff] [blame]1989 <a name="view-cfg">-view-cfg: View CFG of function</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1990</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]1991<div>
Gordon Henriksen9f6c4c42007-11-04 18:10:18 +0000[diff] [blame]1992 <p>
1993 Displays the control flow graph using the GraphViz tool.
1994 </p>
Gordon Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]1995</div>
1996
1997<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]1998<h3>
Duncan Sands83cec972010-07-06 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]2000</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]2001<div>
Gordon Henriksen9f6c4c42007-11-04 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 Henriksen50768f82007-10-25 08:46:12 +0000[diff] [blame]2006</div>
2007
Tobias Grosser4c91c522010-05-07 09:33:18 +0000[diff] [blame]2008<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]2009<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]2010 <a name="view-dom">-view-dom: View dominance tree of function</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]2011</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]2012<div>
Tobias Grosser4c91c522010-05-07 09:33:18 +0000[diff] [blame]2013 <p>
2014 Displays the dominator tree using the GraphViz tool.
2015 </p>
2016</div>
2017
2018<!-------------------------------------------------------------------------- -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]2019<h3>
Eli Friedmanecdb00e2011-03-19 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]2021</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]2022<div>
Tobias Grosser4c91c522010-05-07 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]2030<h3>
Eli Friedmane513e872011-03-19 04:47:52 +0000[diff] [blame]2031 <a name="view-postdom">-view-postdom: View postdominance tree of function</a>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]2032</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]2033<div>
Tobias Grosser4c91c522010-05-07 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]2040<h3>
Eli Friedmanecdb00e2011-03-19 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 Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame]2042</h3>
NAKAMURA Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]2043<div>
Tobias Grosser4c91c522010-05-07 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 Takumiaa3d6242011-04-23 00:30:22 +0000[diff] [blame]2050</div>
2051
Reid Spencer2853e602007-03-26 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 Brukman86242e12008-12-11 17:34:48 +0000[diff] [blame]2057 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]2058 <a href="http://validator.w3.org/check/referer"><img
Misha Brukman86242e12008-12-11 17:34:48 +0000[diff] [blame]2059 src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]2060
2061 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
NAKAMURA Takumica46f5a2011-04-09 02:13:37 +0000[diff] [blame]2062 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Reid Spencer2853e602007-03-26 09:32:31 +0000[diff] [blame]2063 Last modified: $Date$
2064</address>
2065
2066</body>
2067</html>