llvm/unittests/Transforms/Utils/SSAUpdaterBulkTest.cpp

   1 //===- SSAUpdaterBulk.cpp - Unit tests for SSAUpdaterBulk -----------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/Transforms/Utils/SSAUpdaterBulk.h"
  10 #include "llvm/AsmParser/Parser.h"
  11 #include "llvm/IR/BasicBlock.h"
  12 #include "llvm/IR/Dominators.h"
  13 #include "llvm/IR/IRBuilder.h"
  14 #include "llvm/IR/Instructions.h"
  15 #include "llvm/IR/LLVMContext.h"
  16 #include "llvm/IR/Module.h"
  17 #include "gtest/gtest.h"
  18
  19 using namespace llvm;
  20
  21 TEST(SSAUpdaterBulk, SimpleMerge) {
  22   SSAUpdaterBulk Updater;
  23   LLVMContext C;
  24   Module M("SSAUpdaterTest", C);
  25   IRBuilder<> B(C);
  26   Type *I32Ty = B.getInt32Ty();
  27   auto *F = Function::Create(FunctionType::get(B.getVoidTy(), {I32Ty}, false),
  28                              GlobalValue::ExternalLinkage, "F", &M);
  29
  30   // Generate a simple program:
  31   //   if:
  32   //     br i1 true, label %true, label %false
  33   //   true:
  34   //     %1 = add i32 %0, 1
  35   //     %2 = sub i32 %0, 2
  36   //     br label %merge
  37   //   false:
  38   //     %3 = add i32 %0, 3
  39   //     %4 = sub i32 %0, 4
  40   //     br label %merge
  41   //   merge:
  42   //     %5 = add i32 %1, 5
  43   //     %6 = add i32 %3, 6
  44   //     %7 = add i32 %2, %4
  45   //     %8 = sub i32 %2, %4
  46   Argument *FirstArg = &*(F->arg_begin());
  47   BasicBlock *IfBB = BasicBlock::Create(C, "if", F);
  48   BasicBlock *TrueBB = BasicBlock::Create(C, "true", F);
  49   BasicBlock *FalseBB = BasicBlock::Create(C, "false", F);
  50   BasicBlock *MergeBB = BasicBlock::Create(C, "merge", F);
  51
  52   B.SetInsertPoint(IfBB);
  53   B.CreateCondBr(B.getTrue(), TrueBB, FalseBB);
  54
  55   B.SetInsertPoint(TrueBB);
  56   Value *AddOp1 = B.CreateAdd(FirstArg, ConstantInt::get(I32Ty, 1));
  57   Value *SubOp1 = B.CreateSub(FirstArg, ConstantInt::get(I32Ty, 2));
  58   B.CreateBr(MergeBB);
  59
  60   B.SetInsertPoint(FalseBB);
  61   Value *AddOp2 = B.CreateAdd(FirstArg, ConstantInt::get(I32Ty, 3));
  62   Value *SubOp2 = B.CreateSub(FirstArg, ConstantInt::get(I32Ty, 4));
  63   B.CreateBr(MergeBB);
  64
  65   B.SetInsertPoint(MergeBB, MergeBB->begin());
  66   auto *I1 = cast<Instruction>(B.CreateAdd(AddOp1, ConstantInt::get(I32Ty, 5)));
  67   auto *I2 = cast<Instruction>(B.CreateAdd(AddOp2, ConstantInt::get(I32Ty, 6)));
  68   auto *I3 = cast<Instruction>(B.CreateAdd(SubOp1, SubOp2));
  69   auto *I4 = cast<Instruction>(B.CreateSub(SubOp1, SubOp2));
  70
  71   // Now rewrite uses in instructions %5, %6, %7. They need to use a phi, which
  72   // SSAUpdater should insert into %merge.
  73   // Intentionally don't touch %8 to see that SSAUpdater only changes
  74   // instructions that were explicitly specified.
  75   unsigned VarNum = Updater.AddVariable("a", I32Ty);
  76   Updater.AddAvailableValue(VarNum, TrueBB, AddOp1);
  77   Updater.AddAvailableValue(VarNum, FalseBB, AddOp2);
  78   Updater.AddUse(VarNum, &I1->getOperandUse(0));
  79   Updater.AddUse(VarNum, &I2->getOperandUse(0));
  80
  81   VarNum = Updater.AddVariable("b", I32Ty);
  82   Updater.AddAvailableValue(VarNum, TrueBB, SubOp1);
  83   Updater.AddAvailableValue(VarNum, FalseBB, SubOp2);
  84   Updater.AddUse(VarNum, &I3->getOperandUse(0));
  85   Updater.AddUse(VarNum, &I3->getOperandUse(1));
  86
  87   DominatorTree DT(*F);
  88   Updater.RewriteAllUses(&DT);
  89
  90   // Check how %5 and %6 were rewritten.
  91   PHINode *UpdatePhiA = dyn_cast_or_null<PHINode>(I1->getOperand(0));
  92   EXPECT_NE(UpdatePhiA, nullptr);
  93   EXPECT_EQ(UpdatePhiA->getIncomingValueForBlock(TrueBB), AddOp1);
  94   EXPECT_EQ(UpdatePhiA->getIncomingValueForBlock(FalseBB), AddOp2);
  95   EXPECT_EQ(UpdatePhiA, dyn_cast_or_null<PHINode>(I1->getOperand(0)));
  96
  97   // Check how %7 was rewritten.
  98   PHINode *UpdatePhiB = dyn_cast_or_null<PHINode>(I3->getOperand(0));
  99   EXPECT_EQ(UpdatePhiB->getIncomingValueForBlock(TrueBB), SubOp1);
 100   EXPECT_EQ(UpdatePhiB->getIncomingValueForBlock(FalseBB), SubOp2);
 101   EXPECT_EQ(UpdatePhiB, dyn_cast_or_null<PHINode>(I3->getOperand(1)));
 102
 103   // Check that %8 was kept untouched.
 104   EXPECT_EQ(I4->getOperand(0), SubOp1);
 105   EXPECT_EQ(I4->getOperand(1), SubOp2);
 106 }
 107
 108 TEST(SSAUpdaterBulk, Irreducible) {
 109   SSAUpdaterBulk Updater;
 110   LLVMContext C;
 111   Module M("SSAUpdaterTest", C);
 112   IRBuilder<> B(C);
 113   Type *I32Ty = B.getInt32Ty();
 114   auto *F = Function::Create(FunctionType::get(B.getVoidTy(), {I32Ty}, false),
 115                              GlobalValue::ExternalLinkage, "F", &M);
 116
 117   // Generate a small program with a multi-entry loop:
 118   //     if:
 119   //       %1 = add i32 %0, 1
 120   //       br i1 true, label %loopmain, label %loopstart
 121   //
 122   //     loopstart:
 123   //       %2 = add i32 %0, 2
 124   //       br label %loopmain
 125   //
 126   //     loopmain:
 127   //       %3 = add i32 %1, 3
 128   //       br i1 true, label %loopstart, label %afterloop
 129   //
 130   //     afterloop:
 131   //       %4 = add i32 %2, 4
 132   //       ret i32 %0
 133   Argument *FirstArg = &*F->arg_begin();
 134   BasicBlock *IfBB = BasicBlock::Create(C, "if", F);
 135   BasicBlock *LoopStartBB = BasicBlock::Create(C, "loopstart", F);
 136   BasicBlock *LoopMainBB = BasicBlock::Create(C, "loopmain", F);
 137   BasicBlock *AfterLoopBB = BasicBlock::Create(C, "afterloop", F);
 138
 139   B.SetInsertPoint(IfBB);
 140   Value *AddOp1 = B.CreateAdd(FirstArg, ConstantInt::get(I32Ty, 1));
 141   B.CreateCondBr(B.getTrue(), LoopMainBB, LoopStartBB);
 142
 143   B.SetInsertPoint(LoopStartBB);
 144   Value *AddOp2 = B.CreateAdd(FirstArg, ConstantInt::get(I32Ty, 2));
 145   B.CreateBr(LoopMainBB);
 146
 147   B.SetInsertPoint(LoopMainBB);
 148   auto *I1 = cast<Instruction>(B.CreateAdd(AddOp1, ConstantInt::get(I32Ty, 3)));
 149   B.CreateCondBr(B.getTrue(), LoopStartBB, AfterLoopBB);
 150
 151   B.SetInsertPoint(AfterLoopBB);
 152   auto *I2 = cast<Instruction>(B.CreateAdd(AddOp2, ConstantInt::get(I32Ty, 4)));
 153   ReturnInst *Return = B.CreateRet(FirstArg);
 154
 155   // Now rewrite uses in instructions %3, %4, and 'ret i32 %0'. Only %4 needs a
 156   // new phi, others should be able to work with existing values.
 157   // The phi for %4 should be inserted into LoopMainBB and should look like
 158   // this:
 159   //   %b = phi i32 [ %2, %loopstart ], [ undef, %if ]
 160   // No other rewrites should be made.
 161
 162   // Add use in %3.
 163   unsigned VarNum = Updater.AddVariable("c", I32Ty);
 164   Updater.AddAvailableValue(VarNum, IfBB, AddOp1);
 165   Updater.AddUse(VarNum, &I1->getOperandUse(0));
 166
 167   // Add use in %4.
 168   VarNum = Updater.AddVariable("b", I32Ty);
 169   Updater.AddAvailableValue(VarNum, LoopStartBB, AddOp2);
 170   Updater.AddUse(VarNum, &I2->getOperandUse(0));
 171
 172   // Add use in the return instruction.
 173   VarNum = Updater.AddVariable("a", I32Ty);
 174   Updater.AddAvailableValue(VarNum, &F->getEntryBlock(), FirstArg);
 175   Updater.AddUse(VarNum, &Return->getOperandUse(0));
 176
 177   // Save all inserted phis into a vector.
 178   SmallVector<PHINode *, 8> Inserted;
 179   DominatorTree DT(*F);
 180   Updater.RewriteAllUses(&DT, &Inserted);
 181
 182   // Only one phi should have been inserted.
 183   EXPECT_EQ(Inserted.size(), 1u);
 184
 185   // I1 and Return should use the same values as they used before.
 186   EXPECT_EQ(I1->getOperand(0), AddOp1);
 187   EXPECT_EQ(Return->getOperand(0), FirstArg);
 188
 189   // I2 should use the new phi.
 190   PHINode *UpdatePhi = dyn_cast_or_null<PHINode>(I2->getOperand(0));
 191   EXPECT_NE(UpdatePhi, nullptr);
 192   EXPECT_EQ(UpdatePhi->getIncomingValueForBlock(LoopStartBB), AddOp2);
 193   EXPECT_EQ(UpdatePhi->getIncomingValueForBlock(IfBB), UndefValue::get(I32Ty));
 194 }