1 //===- PassManagerBuilder.cpp - Build Standard Pass -----------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines the PassManagerBuilder class, which is used to set up a
11 // "standard" optimization sequence suitable for languages like C and C++.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 
16 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
17 #include "llvm-c/Transforms/PassManagerBuilder.h"
18 #include "llvm/ADT/SmallVector.h"
19 #include "llvm/Analysis/Passes.h"
20 #include "llvm/Analysis/Verifier.h"
21 #include "llvm/PassManager.h"
22 #include "llvm/Support/CommandLine.h"
23 #include "llvm/Support/ManagedStatic.h"
24 #include "llvm/Target/TargetLibraryInfo.h"
25 #include "llvm/Transforms/IPO.h"
26 #include "llvm/Transforms/Scalar.h"
27 #include "llvm/Transforms/Vectorize.h"
28 
29 using namespace llvm;
30 
31 static cl::opt<bool>
32 RunLoopVectorization("vectorize-loops",
33                      cl::desc("Run the Loop vectorization passes"));
34 
35 // This is a helper flag that we use for testing the profitability of
36 // vectorization on -O2 and -Os. It should go away once we make a decision.
37 static cl::opt<bool>
38 VectorizeO2("vectorize-o2",
39             cl::desc("Enable vectorization on all O levels"));
40 
41 static cl::opt<bool>
42 RunSLPVectorization("vectorize-slp",
43                     cl::desc("Run the SLP vectorization passes"));
44 
45 static cl::opt<bool>
46 RunBBVectorization("vectorize-slp-aggressive",
47                     cl::desc("Run the BB vectorization passes"));
48 
49 static cl::opt<bool>
50 UseGVNAfterVectorization("use-gvn-after-vectorization",
51   cl::init(false), cl::Hidden,
52   cl::desc("Run GVN instead of Early CSE after vectorization passes"));
53 
54 static cl::opt<bool> UseNewSROA("use-new-sroa",
55   cl::init(true), cl::Hidden,
56   cl::desc("Enable the new, experimental SROA pass"));
57 
58 PassManagerBuilder::PassManagerBuilder() {
59     OptLevel = 2;
60     SizeLevel = 0;
61     LibraryInfo = 0;
62     Inliner = 0;
63     DisableSimplifyLibCalls = false;
64     DisableUnitAtATime = false;
65     DisableUnrollLoops = false;
66     BBVectorize = RunBBVectorization;
67     SLPVectorize = RunSLPVectorization;
68     LoopVectorize = RunLoopVectorization;
69 }
70 
71 PassManagerBuilder::~PassManagerBuilder() {
72   delete LibraryInfo;
73   delete Inliner;
74 }
75 
76 /// Set of global extensions, automatically added as part of the standard set.
77 static ManagedStatic<SmallVector<std::pair<PassManagerBuilder::ExtensionPointTy,
78    PassManagerBuilder::ExtensionFn>, 8> > GlobalExtensions;
79 
80 void PassManagerBuilder::addGlobalExtension(
81     PassManagerBuilder::ExtensionPointTy Ty,
82     PassManagerBuilder::ExtensionFn Fn) {
83   GlobalExtensions->push_back(std::make_pair(Ty, Fn));
84 }
85 
86 void PassManagerBuilder::addExtension(ExtensionPointTy Ty, ExtensionFn Fn) {
87   Extensions.push_back(std::make_pair(Ty, Fn));
88 }
89 
90 void PassManagerBuilder::addExtensionsToPM(ExtensionPointTy ETy,
91                                            PassManagerBase &PM) const {
92   for (unsigned i = 0, e = GlobalExtensions->size(); i != e; ++i)
93     if ((*GlobalExtensions)[i].first == ETy)
94       (*GlobalExtensions)[i].second(*this, PM);
95   for (unsigned i = 0, e = Extensions.size(); i != e; ++i)
96     if (Extensions[i].first == ETy)
97       Extensions[i].second(*this, PM);
98 }
99 
100 void
101 PassManagerBuilder::addInitialAliasAnalysisPasses(PassManagerBase &PM) const {
102   // Add TypeBasedAliasAnalysis before BasicAliasAnalysis so that
103   // BasicAliasAnalysis wins if they disagree. This is intended to help
104   // support "obvious" type-punning idioms.
105   PM.add(createTypeBasedAliasAnalysisPass());
106   PM.add(createBasicAliasAnalysisPass());
107 }
108 
109 void PassManagerBuilder::populateFunctionPassManager(FunctionPassManager &FPM) {
110   addExtensionsToPM(EP_EarlyAsPossible, FPM);
111 
112   // Add LibraryInfo if we have some.
113   if (LibraryInfo) FPM.add(new TargetLibraryInfo(*LibraryInfo));
114 
115   if (OptLevel == 0) return;
116 
117   addInitialAliasAnalysisPasses(FPM);
118 
119   FPM.add(createCFGSimplificationPass());
120   if (UseNewSROA)
121     FPM.add(createSROAPass());
122   else
123     FPM.add(createScalarReplAggregatesPass());
124   FPM.add(createEarlyCSEPass());
125   FPM.add(createLowerExpectIntrinsicPass());
126 }
127 
128 void PassManagerBuilder::populateModulePassManager(PassManagerBase &MPM) {
129   // If all optimizations are disabled, just run the always-inline pass.
130   if (OptLevel == 0) {
131     if (Inliner) {
132       MPM.add(Inliner);
133       Inliner = 0;
134     }
135 
136     // FIXME: This is a HACK! The inliner pass above implicitly creates a CGSCC
137     // pass manager, but we don't want to add extensions into that pass manager.
138     // To prevent this we must insert a no-op module pass to reset the pass
139     // manager to get the same behavior as EP_OptimizerLast in non-O0 builds.
140     if (!GlobalExtensions->empty() || !Extensions.empty())
141       MPM.add(createBarrierNoopPass());
142 
143     addExtensionsToPM(EP_EnabledOnOptLevel0, MPM);
144     return;
145   }
146 
147   // Add LibraryInfo if we have some.
148   if (LibraryInfo) MPM.add(new TargetLibraryInfo(*LibraryInfo));
149 
150   addInitialAliasAnalysisPasses(MPM);
151 
152   if (!DisableUnitAtATime) {
153     addExtensionsToPM(EP_ModuleOptimizerEarly, MPM);
154 
155     MPM.add(createGlobalOptimizerPass());     // Optimize out global vars
156 
157     MPM.add(createIPSCCPPass());              // IP SCCP
158     MPM.add(createDeadArgEliminationPass());  // Dead argument elimination
159 
160     MPM.add(createInstructionCombiningPass());// Clean up after IPCP & DAE
161     MPM.add(createCFGSimplificationPass());   // Clean up after IPCP & DAE
162   }
163 
164   // Start of CallGraph SCC passes.
165   if (!DisableUnitAtATime)
166     MPM.add(createPruneEHPass());             // Remove dead EH info
167   if (Inliner) {
168     MPM.add(Inliner);
169     Inliner = 0;
170   }
171   if (!DisableUnitAtATime)
172     MPM.add(createFunctionAttrsPass());       // Set readonly/readnone attrs
173   if (OptLevel > 2)
174     MPM.add(createArgumentPromotionPass());   // Scalarize uninlined fn args
175 
176   // Start of function pass.
177   // Break up aggregate allocas, using SSAUpdater.
178   if (UseNewSROA)
179     MPM.add(createSROAPass(/*RequiresDomTree*/ false));
180   else
181     MPM.add(createScalarReplAggregatesPass(-1, false));
182   MPM.add(createEarlyCSEPass());              // Catch trivial redundancies
183   if (!DisableSimplifyLibCalls)
184     MPM.add(createSimplifyLibCallsPass());    // Library Call Optimizations
185   MPM.add(createJumpThreadingPass());         // Thread jumps.
186   MPM.add(createCorrelatedValuePropagationPass()); // Propagate conditionals
187   MPM.add(createCFGSimplificationPass());     // Merge & remove BBs
188   MPM.add(createInstructionCombiningPass());  // Combine silly seq's
189 
190   MPM.add(createTailCallEliminationPass());   // Eliminate tail calls
191   MPM.add(createCFGSimplificationPass());     // Merge & remove BBs
192   MPM.add(createReassociatePass());           // Reassociate expressions
193   MPM.add(createLoopRotatePass());            // Rotate Loop
194   MPM.add(createLICMPass());                  // Hoist loop invariants
195   MPM.add(createLoopUnswitchPass(SizeLevel || OptLevel < 3));
196   MPM.add(createInstructionCombiningPass());
197   MPM.add(createIndVarSimplifyPass());        // Canonicalize indvars
198   MPM.add(createLoopIdiomPass());             // Recognize idioms like memset.
199   MPM.add(createLoopDeletionPass());          // Delete dead loops
200 
201   if (LoopVectorize && (OptLevel > 2 || VectorizeO2))
202     MPM.add(createLoopVectorizePass());
203 
204   if (!DisableUnrollLoops)
205     MPM.add(createLoopUnrollPass());          // Unroll small loops
206   addExtensionsToPM(EP_LoopOptimizerEnd, MPM);
207 
208   if (OptLevel > 1)
209     MPM.add(createGVNPass());                 // Remove redundancies
210   MPM.add(createMemCpyOptPass());             // Remove memcpy / form memset
211   MPM.add(createSCCPPass());                  // Constant prop with SCCP
212 
213   // Run instcombine after redundancy elimination to exploit opportunities
214   // opened up by them.
215   MPM.add(createInstructionCombiningPass());
216   MPM.add(createJumpThreadingPass());         // Thread jumps
217   MPM.add(createCorrelatedValuePropagationPass());
218   MPM.add(createDeadStoreEliminationPass());  // Delete dead stores
219 
220   addExtensionsToPM(EP_ScalarOptimizerLate, MPM);
221 
222   if (SLPVectorize)
223     MPM.add(createSLPVectorizerPass());     // Vectorize parallel scalar chains.
224 
225   if (BBVectorize) {
226     MPM.add(createBBVectorizePass());
227     MPM.add(createInstructionCombiningPass());
228     if (OptLevel > 1 && UseGVNAfterVectorization)
229       MPM.add(createGVNPass());                   // Remove redundancies
230     else
231       MPM.add(createEarlyCSEPass());              // Catch trivial redundancies
232 
233     // BBVectorize may have significantly shortened a loop body; unroll again.
234     if (!DisableUnrollLoops)
235       MPM.add(createLoopUnrollPass());
236   }
237 
238   MPM.add(createAggressiveDCEPass());         // Delete dead instructions
239   MPM.add(createCFGSimplificationPass());     // Merge & remove BBs
240   MPM.add(createInstructionCombiningPass());  // Clean up after everything.
241 
242   if (!DisableUnitAtATime) {
243     // FIXME: We shouldn't bother with this anymore.
244     MPM.add(createStripDeadPrototypesPass()); // Get rid of dead prototypes
245 
246     // GlobalOpt already deletes dead functions and globals, at -O2 try a
247     // late pass of GlobalDCE.  It is capable of deleting dead cycles.
248     if (OptLevel > 1) {
249       MPM.add(createGlobalDCEPass());         // Remove dead fns and globals.
250       MPM.add(createConstantMergePass());     // Merge dup global constants
251     }
252   }
253   addExtensionsToPM(EP_OptimizerLast, MPM);
254 }
255 
256 void PassManagerBuilder::populateLTOPassManager(PassManagerBase &PM,
257                                                 bool Internalize,
258                                                 bool RunInliner,
259                                                 bool DisableGVNLoadPRE) {
260   // Provide AliasAnalysis services for optimizations.
261   addInitialAliasAnalysisPasses(PM);
262 
263   // Now that composite has been compiled, scan through the module, looking
264   // for a main function.  If main is defined, mark all other functions
265   // internal.
266   if (Internalize) {
267     std::vector<const char*> E;
268     E.push_back("main");
269     PM.add(createInternalizePass(E));
270   }
271 
272   // Propagate constants at call sites into the functions they call.  This
273   // opens opportunities for globalopt (and inlining) by substituting function
274   // pointers passed as arguments to direct uses of functions.
275   PM.add(createIPSCCPPass());
276 
277   // Now that we internalized some globals, see if we can hack on them!
278   PM.add(createGlobalOptimizerPass());
279 
280   // Linking modules together can lead to duplicated global constants, only
281   // keep one copy of each constant.
282   PM.add(createConstantMergePass());
283 
284   // Remove unused arguments from functions.
285   PM.add(createDeadArgEliminationPass());
286 
287   // Reduce the code after globalopt and ipsccp.  Both can open up significant
288   // simplification opportunities, and both can propagate functions through
289   // function pointers.  When this happens, we often have to resolve varargs
290   // calls, etc, so let instcombine do this.
291   PM.add(createInstructionCombiningPass());
292 
293   // Inline small functions
294   if (RunInliner)
295     PM.add(createFunctionInliningPass());
296 
297   PM.add(createPruneEHPass());   // Remove dead EH info.
298 
299   // Optimize globals again if we ran the inliner.
300   if (RunInliner)
301     PM.add(createGlobalOptimizerPass());
302   PM.add(createGlobalDCEPass()); // Remove dead functions.
303 
304   // If we didn't decide to inline a function, check to see if we can
305   // transform it to pass arguments by value instead of by reference.
306   PM.add(createArgumentPromotionPass());
307 
308   // The IPO passes may leave cruft around.  Clean up after them.
309   PM.add(createInstructionCombiningPass());
310   PM.add(createJumpThreadingPass());
311   // Break up allocas
312   if (UseNewSROA)
313     PM.add(createSROAPass());
314   else
315     PM.add(createScalarReplAggregatesPass());
316 
317   // Run a few AA driven optimizations here and now, to cleanup the code.
318   PM.add(createFunctionAttrsPass()); // Add nocapture.
319   PM.add(createGlobalsModRefPass()); // IP alias analysis.
320 
321   PM.add(createLICMPass());                 // Hoist loop invariants.
322   PM.add(createGVNPass(DisableGVNLoadPRE)); // Remove redundancies.
323   PM.add(createMemCpyOptPass());            // Remove dead memcpys.
324   // Nuke dead stores.
325   PM.add(createDeadStoreEliminationPass());
326 
327   // Cleanup and simplify the code after the scalar optimizations.
328   PM.add(createInstructionCombiningPass());
329 
330   PM.add(createJumpThreadingPass());
331 
332   // Delete basic blocks, which optimization passes may have killed.
333   PM.add(createCFGSimplificationPass());
334 
335   // Now that we have optimized the program, discard unreachable functions.
336   PM.add(createGlobalDCEPass());
337 }
338 
339 inline PassManagerBuilder *unwrap(LLVMPassManagerBuilderRef P) {
340     return reinterpret_cast<PassManagerBuilder*>(P);
341 }
342 
343 inline LLVMPassManagerBuilderRef wrap(PassManagerBuilder *P) {
344   return reinterpret_cast<LLVMPassManagerBuilderRef>(P);
345 }
346 
347 LLVMPassManagerBuilderRef LLVMPassManagerBuilderCreate() {
348   PassManagerBuilder *PMB = new PassManagerBuilder();
349   return wrap(PMB);
350 }
351 
352 void LLVMPassManagerBuilderDispose(LLVMPassManagerBuilderRef PMB) {
353   PassManagerBuilder *Builder = unwrap(PMB);
354   delete Builder;
355 }
356 
357 void
358 LLVMPassManagerBuilderSetOptLevel(LLVMPassManagerBuilderRef PMB,
359                                   unsigned OptLevel) {
360   PassManagerBuilder *Builder = unwrap(PMB);
361   Builder->OptLevel = OptLevel;
362 }
363 
364 void
365 LLVMPassManagerBuilderSetSizeLevel(LLVMPassManagerBuilderRef PMB,
366                                    unsigned SizeLevel) {
367   PassManagerBuilder *Builder = unwrap(PMB);
368   Builder->SizeLevel = SizeLevel;
369 }
370 
371 void
372 LLVMPassManagerBuilderSetDisableUnitAtATime(LLVMPassManagerBuilderRef PMB,
373                                             LLVMBool Value) {
374   PassManagerBuilder *Builder = unwrap(PMB);
375   Builder->DisableUnitAtATime = Value;
376 }
377 
378 void
379 LLVMPassManagerBuilderSetDisableUnrollLoops(LLVMPassManagerBuilderRef PMB,
380                                             LLVMBool Value) {
381   PassManagerBuilder *Builder = unwrap(PMB);
382   Builder->DisableUnrollLoops = Value;
383 }
384 
385 void
386 LLVMPassManagerBuilderSetDisableSimplifyLibCalls(LLVMPassManagerBuilderRef PMB,
387                                                  LLVMBool Value) {
388   PassManagerBuilder *Builder = unwrap(PMB);
389   Builder->DisableSimplifyLibCalls = Value;
390 }
391 
392 void
393 LLVMPassManagerBuilderUseInlinerWithThreshold(LLVMPassManagerBuilderRef PMB,
394                                               unsigned Threshold) {
395   PassManagerBuilder *Builder = unwrap(PMB);
396   Builder->Inliner = createFunctionInliningPass(Threshold);
397 }
398 
399 void
400 LLVMPassManagerBuilderPopulateFunctionPassManager(LLVMPassManagerBuilderRef PMB,
401                                                   LLVMPassManagerRef PM) {
402   PassManagerBuilder *Builder = unwrap(PMB);
403   FunctionPassManager *FPM = unwrap<FunctionPassManager>(PM);
404   Builder->populateFunctionPassManager(*FPM);
405 }
406 
407 void
408 LLVMPassManagerBuilderPopulateModulePassManager(LLVMPassManagerBuilderRef PMB,
409                                                 LLVMPassManagerRef PM) {
410   PassManagerBuilder *Builder = unwrap(PMB);
411   PassManagerBase *MPM = unwrap(PM);
412   Builder->populateModulePassManager(*MPM);
413 }
414 
415 void LLVMPassManagerBuilderPopulateLTOPassManager(LLVMPassManagerBuilderRef PMB,
416                                                   LLVMPassManagerRef PM,
417                                                   LLVMBool Internalize,
418                                                   LLVMBool RunInliner) {
419   PassManagerBuilder *Builder = unwrap(PMB);
420   PassManagerBase *LPM = unwrap(PM);
421   Builder->populateLTOPassManager(*LPM, Internalize != 0, RunInliner != 0);
422 }
423