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Cameron Zwarichcab9a0a2011-01-03 00:25:16 +00001//===- LoopInstSimplify.cpp - Loop Instruction Simplification 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 pass performs lightweight instruction simplification on loop bodies.
11//
12//===----------------------------------------------------------------------===//
13
Chandler Carruthed0881b2012-12-03 16:50:05 +000014#include "llvm/Transforms/Scalar.h"
Jakub Staszakf23980a2013-02-09 01:04:28 +000015#include "llvm/ADT/STLExtras.h"
Chandler Carruth8a8cd2b2014-01-07 11:48:04 +000016#include "llvm/ADT/Statistic.h"
Chandler Carruth66b31302015-01-04 12:03:27 +000017#include "llvm/Analysis/AssumptionCache.h"
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000018#include "llvm/Analysis/InstructionSimplify.h"
Cameron Zwariche9249692011-01-04 00:12:46 +000019#include "llvm/Analysis/LoopInfo.h"
Cameron Zwarich4c51d122011-01-05 05:15:53 +000020#include "llvm/Analysis/LoopPass.h"
Chandler Carruthb81dfa62015-01-28 04:57:56 +000021#include "llvm/Analysis/ScalarEvolution.h"
Chandler Carruth9fb823b2013-01-02 11:36:10 +000022#include "llvm/IR/DataLayout.h"
Chandler Carruth5ad5f152014-01-13 09:26:24 +000023#include "llvm/IR/Dominators.h"
Chandler Carruth9fb823b2013-01-02 11:36:10 +000024#include "llvm/IR/Instructions.h"
Chandler Carruthed0881b2012-12-03 16:50:05 +000025#include "llvm/Support/Debug.h"
Chandler Carruth62d42152015-01-15 02:16:27 +000026#include "llvm/Analysis/TargetLibraryInfo.h"
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000027#include "llvm/Transforms/Utils/Local.h"
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000028using namespace llvm;
29
Chandler Carruth964daaa2014-04-22 02:55:47 +000030#define DEBUG_TYPE "loop-instsimplify"
31
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000032STATISTIC(NumSimplified, "Number of redundant instructions simplified");
33
34namespace {
Cameron Zwarich4c51d122011-01-05 05:15:53 +000035 class LoopInstSimplify : public LoopPass {
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000036 public:
37 static char ID; // Pass ID, replacement for typeid
Cameron Zwarich4c51d122011-01-05 05:15:53 +000038 LoopInstSimplify() : LoopPass(ID) {
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000039 initializeLoopInstSimplifyPass(*PassRegistry::getPassRegistry());
40 }
41
Craig Topper3e4c6972014-03-05 09:10:37 +000042 bool runOnLoop(Loop*, LPPassManager&) override;
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000043
Craig Topper3e4c6972014-03-05 09:10:37 +000044 void getAnalysisUsage(AnalysisUsage &AU) const override {
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000045 AU.setPreservesCFG();
Chandler Carruth66b31302015-01-04 12:03:27 +000046 AU.addRequired<AssumptionCacheTracker>();
Chandler Carruth4f8f3072015-01-17 14:16:18 +000047 AU.addRequired<LoopInfoWrapperPass>();
Cameron Zwarich4c51d122011-01-05 05:15:53 +000048 AU.addRequiredID(LoopSimplifyID);
Cameron Zwaricha42e5912011-01-09 12:35:16 +000049 AU.addPreservedID(LoopSimplifyID);
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000050 AU.addPreservedID(LCSSAID);
Chandler Carruth2f1fd162015-08-17 02:08:17 +000051 AU.addPreserved<ScalarEvolutionWrapperPass>();
Chandler Carruthb98f63d2015-01-15 10:41:28 +000052 AU.addRequired<TargetLibraryInfoWrapperPass>();
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000053 }
54 };
Alexander Kornienkof00654e2015-06-23 09:49:53 +000055}
Nadav Rotem465834c2012-07-24 10:51:42 +000056
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000057char LoopInstSimplify::ID = 0;
58INITIALIZE_PASS_BEGIN(LoopInstSimplify, "loop-instsimplify",
59 "Simplify instructions in loops", false, false)
Chandler Carruth66b31302015-01-04 12:03:27 +000060INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
Chandler Carruthb98f63d2015-01-15 10:41:28 +000061INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
Chandler Carruth73523022014-01-13 13:07:17 +000062INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
Chandler Carruth4f8f3072015-01-17 14:16:18 +000063INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000064INITIALIZE_PASS_DEPENDENCY(LCSSA)
65INITIALIZE_PASS_END(LoopInstSimplify, "loop-instsimplify",
66 "Simplify instructions in loops", false, false)
67
Cameron Zwarichb4ab2572011-01-08 17:07:11 +000068Pass *llvm::createLoopInstSimplifyPass() {
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000069 return new LoopInstSimplify();
70}
71
Cameron Zwarich4c51d122011-01-05 05:15:53 +000072bool LoopInstSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
Paul Robinsonaf4e64d2014-02-06 00:07:05 +000073 if (skipOptnoneFunction(L))
74 return false;
75
Chandler Carruth73523022014-01-13 13:07:17 +000076 DominatorTreeWrapperPass *DTWP =
77 getAnalysisIfAvailable<DominatorTreeWrapperPass>();
Craig Topperf40110f2014-04-25 05:29:35 +000078 DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
Chandler Carruth4f8f3072015-01-17 14:16:18 +000079 LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
Chandler Carruthb98f63d2015-01-15 10:41:28 +000080 const TargetLibraryInfo *TLI =
81 &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
Chandler Carruth66b31302015-01-04 12:03:27 +000082 auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(
83 *L->getHeader()->getParent());
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000084
Cameron Zwarich4c51d122011-01-05 05:15:53 +000085 SmallVector<BasicBlock*, 8> ExitBlocks;
86 L->getUniqueExitBlocks(ExitBlocks);
87 array_pod_sort(ExitBlocks.begin(), ExitBlocks.end());
88
Cameron Zwarich5a2bb992011-01-05 05:47:47 +000089 SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;
90
Cameron Zwarich80bd9af2011-01-08 15:52:22 +000091 // The bit we are stealing from the pointer represents whether this basic
92 // block is the header of a subloop, in which case we only process its phis.
93 typedef PointerIntPair<BasicBlock*, 1> WorklistItem;
94 SmallVector<WorklistItem, 16> VisitStack;
Cameron Zwarich4c51d122011-01-05 05:15:53 +000095 SmallPtrSet<BasicBlock*, 32> Visited;
96
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +000097 bool Changed = false;
98 bool LocalChanged;
99 do {
100 LocalChanged = false;
101
Cameron Zwarich4c51d122011-01-05 05:15:53 +0000102 VisitStack.clear();
103 Visited.clear();
104
Cameron Zwarich80bd9af2011-01-08 15:52:22 +0000105 VisitStack.push_back(WorklistItem(L->getHeader(), false));
Cameron Zwarich4c51d122011-01-05 05:15:53 +0000106
107 while (!VisitStack.empty()) {
Cameron Zwarich80bd9af2011-01-08 15:52:22 +0000108 WorklistItem Item = VisitStack.pop_back_val();
Cameron Zwarichb4ab2572011-01-08 17:07:11 +0000109 BasicBlock *BB = Item.getPointer();
Cameron Zwarich80bd9af2011-01-08 15:52:22 +0000110 bool IsSubloopHeader = Item.getInt();
Mehdi Aminia28d91d2015-03-10 02:37:25 +0000111 const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
Cameron Zwarich4c51d122011-01-05 05:15:53 +0000112
113 // Simplify instructions in the current basic block.
114 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
Duncan P. N. Exon Smithbe4d8cb2015-10-13 19:26:58 +0000115 Instruction *I = &*BI++;
Cameron Zwarich5a2bb992011-01-05 05:47:47 +0000116
117 // The first time through the loop ToSimplify is empty and we try to
118 // simplify all instructions. On later iterations ToSimplify is not
119 // empty and we only bother simplifying instructions that are in it.
120 if (!ToSimplify->empty() && !ToSimplify->count(I))
121 continue;
122
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +0000123 // Don't bother simplifying unused instructions.
124 if (!I->use_empty()) {
Chandler Carruth66b31302015-01-04 12:03:27 +0000125 Value *V = SimplifyInstruction(I, DL, TLI, DT, &AC);
Cameron Zwariche9249692011-01-04 00:12:46 +0000126 if (V && LI->replacementPreservesLCSSAForm(I, V)) {
Cameron Zwarich5a2bb992011-01-05 05:47:47 +0000127 // Mark all uses for resimplification next time round the loop.
Chandler Carruthcdf47882014-03-09 03:16:01 +0000128 for (User *U : I->users())
129 Next->insert(cast<Instruction>(U));
Cameron Zwarich5a2bb992011-01-05 05:47:47 +0000130
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +0000131 I->replaceAllUsesWith(V);
132 LocalChanged = true;
133 ++NumSimplified;
134 }
135 }
Gerolf Hoflehneraf7a87d2014-04-26 05:58:11 +0000136 bool res = RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
137 if (res) {
138 // RecursivelyDeleteTriviallyDeadInstruction can remove
139 // more than one instruction, so simply incrementing the
140 // iterator does not work. When instructions get deleted
141 // re-iterate instead.
142 BI = BB->begin(); BE = BB->end();
143 LocalChanged |= res;
144 }
Cameron Zwarich80bd9af2011-01-08 15:52:22 +0000145
146 if (IsSubloopHeader && !isa<PHINode>(I))
147 break;
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +0000148 }
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +0000149
Cameron Zwarich80bd9af2011-01-08 15:52:22 +0000150 // Add all successors to the worklist, except for loop exit blocks and the
151 // bodies of subloops. We visit the headers of loops so that we can process
152 // their phis, but we contract the rest of the subloop body and only follow
153 // edges leading back to the original loop.
Duncan P. N. Exon Smith6c990152014-07-21 17:06:51 +0000154 for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE;
155 ++SI) {
156 BasicBlock *SuccBB = *SI;
David Blaikie70573dc2014-11-19 07:49:26 +0000157 if (!Visited.insert(SuccBB).second)
Cameron Zwarich80bd9af2011-01-08 15:52:22 +0000158 continue;
159
160 const Loop *SuccLoop = LI->getLoopFor(SuccBB);
161 if (SuccLoop && SuccLoop->getHeader() == SuccBB
162 && L->contains(SuccLoop)) {
163 VisitStack.push_back(WorklistItem(SuccBB, true));
164
165 SmallVector<BasicBlock*, 8> SubLoopExitBlocks;
166 SuccLoop->getExitBlocks(SubLoopExitBlocks);
167
168 for (unsigned i = 0; i < SubLoopExitBlocks.size(); ++i) {
169 BasicBlock *ExitBB = SubLoopExitBlocks[i];
David Blaikie70573dc2014-11-19 07:49:26 +0000170 if (LI->getLoopFor(ExitBB) == L && Visited.insert(ExitBB).second)
Cameron Zwarich80bd9af2011-01-08 15:52:22 +0000171 VisitStack.push_back(WorklistItem(ExitBB, false));
172 }
173
174 continue;
175 }
176
Cameron Zwarich4c51d122011-01-05 05:15:53 +0000177 bool IsExitBlock = std::binary_search(ExitBlocks.begin(),
Cameron Zwarich80bd9af2011-01-08 15:52:22 +0000178 ExitBlocks.end(), SuccBB);
179 if (IsExitBlock)
180 continue;
181
182 VisitStack.push_back(WorklistItem(SuccBB, false));
Cameron Zwarich4c51d122011-01-05 05:15:53 +0000183 }
184 }
185
Cameron Zwarich5a2bb992011-01-05 05:47:47 +0000186 // Place the list of instructions to simplify on the next loop iteration
187 // into ToSimplify.
188 std::swap(ToSimplify, Next);
189 Next->clear();
190
Cameron Zwariche9249692011-01-04 00:12:46 +0000191 Changed |= LocalChanged;
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +0000192 } while (LocalChanged);
193
Cameron Zwarichcab9a0a2011-01-03 00:25:16 +0000194 return Changed;
195}