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gerrit-public.fairphone.software / fp2-dev / platform / external / llvm / 5c60386dbc74f1e5e30ead158708fac02fedbb40 / . / docs / Passes.html
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Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
2 "http://www.w3.org/TR/html4/strict.dtd">
3<html>
4<head>
5 <title>LLVM's Analysis and Transform Passes</title>
6 <link rel="stylesheet" href="llvm.css" type="text/css">
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]8</head>
9<body>
10
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]11<!--
12
13If Passes.html is up to date, the following "one-liner" should print
14an empty diff.
15
16egrep -e '^<tr><td><a href="#.*">-.*</a></td><td>.*</td></tr>$' \
17 -e '^ <a name=".*">.*</a>$' < Passes.html >html; \
18perl >help <<'EOT' && diff -u help html; rm -f help html
19open HTML, "<Passes.html" or die "open: Passes.html: $!\n";
20while (<HTML>) {
21 m:^<tr><td><a href="#(.*)">-.*</a></td><td>.*</td></tr>$: or next;
22 $order{$1} = sprintf("%03d", 1 + int %order);
23}
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]24open HELP, "../Release/bin/opt -help|" or die "open: opt -help: $!\n";
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]25while (<HELP>) {
26 m:^ -([^ ]+) +- (.*)$: or next;
27 my $o = $order{$1};
28 $o = "000" unless defined $o;
29 push @x, "$o<tr><td><a href=\"#$1\">-$1</a></td><td>$2</td></tr>\n";
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]30 push @y, "$o <a name=\"$1\">-$1: $2</a>\n";
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]31}
32@x = map { s/^\d\d\d//; $_ } sort @x;
33@y = map { s/^\d\d\d//; $_ } sort @y;
34print @x, @y;
35EOT
36
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]37This (real) one-liner can also be helpful when converting comments to HTML:
38
39perl -e '$/ = undef; for (split(/\n/, <>)) { s:^ *///? ?::; print " <p>\n" if !$on && $_ =~ /\S/; print " </p>\n" if $on && $_ =~ /^\s*$/; print " $_\n"; $on = ($_ =~ /\S/); } print " </p>\n" if $on'
40
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]41 -->
42
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]43<div class="doc_title">LLVM's Analysis and Transform Passes</div>
44
45<ol>
46 <li><a href="#intro">Introduction</a></li>
47 <li><a href="#analyses">Analysis Passes</a>
48 <li><a href="#transforms">Transform Passes</a></li>
49 <li><a href="#utilities">Utility Passes</a></li>
50</ol>
51
52<div class="doc_author">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]53 <p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a>
54 and Gordon Henriksen</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]55</div>
56
57<!-- ======================================================================= -->
58<div class="doc_section"> <a name="intro">Introduction</a> </div>
59<div class="doc_text">
60 <p>This document serves as a high level summary of the optimization features
61 that LLVM provides. Optimizations are implemented as Passes that traverse some
62 portion of a program to either collect information or transform the program.
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]63 The table below divides the passes that LLVM provides into three categories.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]64 Analysis passes compute information that other passes can use or for debugging
65 or program visualization purposes. Transform passes can use (or invalidate)
66 the analysis passes. Transform passes all mutate the program in some way.
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]67 Utility passes provides some utility but don't otherwise fit categorization.
Gabor Greif04367bf2007-07-06 22:07:22 +0000[diff] [blame]68 For example passes to extract functions to bitcode or write a module to
69 bitcode are neither analysis nor transform passes.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]70 <p>The table below provides a quick summary of each pass and links to the more
71 complete pass description later in the document.</p>
72</div>
73<div class="doc_text" >
74<table>
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]75<tr><th colspan="2"><b>ANALYSIS PASSES</b></th></tr>
76<tr><th>Option</th><th>Name</th></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]77<tr><td><a href="#aa-eval">-aa-eval</a></td><td>Exhaustive Alias Analysis Precision Evaluator</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]78<tr><td><a href="#basicaa">-basicaa</a></td><td>Basic Alias Analysis (default AA impl)</td></tr>
79<tr><td><a href="#basiccg">-basiccg</a></td><td>Basic CallGraph Construction</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]80<tr><td><a href="#codegenprepare">-codegenprepare</a></td><td>Optimize for code generation</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]81<tr><td><a href="#count-aa">-count-aa</a></td><td>Count Alias Analysis Query Responses</td></tr>
82<tr><td><a href="#debug-aa">-debug-aa</a></td><td>AA use debugger</td></tr>
83<tr><td><a href="#domfrontier">-domfrontier</a></td><td>Dominance Frontier Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]84<tr><td><a href="#domtree">-domtree</a></td><td>Dominator Tree Construction</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]85<tr><td><a href="#dot-callgraph">-dot-callgraph</a></td><td>Print Call Graph to 'dot' file</td></tr>
86<tr><td><a href="#dot-cfg">-dot-cfg</a></td><td>Print CFG of function to 'dot' file</td></tr>
87<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>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]88<tr><td><a href="#dot-dom">-dot-dom</a></td><td>Print dominator tree of function to 'dot' file</td></tr>
89<tr><td><a href="#dot-dom-only">-dot-dom-only</a></td><td>Print dominator tree of function to 'dot' file (with no function bodies)</td></tr>
90<tr><td><a href="#dot-postdom">-dot-postdom</a></td><td>Print post dominator tree of function to 'dot' file</td></tr>
91<tr><td><a href="#dot-postdom-only">-dot-postdom-only</a></td><td>Print post dominator tree of function to 'dot' file (with no function bodies)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]92<tr><td><a href="#globalsmodref-aa">-globalsmodref-aa</a></td><td>Simple mod/ref analysis for globals</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]93<tr><td><a href="#instcount">-instcount</a></td><td>Counts the various types of Instructions</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]94<tr><td><a href="#interprocedural-aa-eval">-interprocedural-aa-eval</a></td><td>Exhaustive Interprocedural Alias Analysis Precision Evaluator</td></tr>
95<tr><td><a href="#interprocedural-basic-aa">-interprocedural-basic-aa</a></td><td>Interprocedural Basic Alias Analysis</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]96<tr><td><a href="#intervals">-intervals</a></td><td>Interval Partition Construction</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]97<tr><td><a href="#iv-users">-iv-users</a></td><td>Induction Variable Users</td></tr>
98<tr><td><a href="#lazy-value-info">-lazy-value-info</a></td><td>Lazy Value Information Analysis</td></tr>
99<tr><td><a href="#lda">-lda</a></td><td>Loop Dependence Analysis</td></tr>
100<tr><td><a href="#libcall-aa">-libcall-aa</a></td><td>LibCall Alias Analysis</td></tr>
101<tr><td><a href="#lint">-lint</a></td><td>Check for common errors in LLVM IR</td></tr>
102<tr><td><a href="#live-values">-live-values</a></td><td>Value Liveness Analysis</td></tr>
103<tr><td><a href="#loops">-loops</a></td><td>Natural Loop Information</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]104<tr><td><a href="#memdep">-memdep</a></td><td>Memory Dependence Analysis</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]105<tr><td><a href="#module-debuginfo">-module-debuginfo</a></td><td>Prints module debug info metadata</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]106<tr><td><a href="#no-aa">-no-aa</a></td><td>No Alias Analysis (always returns 'may' alias)</td></tr>
107<tr><td><a href="#no-profile">-no-profile</a></td><td>No Profile Information</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]108<tr><td><a href="#pointertracking">-pointertracking</a></td><td>Track pointer bounds</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]109<tr><td><a href="#postdomfrontier">-postdomfrontier</a></td><td>Post-Dominance Frontier Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]110<tr><td><a href="#postdomtree">-postdomtree</a></td><td>Post-Dominator Tree Construction</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]111<tr><td><a href="#print-alias-sets">-print-alias-sets</a></td><td>Alias Set Printer</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]112<tr><td><a href="#print-callgraph">-print-callgraph</a></td><td>Print a call graph</td></tr>
113<tr><td><a href="#print-callgraph-sccs">-print-callgraph-sccs</a></td><td>Print SCCs of the Call Graph</td></tr>
114<tr><td><a href="#print-cfg-sccs">-print-cfg-sccs</a></td><td>Print SCCs of each function CFG</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]115<tr><td><a href="#print-dbginfo">-print-dbginfo</a></td><td>Print debug info in human readable form</td></tr>
116<tr><td><a href="#print-dom-info">-print-dom-info</a></td><td>Dominator Info Printer</td></tr>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]117<tr><td><a href="#print-externalfnconstants">-print-externalfnconstants</a></td><td>Print external fn callsites passed constants</td></tr>
118<tr><td><a href="#print-function">-print-function</a></td><td>Print function to stderr</td></tr>
119<tr><td><a href="#print-module">-print-module</a></td><td>Print module to stderr</td></tr>
120<tr><td><a href="#print-used-types">-print-used-types</a></td><td>Find Used Types</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]121<tr><td><a href="#profile-estimator">-profile-estimator</a></td><td>Estimate profiling information</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]122<tr><td><a href="#profile-loader">-profile-loader</a></td><td>Load profile information from llvmprof.out</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]123<tr><td><a href="#profile-verifier">-profile-verifier</a></td><td>Verify profiling information</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]124<tr><td><a href="#scalar-evolution">-scalar-evolution</a></td><td>Scalar Evolution Analysis</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]125<tr><td><a href="#scev-aa">-scev-aa</a></td><td>ScalarEvolution-based Alias Analysis</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]126<tr><td><a href="#targetdata">-targetdata</a></td><td>Target Data Layout</td></tr>
127
128
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]129<tr><th colspan="2"><b>TRANSFORM PASSES</b></th></tr>
130<tr><th>Option</th><th>Name</th></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]131<tr><td><a href="#abcd">-abcd</a></td><td>Remove redundant conditional branches</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]132<tr><td><a href="#adce">-adce</a></td><td>Aggressive Dead Code Elimination</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]133<tr><td><a href="#always-inline">-always-inline</a></td><td>Inliner for always_inline functions</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]134<tr><td><a href="#argpromotion">-argpromotion</a></td><td>Promote 'by reference' arguments to scalars</td></tr>
135<tr><td><a href="#block-placement">-block-placement</a></td><td>Profile Guided Basic Block Placement</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]136<tr><td><a href="#break-crit-edges">-break-crit-edges</a></td><td>Break critical edges in CFG</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]137<tr><td><a href="#codegenprepare">-codegenprepare</a></td><td>Prepare a function for code generation </td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]138<tr><td><a href="#constmerge">-constmerge</a></td><td>Merge Duplicate Global Constants</td></tr>
139<tr><td><a href="#constprop">-constprop</a></td><td>Simple constant propagation</td></tr>
140<tr><td><a href="#dce">-dce</a></td><td>Dead Code Elimination</td></tr>
141<tr><td><a href="#deadargelim">-deadargelim</a></td><td>Dead Argument Elimination</td></tr>
142<tr><td><a href="#deadtypeelim">-deadtypeelim</a></td><td>Dead Type Elimination</td></tr>
143<tr><td><a href="#die">-die</a></td><td>Dead Instruction Elimination</td></tr>
144<tr><td><a href="#dse">-dse</a></td><td>Dead Store Elimination</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]145<tr><td><a href="#functionattrs">-functionattrs</a></td><td>Deduce function attributes</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]146<tr><td><a href="#globaldce">-globaldce</a></td><td>Dead Global Elimination</td></tr>
147<tr><td><a href="#globalopt">-globalopt</a></td><td>Global Variable Optimizer</td></tr>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]148<tr><td><a href="#gvn">-gvn</a></td><td>Global Value Numbering</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]149<tr><td><a href="#indvars">-indvars</a></td><td>Canonicalize Induction Variables</td></tr>
150<tr><td><a href="#inline">-inline</a></td><td>Function Integration/Inlining</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]151<tr><td><a href="#insert-edge-profiling">-insert-edge-profiling</a></td><td>Insert instrumentation for edge profiling</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]152<tr><td><a href="#insert-optimal-edge-profiling">-insert-optimal-edge-profiling</a></td><td>Insert optimal instrumentation for edge profiling</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]153<tr><td><a href="#instcombine">-instcombine</a></td><td>Combine redundant instructions</td></tr>
154<tr><td><a href="#internalize">-internalize</a></td><td>Internalize Global Symbols</td></tr>
155<tr><td><a href="#ipconstprop">-ipconstprop</a></td><td>Interprocedural constant propagation</td></tr>
156<tr><td><a href="#ipsccp">-ipsccp</a></td><td>Interprocedural Sparse Conditional Constant Propagation</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]157<tr><td><a href="#jump-threading">-jump-threading</a></td><td>Thread control through conditional blocks </td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]158<tr><td><a href="#lcssa">-lcssa</a></td><td>Loop-Closed SSA Form Pass</td></tr>
159<tr><td><a href="#licm">-licm</a></td><td>Loop Invariant Code Motion</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]160<tr><td><a href="#loop-deletion">-loop-deletion</a></td><td>Dead Loop Deletion Pass </td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]161<tr><td><a href="#loop-extract">-loop-extract</a></td><td>Extract loops into new functions</td></tr>
162<tr><td><a href="#loop-extract-single">-loop-extract-single</a></td><td>Extract at most one loop into a new function</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]163<tr><td><a href="#loop-index-split">-loop-index-split</a></td><td>Index Split Loops</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]164<tr><td><a href="#loop-reduce">-loop-reduce</a></td><td>Loop Strength Reduction</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]165<tr><td><a href="#loop-rotate">-loop-rotate</a></td><td>Rotate Loops</td></tr>
166<tr><td><a href="#loop-unroll">-loop-unroll</a></td><td>Unroll loops</td></tr>
167<tr><td><a href="#loop-unswitch">-loop-unswitch</a></td><td>Unswitch loops</td></tr>
168<tr><td><a href="#loopsimplify">-loopsimplify</a></td><td>Canonicalize natural loops</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]169<tr><td><a href="#lowerinvoke">-lowerinvoke</a></td><td>Lower invoke and unwind, for unwindless code generators</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]170<tr><td><a href="#lowersetjmp">-lowersetjmp</a></td><td>Lower Set Jump</td></tr>
171<tr><td><a href="#lowerswitch">-lowerswitch</a></td><td>Lower SwitchInst's to branches</td></tr>
172<tr><td><a href="#mem2reg">-mem2reg</a></td><td>Promote Memory to Register</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]173<tr><td><a href="#memcpyopt">-memcpyopt</a></td><td>Optimize use of memcpy and friends</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]174<tr><td><a href="#mergefunc">-mergefunc</a></td><td>Merge Functions</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]175<tr><td><a href="#mergereturn">-mergereturn</a></td><td>Unify function exit nodes</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]176<tr><td><a href="#partial-inliner">-partial-inliner</a></td><td>Partial Inliner</td></tr>
177<tr><td><a href="#partialspecialization">-partialspecialization</a></td><td>Partial Specialization</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]178<tr><td><a href="#prune-eh">-prune-eh</a></td><td>Remove unused exception handling info</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]179<tr><td><a href="#reassociate">-reassociate</a></td><td>Reassociate expressions</td></tr>
180<tr><td><a href="#reg2mem">-reg2mem</a></td><td>Demote all values to stack slots</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]181<tr><td><a href="#scalarrepl">-scalarrepl</a></td><td>Scalar Replacement of Aggregates</td></tr>
182<tr><td><a href="#sccp">-sccp</a></td><td>Sparse Conditional Constant Propagation</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]183<tr><td><a href="#sink">-sink</a></td><td>Code Sinking</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]184<tr><td><a href="#simplify-libcalls">-simplify-libcalls</a></td><td>Simplify well-known library calls</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]185<tr><td><a href="#simplify-libcalls-halfpowr">-simplify-libcalls-halfpowr</a></td><td>Simplify half_powr library calls</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]186<tr><td><a href="#simplifycfg">-simplifycfg</a></td><td>Simplify the CFG</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]187<tr><td><a href="#split-geps">-split-geps</a></td><td>Split complex GEPs into simple GEPs</td></tr>
188<tr><td><a href="#ssi">-ssi</a></td><td>Static Single Information Construction</td></tr>
189<tr><td><a href="#ssi-everything">-ssi-everything</a></td><td>Static Single Information Construction (everything, intended for debugging)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]190<tr><td><a href="#strip">-strip</a></td><td>Strip all symbols from a module</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]191<tr><td><a href="#strip-dead-debug-info">-strip-dead-debug-info</a></td><td>Strip debug info for unused symbols</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]192<tr><td><a href="#strip-dead-prototypes">-strip-dead-prototypes</a></td><td>Remove unused function declarations</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]193<tr><td><a href="#strip-debug-declare">-strip-debug-declare</a></td><td>Strip all llvm.dbg.declare intrinsics</td></tr>
194<tr><td><a href="#strip-nondebug">-strip-nondebug</a></td><td>Strip all symbols, except dbg symbols, from a module</td></tr>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]195<tr><td><a href="#sretpromotion">-sretpromotion</a></td><td>Promote sret arguments</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]196<tr><td><a href="#tailcallelim">-tailcallelim</a></td><td>Tail Call Elimination</td></tr>
197<tr><td><a href="#tailduplicate">-tailduplicate</a></td><td>Tail Duplication</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]198
199
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]200<tr><th colspan="2"><b>UTILITY PASSES</b></th></tr>
201<tr><th>Option</th><th>Name</th></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]202<tr><td><a href="#deadarghaX0r">-deadarghaX0r</a></td><td>Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</td></tr>
203<tr><td><a href="#extract-blocks">-extract-blocks</a></td><td>Extract Basic Blocks From Module (for bugpoint use)</td></tr>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]204<tr><td><a href="#instnamer">-instnamer</a></td><td>Assign names to anonymous instructions</td></tr>
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]205<tr><td><a href="#preverify">-preverify</a></td><td>Preliminary module verification</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]206<tr><td><a href="#verify">-verify</a></td><td>Module Verifier</td></tr>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]207<tr><td><a href="#view-cfg">-view-cfg</a></td><td>View CFG of function</td></tr>
208<tr><td><a href="#view-cfg-only">-view-cfg-only</a></td><td>View CFG of function (with no function bodies)</td></tr>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]209<tr><td><a href="#view-dom">-view-dom</a></td><td>View dominator tree of function</td></tr>
210<tr><td><a href="#view-dom-only">-view-dom-only</a></td><td>View dominator tree of function (with no function bodies)</td></tr>
211<tr><td><a href="#view-postdom">-view-postdom</a></td><td>View post dominator tree of function</td></tr>
212<tr><td><a href="#view-postdom-only">-view-postdom-only</a></td><td>View post dominator tree of function (with no function bodies)</td></tr>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]213</table>
214</div>
215
216<!-- ======================================================================= -->
217<div class="doc_section"> <a name="example">Analysis Passes</a></div>
218<div class="doc_text">
219 <p>This section describes the LLVM Analysis Passes.</p>
220</div>
221
222<!-------------------------------------------------------------------------- -->
223<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]224 <a name="aa-eval">-aa-eval: Exhaustive Alias Analysis Precision Evaluator</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]225</div>
226<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]227 <p>This is a simple N^2 alias analysis accuracy evaluator.
228 Basically, for each function in the program, it simply queries to see how the
229 alias analysis implementation answers alias queries between each pair of
230 pointers in the function.</p>
231
232 <p>This is inspired and adapted from code by: Naveen Neelakantam, Francesco
233 Spadini, and Wojciech Stryjewski.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]234</div>
235
236<!-------------------------------------------------------------------------- -->
237<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]238 <a name="basicaa">-basicaa: Basic Alias Analysis (default AA impl)</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]239</div>
240<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]241 <p>
242 This is the default implementation of the Alias Analysis interface
243 that simply implements a few identities (two different globals cannot alias,
244 etc), but otherwise does no analysis.
245 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]246</div>
247
248<!-------------------------------------------------------------------------- -->
249<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]250 <a name="basiccg">-basiccg: Basic CallGraph Construction</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]251</div>
252<div class="doc_text">
253 <p>Yet to be written.</p>
254</div>
255
256<!-------------------------------------------------------------------------- -->
257<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]258 <a name="codegenprepare">-codegenprepare: Optimize for code generation</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]259</div>
260<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]261 <p>
262 This pass munges the code in the input function to better prepare it for
263 SelectionDAG-based code generation. This works around limitations in it's
264 basic-block-at-a-time approach. It should eventually be removed.
265 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]266</div>
267
268<!-------------------------------------------------------------------------- -->
269<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]270 <a name="count-aa">-count-aa: Count Alias Analysis Query Responses</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]271</div>
272<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]273 <p>
274 A pass which can be used to count how many alias queries
275 are being made and how the alias analysis implementation being used responds.
276 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]277</div>
278
279<!-------------------------------------------------------------------------- -->
280<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]281 <a name="debug-aa">-debug-aa: AA use debugger</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]282</div>
283<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]284 <p>
285 This simple pass checks alias analysis users to ensure that if they
286 create a new value, they do not query AA without informing it of the value.
287 It acts as a shim over any other AA pass you want.
288 </p>
289
290 <p>
291 Yes keeping track of every value in the program is expensive, but this is
292 a debugging pass.
293 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]294</div>
295
296<!-------------------------------------------------------------------------- -->
297<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]298 <a name="domfrontier">-domfrontier: Dominance Frontier Construction</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]299</div>
300<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]301 <p>
302 This pass is a simple dominator construction algorithm for finding forward
303 dominator frontiers.
304 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]305</div>
306
307<!-------------------------------------------------------------------------- -->
308<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]309 <a name="domtree">-domtree: Dominator Tree Construction</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]310</div>
311<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]312 <p>
313 This pass is a simple dominator construction algorithm for finding forward
314 dominators.
315 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]316</div>
317
318<!-------------------------------------------------------------------------- -->
319<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]320 <a name="dot-callgraph">-dot-callgraph: Print Call Graph to 'dot' file</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]321</div>
322<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]323 <p>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]324 This pass, only available in <code>opt</code>, prints the call graph into a
325 <code>.dot</code> graph. This graph can then be processed with the "dot" tool
326 to convert it to postscript or some other suitable format.
327 </p>
328</div>
329
330<!-------------------------------------------------------------------------- -->
331<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]332 <a name="dot-cfg">-dot-cfg: Print CFG of function to 'dot' file</a>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]333</div>
334<div class="doc_text">
335 <p>
336 This pass, only available in <code>opt</code>, prints the control flow graph
337 into a <code>.dot</code> graph. This graph can then be processed with the
338 "dot" tool to convert it to postscript or some other suitable format.
339 </p>
340</div>
341
342<!-------------------------------------------------------------------------- -->
343<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]344 <a name="dot-cfg-only">-dot-cfg-only: Print CFG of function to 'dot' file (with no function bodies)</a>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]345</div>
346<div class="doc_text">
347 <p>
348 This pass, only available in <code>opt</code>, prints the control flow graph
349 into a <code>.dot</code> graph, omitting the function bodies. This graph can
350 then be processed with the "dot" tool to convert it to postscript or some
351 other suitable format.
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]352 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]353</div>
354
355<!-------------------------------------------------------------------------- -->
356<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]357 <a name="dot-dom">-dot-dom: Print dominator tree of function to 'dot' file</a>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]358</div>
359<div class="doc_text">
360 <p>
361 This pass, only available in <code>opt</code>, prints the dominator tree
362 into a <code>.dot</code> graph. This graph can then be processed with the
363 "dot" tool to convert it to postscript or some other suitable format.
364 </p>
365</div>
366
367<!-------------------------------------------------------------------------- -->
368<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]369 <a name="dot-dom-only">-dot-dom-only: Print dominator tree of function to 'dot' file (with no
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]370 function bodies)</a>
371</div>
372<div class="doc_text">
373 <p>
374 This pass, only available in <code>opt</code>, prints the dominator tree
375 into a <code>.dot</code> graph, omitting the function bodies. This graph can
376 then be processed with the "dot" tool to convert it to postscript or some
377 other suitable format.
378 </p>
379</div>
380
381<!-------------------------------------------------------------------------- -->
382<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]383 <a name="dot-postdom">dot-postdom: Print post dominator tree of function to 'dot' file</a>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]384</div>
385<div class="doc_text">
386 <p>
387 This pass, only available in <code>opt</code>, prints the post dominator tree
388 into a <code>.dot</code> graph. This graph can then be processed with the
389 "dot" tool to convert it to postscript or some other suitable format.
390 </p>
391</div>
392
393<!-------------------------------------------------------------------------- -->
394<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]395 <a name="dot-postdom-only">dot-postdom-only: Print post dominator tree of function to 'dot' file
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]396 (with no function bodies)</a>
397</div>
398<div class="doc_text">
399 <p>
400 This pass, only available in <code>opt</code>, prints the post dominator tree
401 into a <code>.dot</code> graph, omitting the function bodies. This graph can
402 then be processed with the "dot" tool to convert it to postscript or some
403 other suitable format.
404 </p>
405</div>
406
407<!-------------------------------------------------------------------------- -->
408<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]409 <a name="globalsmodref-aa">-globalsmodref-aa: Simple mod/ref analysis for globals</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]410</div>
411<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]412 <p>
413 This simple pass provides alias and mod/ref information for global values
414 that do not have their address taken, and keeps track of whether functions
415 read or write memory (are "pure"). For this simple (but very common) case,
416 we can provide pretty accurate and useful information.
417 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]418</div>
419
420<!-------------------------------------------------------------------------- -->
421<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]422 <a name="instcount">-instcount: Counts the various types of Instructions</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]423</div>
424<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]425 <p>
426 This pass collects the count of all instructions and reports them
427 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]428</div>
429
430<!-------------------------------------------------------------------------- -->
431<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]432 <a name="interprocedural-aa-eval">-interprocedural-aa-eval: Exhaustive Interprocedural Alias Analysis Precision Evaluator</a>
433</div>
434<div class="doc_text">
435 <p>This pass implements a simple N^2 alias analysis accuracy evaluator.
436 Basically, for each function in the program, it simply queries to see how the
437 alias analysis implementation answers alias queries between each pair of
438 pointers in the function.
439 </p>
440</div>
441
442<!-------------------------------------------------------------------------- -->
443<div class="doc_subsection">
444 <a name="interprocedural-basic-aa">-interprocedural-basic-aa: Interprocedural Basic Alias Analysis</a>
445</div>
446<div class="doc_text">
447 <p>This pass defines the default implementation of the Alias Analysis interface
448 that simply implements a few identities (two different globals cannot alias,
449 etc), but otherwise does no analysis.
450 </p>
451</div>
452
453<!-------------------------------------------------------------------------- -->
454<div class="doc_subsection">
455 <a name="intervals">-intervals: Interval Partition Construction</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]456</div>
457<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]458 <p>
459 This analysis calculates and represents the interval partition of a function,
460 or a preexisting interval partition.
461 </p>
462
463 <p>
464 In this way, the interval partition may be used to reduce a flow graph down
465 to its degenerate single node interval partition (unless it is irreducible).
466 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]467</div>
468
469<!-------------------------------------------------------------------------- -->
470<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]471 <a name="iv-users">-iv-users: Induction Variable Users</a>
472</div>
473<div class="doc_text">
474 <p>Bookkeeping for "interesting" users of expressions computed from
475 induction variables.</p>
476</div>
477
478<!-------------------------------------------------------------------------- -->
479<div class="doc_subsection">
480 <a name="lazy-value-info">-lazy-value-info: Lazy Value Information Analysis</a>
481</div>
482<div class="doc_text">
483 <p>Interface for lazy computation of value constraint information.</p>
484</div>
485
486<!-------------------------------------------------------------------------- -->
487<div class="doc_subsection">
488 <a name="lda">-lda: Loop Dependence Analysis</a>
489</div>
490<div class="doc_text">
491 <p>Loop dependence analysis framework, which is used to detect dependences in
492 memory accesses in loops.</p>
493</div>
494
495<!-------------------------------------------------------------------------- -->
496<div class="doc_subsection">
497 <a name="libcall-aa">-libcall-aa: LibCall Alias Analysis</a>
498</div>
499<div class="doc_text">
500 <p>LibCall Alias Analysis.</p>
501</div>
502
503<!-------------------------------------------------------------------------- -->
504<div class="doc_subsection">
505 <a name="lint">-lint: Check for common errors in LLVM IR</a>
506</div>
507<div class="doc_text">
508 <p>This pass statically checks for common and easily-identified constructs
509 which produce undefined or likely unintended behavior in LLVM IR.</p>
510
511 <p>It is not a guarantee of correctness, in two ways. First, it isn't
512 comprehensive. There are checks which could be done statically which are
513 not yet implemented. Some of these are indicated by TODO comments, but
514 those aren't comprehensive either. Second, many conditions cannot be
515 checked statically. This pass does no dynamic instrumentation, so it
516 can't check for all possible problems.</p>
517
518 <p>Another limitation is that it assumes all code will be executed. A store
519 through a null pointer in a basic block which is never reached is harmless,
520 but this pass will warn about it anyway.</p>
521
522 <p>Optimization passes may make conditions that this pass checks for more or
523 less obvious. If an optimization pass appears to be introducing a warning,
524 it may be that the optimization pass is merely exposing an existing
525 condition in the code.</p>
526
527 <p>This code may be run before instcombine. In many cases, instcombine checks
528 for the same kinds of things and turns instructions with undefined behavior
529 into unreachable (or equivalent). Because of this, this pass makes some
530 effort to look through bitcasts and so on.
531 </p>
532</div>
533
534<!-------------------------------------------------------------------------- -->
535<div class="doc_subsection">
536 <a name="live-values">-live-values: Values Liveness Analysis</a>
537</div>
538<div class="doc_text">
539 <p>LLVM IR Value liveness analysis pass.</p>
540</div>
541
542<!-------------------------------------------------------------------------- -->
543<div class="doc_subsection">
544 <a name="loops">-loops: Natural Loop Construction</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]545</div>
546<div class="doc_text">
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]547 <p>
548 This analysis is used to identify natural loops and determine the loop depth
549 of various nodes of the CFG. Note that the loops identified may actually be
550 several natural loops that share the same header node... not just a single
551 natural loop.
552 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]553</div>
554
555<!-------------------------------------------------------------------------- -->
556<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]557 <a name="memdep">-memdep: Memory Dependence Analysis</a>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]558</div>
559<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]560 <p>
561 An analysis that determines, for a given memory operation, what preceding
562 memory operations it depends on. It builds on alias analysis information, and
563 tries to provide a lazy, caching interface to a common kind of alias
564 information query.
565 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]566</div>
567
568<!-------------------------------------------------------------------------- -->
569<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]570 <a name="module-debuginfo">-module-debuginfo: Prints module debug info metadata</a>
571</div>
572<div class="doc_text">
573 <p>This pass decodes the debug info metadata in a module and prints in a
574 (sufficiently-prepared-) human-readable form.
575
576 For example, run this pass from opt along with the -analyze option, and
577 it'll print to standard output.
578 </p>
579</div>
580
581<!-------------------------------------------------------------------------- -->
582<div class="doc_subsection">
583 <a name="no-aa">-no-aa: No Alias Analysis (always returns 'may' alias)</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]584</div>
585<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]586 <p>
587 Always returns "I don't know" for alias queries. NoAA is unlike other alias
588 analysis implementations, in that it does not chain to a previous analysis. As
589 such it doesn't follow many of the rules that other alias analyses must.
590 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]591</div>
592
593<!-------------------------------------------------------------------------- -->
594<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]595 <a name="no-profile">-no-profile: No Profile Information</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]596</div>
597<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]598 <p>
599 The default "no profile" implementation of the abstract
600 <code>ProfileInfo</code> interface.
601 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]602</div>
603
604<!-------------------------------------------------------------------------- -->
605<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]606 <a name="pointertracking">-pointertracking: Track pointer bounds.</a>
607</div>
608<div class="doc_text">
609 <p>Tracking of pointer bounds.
610 </p>
611</div>
612
613<!-------------------------------------------------------------------------- -->
614<div class="doc_subsection">
615 <a name="postdomfrontier">-postdomfrontier: Post-Dominance Frontier Construction</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]616</div>
617<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]618 <p>
619 This pass is a simple post-dominator construction algorithm for finding
620 post-dominator frontiers.
621 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]622</div>
623
624<!-------------------------------------------------------------------------- -->
625<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]626 <a name="postdomtree">-postdomtree: Post-Dominator Tree Construction</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]627</div>
628<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]629 <p>
630 This pass is a simple post-dominator construction algorithm for finding
631 post-dominators.
632 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]633</div>
634
635<!-------------------------------------------------------------------------- -->
636<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]637 <a name="print-alias-sets">-print-alias-sets: Alias Set Printer</a>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]638</div>
639<div class="doc_text">
640 <p>Yet to be written.</p>
641</div>
642
643<!-------------------------------------------------------------------------- -->
644<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]645 <a name="print-callgraph">-print-callgraph: Print a call graph</a>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]646</div>
647<div class="doc_text">
648 <p>
649 This pass, only available in <code>opt</code>, prints the call graph to
650 standard output in a human-readable form.
651 </p>
652</div>
653
654<!-------------------------------------------------------------------------- -->
655<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]656 <a name="print-callgraph-sccs">-print-callgraph-sccs: Print SCCs of the Call Graph</a>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]657</div>
658<div class="doc_text">
659 <p>
660 This pass, only available in <code>opt</code>, prints the SCCs of the call
661 graph to standard output in a human-readable form.
662 </p>
663</div>
664
665<!-------------------------------------------------------------------------- -->
666<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]667 <a name="print-cfg-sccs">-print-cfg-sccs: Print SCCs of each function CFG</a>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]668</div>
669<div class="doc_text">
670 <p>
671 This pass, only available in <code>opt</code>, prints the SCCs of each
672 function CFG to standard output in a human-readable form.
673 </p>
674</div>
675
676<!-------------------------------------------------------------------------- -->
677<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]678 <a name="print-dbginfo">-print-dbginfo: Print debug info in human readable form</a>
679</div>
680<div class="doc_text">
681 <p>Pass that prints instructions, and associated debug info:
682 <ul>
683
684 <li>source/line/col information</li>
685 <li>original variable name</li>
686 <li>original type name</li>
687 </ul>
688
689 </p>
690</div>
691
692<!-------------------------------------------------------------------------- -->
693<div class="doc_subsection">
694 <a name="print-dom-info">-print-dom-info: Dominator Info Printer</a>
695</div>
696<div class="doc_text">
697 <p>Dominator Info Printer.</p>
698</div>
699
700<!-------------------------------------------------------------------------- -->
701<div class="doc_subsection">
702 <a name="print-externalfnconstants">-print-externalfnconstants: Print external fn callsites passed constants</a>
Duncan Sands3ee8fc92008-09-23 12:47:39 +0000[diff] [blame]703</div>
704<div class="doc_text">
705 <p>
706 This pass, only available in <code>opt</code>, prints out call sites to
707 external functions that are called with constant arguments. This can be
708 useful when looking for standard library functions we should constant fold
709 or handle in alias analyses.
710 </p>
711</div>
712
713<!-------------------------------------------------------------------------- -->
714<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]715 <a name="print-function">-print-function: Print function to stderr</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]716</div>
717<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]718 <p>
719 The <code>PrintFunctionPass</code> class is designed to be pipelined with
720 other <code>FunctionPass</code>es, and prints out the functions of the module
721 as they are processed.
722 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]723</div>
724
725<!-------------------------------------------------------------------------- -->
726<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]727 <a name="print-module">-print-module: Print module to stderr</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]728</div>
729<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]730 <p>
731 This pass simply prints out the entire module when it is executed.
732 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]733</div>
734
735<!-------------------------------------------------------------------------- -->
736<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]737 <a name="print-used-types">-print-used-types: Find Used Types</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]738</div>
739<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]740 <p>
741 This pass is used to seek out all of the types in use by the program. Note
742 that this analysis explicitly does not include types only used by the symbol
743 table.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]744</div>
745
746<!-------------------------------------------------------------------------- -->
747<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]748 <a name="profile-estimator">-profile-estimator: Estimate profiling information</a>
749</div>
750<div class="doc_text">
751 <p>Profiling information that estimates the profiling information
752 in a very crude and unimaginative way.
753 </p>
754</div>
755
756<!-------------------------------------------------------------------------- -->
757<div class="doc_subsection">
758 <a name="profile-loader">-profile-loader: Load profile information from llvmprof.out</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]759</div>
760<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]761 <p>
762 A concrete implementation of profiling information that loads the information
763 from a profile dump file.
764 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]765</div>
766
767<!-------------------------------------------------------------------------- -->
768<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]769 <a name="profile-verifier">-profile-verifier: Verify profiling information</a>
770</div>
771<div class="doc_text">
772 <p>Pass that checks profiling information for plausibility.</p>
773</div>
774
775<!-------------------------------------------------------------------------- -->
776<div class="doc_subsection">
777 <a name="scalar-evolution">-scalar-evolution: Scalar Evolution Analysis</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]778</div>
779<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]780 <p>
781 The <code>ScalarEvolution</code> analysis can be used to analyze and
782 catagorize scalar expressions in loops. It specializes in recognizing general
783 induction variables, representing them with the abstract and opaque
784 <code>SCEV</code> class. Given this analysis, trip counts of loops and other
785 important properties can be obtained.
786 </p>
787
788 <p>
789 This analysis is primarily useful for induction variable substitution and
790 strength reduction.
791 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]792</div>
793
794<!-------------------------------------------------------------------------- -->
795<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]796 <a name="scev-aa">-scev-aa: </a>
797</div>
798<div class="doc_text">
799 <p>Simple alias analysis implemented in terms of ScalarEvolution queries.
800
801 This differs from traditional loop dependence analysis in that it tests
802 for dependencies within a single iteration of a loop, rather than
803 dependencies between different iterations.
804
805 ScalarEvolution has a more complete understanding of pointer arithmetic
806 than BasicAliasAnalysis' collection of ad-hoc analyses.
807 </p>
808</div>
809
810<!-------------------------------------------------------------------------- -->
811<div class="doc_subsection">
812 <a name="strip-dead-debug-info">-strip-dead-debug-info: Strip debug info for unused symbols</a>
813</div>
814<div class="doc_text">
815 <p>
816 performs code stripping. this transformation can delete:
817 </p>
818
819 <ol>
820 <li>names for virtual registers</li>
821 <li>symbols for internal globals and functions</li>
822 <li>debug information</li>
823 </ol>
824
825 <p>
826 note that this transformation makes code much less readable, so it should
827 only be used in situations where the <tt>strip</tt> utility would be used,
828 such as reducing code size or making it harder to reverse engineer code.
829 </p>
830</div>
831
832<!-------------------------------------------------------------------------- -->
833<div class="doc_subsection">
834 <a name="targetdata">-targetdata: Target Data Layout</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]835</div>
836<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]837 <p>Provides other passes access to information on how the size and alignment
838 required by the the target ABI for various data types.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]839</div>
840
841<!-- ======================================================================= -->
842<div class="doc_section"> <a name="transform">Transform Passes</a></div>
843<div class="doc_text">
844 <p>This section describes the LLVM Transform Passes.</p>
845</div>
846
847<!-------------------------------------------------------------------------- -->
848<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]849 <a name="abcd">-abcd: Remove redundant conditional branches</a>
850</div>
851<div class="doc_text">
852 <p>ABCD removes conditional branch instructions that can be proved redundant.
853 With the SSI representation, each variable has a constraint. By analyzing these
854 constraints we can prove that a branch is redundant. When a branch is proved
855 redundant it means that one direction will always be taken; thus, we can change
856 this branch into an unconditional jump.</p>
857 <p>It is advisable to run <a href="#simplifycfg">SimplifyCFG</a> and
858 <a href="#adce">Aggressive Dead Code Elimination</a> after ABCD
859 to clean up the code.</p>
860</div>
861
862<!-------------------------------------------------------------------------- -->
863<div class="doc_subsection">
864 <a name="adce">-adce: Aggressive Dead Code Elimination</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]865</div>
866<div class="doc_text">
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]867 <p>ADCE aggressively tries to eliminate code. This pass is similar to
868 <a href="#dce">DCE</a> but it assumes that values are dead until proven
869 otherwise. This is similar to <a href="#sccp">SCCP</a>, except applied to
870 the liveness of values.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]871</div>
872
873<!-------------------------------------------------------------------------- -->
874<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]875 <a name="always-inline">-always-inline: Inliner for always_inline functions</a>
876</div>
877<div class="doc_text">
878 <p>A custom inliner that handles only functions that are marked as
879 "always inline".</p>
880</div>
881
882<!-------------------------------------------------------------------------- -->
883<div class="doc_subsection">
884 <a name="argpromotion">-argpromotion: Promote 'by reference' arguments to scalars</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]885</div>
886<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]887 <p>
888 This pass promotes "by reference" arguments to be "by value" arguments. In
889 practice, this means looking for internal functions that have pointer
890 arguments. If it can prove, through the use of alias analysis, that an
891 argument is *only* loaded, then it can pass the value into the function
892 instead of the address of the value. This can cause recursive simplification
893 of code and lead to the elimination of allocas (especially in C++ template
894 code like the STL).
895 </p>
896
897 <p>
898 This pass also handles aggregate arguments that are passed into a function,
899 scalarizing them if the elements of the aggregate are only loaded. Note that
900 it refuses to scalarize aggregates which would require passing in more than
901 three operands to the function, because passing thousands of operands for a
902 large array or structure is unprofitable!
903 </p>
904
905 <p>
906 Note that this transformation could also be done for arguments that are only
907 stored to (returning the value instead), but does not currently. This case
908 would be best handled when and if LLVM starts supporting multiple return
909 values from functions.
910 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]911</div>
912
913<!-------------------------------------------------------------------------- -->
914<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]915 <a name="block-placement">-block-placement: Profile Guided Basic Block Placement</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]916</div>
917<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]918 <p>This pass is a very simple profile guided basic block placement algorithm.
919 The idea is to put frequently executed blocks together at the start of the
920 function and hopefully increase the number of fall-through conditional
921 branches. If there is no profile information for a particular function, this
922 pass basically orders blocks in depth-first order.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]923</div>
924
925<!-------------------------------------------------------------------------- -->
926<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]927 <a name="break-crit-edges">-break-crit-edges: Break critical edges in CFG</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]928</div>
929<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]930 <p>
931 Break all of the critical edges in the CFG by inserting a dummy basic block.
932 It may be "required" by passes that cannot deal with critical edges. This
933 transformation obviously invalidates the CFG, but can update forward dominator
934 (set, immediate dominators, tree, and frontier) information.
935 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]936</div>
937
938<!-------------------------------------------------------------------------- -->
939<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]940 <a name="codegenprepare">-codegenprepare: Prepare a function for code generation</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]941</div>
942<div class="doc_text">
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]943 This pass munges the code in the input function to better prepare it for
944 SelectionDAG-based code generation. This works around limitations in it's
945 basic-block-at-a-time approach. It should eventually be removed.
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]946</div>
947
948<!-------------------------------------------------------------------------- -->
949<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]950 <a name="constmerge">-constmerge: Merge Duplicate Global Constants</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]951</div>
952<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]953 <p>
954 Merges duplicate global constants together into a single constant that is
955 shared. This is useful because some passes (ie TraceValues) insert a lot of
956 string constants into the program, regardless of whether or not an existing
957 string is available.
958 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]959</div>
960
961<!-------------------------------------------------------------------------- -->
962<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]963 <a name="constprop">-constprop: Simple constant propagation</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]964</div>
965<div class="doc_text">
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]966 <p>This file implements constant propagation and merging. It looks for
967 instructions involving only constant operands and replaces them with a
Gordon Henriksenddaa61d2007-10-25 08:58:56 +0000[diff] [blame]968 constant value instead of an instruction. For example:</p>
969 <blockquote><pre>add i32 1, 2</pre></blockquote>
970 <p>becomes</p>
971 <blockquote><pre>i32 3</pre></blockquote>
Reid Spenceraf4af3a2007-03-27 02:49:31 +0000[diff] [blame]972 <p>NOTE: this pass has a habit of making definitions be dead. It is a good
973 idea to to run a <a href="#die">DIE</a> (Dead Instruction Elimination) pass
974 sometime after running this pass.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]975</div>
976
977<!-------------------------------------------------------------------------- -->
978<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]979 <a name="dce">-dce: Dead Code Elimination</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]980</div>
981<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]982 <p>
983 Dead code elimination is similar to <a href="#die">dead instruction
984 elimination</a>, but it rechecks instructions that were used by removed
985 instructions to see if they are newly dead.
986 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]987</div>
988
989<!-------------------------------------------------------------------------- -->
990<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]991 <a name="deadargelim">-deadargelim: Dead Argument Elimination</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]992</div>
993<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]994 <p>
995 This pass deletes dead arguments from internal functions. Dead argument
996 elimination removes arguments which are directly dead, as well as arguments
997 only passed into function calls as dead arguments of other functions. This
998 pass also deletes dead arguments in a similar way.
999 </p>
1000
1001 <p>
1002 This pass is often useful as a cleanup pass to run after aggressive
1003 interprocedural passes, which add possibly-dead arguments.
1004 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1005</div>
1006
1007<!-------------------------------------------------------------------------- -->
1008<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1009 <a name="deadtypeelim">-deadtypeelim: Dead Type Elimination</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1010</div>
1011<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1012 <p>
1013 This pass is used to cleanup the output of GCC. It eliminate names for types
1014 that are unused in the entire translation unit, using the <a
1015 href="#findusedtypes">find used types</a> pass.
1016 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1017</div>
1018
1019<!-------------------------------------------------------------------------- -->
1020<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1021 <a name="die">-die: Dead Instruction Elimination</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1022</div>
1023<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1024 <p>
1025 Dead instruction elimination performs a single pass over the function,
1026 removing instructions that are obviously dead.
1027 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1028</div>
1029
1030<!-------------------------------------------------------------------------- -->
1031<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1032 <a name="dse">-dse: Dead Store Elimination</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1033</div>
1034<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1035 <p>
1036 A trivial dead store elimination that only considers basic-block local
1037 redundant stores.
1038 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1039</div>
1040
1041<!-------------------------------------------------------------------------- -->
1042<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1043 <a name="functionattrs">-functionattrs: Deduce function attributes</a>
1044</div>
1045<div class="doc_text">
1046 <p>A simple interprocedural pass which walks the call-graph, looking for
1047 functions which do not access or only read non-local memory, and marking them
1048 readnone/readonly. In addition, it marks function arguments (of pointer type)
1049 'nocapture' if a call to the function does not create any copies of the pointer
1050 value that outlive the call. This more or less means that the pointer is only
1051 dereferenced, and not returned from the function or stored in a global.
1052 This pass is implemented as a bottom-up traversal of the call-graph.
1053 </p>
1054</div>
1055
1056<!-------------------------------------------------------------------------- -->
1057<div class="doc_subsection">
1058 <a name="globaldce">-globaldce: Dead Global Elimination</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1059</div>
1060<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1061 <p>
1062 This transform is designed to eliminate unreachable internal globals from the
1063 program. It uses an aggressive algorithm, searching out globals that are
1064 known to be alive. After it finds all of the globals which are needed, it
1065 deletes whatever is left over. This allows it to delete recursive chunks of
1066 the program which are unreachable.
1067 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1068</div>
1069
1070<!-------------------------------------------------------------------------- -->
1071<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1072 <a name="globalopt">-globalopt: Global Variable Optimizer</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1073</div>
1074<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1075 <p>
1076 This pass transforms simple global variables that never have their address
1077 taken. If obviously true, it marks read/write globals as constant, deletes
1078 variables only stored to, etc.
1079 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1080</div>
1081
1082<!-------------------------------------------------------------------------- -->
1083<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1084 <a name="gvn">-gvn: Global Value Numbering</a>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]1085</div>
1086<div class="doc_text">
1087 <p>
Chris Lattner60f03402009-10-10 18:40:48 +0000[diff] [blame]1088 This pass performs global value numbering to eliminate fully and partially
1089 redundant instructions. It also performs redundant load elimination.
Matthijs Kooijman845f5242008-06-05 07:55:49 +0000[diff] [blame]1090 </p>
Gordon Henriksen0e15dc22007-10-25 10:18:27 +0000[diff] [blame]1091</div>
1092
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1093<!-------------------------------------------------------------------------- -->
1094<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1095 <a name="indvars">-indvars: Canonicalize Induction Variables</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1096</div>
1097<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1098 <p>
1099 This transformation analyzes and transforms the induction variables (and
1100 computations derived from them) into simpler forms suitable for subsequent
1101 analysis and transformation.
1102 </p>
1103
1104 <p>
1105 This transformation makes the following changes to each loop with an
1106 identifiable induction variable:
1107 </p>
1108
1109 <ol>
1110 <li>All loops are transformed to have a <em>single</em> canonical
1111 induction variable which starts at zero and steps by one.</li>
1112 <li>The canonical induction variable is guaranteed to be the first PHI node
1113 in the loop header block.</li>
1114 <li>Any pointer arithmetic recurrences are raised to use array
1115 subscripts.</li>
1116 </ol>
1117
1118 <p>
1119 If the trip count of a loop is computable, this pass also makes the following
1120 changes:
1121 </p>
1122
1123 <ol>
1124 <li>The exit condition for the loop is canonicalized to compare the
1125 induction value against the exit value. This turns loops like:
1126 <blockquote><pre>for (i = 7; i*i < 1000; ++i)</pre></blockquote>
1127 into
1128 <blockquote><pre>for (i = 0; i != 25; ++i)</pre></blockquote></li>
1129 <li>Any use outside of the loop of an expression derived from the indvar
1130 is changed to compute the derived value outside of the loop, eliminating
1131 the dependence on the exit value of the induction variable. If the only
1132 purpose of the loop is to compute the exit value of some derived
1133 expression, this transformation will make the loop dead.</li>
Gordon Henriksene626bbe2007-11-04 16:17:00 +0000[diff] [blame]1134 </ol>
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1135
1136 <p>
1137 This transformation should be followed by strength reduction after all of the
1138 desired loop transformations have been performed. Additionally, on targets
1139 where it is profitable, the loop could be transformed to count down to zero
1140 (the "do loop" optimization).
1141 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1142</div>
1143
1144<!-------------------------------------------------------------------------- -->
1145<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1146 <a name="inline">-inline: Function Integration/Inlining</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1147</div>
1148<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1149 <p>
1150 Bottom-up inlining of functions into callees.
1151 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1152</div>
1153
1154<!-------------------------------------------------------------------------- -->
1155<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1156 <a name="insert-edge-profiling">-insert-edge-profiling: Insert instrumentation for edge profiling</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1157</div>
1158<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1159 <p>
1160 This pass instruments the specified program with counters for edge profiling.
1161 Edge profiling can give a reasonable approximation of the hot paths through a
1162 program, and is used for a wide variety of program transformations.
1163 </p>
1164
1165 <p>
1166 Note that this implementation is very naïve. It inserts a counter for
1167 <em>every</em> edge in the program, instead of using control flow information
1168 to prune the number of counters inserted.
1169 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1170</div>
1171
1172<!-------------------------------------------------------------------------- -->
1173<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1174 <a name="insert-optimal-edge-profiling">-insert-optimal-edge-profiling: Insert optimal instrumentation for edge profiling</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1175</div>
1176<div class="doc_text">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1177 <p>This pass instruments the specified program with counters for edge profiling.
1178 Edge profiling can give a reasonable approximation of the hot paths through a
1179 program, and is used for a wide variety of program transformations.
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1180 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1181</div>
1182
1183<!-------------------------------------------------------------------------- -->
1184<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1185 <a name="instcombine">-instcombine: Combine redundant instructions</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1186</div>
1187<div class="doc_text">
Gordon Henriksen55cbec32007-10-26 03:03:51 +0000[diff] [blame]1188 <p>
1189 Combine instructions to form fewer, simple
1190 instructions. This pass does not modify the CFG This pass is where algebraic
1191 simplification happens.
1192 </p>
1193
1194 <p>
1195 This pass combines things like:
1196 </p>
1197
1198<blockquote><pre
1199>%Y = add i32 %X, 1
1200%Z = add i32 %Y, 1</pre></blockquote>
1201
1202 <p>
1203 into:
1204 </p>
1205
1206<blockquote><pre
1207>%Z = add i32 %X, 2</pre></blockquote>
1208
1209 <p>
1210 This is a simple worklist driven algorithm.
1211 </p>
1212
1213 <p>
1214 This pass guarantees that the following canonicalizations are performed on
1215 the program:
1216 </p>
1217
1218 <ul>
1219 <li>If a binary operator has a constant operand, it is moved to the right-
1220 hand side.</li>
1221 <li>Bitwise operators with constant operands are always grouped so that
1222 shifts are performed first, then <code>or</code>s, then
1223 <code>and</code>s, then <code>xor</code>s.</li>
1224 <li>Compare instructions are converted from <code>&lt;</code>,
1225 <code>&gt;</code>, <code>≤</code>, or <code>≥</code> to
1226 <code>=</code> or <code>≠</code> if possible.</li>
1227 <li>All <code>cmp</code> instructions on boolean values are replaced with
1228 logical operations.</li>
1229 <li><code>add <var>X</var>, <var>X</var></code> is represented as
1230 <code>mul <var>X</var>, 2</code> ⇒ <code>shl <var>X</var>, 1</code></li>
1231 <li>Multiplies with a constant power-of-two argument are transformed into
1232 shifts.</li>
1233 <li>… etc.</li>
1234 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1235</div>
1236
1237<!-------------------------------------------------------------------------- -->
1238<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1239 <a name="internalize">-internalize: Internalize Global Symbols</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1240</div>
1241<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1242 <p>
1243 This pass loops over all of the functions in the input module, looking for a
1244 main function. If a main function is found, all other functions and all
1245 global variables with initializers are marked as internal.
1246 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1247</div>
1248
1249<!-------------------------------------------------------------------------- -->
1250<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1251 <a name="ipconstprop">-ipconstprop: Interprocedural constant propagation</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1252</div>
1253<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1254 <p>
1255 This pass implements an <em>extremely</em> simple interprocedural constant
1256 propagation pass. It could certainly be improved in many different ways,
1257 like using a worklist. This pass makes arguments dead, but does not remove
1258 them. The existing dead argument elimination pass should be run after this
1259 to clean up the mess.
1260 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1261</div>
1262
1263<!-------------------------------------------------------------------------- -->
1264<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1265 <a name="ipsccp">-ipsccp: Interprocedural Sparse Conditional Constant Propagation</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1266</div>
1267<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1268 <p>
1269 An interprocedural variant of <a href="#sccp">Sparse Conditional Constant
1270 Propagation</a>.
1271 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1272</div>
1273
1274<!-------------------------------------------------------------------------- -->
1275<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1276 <a name="jump-threading">-jump-threading: Thread control through conditional blocks</a>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1277</div>
1278<div class="doc_text">
1279 <p>
1280 Jump threading tries to find distinct threads of control flow running through
1281 a basic block. This pass looks at blocks that have multiple predecessors and
1282 multiple successors. If one or more of the predecessors of the block can be
1283 proven to always cause a jump to one of the successors, we forward the edge
1284 from the predecessor to the successor by duplicating the contents of this
1285 block.
1286 </p>
1287 <p>
1288 An example of when this can occur is code like this:
1289 </p>
1290
1291 <pre
1292>if () { ...
1293 X = 4;
1294}
1295if (X &lt; 3) {</pre>
1296
1297 <p>
1298 In this case, the unconditional branch at the end of the first if can be
1299 revectored to the false side of the second if.
1300 </p>
1301</div>
1302
1303<!-------------------------------------------------------------------------- -->
1304<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1305 <a name="lcssa">-lcssa: Loop-Closed SSA Form Pass</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1306</div>
1307<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1308 <p>
1309 This pass transforms loops by placing phi nodes at the end of the loops for
1310 all values that are live across the loop boundary. For example, it turns
1311 the left into the right code:
1312 </p>
1313
1314 <pre
1315>for (...) for (...)
1316 if (c) if (c)
1317 X1 = ... X1 = ...
1318 else else
1319 X2 = ... X2 = ...
1320 X3 = phi(X1, X2) X3 = phi(X1, X2)
1321... = X3 + 4 X4 = phi(X3)
1322 ... = X4 + 4</pre>
1323
1324 <p>
1325 This is still valid LLVM; the extra phi nodes are purely redundant, and will
1326 be trivially eliminated by <code>InstCombine</code>. The major benefit of
1327 this transformation is that it makes many other loop optimizations, such as
1328 LoopUnswitching, simpler.
1329 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1330</div>
1331
1332<!-------------------------------------------------------------------------- -->
1333<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1334 <a name="licm">-licm: Loop Invariant Code Motion</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1335</div>
1336<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1337 <p>
1338 This pass performs loop invariant code motion, attempting to remove as much
1339 code from the body of a loop as possible. It does this by either hoisting
1340 code into the preheader block, or by sinking code to the exit blocks if it is
1341 safe. This pass also promotes must-aliased memory locations in the loop to
1342 live in registers, thus hoisting and sinking "invariant" loads and stores.
1343 </p>
1344
1345 <p>
1346 This pass uses alias analysis for two purposes:
1347 </p>
1348
1349 <ul>
1350 <li>Moving loop invariant loads and calls out of loops. If we can determine
1351 that a load or call inside of a loop never aliases anything stored to,
1352 we can hoist it or sink it like any other instruction.</li>
1353 <li>Scalar Promotion of Memory - If there is a store instruction inside of
1354 the loop, we try to move the store to happen AFTER the loop instead of
1355 inside of the loop. This can only happen if a few conditions are true:
1356 <ul>
1357 <li>The pointer stored through is loop invariant.</li>
1358 <li>There are no stores or loads in the loop which <em>may</em> alias
1359 the pointer. There are no calls in the loop which mod/ref the
1360 pointer.</li>
1361 </ul>
1362 If these conditions are true, we can promote the loads and stores in the
1363 loop of the pointer to use a temporary alloca'd variable. We then use
1364 the mem2reg functionality to construct the appropriate SSA form for the
1365 variable.</li>
1366 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1367</div>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1368<!-------------------------------------------------------------------------- -->
1369<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1370 <a name="loop-deletion">-loop-deletion: Dead Loop Deletion Pass</a>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1371</div>
1372<div class="doc_text">
1373 <p>
1374 This file implements the Dead Loop Deletion Pass. This pass is responsible
1375 for eliminating loops with non-infinite computable trip counts that have no
1376 side effects or volatile instructions, and do not contribute to the
1377 computation of the function's return value.
1378 </p>
1379</div>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1380
1381<!-------------------------------------------------------------------------- -->
1382<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1383 <a name="loop-extract">-loop-extract: Extract loops into new functions</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1384</div>
1385<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1386 <p>
1387 A pass wrapper around the <code>ExtractLoop()</code> scalar transformation to
1388 extract each top-level loop into its own new function. If the loop is the
1389 <em>only</em> loop in a given function, it is not touched. This is a pass most
1390 useful for debugging via bugpoint.
1391 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1392</div>
1393
1394<!-------------------------------------------------------------------------- -->
1395<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1396 <a name="loop-extract-single">-loop-extract-single: Extract at most one loop into a new function</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1397</div>
1398<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1399 <p>
1400 Similar to <a href="#loop-extract">Extract loops into new functions</a>,
1401 this pass extracts one natural loop from the program into a function if it
1402 can. This is used by bugpoint.
1403 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1404</div>
1405
1406<!-------------------------------------------------------------------------- -->
1407<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1408 <a name="loop-index-split">-loop-index-split: Index Split Loops</a>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1409</div>
1410<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1411 <p>
1412 This pass divides loop's iteration range by spliting loop such that each
1413 individual loop is executed efficiently.
1414 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1415</div>
1416
1417<!-------------------------------------------------------------------------- -->
1418<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1419 <a name="loop-reduce">-loop-reduce: Loop Strength Reduction</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1420</div>
1421<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1422 <p>
1423 This pass performs a strength reduction on array references inside loops that
1424 have as one or more of their components the loop induction variable. This is
1425 accomplished by creating a new value to hold the initial value of the array
1426 access for the first iteration, and then creating a new GEP instruction in
1427 the loop to increment the value by the appropriate amount.
1428 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1429</div>
1430
1431<!-------------------------------------------------------------------------- -->
1432<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1433 <a name="loop-rotate">-loop-rotate: Rotate Loops</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1434</div>
1435<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1436 <p>A simple loop rotation transformation.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1437</div>
1438
1439<!-------------------------------------------------------------------------- -->
1440<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1441 <a name="loop-unroll">-loop-unroll: Unroll loops</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1442</div>
1443<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1444 <p>
1445 This pass implements a simple loop unroller. It works best when loops have
1446 been canonicalized by the <a href="#indvars"><tt>-indvars</tt></a> pass,
1447 allowing it to determine the trip counts of loops easily.
1448 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1449</div>
1450
1451<!-------------------------------------------------------------------------- -->
1452<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1453 <a name="loop-unswitch">-loop-unswitch: Unswitch loops</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1454</div>
1455<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1456 <p>
1457 This pass transforms loops that contain branches on loop-invariant conditions
1458 to have multiple loops. For example, it turns the left into the right code:
1459 </p>
1460
1461 <pre
1462>for (...) if (lic)
1463 A for (...)
1464 if (lic) A; B; C
1465 B else
1466 C for (...)
1467 A; C</pre>
1468
1469 <p>
1470 This can increase the size of the code exponentially (doubling it every time
1471 a loop is unswitched) so we only unswitch if the resultant code will be
1472 smaller than a threshold.
1473 </p>
1474
1475 <p>
1476 This pass expects LICM to be run before it to hoist invariant conditions out
1477 of the loop, to make the unswitching opportunity obvious.
1478 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1479</div>
1480
1481<!-------------------------------------------------------------------------- -->
1482<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1483 <a name="loopsimplify">-loopsimplify: Canonicalize natural loops</a>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1484</div>
1485<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1486 <p>
1487 This pass performs several transformations to transform natural loops into a
1488 simpler form, which makes subsequent analyses and transformations simpler and
1489 more effective.
1490 </p>
1491
1492 <p>
1493 Loop pre-header insertion guarantees that there is a single, non-critical
1494 entry edge from outside of the loop to the loop header. This simplifies a
1495 number of analyses and transformations, such as LICM.
1496 </p>
1497
1498 <p>
1499 Loop exit-block insertion guarantees that all exit blocks from the loop
1500 (blocks which are outside of the loop that have predecessors inside of the
1501 loop) only have predecessors from inside of the loop (and are thus dominated
1502 by the loop header). This simplifies transformations such as store-sinking
1503 that are built into LICM.
1504 </p>
1505
1506 <p>
1507 This pass also guarantees that loops will have exactly one backedge.
1508 </p>
1509
1510 <p>
1511 Note that the simplifycfg pass will clean up blocks which are split out but
1512 end up being unnecessary, so usage of this pass should not pessimize
1513 generated code.
1514 </p>
1515
1516 <p>
1517 This pass obviously modifies the CFG, but updates loop information and
1518 dominator information.
1519 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]1520</div>
1521
1522<!-------------------------------------------------------------------------- -->
1523<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1524 <a name="lowerallocs">-lowerallocs: Lower allocations from instructions to calls</a>
1525</div>
1526<div class="doc_text">
1527 <p>
1528 Turn <tt>malloc</tt> and <tt>free</tt> instructions into <tt>@malloc</tt> and
1529 <tt>@free</tt> calls.
1530 </p>
1531
1532 <p>
1533 This is a target-dependent tranformation because it depends on the size of
1534 data types and alignment constraints.
1535 </p>
1536</div>
1537
1538<!-------------------------------------------------------------------------- -->
1539<div class="doc_subsection">
1540 <a name="lowerinvoke">-lowerinvoke: Lower invoke and unwind, for unwindless code generators</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1541</div>
1542<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1543 <p>
1544 This transformation is designed for use by code generators which do not yet
1545 support stack unwinding. This pass supports two models of exception handling
1546 lowering, the 'cheap' support and the 'expensive' support.
1547 </p>
1548
1549 <p>
1550 'Cheap' exception handling support gives the program the ability to execute
1551 any program which does not "throw an exception", by turning 'invoke'
1552 instructions into calls and by turning 'unwind' instructions into calls to
1553 abort(). If the program does dynamically use the unwind instruction, the
1554 program will print a message then abort.
1555 </p>
1556
1557 <p>
1558 'Expensive' exception handling support gives the full exception handling
1559 support to the program at the cost of making the 'invoke' instruction
1560 really expensive. It basically inserts setjmp/longjmp calls to emulate the
1561 exception handling as necessary.
1562 </p>
1563
1564 <p>
1565 Because the 'expensive' support slows down programs a lot, and EH is only
1566 used for a subset of the programs, it must be specifically enabled by the
1567 <tt>-enable-correct-eh-support</tt> option.
1568 </p>
1569
1570 <p>
1571 Note that after this pass runs the CFG is not entirely accurate (exceptional
1572 control flow edges are not correct anymore) so only very simple things should
1573 be done after the lowerinvoke pass has run (like generation of native code).
1574 This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't
1575 support the invoke instruction yet" lowering pass.
1576 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1577</div>
1578
1579<!-------------------------------------------------------------------------- -->
1580<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1581 <a name="lowersetjmp">-lowersetjmp: Lower Set Jump</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1582</div>
1583<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1584 <p>
1585 Lowers <tt>setjmp</tt> and <tt>longjmp</tt> to use the LLVM invoke and unwind
1586 instructions as necessary.
1587 </p>
1588
1589 <p>
1590 Lowering of <tt>longjmp</tt> is fairly trivial. We replace the call with a
1591 call to the LLVM library function <tt>__llvm_sjljeh_throw_longjmp()</tt>.
1592 This unwinds the stack for us calling all of the destructors for
1593 objects allocated on the stack.
1594 </p>
1595
1596 <p>
1597 At a <tt>setjmp</tt> call, the basic block is split and the <tt>setjmp</tt>
1598 removed. The calls in a function that have a <tt>setjmp</tt> are converted to
1599 invoke where the except part checks to see if it's a <tt>longjmp</tt>
1600 exception and, if so, if it's handled in the function. If it is, then it gets
1601 the value returned by the <tt>longjmp</tt> and goes to where the basic block
1602 was split. <tt>invoke</tt> instructions are handled in a similar fashion with
1603 the original except block being executed if it isn't a <tt>longjmp</tt>
1604 except that is handled by that function.
1605 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1606</div>
1607
1608<!-------------------------------------------------------------------------- -->
1609<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1610 <a name="lowerswitch">-lowerswitch: Lower SwitchInst's to branches</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1611</div>
1612<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1613 <p>
1614 Rewrites <tt>switch</tt> instructions with a sequence of branches, which
1615 allows targets to get away with not implementing the switch instruction until
1616 it is convenient.
1617 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1618</div>
1619
1620<!-------------------------------------------------------------------------- -->
1621<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1622 <a name="mem2reg">-mem2reg: Promote Memory to Register</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1623</div>
1624<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1625 <p>
1626 This file promotes memory references to be register references. It promotes
1627 <tt>alloca</tt> instructions which only have <tt>load</tt>s and
1628 <tt>store</tt>s as uses. An <tt>alloca</tt> is transformed by using dominator
1629 frontiers to place <tt>phi</tt> nodes, then traversing the function in
1630 depth-first order to rewrite <tt>load</tt>s and <tt>store</tt>s as
1631 appropriate. This is just the standard SSA construction algorithm to construct
1632 "pruned" SSA form.
1633 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1634</div>
1635
1636<!-------------------------------------------------------------------------- -->
1637<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1638 <a name="memcpyopt">-memcpyopt: Optimize use of memcpy and friend</a>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1639</div>
1640<div class="doc_text">
1641 <p>
1642 This pass performs various transformations related to eliminating memcpy
1643 calls, or transforming sets of stores into memset's.
1644 </p>
1645</div>
1646
1647<!-------------------------------------------------------------------------- -->
1648<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1649 <a name="mergefunc">-mergefunc: Merge Functions</a>
1650</div>
1651<div class="doc_text">
1652 <p>This pass looks for equivalent functions that are mergable and folds them.
1653
1654 A hash is computed from the function, based on its type and number of
1655 basic blocks.
1656
1657 Once all hashes are computed, we perform an expensive equality comparison
1658 on each function pair. This takes n^2/2 comparisons per bucket, so it's
1659 important that the hash function be high quality. The equality comparison
1660 iterates through each instruction in each basic block.
1661
1662 When a match is found the functions are folded. If both functions are
1663 overridable, we move the functionality into a new internal function and
1664 leave two overridable thunks to it.
1665 </p>
1666</div>
1667
1668<!-------------------------------------------------------------------------- -->
1669<div class="doc_subsection">
1670 <a name="mergereturn">-mergereturn: Unify function exit nodes</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1671</div>
1672<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1673 <p>
1674 Ensure that functions have at most one <tt>ret</tt> instruction in them.
1675 Additionally, it keeps track of which node is the new exit node of the CFG.
1676 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1677</div>
1678
1679<!-------------------------------------------------------------------------- -->
1680<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1681 <a name="partial-inliner">-partial-inliner: Partial Inliner</a>
1682</div>
1683<div class="doc_text">
1684 <p>This pass performs partial inlining, typically by inlining an if
1685 statement that surrounds the body of the function.
1686 </p>
1687</div>
1688
1689<!-------------------------------------------------------------------------- -->
1690<div class="doc_subsection">
1691 <a name="partialspecialization">-partialspecialization: Partial Specialization</a>
1692</div>
1693<div class="doc_text">
1694 <p>This pass finds function arguments that are often a common constant and
1695 specializes a version of the called function for that constant.
1696
1697 This pass simply does the cloning for functions it specializes. It depends
1698 on <a href="#ipsccp">IPSCCP</a> and <a href="#deadargelim">DAE</a> to clean up the results.
1699
1700 The initial heuristic favors constant arguments that are used in control
1701 flow.
1702 </p>
1703</div>
1704
1705<!-------------------------------------------------------------------------- -->
1706<div class="doc_subsection">
1707 <a name="prune-eh">-prune-eh: Remove unused exception handling info</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1708</div>
1709<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1710 <p>
1711 This file implements a simple interprocedural pass which walks the call-graph,
1712 turning <tt>invoke</tt> instructions into <tt>call</tt> instructions if and
1713 only if the callee cannot throw an exception. It implements this as a
1714 bottom-up traversal of the call-graph.
1715 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1716</div>
1717
1718<!-------------------------------------------------------------------------- -->
1719<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1720 <a name="reassociate">-reassociate: Reassociate expressions</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1721</div>
1722<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1723 <p>
1724 This pass reassociates commutative expressions in an order that is designed
1725 to promote better constant propagation, GCSE, LICM, PRE, etc.
1726 </p>
1727
1728 <p>
1729 For example: 4 + (<var>x</var> + 5) ⇒ <var>x</var> + (4 + 5)
1730 </p>
1731
1732 <p>
1733 In the implementation of this algorithm, constants are assigned rank = 0,
1734 function arguments are rank = 1, and other values are assigned ranks
1735 corresponding to the reverse post order traversal of current function
1736 (starting at 2), which effectively gives values in deep loops higher rank
1737 than values not in loops.
1738 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1739</div>
1740
1741<!-------------------------------------------------------------------------- -->
1742<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1743 <a name="reg2mem">-reg2mem: Demote all values to stack slots</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1744</div>
1745<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1746 <p>
1747 This file demotes all registers to memory references. It is intented to be
1748 the inverse of <a href="#mem2reg"><tt>-mem2reg</tt></a>. By converting to
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]1749 <tt>load</tt> instructions, the only values live across basic blocks are
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1750 <tt>alloca</tt> instructions and <tt>load</tt> instructions before
1751 <tt>phi</tt> nodes. It is intended that this should make CFG hacking much
1752 easier. To make later hacking easier, the entry block is split into two, such
1753 that all introduced <tt>alloca</tt> instructions (and nothing else) are in the
1754 entry block.
1755 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1756</div>
1757
1758<!-------------------------------------------------------------------------- -->
1759<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1760 <a name="scalarrepl">-scalarrepl: Scalar Replacement of Aggregates</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1761</div>
1762<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1763 <p>
1764 The well-known scalar replacement of aggregates transformation. This
1765 transform breaks up <tt>alloca</tt> instructions of aggregate type (structure
1766 or array) into individual <tt>alloca</tt> instructions for each member if
1767 possible. Then, if possible, it transforms the individual <tt>alloca</tt>
1768 instructions into nice clean scalar SSA form.
1769 </p>
1770
1771 <p>
1772 This combines a simple scalar replacement of aggregates algorithm with the <a
1773 href="#mem2reg"><tt>mem2reg</tt></a> algorithm because often interact,
1774 especially for C++ programs. As such, iterating between <tt>scalarrepl</tt>,
1775 then <a href="#mem2reg"><tt>mem2reg</tt></a> until we run out of things to
1776 promote works well.
1777 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1778</div>
1779
1780<!-------------------------------------------------------------------------- -->
1781<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1782 <a name="sccp">-sccp: Sparse Conditional Constant Propagation</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1783</div>
1784<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1785 <p>
1786 Sparse conditional constant propagation and merging, which can be summarized
1787 as:
1788 </p>
1789
1790 <ol>
1791 <li>Assumes values are constant unless proven otherwise</li>
1792 <li>Assumes BasicBlocks are dead unless proven otherwise</li>
1793 <li>Proves values to be constant, and replaces them with constants</li>
1794 <li>Proves conditional branches to be unconditional</li>
1795 </ol>
1796
1797 <p>
1798 Note that this pass has a habit of making definitions be dead. It is a good
1799 idea to to run a DCE pass sometime after running this pass.
1800 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1801</div>
1802
1803<!-------------------------------------------------------------------------- -->
1804<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1805 <a name="sink">-sink: Code Sinking</a>
1806</div>
1807<div class="doc_text">
1808 <p>This pass moves instructions into successor blocks, when possible, so that
1809 they aren't executed on paths where their results aren't needed.
1810 </p>
1811</div>
1812
1813<!-------------------------------------------------------------------------- -->
1814<div class="doc_subsection">
1815 <a name="simplify-libcalls">-simplify-libcalls: Simplify well-known library calls</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1816</div>
1817<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1818 <p>
1819 Applies a variety of small optimizations for calls to specific well-known
1820 function calls (e.g. runtime library functions). For example, a call
1821 <tt>exit(3)</tt> that occurs within the <tt>main()</tt> function can be
1822 transformed into simply <tt>return 3</tt>.
1823 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1824</div>
1825
1826<!-------------------------------------------------------------------------- -->
1827<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1828 <a name="simplify-libcalls-halfpowr">-simplify-libcalls-halfpowr: Simplify half_powr library calls</a>
1829</div>
1830<div class="doc_text">
1831 <p>Simple pass that applies an experimental transformation on calls
1832 to specific functions.
1833 </p>
1834</div>
1835
1836<!-------------------------------------------------------------------------- -->
1837<div class="doc_subsection">
1838 <a name="simplifycfg">-simplifycfg: Simplify the CFG</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1839</div>
1840<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1841 <p>
1842 Performs dead code elimination and basic block merging. Specifically:
1843 </p>
1844
1845 <ol>
1846 <li>Removes basic blocks with no predecessors.</li>
1847 <li>Merges a basic block into its predecessor if there is only one and the
1848 predecessor only has one successor.</li>
1849 <li>Eliminates PHI nodes for basic blocks with a single predecessor.</li>
1850 <li>Eliminates a basic block that only contains an unconditional
1851 branch.</li>
1852 </ol>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1853</div>
1854
1855<!-------------------------------------------------------------------------- -->
1856<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1857 <a name="split-geps">-split-geps: Split complex GEPs into simple GEPs</a>
1858</div>
1859<div class="doc_text">
1860 <p>This function breaks GEPs with more than 2 non-zero operands into smaller
1861 GEPs each with no more than 2 non-zero operands. This exposes redundancy
1862 between GEPs with common initial operand sequences.
1863 </p>
1864</div>
1865
1866<!-------------------------------------------------------------------------- -->
1867<div class="doc_subsection">
1868 <a name="ssi">-ssi: Static Single Information Construction</a>
1869</div>
1870<div class="doc_text">
1871 <p>This pass converts a list of variables to the Static Single Information
1872 form.
1873
1874 We are building an on-demand representation, that is, we do not convert
1875 every single variable in the target function to SSI form. Rather, we receive
1876 a list of target variables that must be converted. We also do not
1877 completely convert a target variable to the SSI format. Instead, we only
1878 change the variable in the points where new information can be attached
1879 to its live range, that is, at branch points.
1880 </p>
1881</div>
1882
1883<!-------------------------------------------------------------------------- -->
1884<div class="doc_subsection">
1885 <a name="ssi-everything">-ssi-everything: Static Single Information Construction (everything, intended for debugging)</a>
1886</div>
1887<div class="doc_text">
1888 <p>A pass that runs <a href="#ssi">SSI</a> on every non-void variable, intended for debugging.
1889 </p>
1890</div>
1891
1892<!-------------------------------------------------------------------------- -->
1893<div class="doc_subsection">
1894 <a name="strip">-strip: Strip all symbols from a module</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1895</div>
1896<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1897 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1898 performs code stripping. this transformation can delete:
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1899 </p>
1900
1901 <ol>
1902 <li>names for virtual registers</li>
1903 <li>symbols for internal globals and functions</li>
1904 <li>debug information</li>
1905 </ol>
1906
1907 <p>
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1908 note that this transformation makes code much less readable, so it should
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1909 only be used in situations where the <tt>strip</tt> utility would be used,
1910 such as reducing code size or making it harder to reverse engineer code.
1911 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1912</div>
1913
1914<!-------------------------------------------------------------------------- -->
1915<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1916 <a name="strip-dead-prototypes">-strip-dead-prototypes: Remove unused function declarations</a>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1917</div>
1918<div class="doc_text">
1919 <p>
1920 This pass loops over all of the functions in the input module, looking for
1921 dead declarations and removes them. Dead declarations are declarations of
1922 functions for which no implementation is available (i.e., declarations for
1923 unused library functions).
1924 </p>
1925</div>
1926
1927<!-------------------------------------------------------------------------- -->
1928<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1929 <a name="strip-debug-declare">-strip-debug-declare: Strip all llvm.dbg.declare intrinsics</a>
1930</div>
1931<div class="doc_text">
1932 <p>This pass implements code stripping. Specifically, it can delete:
1933 <ul>
1934 <li>names for virtual registers</li>
1935 <li>symbols for internal globals and functions</li>
1936 <li>debug information</li>
1937 </ul>
1938 Note that this transformation makes code much less readable, so it should
1939 only be used in situations where the 'strip' utility would be used, such as
1940 reducing code size or making it harder to reverse engineer code.
1941 </p>
1942</div>
1943
1944<!-------------------------------------------------------------------------- -->
1945<div class="doc_subsection">
1946 <a name="strip-nondebug">-strip-nondebug: Strip all symbols, except dbg symbols, from a module</a>
1947</div>
1948<div class="doc_text">
1949 <p>This pass implements code stripping. Specifically, it can delete:
1950 <ul>
1951 <li>names for virtual registers</li>
1952 <li>symbols for internal globals and functions</li>
1953 <li>debug information</li>
1954 </ul>
1955 Note that this transformation makes code much less readable, so it should
1956 only be used in situations where the 'strip' utility would be used, such as
1957 reducing code size or making it harder to reverse engineer code.
1958 </p>
1959</div>
1960
1961<!-------------------------------------------------------------------------- -->
1962<div class="doc_subsection">
1963 <a name="sretpromotion">-sretpromotion: Promote sret arguments</a>
Gordon Henriksena8a118b2008-05-08 17:46:35 +0000[diff] [blame]1964</div>
1965<div class="doc_text">
1966 <p>
1967 This pass finds functions that return a struct (using a pointer to the struct
1968 as the first argument of the function, marked with the '<tt>sret</tt>' attribute) and
1969 replaces them with a new function that simply returns each of the elements of
1970 that struct (using multiple return values).
1971 </p>
1972
1973 <p>
1974 This pass works under a number of conditions:
1975 </p>
1976
1977 <ul>
1978 <li>The returned struct must not contain other structs</li>
1979 <li>The returned struct must only be used to load values from</li>
1980 <li>The placeholder struct passed in is the result of an <tt>alloca</tt></li>
1981 </ul>
1982</div>
1983
1984<!-------------------------------------------------------------------------- -->
1985<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]1986 <a name="tailcallelim">-tailcallelim: Tail Call Elimination</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]1987</div>
1988<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]1989 <p>
1990 This file transforms calls of the current function (self recursion) followed
1991 by a return instruction with a branch to the entry of the function, creating
1992 a loop. This pass also implements the following extensions to the basic
1993 algorithm:
1994 </p>
1995
1996 <ul>
1997 <li>Trivial instructions between the call and return do not prevent the
1998 transformation from taking place, though currently the analysis cannot
1999 support moving any really useful instructions (only dead ones).
2000 <li>This pass transforms functions that are prevented from being tail
2001 recursive by an associative expression to use an accumulator variable,
2002 thus compiling the typical naive factorial or <tt>fib</tt> implementation
2003 into efficient code.
2004 <li>TRE is performed if the function returns void, if the return
2005 returns the result returned by the call, or if the function returns a
2006 run-time constant on all exits from the function. It is possible, though
2007 unlikely, that the return returns something else (like constant 0), and
2008 can still be TRE'd. It can be TRE'd if <em>all other</em> return
2009 instructions in the function return the exact same value.
2010 <li>If it can prove that callees do not access theier caller stack frame,
2011 they are marked as eligible for tail call elimination (by the code
2012 generator).
2013 </ul>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2014</div>
2015
2016<!-------------------------------------------------------------------------- -->
2017<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2018 <a name="tailduplicate">-tailduplicate: Tail Duplication</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2019</div>
2020<div class="doc_text">
Gordon Henriksenc86b6772007-11-04 16:15:04 +0000[diff] [blame]2021 <p>
2022 This pass performs a limited form of tail duplication, intended to simplify
2023 CFGs by removing some unconditional branches. This pass is necessary to
2024 straighten out loops created by the C front-end, but also is capable of
2025 making other code nicer. After this pass is run, the CFG simplify pass
2026 should be run to clean up the mess.
2027 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2028</div>
2029
2030<!-- ======================================================================= -->
2031<div class="doc_section"> <a name="transform">Utility Passes</a></div>
2032<div class="doc_text">
2033 <p>This section describes the LLVM Utility Passes.</p>
2034</div>
2035
2036<!-------------------------------------------------------------------------- -->
2037<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2038 <a name="deadarghaX0r">-deadarghaX0r: Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2039</div>
2040<div class="doc_text">
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]2041 <p>
2042 Same as dead argument elimination, but deletes arguments to functions which
2043 are external. This is only for use by <a
2044 href="Bugpoint.html">bugpoint</a>.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2045</div>
2046
2047<!-------------------------------------------------------------------------- -->
2048<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2049 <a name="extract-blocks">-extract-blocks: Extract Basic Blocks From Module (for bugpoint use)</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2050</div>
2051<div class="doc_text">
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]2052 <p>
2053 This pass is used by bugpoint to extract all blocks from the module into their
2054 own functions.</p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2055</div>
2056
2057<!-------------------------------------------------------------------------- -->
2058<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2059 <a name="instnamer">-instnamer: Assign names to anonymous instructions</a>
2060</div>
2061<div class="doc_text">
2062 <p>This is a little utility pass that gives instructions names, this is mostly
2063 useful when diffing the effect of an optimization because deleting an
2064 unnamed instruction can change all other instruction numbering, making the
2065 diff very noisy.
2066 </p>
2067</div>
2068
2069<!-------------------------------------------------------------------------- -->
2070<div class="doc_subsection">
2071 <a name="preverify">-preverify: Preliminary module verification</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2072</div>
2073<div class="doc_text">
Gordon Henriksen90a52142007-11-05 02:05:35 +0000[diff] [blame]2074 <p>
2075 Ensures that the module is in the form required by the <a
2076 href="#verifier">Module Verifier</a> pass.
2077 </p>
2078
2079 <p>
2080 Running the verifier runs this pass automatically, so there should be no need
2081 to use it directly.
2082 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2083</div>
2084
2085<!-------------------------------------------------------------------------- -->
2086<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2087 <a name="verify">-verify: Module Verifier</a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2088</div>
2089<div class="doc_text">
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]2090 <p>
2091 Verifies an LLVM IR code. This is useful to run after an optimization which is
2092 undergoing testing. Note that <tt>llvm-as</tt> verifies its input before
2093 emitting bitcode, and also that malformed bitcode is likely to make LLVM
2094 crash. All language front-ends are therefore encouraged to verify their output
2095 before performing optimizing transformations.
2096 </p>
2097
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]2098 <ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]2099 <li>Both of a binary operator's parameters are of the same type.</li>
2100 <li>Verify that the indices of mem access instructions match other
2101 operands.</li>
2102 <li>Verify that arithmetic and other things are only performed on
2103 first-class types. Verify that shifts and logicals only happen on
2104 integrals f.e.</li>
2105 <li>All of the constants in a switch statement are of the correct type.</li>
2106 <li>The code is in valid SSA form.</li>
Chris Lattner46b3abc2009-10-28 04:47:06 +0000[diff] [blame]2107 <li>It is illegal to put a label into any other type (like a structure) or
2108 to return one.</li>
Nick Lewycky0c78ac12008-03-28 06:46:51 +0000[diff] [blame]2109 <li>Only phi nodes can be self referential: <tt>%x = add i32 %x, %x</tt> is
Gordon Henriksen873390e2007-11-04 18:17:58 +0000[diff] [blame]2110 invalid.</li>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]2111 <li>PHI nodes must have an entry for each predecessor, with no extras.</li>
2112 <li>PHI nodes must be the first thing in a basic block, all grouped
2113 together.</li>
2114 <li>PHI nodes must have at least one entry.</li>
2115 <li>All basic blocks should only end with terminator insts, not contain
2116 them.</li>
2117 <li>The entry node to a function must not have predecessors.</li>
2118 <li>All Instructions must be embedded into a basic block.</li>
2119 <li>Functions cannot take a void-typed parameter.</li>
2120 <li>Verify that a function's argument list agrees with its declared
2121 type.</li>
2122 <li>It is illegal to specify a name for a void value.</li>
2123 <li>It is illegal to have a internal global value with no initializer.</li>
2124 <li>It is illegal to have a ret instruction that returns a value that does
2125 not agree with the function return value type.</li>
2126 <li>Function call argument types match the function prototype.</li>
2127 <li>All other things that are tested by asserts spread about the code.</li>
Gordon Henriksen23a8ce52007-11-04 18:14:08 +0000[diff] [blame]2128 </ul>
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]2129
2130 <p>
2131 Note that this does not provide full security verification (like Java), but
2132 instead just tries to ensure that code is well-formed.
2133 </p>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2134</div>
2135
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]2136<!-------------------------------------------------------------------------- -->
2137<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2138 <a name="view-cfg">-view-cfg: View CFG of function</a>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]2139</div>
2140<div class="doc_text">
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]2141 <p>
2142 Displays the control flow graph using the GraphViz tool.
2143 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]2144</div>
2145
2146<!-------------------------------------------------------------------------- -->
2147<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2148 <a name="view-cfg-only">-view-cfg-only: View CFG of function (with no function bodies)</a>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]2149</div>
2150<div class="doc_text">
Gordon Henriksen75ff18e2007-11-04 18:10:18 +0000[diff] [blame]2151 <p>
2152 Displays the control flow graph using the GraphViz tool, but omitting function
2153 bodies.
2154 </p>
Gordon Henriksen1f5cce02007-10-25 08:46:12 +0000[diff] [blame]2155</div>
2156
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2157<!-------------------------------------------------------------------------- -->
2158<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2159 <a name="view-dom">-view-dom: View dominator tree of function</a>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2160</div>
2161<div class="doc_text">
2162 <p>
2163 Displays the dominator tree using the GraphViz tool.
2164 </p>
2165</div>
2166
2167<!-------------------------------------------------------------------------- -->
2168<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2169 <a name="view-dom-only">-view-dom-only: View dominator tree of function (with no function
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2170 bodies)
2171 </a>
2172</div>
2173<div class="doc_text">
2174 <p>
2175 Displays the dominator tree using the GraphViz tool, but omitting function
2176 bodies.
2177 </p>
2178</div>
2179
2180<!-------------------------------------------------------------------------- -->
2181<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2182 <a name="view-postdom">-view-postdom: View post dominator tree of function</a>
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2183</div>
2184<div class="doc_text">
2185 <p>
2186 Displays the post dominator tree using the GraphViz tool.
2187 </p>
2188</div>
2189
2190<!-------------------------------------------------------------------------- -->
2191<div class="doc_subsection">
Duncan Sands5c603862010-07-06 15:52:15 +0000[diff] [blame^]2192 <a name="view-postdom-only">-view-postdom-only: View post dominator tree of function (with no
Tobias Grosser733783b2010-05-07 09:33:18 +0000[diff] [blame]2193 function bodies)
2194 </a>
2195</div>
2196<div class="doc_text">
2197 <p>
2198 Displays the post dominator tree using the GraphViz tool, but omitting
2199 function bodies.
2200 </p>
2201</div>
2202
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2203<!-- *********************************************************************** -->
2204
2205<hr>
2206<address>
2207 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]2208 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2209 <a href="http://validator.w3.org/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]2210 src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
Reid Spencerd9aac122007-03-26 09:32:31 +0000[diff] [blame]2211
2212 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
2213 <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
2214 Last modified: $Date$
2215</address>
2216
2217</body>
2218</html>