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43 <div class="doc_title">LLVM's Analysis and Transform Passes</div>
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>
52 <div class="doc_author">
53 <p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a>
54 and Gordon Henriksen</p>
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.
63 The table below divides the passes that LLVM provides into three categories.
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.
67 Utility passes provides some utility but don't otherwise fit categorization.
68 For example passes to extract functions to bitcode or write a module to
69 bitcode are neither analysis nor transform passes.
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>
73 <div class="doc_text" >
75 <tr><th colspan="2"><b>ANALYSIS PASSES</b></th></tr>
76 <tr><th>Option</th><th>Name</th></tr>
77 <tr><td><a href="#aa-eval">-aa-eval</a></td><td>Exhaustive Alias Analysis Precision Evaluator</td></tr>
78 <tr><td><a href="#anders-aa">-anders-aa</a></td><td>Andersen's Interprocedural Alias Analysis</td></tr>
79 <tr><td><a href="#basicaa">-basicaa</a></td><td>Basic Alias Analysis (default AA impl)</td></tr>
80 <tr><td><a href="#basiccg">-basiccg</a></td><td>Basic CallGraph Construction</td></tr>
81 <tr><td><a href="#basicvn">-basicvn</a></td><td>Basic Value Numbering (default GVN impl)</td></tr>
82 <tr><td><a href="#callgraph">-callgraph</a></td><td>Print a call graph</td></tr>
83 <tr><td><a href="#callscc">-callscc</a></td><td>Print SCCs of the Call Graph</td></tr>
84 <tr><td><a href="#cfgscc">-cfgscc</a></td><td>Print SCCs of each function CFG</td></tr>
85 <tr><td><a href="#codegenprepare">-codegenprepare</a></td><td>Optimize for code generation</td></tr>
86 <tr><td><a href="#count-aa">-count-aa</a></td><td>Count Alias Analysis Query Responses</td></tr>
87 <tr><td><a href="#debug-aa">-debug-aa</a></td><td>AA use debugger</td></tr>
88 <tr><td><a href="#domfrontier">-domfrontier</a></td><td>Dominance Frontier Construction</td></tr>
89 <tr><td><a href="#domtree">-domtree</a></td><td>Dominator Tree Construction</td></tr>
90 <tr><td><a href="#externalfnconstants">-externalfnconstants</a></td><td>Print external fn callsites passed constants</td></tr>
91 <tr><td><a href="#globalsmodref-aa">-globalsmodref-aa</a></td><td>Simple mod/ref analysis for globals</td></tr>
92 <tr><td><a href="#instcount">-instcount</a></td><td>Counts the various types of Instructions</td></tr>
93 <tr><td><a href="#intervals">-intervals</a></td><td>Interval Partition Construction</td></tr>
94 <tr><td><a href="#load-vn">-load-vn</a></td><td>Load Value Numbering</td></tr>
95 <tr><td><a href="#loops">-loops</a></td><td>Natural Loop Construction</td></tr>
96 <tr><td><a href="#memdep">-memdep</a></td><td>Memory Dependence Analysis</td></tr>
97 <tr><td><a href="#no-aa">-no-aa</a></td><td>No Alias Analysis (always returns 'may' alias)</td></tr>
98 <tr><td><a href="#no-profile">-no-profile</a></td><td>No Profile Information</td></tr>
99 <tr><td><a href="#postdomfrontier">-postdomfrontier</a></td><td>Post-Dominance Frontier Construction</td></tr>
100 <tr><td><a href="#postdomtree">-postdomtree</a></td><td>Post-Dominator Tree Construction</td></tr>
101 <tr><td><a href="#print">-print</a></td><td>Print function to stderr</td></tr>
102 <tr><td><a href="#print-alias-sets">-print-alias-sets</a></td><td>Alias Set Printer</td></tr>
103 <tr><td><a href="#print-callgraph">-print-callgraph</a></td><td>Print Call Graph to 'dot' file</td></tr>
104 <tr><td><a href="#print-cfg">-print-cfg</a></td><td>Print CFG of function to 'dot' file</td></tr>
105 <tr><td><a href="#print-cfg-only">-print-cfg-only</a></td><td>Print CFG of function to 'dot' file (with no function bodies)</td></tr>
106 <tr><td><a href="#printm">-printm</a></td><td>Print module to stderr</td></tr>
107 <tr><td><a href="#printusedtypes">-printusedtypes</a></td><td>Find Used Types</td></tr>
108 <tr><td><a href="#profile-loader">-profile-loader</a></td><td>Load profile information from llvmprof.out</td></tr>
109 <tr><td><a href="#scalar-evolution">-scalar-evolution</a></td><td>Scalar Evolution Analysis</td></tr>
110 <tr><td><a href="#targetdata">-targetdata</a></td><td>Target Data Layout</td></tr>
113 <tr><th colspan="2"><b>TRANSFORM PASSES</b></th></tr>
114 <tr><th>Option</th><th>Name</th></tr>
115 <tr><td><a href="#adce">-adce</a></td><td>Aggressive Dead Code Elimination</td></tr>
116 <tr><td><a href="#argpromotion">-argpromotion</a></td><td>Promote 'by reference' arguments to scalars</td></tr>
117 <tr><td><a href="#block-placement">-block-placement</a></td><td>Profile Guided Basic Block Placement</td></tr>
118 <tr><td><a href="#break-crit-edges">-break-crit-edges</a></td><td>Break critical edges in CFG</td></tr>
119 <tr><td><a href="#cee">-cee</a></td><td>Correlated Expression Elimination</td></tr>
120 <tr><td><a href="#condprop">-condprop</a></td><td>Conditional Propagation</td></tr>
121 <tr><td><a href="#constmerge">-constmerge</a></td><td>Merge Duplicate Global Constants</td></tr>
122 <tr><td><a href="#constprop">-constprop</a></td><td>Simple constant propagation</td></tr>
123 <tr><td><a href="#dce">-dce</a></td><td>Dead Code Elimination</td></tr>
124 <tr><td><a href="#deadargelim">-deadargelim</a></td><td>Dead Argument Elimination</td></tr>
125 <tr><td><a href="#deadtypeelim">-deadtypeelim</a></td><td>Dead Type Elimination</td></tr>
126 <tr><td><a href="#die">-die</a></td><td>Dead Instruction Elimination</td></tr>
127 <tr><td><a href="#dse">-dse</a></td><td>Dead Store Elimination</td></tr>
128 <tr><td><a href="#gcse">-gcse</a></td><td>Global Common Subexpression Elimination</td></tr>
129 <tr><td><a href="#globaldce">-globaldce</a></td><td>Dead Global Elimination</td></tr>
130 <tr><td><a href="#globalopt">-globalopt</a></td><td>Global Variable Optimizer</td></tr>
131 <tr><td><a href="#gvn">-gvn</a></td><td>Global Value Numbering</td></tr>
132 <tr><td><a href="#gvnpre">-gvnpre</a></td><td>Global Value Numbering/Partial Redundancy Elimination</td></tr>
133 <tr><td><a href="#indmemrem">-indmemrem</a></td><td>Indirect Malloc and Free Removal</td></tr>
134 <tr><td><a href="#indvars">-indvars</a></td><td>Canonicalize Induction Variables</td></tr>
135 <tr><td><a href="#inline">-inline</a></td><td>Function Integration/Inlining</td></tr>
136 <tr><td><a href="#insert-block-profiling">-insert-block-profiling</a></td><td>Insert instrumentation for block profiling</td></tr>
137 <tr><td><a href="#insert-edge-profiling">-insert-edge-profiling</a></td><td>Insert instrumentation for edge profiling</td></tr>
138 <tr><td><a href="#insert-function-profiling">-insert-function-profiling</a></td><td>Insert instrumentation for function profiling</td></tr>
139 <tr><td><a href="#insert-null-profiling-rs">-insert-null-profiling-rs</a></td><td>Measure profiling framework overhead</td></tr>
140 <tr><td><a href="#insert-rs-profiling-framework">-insert-rs-profiling-framework</a></td><td>Insert random sampling instrumentation framework</td></tr>
141 <tr><td><a href="#instcombine">-instcombine</a></td><td>Combine redundant instructions</td></tr>
142 <tr><td><a href="#internalize">-internalize</a></td><td>Internalize Global Symbols</td></tr>
143 <tr><td><a href="#ipconstprop">-ipconstprop</a></td><td>Interprocedural constant propagation</td></tr>
144 <tr><td><a href="#ipsccp">-ipsccp</a></td><td>Interprocedural Sparse Conditional Constant Propagation</td></tr>
145 <tr><td><a href="#lcssa">-lcssa</a></td><td>Loop-Closed SSA Form Pass</td></tr>
146 <tr><td><a href="#licm">-licm</a></td><td>Loop Invariant Code Motion</td></tr>
147 <tr><td><a href="#loop-extract">-loop-extract</a></td><td>Extract loops into new functions</td></tr>
148 <tr><td><a href="#loop-extract-single">-loop-extract-single</a></td><td>Extract at most one loop into a new function</td></tr>
149 <tr><td><a href="#loop-index-split">-loop-index-split</a></td><td>Index Split Loops</td></tr>
150 <tr><td><a href="#loop-reduce">-loop-reduce</a></td><td>Loop Strength Reduction</td></tr>
151 <tr><td><a href="#loop-rotate">-loop-rotate</a></td><td>Rotate Loops</td></tr>
152 <tr><td><a href="#loop-unroll">-loop-unroll</a></td><td>Unroll loops</td></tr>
153 <tr><td><a href="#loop-unswitch">-loop-unswitch</a></td><td>Unswitch loops</td></tr>
154 <tr><td><a href="#loopsimplify">-loopsimplify</a></td><td>Canonicalize natural loops</td></tr>
155 <tr><td><a href="#lower-packed">-lower-packed</a></td><td>lowers packed operations to operations on smaller packed datatypes</td></tr>
156 <tr><td><a href="#lowerallocs">-lowerallocs</a></td><td>Lower allocations from instructions to calls</td></tr>
157 <tr><td><a href="#lowergc">-lowergc</a></td><td>Lower GC intrinsics, for GCless code generators</td></tr>
158 <tr><td><a href="#lowerinvoke">-lowerinvoke</a></td><td>Lower invoke and unwind, for unwindless code generators</td></tr>
159 <tr><td><a href="#lowerselect">-lowerselect</a></td><td>Lower select instructions to branches</td></tr>
160 <tr><td><a href="#lowersetjmp">-lowersetjmp</a></td><td>Lower Set Jump</td></tr>
161 <tr><td><a href="#lowerswitch">-lowerswitch</a></td><td>Lower SwitchInst's to branches</td></tr>
162 <tr><td><a href="#mem2reg">-mem2reg</a></td><td>Promote Memory to Register</td></tr>
163 <tr><td><a href="#mergereturn">-mergereturn</a></td><td>Unify function exit nodes</td></tr>
164 <tr><td><a href="#predsimplify">-predsimplify</a></td><td>Predicate Simplifier</td></tr>
165 <tr><td><a href="#prune-eh">-prune-eh</a></td><td>Remove unused exception handling info</td></tr>
166 <tr><td><a href="#raiseallocs">-raiseallocs</a></td><td>Raise allocations from calls to instructions</td></tr>
167 <tr><td><a href="#reassociate">-reassociate</a></td><td>Reassociate expressions</td></tr>
168 <tr><td><a href="#reg2mem">-reg2mem</a></td><td>Demote all values to stack slots</td></tr>
169 <tr><td><a href="#scalarrepl">-scalarrepl</a></td><td>Scalar Replacement of Aggregates</td></tr>
170 <tr><td><a href="#sccp">-sccp</a></td><td>Sparse Conditional Constant Propagation</td></tr>
171 <tr><td><a href="#simplify-libcalls">-simplify-libcalls</a></td><td>Simplify well-known library calls</td></tr>
172 <tr><td><a href="#simplifycfg">-simplifycfg</a></td><td>Simplify the CFG</td></tr>
173 <tr><td><a href="#strip">-strip</a></td><td>Strip all symbols from a module</td></tr>
174 <tr><td><a href="#tailcallelim">-tailcallelim</a></td><td>Tail Call Elimination</td></tr>
175 <tr><td><a href="#tailduplicate">-tailduplicate</a></td><td>Tail Duplication</td></tr>
178 <tr><th colspan="2"><b>UTILITY PASSES</b></th></tr>
179 <tr><th>Option</th><th>Name</th></tr>
180 <tr><td><a href="#deadarghaX0r">-deadarghaX0r</a></td><td>Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</td></tr>
181 <tr><td><a href="#extract-blocks">-extract-blocks</a></td><td>Extract Basic Blocks From Module (for bugpoint use)</td></tr>
182 <tr><td><a href="#emitbitcode">-emitbitcode</a></td><td>Bitcode Writer</td></tr>
183 <tr><td><a href="#verify">-verify</a></td><td>Module Verifier</td></tr>
184 <tr><td><a href="#view-cfg">-view-cfg</a></td><td>View CFG of function</td></tr>
185 <tr><td><a href="#view-cfg-only">-view-cfg-only</a></td><td>View CFG of function (with no function bodies)</td></tr>
189 <!-- ======================================================================= -->
190 <div class="doc_section"> <a name="example">Analysis Passes</a></div>
191 <div class="doc_text">
192 <p>This section describes the LLVM Analysis Passes.</p>
195 <!-------------------------------------------------------------------------- -->
196 <div class="doc_subsection">
197 <a name="aa-eval">Exhaustive Alias Analysis Precision Evaluator</a>
199 <div class="doc_text">
200 <p>This is a simple N^2 alias analysis accuracy evaluator.
201 Basically, for each function in the program, it simply queries to see how the
202 alias analysis implementation answers alias queries between each pair of
203 pointers in the function.</p>
205 <p>This is inspired and adapted from code by: Naveen Neelakantam, Francesco
206 Spadini, and Wojciech Stryjewski.</p>
209 <!-------------------------------------------------------------------------- -->
210 <div class="doc_subsection">
211 <a name="anders-aa">Andersen's Interprocedural Alias Analysis</a>
213 <div class="doc_text">
215 This is an implementation of Andersen's interprocedural alias
220 In pointer analysis terms, this is a subset-based, flow-insensitive,
221 field-sensitive, and context-insensitive algorithm pointer algorithm.
225 This algorithm is implemented as three stages:
229 <li>Object identification.</li>
230 <li>Inclusion constraint identification.</li>
231 <li>Offline constraint graph optimization.</li>
232 <li>Inclusion constraint solving.</li>
236 The object identification stage identifies all of the memory objects in the
237 program, which includes globals, heap allocated objects, and stack allocated
242 The inclusion constraint identification stage finds all inclusion constraints
243 in the program by scanning the program, looking for pointer assignments and
244 other statements that effect the points-to graph. For a statement like
245 <code><var>A</var> = <var>B</var></code>, this statement is processed to
246 indicate that <var>A</var> can point to anything that <var>B</var> can point
247 to. Constraints can handle copies, loads, and stores, and address taking.
251 The offline constraint graph optimization portion includes offline variable
252 substitution algorithms intended to computer pointer and location
253 equivalences. Pointer equivalences are those pointers that will have the
254 same points-to sets, and location equivalences are those variables that
255 always appear together in points-to sets.
259 The inclusion constraint solving phase iteratively propagates the inclusion
260 constraints until a fixed point is reached. This is an O(<var>n</var>³)
265 Function constraints are handled as if they were structs with <var>X</var>
266 fields. Thus, an access to argument <var>X</var> of function <var>Y</var> is
267 an access to node index <code>getNode(<var>Y</var>) + <var>X</var></code>.
268 This representation allows handling of indirect calls without any issues. To
269 wit, an indirect call <code><var>Y</var>(<var>a</var>,<var>b</var>)</code> is
270 equivalent to <code>*(<var>Y</var> + 1) = <var>a</var>, *(<var>Y</var> + 2) =
271 <var>b</var></code>. The return node for a function <var>F</var> is always
272 located at <code>getNode(<var>F</var>) + CallReturnPos</code>. The arguments
273 start at <code>getNode(<var>F</var>) + CallArgPos</code>.
277 <!-------------------------------------------------------------------------- -->
278 <div class="doc_subsection">
279 <a name="basicaa">Basic Alias Analysis (default AA impl)</a>
281 <div class="doc_text">
283 This is the default implementation of the Alias Analysis interface
284 that simply implements a few identities (two different globals cannot alias,
285 etc), but otherwise does no analysis.
289 <!-------------------------------------------------------------------------- -->
290 <div class="doc_subsection">
291 <a name="basiccg">Basic CallGraph Construction</a>
293 <div class="doc_text">
294 <p>Yet to be written.</p>
297 <!-------------------------------------------------------------------------- -->
298 <div class="doc_subsection">
299 <a name="basicvn">Basic Value Numbering (default GVN impl)</a>
301 <div class="doc_text">
303 This is the default implementation of the <code>ValueNumbering</code>
304 interface. It walks the SSA def-use chains to trivially identify
305 lexically identical expressions. This does not require any ahead of time
306 analysis, so it is a very fast default implementation.
310 <!-------------------------------------------------------------------------- -->
311 <div class="doc_subsection">
312 <a name="callgraph">Print a call graph</a>
314 <div class="doc_text">
316 This pass, only available in <code>opt</code>, prints the call graph to
317 standard output in a human-readable form.
321 <!-------------------------------------------------------------------------- -->
322 <div class="doc_subsection">
323 <a name="callscc">Print SCCs of the Call Graph</a>
325 <div class="doc_text">
327 This pass, only available in <code>opt</code>, prints the SCCs of the call
328 graph to standard output in a human-readable form.
332 <!-------------------------------------------------------------------------- -->
333 <div class="doc_subsection">
334 <a name="cfgscc">Print SCCs of each function CFG</a>
336 <div class="doc_text">
338 This pass, only available in <code>opt</code>, prints the SCCs of each
339 function CFG to standard output in a human-readable form.
343 <!-------------------------------------------------------------------------- -->
344 <div class="doc_subsection">
345 <a name="codegenprepare">Optimize for code generation</a>
347 <div class="doc_text">
349 This pass munges the code in the input function to better prepare it for
350 SelectionDAG-based code generation. This works around limitations in it's
351 basic-block-at-a-time approach. It should eventually be removed.
355 <!-------------------------------------------------------------------------- -->
356 <div class="doc_subsection">
357 <a name="count-aa">Count Alias Analysis Query Responses</a>
359 <div class="doc_text">
361 A pass which can be used to count how many alias queries
362 are being made and how the alias analysis implementation being used responds.
366 <!-------------------------------------------------------------------------- -->
367 <div class="doc_subsection">
368 <a name="debug-aa">AA use debugger</a>
370 <div class="doc_text">
372 This simple pass checks alias analysis users to ensure that if they
373 create a new value, they do not query AA without informing it of the value.
374 It acts as a shim over any other AA pass you want.
378 Yes keeping track of every value in the program is expensive, but this is
383 <!-------------------------------------------------------------------------- -->
384 <div class="doc_subsection">
385 <a name="domfrontier">Dominance Frontier Construction</a>
387 <div class="doc_text">
389 This pass is a simple dominator construction algorithm for finding forward
394 <!-------------------------------------------------------------------------- -->
395 <div class="doc_subsection">
396 <a name="domtree">Dominator Tree Construction</a>
398 <div class="doc_text">
400 This pass is a simple dominator construction algorithm for finding forward
405 <!-------------------------------------------------------------------------- -->
406 <div class="doc_subsection">
407 <a name="externalfnconstants">Print external fn callsites passed constants</a>
409 <div class="doc_text">
411 This pass, only available in <code>opt</code>, prints out call sites to
412 external functions that are called with constant arguments. This can be
413 useful when looking for standard library functions we should constant fold
414 or handle in alias analyses.
418 <!-------------------------------------------------------------------------- -->
419 <div class="doc_subsection">
420 <a name="globalsmodref-aa">Simple mod/ref analysis for globals</a>
422 <div class="doc_text">
424 This simple pass provides alias and mod/ref information for global values
425 that do not have their address taken, and keeps track of whether functions
426 read or write memory (are "pure"). For this simple (but very common) case,
427 we can provide pretty accurate and useful information.
431 <!-------------------------------------------------------------------------- -->
432 <div class="doc_subsection">
433 <a name="instcount">Counts the various types of Instructions</a>
435 <div class="doc_text">
437 This pass collects the count of all instructions and reports them
441 <!-------------------------------------------------------------------------- -->
442 <div class="doc_subsection">
443 <a name="intervals">Interval Partition Construction</a>
445 <div class="doc_text">
447 This analysis calculates and represents the interval partition of a function,
448 or a preexisting interval partition.
452 In this way, the interval partition may be used to reduce a flow graph down
453 to its degenerate single node interval partition (unless it is irreducible).
457 <!-------------------------------------------------------------------------- -->
458 <div class="doc_subsection">
459 <a name="load-vn">Load Value Numbering</a>
461 <div class="doc_text">
463 This pass value numbers load and call instructions. To do this, it finds
464 lexically identical load instructions, and uses alias analysis to determine
465 which loads are guaranteed to produce the same value. To value number call
466 instructions, it looks for calls to functions that do not write to memory
467 which do not have intervening instructions that clobber the memory that is
472 This pass builds off of another value numbering pass to implement value
473 numbering for non-load and non-call instructions. It uses Alias Analysis so
474 that it can disambiguate the load instructions. The more powerful these base
475 analyses are, the more powerful the resultant value numbering will be.
479 <!-------------------------------------------------------------------------- -->
480 <div class="doc_subsection">
481 <a name="loops">Natural Loop Construction</a>
483 <div class="doc_text">
485 This analysis is used to identify natural loops and determine the loop depth
486 of various nodes of the CFG. Note that the loops identified may actually be
487 several natural loops that share the same header node... not just a single
492 <!-------------------------------------------------------------------------- -->
493 <div class="doc_subsection">
494 <a name="memdep">Memory Dependence Analysis</a>
496 <div class="doc_text">
498 An analysis that determines, for a given memory operation, what preceding
499 memory operations it depends on. It builds on alias analysis information, and
500 tries to provide a lazy, caching interface to a common kind of alias
505 <!-------------------------------------------------------------------------- -->
506 <div class="doc_subsection">
507 <a name="no-aa">No Alias Analysis (always returns 'may' alias)</a>
509 <div class="doc_text">
511 Always returns "I don't know" for alias queries. NoAA is unlike other alias
512 analysis implementations, in that it does not chain to a previous analysis. As
513 such it doesn't follow many of the rules that other alias analyses must.
517 <!-------------------------------------------------------------------------- -->
518 <div class="doc_subsection">
519 <a name="no-profile">No Profile Information</a>
521 <div class="doc_text">
523 The default "no profile" implementation of the abstract
524 <code>ProfileInfo</code> interface.
528 <!-------------------------------------------------------------------------- -->
529 <div class="doc_subsection">
530 <a name="postdomfrontier">Post-Dominance Frontier Construction</a>
532 <div class="doc_text">
534 This pass is a simple post-dominator construction algorithm for finding
535 post-dominator frontiers.
539 <!-------------------------------------------------------------------------- -->
540 <div class="doc_subsection">
541 <a name="postdomtree">Post-Dominator Tree Construction</a>
543 <div class="doc_text">
545 This pass is a simple post-dominator construction algorithm for finding
550 <!-------------------------------------------------------------------------- -->
551 <div class="doc_subsection">
552 <a name="print">Print function to stderr</a>
554 <div class="doc_text">
556 The <code>PrintFunctionPass</code> class is designed to be pipelined with
557 other <code>FunctionPass</code>es, and prints out the functions of the module
558 as they are processed.
562 <!-------------------------------------------------------------------------- -->
563 <div class="doc_subsection">
564 <a name="print-alias-sets">Alias Set Printer</a>
566 <div class="doc_text">
567 <p>Yet to be written.</p>
570 <!-------------------------------------------------------------------------- -->
571 <div class="doc_subsection">
572 <a name="print-callgraph">Print Call Graph to 'dot' file</a>
574 <div class="doc_text">
576 This pass, only available in <code>opt</code>, prints the call graph into a
577 <code>.dot</code> graph. This graph can then be processed with the "dot" tool
578 to convert it to postscript or some other suitable format.
582 <!-------------------------------------------------------------------------- -->
583 <div class="doc_subsection">
584 <a name="print-cfg">Print CFG of function to 'dot' file</a>
586 <div class="doc_text">
588 This pass, only available in <code>opt</code>, prints the control flow graph
589 into a <code>.dot</code> graph. This graph can then be processed with the
590 "dot" tool to convert it to postscript or some other suitable format.
594 <!-------------------------------------------------------------------------- -->
595 <div class="doc_subsection">
596 <a name="print-cfg-only">Print CFG of function to 'dot' file (with no function bodies)</a>
598 <div class="doc_text">
600 This pass, only available in <code>opt</code>, prints the control flow graph
601 into a <code>.dot</code> graph, omitting the function bodies. This graph can
602 then be processed with the "dot" tool to convert it to postscript or some
603 other suitable format.
607 <!-------------------------------------------------------------------------- -->
608 <div class="doc_subsection">
609 <a name="printm">Print module to stderr</a>
611 <div class="doc_text">
613 This pass simply prints out the entire module when it is executed.
617 <!-------------------------------------------------------------------------- -->
618 <div class="doc_subsection">
619 <a name="printusedtypes">Find Used Types</a>
621 <div class="doc_text">
623 This pass is used to seek out all of the types in use by the program. Note
624 that this analysis explicitly does not include types only used by the symbol
628 <!-------------------------------------------------------------------------- -->
629 <div class="doc_subsection">
630 <a name="profile-loader">Load profile information from llvmprof.out</a>
632 <div class="doc_text">
634 A concrete implementation of profiling information that loads the information
635 from a profile dump file.
639 <!-------------------------------------------------------------------------- -->
640 <div class="doc_subsection">
641 <a name="scalar-evolution">Scalar Evolution Analysis</a>
643 <div class="doc_text">
645 The <code>ScalarEvolution</code> analysis can be used to analyze and
646 catagorize scalar expressions in loops. It specializes in recognizing general
647 induction variables, representing them with the abstract and opaque
648 <code>SCEV</code> class. Given this analysis, trip counts of loops and other
649 important properties can be obtained.
653 This analysis is primarily useful for induction variable substitution and
658 <!-------------------------------------------------------------------------- -->
659 <div class="doc_subsection">
660 <a name="targetdata">Target Data Layout</a>
662 <div class="doc_text">
663 <p>Provides other passes access to information on how the size and alignment
664 required by the the target ABI for various data types.</p>
667 <!-- ======================================================================= -->
668 <div class="doc_section"> <a name="transform">Transform Passes</a></div>
669 <div class="doc_text">
670 <p>This section describes the LLVM Transform Passes.</p>
673 <!-------------------------------------------------------------------------- -->
674 <div class="doc_subsection">
675 <a name="adce">Aggressive Dead Code Elimination</a>
677 <div class="doc_text">
678 <p>ADCE aggressively tries to eliminate code. This pass is similar to
679 <a href="#dce">DCE</a> but it assumes that values are dead until proven
680 otherwise. This is similar to <a href="#sccp">SCCP</a>, except applied to
681 the liveness of values.</p>
684 <!-------------------------------------------------------------------------- -->
685 <div class="doc_subsection">
686 <a name="argpromotion">Promote 'by reference' arguments to scalars</a>
688 <div class="doc_text">
690 This pass promotes "by reference" arguments to be "by value" arguments. In
691 practice, this means looking for internal functions that have pointer
692 arguments. If it can prove, through the use of alias analysis, that an
693 argument is *only* loaded, then it can pass the value into the function
694 instead of the address of the value. This can cause recursive simplification
695 of code and lead to the elimination of allocas (especially in C++ template
700 This pass also handles aggregate arguments that are passed into a function,
701 scalarizing them if the elements of the aggregate are only loaded. Note that
702 it refuses to scalarize aggregates which would require passing in more than
703 three operands to the function, because passing thousands of operands for a
704 large array or structure is unprofitable!
708 Note that this transformation could also be done for arguments that are only
709 stored to (returning the value instead), but does not currently. This case
710 would be best handled when and if LLVM starts supporting multiple return
711 values from functions.
715 <!-------------------------------------------------------------------------- -->
716 <div class="doc_subsection">
717 <a name="block-placement">Profile Guided Basic Block Placement</a>
719 <div class="doc_text">
720 <p>This pass is a very simple profile guided basic block placement algorithm.
721 The idea is to put frequently executed blocks together at the start of the
722 function and hopefully increase the number of fall-through conditional
723 branches. If there is no profile information for a particular function, this
724 pass basically orders blocks in depth-first order.</p>
727 <!-------------------------------------------------------------------------- -->
728 <div class="doc_subsection">
729 <a name="break-crit-edges">Break critical edges in CFG</a>
731 <div class="doc_text">
733 Break all of the critical edges in the CFG by inserting a dummy basic block.
734 It may be "required" by passes that cannot deal with critical edges. This
735 transformation obviously invalidates the CFG, but can update forward dominator
736 (set, immediate dominators, tree, and frontier) information.
740 <!-------------------------------------------------------------------------- -->
741 <div class="doc_subsection">
742 <a name="cee">Correlated Expression Elimination</a>
744 <div class="doc_text">
745 <p>Correlated Expression Elimination propagates information from conditional
746 branches to blocks dominated by destinations of the branch. It propagates
747 information from the condition check itself into the body of the branch,
748 allowing transformations like these for example:</p>
752 ... 4*i; // constant propagation
756 X = M-N; // = M-M == 0;
759 <p>This is called Correlated Expression Elimination because we eliminate or
760 simplify expressions that are correlated with the direction of a branch. In
761 this way we use static information to give us some information about the
762 dynamic value of a variable.</p>
765 <!-------------------------------------------------------------------------- -->
766 <div class="doc_subsection">
767 <a name="condprop">Conditional Propagation</a>
769 <div class="doc_text">
770 <p>This pass propagates information about conditional expressions through the
771 program, allowing it to eliminate conditional branches in some cases.</p>
774 <!-------------------------------------------------------------------------- -->
775 <div class="doc_subsection">
776 <a name="constmerge">Merge Duplicate Global Constants</a>
778 <div class="doc_text">
780 Merges duplicate global constants together into a single constant that is
781 shared. This is useful because some passes (ie TraceValues) insert a lot of
782 string constants into the program, regardless of whether or not an existing
787 <!-------------------------------------------------------------------------- -->
788 <div class="doc_subsection">
789 <a name="constprop">Simple constant propagation</a>
791 <div class="doc_text">
792 <p>This file implements constant propagation and merging. It looks for
793 instructions involving only constant operands and replaces them with a
794 constant value instead of an instruction. For example:</p>
795 <blockquote><pre>add i32 1, 2</pre></blockquote>
797 <blockquote><pre>i32 3</pre></blockquote>
798 <p>NOTE: this pass has a habit of making definitions be dead. It is a good
799 idea to to run a <a href="#die">DIE</a> (Dead Instruction Elimination) pass
800 sometime after running this pass.</p>
803 <!-------------------------------------------------------------------------- -->
804 <div class="doc_subsection">
805 <a name="dce">Dead Code Elimination</a>
807 <div class="doc_text">
809 Dead code elimination is similar to <a href="#die">dead instruction
810 elimination</a>, but it rechecks instructions that were used by removed
811 instructions to see if they are newly dead.
815 <!-------------------------------------------------------------------------- -->
816 <div class="doc_subsection">
817 <a name="deadargelim">Dead Argument Elimination</a>
819 <div class="doc_text">
821 This pass deletes dead arguments from internal functions. Dead argument
822 elimination removes arguments which are directly dead, as well as arguments
823 only passed into function calls as dead arguments of other functions. This
824 pass also deletes dead arguments in a similar way.
828 This pass is often useful as a cleanup pass to run after aggressive
829 interprocedural passes, which add possibly-dead arguments.
833 <!-------------------------------------------------------------------------- -->
834 <div class="doc_subsection">
835 <a name="deadtypeelim">Dead Type Elimination</a>
837 <div class="doc_text">
839 This pass is used to cleanup the output of GCC. It eliminate names for types
840 that are unused in the entire translation unit, using the <a
841 href="#findusedtypes">find used types</a> pass.
845 <!-------------------------------------------------------------------------- -->
846 <div class="doc_subsection">
847 <a name="die">Dead Instruction Elimination</a>
849 <div class="doc_text">
851 Dead instruction elimination performs a single pass over the function,
852 removing instructions that are obviously dead.
856 <!-------------------------------------------------------------------------- -->
857 <div class="doc_subsection">
858 <a name="dse">Dead Store Elimination</a>
860 <div class="doc_text">
862 A trivial dead store elimination that only considers basic-block local
867 <!-------------------------------------------------------------------------- -->
868 <div class="doc_subsection">
869 <a name="gcse">Global Common Subexpression Elimination</a>
871 <div class="doc_text">
873 This pass is designed to be a very quick global transformation that
874 eliminates global common subexpressions from a function. It does this by
875 using an existing value numbering implementation to identify the common
876 subexpressions, eliminating them when possible.
880 <!-------------------------------------------------------------------------- -->
881 <div class="doc_subsection">
882 <a name="globaldce">Dead Global Elimination</a>
884 <div class="doc_text">
886 This transform is designed to eliminate unreachable internal globals from the
887 program. It uses an aggressive algorithm, searching out globals that are
888 known to be alive. After it finds all of the globals which are needed, it
889 deletes whatever is left over. This allows it to delete recursive chunks of
890 the program which are unreachable.
894 <!-------------------------------------------------------------------------- -->
895 <div class="doc_subsection">
896 <a name="globalopt">Global Variable Optimizer</a>
898 <div class="doc_text">
900 This pass transforms simple global variables that never have their address
901 taken. If obviously true, it marks read/write globals as constant, deletes
902 variables only stored to, etc.
906 <!-------------------------------------------------------------------------- -->
907 <div class="doc_subsection">
908 <a name="gvn">Global Value Numbering</a>
910 <div class="doc_text">
912 This pass performs global value numbering to eliminate fully redundant
913 instructions. It also performs simple dead load elimination.
917 <!-------------------------------------------------------------------------- -->
918 <div class="doc_subsection">
919 <a name="gvnpre">Global Value Numbering/Partial Redundancy Elimination</a>
921 <div class="doc_text">
923 This pass performs a hybrid of global value numbering and partial redundancy
924 elimination, known as GVN-PRE. It performs partial redundancy elimination on
925 values, rather than lexical expressions, allowing a more comprehensive view
926 the optimization. It replaces redundant values with uses of earlier
927 occurences of the same value. While this is beneficial in that it eliminates
928 unneeded computation, it also increases register pressure by creating large
929 live ranges, and should be used with caution on platforms that are very
930 sensitive to register pressure.
934 <!-------------------------------------------------------------------------- -->
935 <div class="doc_subsection">
936 <a name="indmemrem">Indirect Malloc and Free Removal</a>
938 <div class="doc_text">
940 This pass finds places where memory allocation functions may escape into
941 indirect land. Some transforms are much easier (aka possible) only if free
942 or malloc are not called indirectly.
946 Thus find places where the address of memory functions are taken and construct
947 bounce functions with direct calls of those functions.
951 <!-------------------------------------------------------------------------- -->
952 <div class="doc_subsection">
953 <a name="indvars">Canonicalize Induction Variables</a>
955 <div class="doc_text">
957 This transformation analyzes and transforms the induction variables (and
958 computations derived from them) into simpler forms suitable for subsequent
959 analysis and transformation.
963 This transformation makes the following changes to each loop with an
964 identifiable induction variable:
968 <li>All loops are transformed to have a <em>single</em> canonical
969 induction variable which starts at zero and steps by one.</li>
970 <li>The canonical induction variable is guaranteed to be the first PHI node
971 in the loop header block.</li>
972 <li>Any pointer arithmetic recurrences are raised to use array
977 If the trip count of a loop is computable, this pass also makes the following
982 <li>The exit condition for the loop is canonicalized to compare the
983 induction value against the exit value. This turns loops like:
984 <blockquote><pre>for (i = 7; i*i < 1000; ++i)</pre></blockquote>
986 <blockquote><pre>for (i = 0; i != 25; ++i)</pre></blockquote></li>
987 <li>Any use outside of the loop of an expression derived from the indvar
988 is changed to compute the derived value outside of the loop, eliminating
989 the dependence on the exit value of the induction variable. If the only
990 purpose of the loop is to compute the exit value of some derived
991 expression, this transformation will make the loop dead.</li>
995 This transformation should be followed by strength reduction after all of the
996 desired loop transformations have been performed. Additionally, on targets
997 where it is profitable, the loop could be transformed to count down to zero
998 (the "do loop" optimization).
1002 <!-------------------------------------------------------------------------- -->
1003 <div class="doc_subsection">
1004 <a name="inline">Function Integration/Inlining</a>
1006 <div class="doc_text">
1008 Bottom-up inlining of functions into callees.
1012 <!-------------------------------------------------------------------------- -->
1013 <div class="doc_subsection">
1014 <a name="insert-block-profiling">Insert instrumentation for block profiling</a>
1016 <div class="doc_text">
1018 This pass instruments the specified program with counters for basic block
1019 profiling, which counts the number of times each basic block executes. This
1020 is the most basic form of profiling, which can tell which blocks are hot, but
1021 cannot reliably detect hot paths through the CFG.
1025 Note that this implementation is very naïve. Control equivalent regions of
1026 the CFG should not require duplicate counters, but it does put duplicate
1031 <!-------------------------------------------------------------------------- -->
1032 <div class="doc_subsection">
1033 <a name="insert-edge-profiling">Insert instrumentation for edge profiling</a>
1035 <div class="doc_text">
1037 This pass instruments the specified program with counters for edge profiling.
1038 Edge profiling can give a reasonable approximation of the hot paths through a
1039 program, and is used for a wide variety of program transformations.
1043 Note that this implementation is very naïve. It inserts a counter for
1044 <em>every</em> edge in the program, instead of using control flow information
1045 to prune the number of counters inserted.
1049 <!-------------------------------------------------------------------------- -->
1050 <div class="doc_subsection">
1051 <a name="insert-function-profiling">Insert instrumentation for function profiling</a>
1053 <div class="doc_text">
1055 This pass instruments the specified program with counters for function
1056 profiling, which counts the number of times each function is called.
1060 <!-------------------------------------------------------------------------- -->
1061 <div class="doc_subsection">
1062 <a name="insert-null-profiling-rs">Measure profiling framework overhead</a>
1064 <div class="doc_text">
1066 The basic profiler that does nothing. It is the default profiler and thus
1067 terminates <code>RSProfiler</code> chains. It is useful for measuring
1072 <!-------------------------------------------------------------------------- -->
1073 <div class="doc_subsection">
1074 <a name="insert-rs-profiling-framework">Insert random sampling instrumentation framework</a>
1076 <div class="doc_text">
1078 The second stage of the random-sampling instrumentation framework, duplicates
1079 all instructions in a function, ignoring the profiling code, then connects the
1080 two versions together at the entry and at backedges. At each connection point
1081 a choice is made as to whether to jump to the profiled code (take a sample) or
1082 execute the unprofiled code.
1086 After this pass, it is highly recommended to run<a href="#mem2reg">mem2reg</a>
1087 and <a href="#adce">adce</a>. <a href="#instcombine">instcombine</a>,
1088 <a href="#load-vn">load-vn</a>, <a href="#gdce">gdce</a>, and
1089 <a href="#dse">dse</a> also are good to run afterwards.
1093 <!-------------------------------------------------------------------------- -->
1094 <div class="doc_subsection">
1095 <a name="instcombine">Combine redundant instructions</a>
1097 <div class="doc_text">
1099 Combine instructions to form fewer, simple
1100 instructions. This pass does not modify the CFG This pass is where algebraic
1101 simplification happens.
1105 This pass combines things like:
1110 %Z = add i32 %Y, 1</pre></blockquote>
1117 >%Z = add i32 %X, 2</pre></blockquote>
1120 This is a simple worklist driven algorithm.
1124 This pass guarantees that the following canonicalizations are performed on
1129 <li>If a binary operator has a constant operand, it is moved to the right-
1131 <li>Bitwise operators with constant operands are always grouped so that
1132 shifts are performed first, then <code>or</code>s, then
1133 <code>and</code>s, then <code>xor</code>s.</li>
1134 <li>Compare instructions are converted from <code><</code>,
1135 <code>></code>, <code>≤</code>, or <code>≥</code> to
1136 <code>=</code> or <code>≠</code> if possible.</li>
1137 <li>All <code>cmp</code> instructions on boolean values are replaced with
1138 logical operations.</li>
1139 <li><code>add <var>X</var>, <var>X</var></code> is represented as
1140 <code>mul <var>X</var>, 2</code> ⇒ <code>shl <var>X</var>, 1</code></li>
1141 <li>Multiplies with a constant power-of-two argument are transformed into
1147 <!-------------------------------------------------------------------------- -->
1148 <div class="doc_subsection">
1149 <a name="internalize">Internalize Global Symbols</a>
1151 <div class="doc_text">
1152 <p>Yet to be written.</p>
1155 <!-------------------------------------------------------------------------- -->
1156 <div class="doc_subsection">
1157 <a name="ipconstprop">Interprocedural constant propagation</a>
1159 <div class="doc_text">
1160 <p>Yet to be written.</p>
1163 <!-------------------------------------------------------------------------- -->
1164 <div class="doc_subsection">
1165 <a name="ipsccp">Interprocedural Sparse Conditional Constant Propagation</a>
1167 <div class="doc_text">
1168 <p>Yet to be written.</p>
1171 <!-------------------------------------------------------------------------- -->
1172 <div class="doc_subsection">
1173 <a name="lcssa">Loop-Closed SSA Form Pass</a>
1175 <div class="doc_text">
1176 <p>Yet to be written.</p>
1179 <!-------------------------------------------------------------------------- -->
1180 <div class="doc_subsection">
1181 <a name="licm">Loop Invariant Code Motion</a>
1183 <div class="doc_text">
1184 <p>Yet to be written.</p>
1187 <!-------------------------------------------------------------------------- -->
1188 <div class="doc_subsection">
1189 <a name="loop-extract">Extract loops into new functions</a>
1191 <div class="doc_text">
1192 <p>Yet to be written.</p>
1195 <!-------------------------------------------------------------------------- -->
1196 <div class="doc_subsection">
1197 <a name="loop-extract-single">Extract at most one loop into a new function</a>
1199 <div class="doc_text">
1200 <p>Yet to be written.</p>
1203 <!-------------------------------------------------------------------------- -->
1204 <div class="doc_subsection">
1205 <a name="loop-index-split">Index Split Loops</a>
1207 <div class="doc_text">
1208 <p>Yet to be written.</p>
1211 <!-------------------------------------------------------------------------- -->
1212 <div class="doc_subsection">
1213 <a name="loop-reduce">Loop Strength Reduction</a>
1215 <div class="doc_text">
1216 <p>Yet to be written.</p>
1219 <!-------------------------------------------------------------------------- -->
1220 <div class="doc_subsection">
1221 <a name="loop-rotate">Rotate Loops</a>
1223 <div class="doc_text">
1224 <p>Yet to be written.</p>
1227 <!-------------------------------------------------------------------------- -->
1228 <div class="doc_subsection">
1229 <a name="loop-unroll">Unroll loops</a>
1231 <div class="doc_text">
1232 <p>Yet to be written.</p>
1235 <!-------------------------------------------------------------------------- -->
1236 <div class="doc_subsection">
1237 <a name="loop-unswitch">Unswitch loops</a>
1239 <div class="doc_text">
1240 <p>Yet to be written.</p>
1243 <!-------------------------------------------------------------------------- -->
1244 <div class="doc_subsection">
1245 <a name="loopsimplify">Canonicalize natural loops</a>
1247 <div class="doc_text">
1248 <p>Yet to be written.</p>
1251 <!-------------------------------------------------------------------------- -->
1252 <div class="doc_subsection">
1253 <a name="lower-packed">lowers packed operations to operations on smaller packed datatypes</a>
1255 <div class="doc_text">
1256 <p>Yet to be written.</p>
1259 <!-------------------------------------------------------------------------- -->
1260 <div class="doc_subsection">
1261 <a name="lowerallocs">Lower allocations from instructions to calls</a>
1263 <div class="doc_text">
1264 <p>Yet to be written.</p>
1267 <!-------------------------------------------------------------------------- -->
1268 <div class="doc_subsection">
1269 <a name="lowergc">Lower GC intrinsics, for GCless code generators</a>
1271 <div class="doc_text">
1272 <p>Yet to be written.</p>
1275 <!-------------------------------------------------------------------------- -->
1276 <div class="doc_subsection">
1277 <a name="lowerinvoke">Lower invoke and unwind, for unwindless code generators</a>
1279 <div class="doc_text">
1280 <p>Yet to be written.</p>
1283 <!-------------------------------------------------------------------------- -->
1284 <div class="doc_subsection">
1285 <a name="lowerselect">Lower select instructions to branches</a>
1287 <div class="doc_text">
1288 <p>Yet to be written.</p>
1291 <!-------------------------------------------------------------------------- -->
1292 <div class="doc_subsection">
1293 <a name="lowersetjmp">Lower Set Jump</a>
1295 <div class="doc_text">
1296 <p>Yet to be written.</p>
1299 <!-------------------------------------------------------------------------- -->
1300 <div class="doc_subsection">
1301 <a name="lowerswitch">Lower SwitchInst's to branches</a>
1303 <div class="doc_text">
1304 <p>Yet to be written.</p>
1307 <!-------------------------------------------------------------------------- -->
1308 <div class="doc_subsection">
1309 <a name="mem2reg">Promote Memory to Register</a>
1311 <div class="doc_text">
1312 <p>Yet to be written.</p>
1315 <!-------------------------------------------------------------------------- -->
1316 <div class="doc_subsection">
1317 <a name="mergereturn">Unify function exit nodes</a>
1319 <div class="doc_text">
1320 <p>Yet to be written.</p>
1323 <!-------------------------------------------------------------------------- -->
1324 <div class="doc_subsection">
1325 <a name="predsimplify">Predicate Simplifier</a>
1327 <div class="doc_text">
1328 <p>Yet to be written.</p>
1331 <!-------------------------------------------------------------------------- -->
1332 <div class="doc_subsection">
1333 <a name="prune-eh">Remove unused exception handling info</a>
1335 <div class="doc_text">
1336 <p>Yet to be written.</p>
1339 <!-------------------------------------------------------------------------- -->
1340 <div class="doc_subsection">
1341 <a name="raiseallocs">Raise allocations from calls to instructions</a>
1343 <div class="doc_text">
1344 <p>Yet to be written.</p>
1347 <!-------------------------------------------------------------------------- -->
1348 <div class="doc_subsection">
1349 <a name="reassociate">Reassociate expressions</a>
1351 <div class="doc_text">
1352 <p>Yet to be written.</p>
1355 <!-------------------------------------------------------------------------- -->
1356 <div class="doc_subsection">
1357 <a name="reg2mem">Demote all values to stack slots</a>
1359 <div class="doc_text">
1360 <p>Yet to be written.</p>
1363 <!-------------------------------------------------------------------------- -->
1364 <div class="doc_subsection">
1365 <a name="scalarrepl">Scalar Replacement of Aggregates</a>
1367 <div class="doc_text">
1368 <p>Yet to be written.</p>
1371 <!-------------------------------------------------------------------------- -->
1372 <div class="doc_subsection">
1373 <a name="sccp">Sparse Conditional Constant Propagation</a>
1375 <div class="doc_text">
1376 <p>Yet to be written.</p>
1379 <!-------------------------------------------------------------------------- -->
1380 <div class="doc_subsection">
1381 <a name="simplify-libcalls">Simplify well-known library calls</a>
1383 <div class="doc_text">
1384 <p>Yet to be written.</p>
1387 <!-------------------------------------------------------------------------- -->
1388 <div class="doc_subsection">
1389 <a name="simplifycfg">Simplify the CFG</a>
1391 <div class="doc_text">
1392 <p>Yet to be written.</p>
1395 <!-------------------------------------------------------------------------- -->
1396 <div class="doc_subsection">
1397 <a name="strip">Strip all symbols from a module</a>
1399 <div class="doc_text">
1400 <p>Yet to be written.</p>
1403 <!-------------------------------------------------------------------------- -->
1404 <div class="doc_subsection">
1405 <a name="tailcallelim">Tail Call Elimination</a>
1407 <div class="doc_text">
1408 <p>Yet to be written.</p>
1411 <!-------------------------------------------------------------------------- -->
1412 <div class="doc_subsection">
1413 <a name="tailduplicate">Tail Duplication</a>
1415 <div class="doc_text">
1416 <p>Yet to be written.</p>
1419 <!-- ======================================================================= -->
1420 <div class="doc_section"> <a name="transform">Utility Passes</a></div>
1421 <div class="doc_text">
1422 <p>This section describes the LLVM Utility Passes.</p>
1425 <!-------------------------------------------------------------------------- -->
1426 <div class="doc_subsection">
1427 <a name="deadarghaX0r">Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)</a>
1429 <div class="doc_text">
1430 <p>Yet to be written.</p>
1433 <!-------------------------------------------------------------------------- -->
1434 <div class="doc_subsection">
1435 <a name="extract-blocks">Extract Basic Blocks From Module (for bugpoint use)</a>
1437 <div class="doc_text">
1438 <p>Yet to be written.</p>
1441 <!-------------------------------------------------------------------------- -->
1442 <div class="doc_subsection">
1443 <a name="emitbitcode">Bitcode Writer</a>
1445 <div class="doc_text">
1446 <p>Yet to be written.</p>
1449 <!-------------------------------------------------------------------------- -->
1450 <div class="doc_subsection">
1451 <a name="verify">Module Verifier</a>
1453 <div class="doc_text">
1454 <p>Yet to be written.</p>
1457 <!-------------------------------------------------------------------------- -->
1458 <div class="doc_subsection">
1459 <a name="view-cfg">View CFG of function</a>
1461 <div class="doc_text">
1462 <p>Yet to be written.</p>
1465 <!-------------------------------------------------------------------------- -->
1466 <div class="doc_subsection">
1467 <a name="view-cfg-only">View CFG of function (with no function bodies)</a>
1469 <div class="doc_text">
1470 <p>Yet to be written.</p>
1473 <!-- *********************************************************************** -->
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1482 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
1483 <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
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