1 //===- LoopRotation.cpp - Loop Rotation 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 implements Loop Rotation Pass.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "llvm/Transforms/Scalar/LoopRotation.h"
15 #include "llvm/ADT/Statistic.h"
16 #include "llvm/Analysis/InstructionSimplify.h"
17 #include "llvm/Analysis/LoopPass.h"
18 #include "llvm/Analysis/MemorySSA.h"
19 #include "llvm/Analysis/MemorySSAUpdater.h"
20 #include "llvm/Analysis/ScalarEvolution.h"
21 #include "llvm/Analysis/TargetTransformInfo.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Transforms/Scalar.h"
24 #include "llvm/Transforms/Scalar/LoopPassManager.h"
25 #include "llvm/Transforms/Utils/LoopRotationUtils.h"
26 #include "llvm/Transforms/Utils/LoopUtils.h"
27 using namespace llvm;
28
29 #define DEBUG_TYPE "loop-rotate"
30
31 static cl::opt<unsigned> DefaultRotationThreshold(
32 "rotation-max-header-size", cl::init(16), cl::Hidden,
33 cl::desc("The default maximum header size for automatic loop rotation"));
34
LoopRotatePass(bool EnableHeaderDuplication)35 LoopRotatePass::LoopRotatePass(bool EnableHeaderDuplication)
36 : EnableHeaderDuplication(EnableHeaderDuplication) {}
37
run(Loop & L,LoopAnalysisManager & AM,LoopStandardAnalysisResults & AR,LPMUpdater &)38 PreservedAnalyses LoopRotatePass::run(Loop &L, LoopAnalysisManager &AM,
39 LoopStandardAnalysisResults &AR,
40 LPMUpdater &) {
41 int Threshold = EnableHeaderDuplication ? DefaultRotationThreshold : 0;
42 const DataLayout &DL = L.getHeader()->getModule()->getDataLayout();
43 const SimplifyQuery SQ = getBestSimplifyQuery(AR, DL);
44
45 Optional<MemorySSAUpdater> MSSAU;
46 if (AR.MSSA)
47 MSSAU = MemorySSAUpdater(AR.MSSA);
48 bool Changed = LoopRotation(&L, &AR.LI, &AR.TTI, &AR.AC, &AR.DT, &AR.SE,
49 MSSAU.hasValue() ? MSSAU.getPointer() : nullptr,
50 SQ, false, Threshold, false);
51
52 if (!Changed)
53 return PreservedAnalyses::all();
54
55 if (AR.MSSA && VerifyMemorySSA)
56 AR.MSSA->verifyMemorySSA();
57
58 return getLoopPassPreservedAnalyses();
59 }
60
61 namespace {
62
63 class LoopRotateLegacyPass : public LoopPass {
64 unsigned MaxHeaderSize;
65
66 public:
67 static char ID; // Pass ID, replacement for typeid
LoopRotateLegacyPass(int SpecifiedMaxHeaderSize=-1)68 LoopRotateLegacyPass(int SpecifiedMaxHeaderSize = -1) : LoopPass(ID) {
69 initializeLoopRotateLegacyPassPass(*PassRegistry::getPassRegistry());
70 if (SpecifiedMaxHeaderSize == -1)
71 MaxHeaderSize = DefaultRotationThreshold;
72 else
73 MaxHeaderSize = unsigned(SpecifiedMaxHeaderSize);
74 }
75
76 // LCSSA form makes instruction renaming easier.
getAnalysisUsage(AnalysisUsage & AU) const77 void getAnalysisUsage(AnalysisUsage &AU) const override {
78 AU.addRequired<AssumptionCacheTracker>();
79 AU.addRequired<TargetTransformInfoWrapperPass>();
80 if (EnableMSSALoopDependency) {
81 AU.addRequired<MemorySSAWrapperPass>();
82 AU.addPreserved<MemorySSAWrapperPass>();
83 }
84 getLoopAnalysisUsage(AU);
85 }
86
runOnLoop(Loop * L,LPPassManager & LPM)87 bool runOnLoop(Loop *L, LPPassManager &LPM) override {
88 if (skipLoop(L))
89 return false;
90 Function &F = *L->getHeader()->getParent();
91
92 auto *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
93 const auto *TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
94 auto *AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
95 auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
96 auto *DT = DTWP ? &DTWP->getDomTree() : nullptr;
97 auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
98 auto *SE = SEWP ? &SEWP->getSE() : nullptr;
99 const SimplifyQuery SQ = getBestSimplifyQuery(*this, F);
100 Optional<MemorySSAUpdater> MSSAU;
101 if (EnableMSSALoopDependency) {
102 MemorySSA *MSSA = &getAnalysis<MemorySSAWrapperPass>().getMSSA();
103 MSSAU = MemorySSAUpdater(MSSA);
104 }
105 return LoopRotation(L, LI, TTI, AC, DT, SE,
106 MSSAU.hasValue() ? MSSAU.getPointer() : nullptr, SQ,
107 false, MaxHeaderSize, false);
108 }
109 };
110 }
111
112 char LoopRotateLegacyPass::ID = 0;
113 INITIALIZE_PASS_BEGIN(LoopRotateLegacyPass, "loop-rotate", "Rotate Loops",
114 false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)115 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
116 INITIALIZE_PASS_DEPENDENCY(LoopPass)
117 INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
118 INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)
119 INITIALIZE_PASS_END(LoopRotateLegacyPass, "loop-rotate", "Rotate Loops", false,
120 false)
121
122 Pass *llvm::createLoopRotatePass(int MaxHeaderSize) {
123 return new LoopRotateLegacyPass(MaxHeaderSize);
124 }
125