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* Cleanups of instcombine
- Reenable gep (gep x) -> x
- Make instcombine do dead instruction elimination where it's really
easy. Now visitors don't have to ensure they aren't not processing
dead instructions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3222 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
parent
4a6e4b30b4
commit
90ac28cf3e
@ -17,6 +17,7 @@
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/ConstantHandling.h"
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#include "llvm/iMemory.h"
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#include "llvm/iOther.h"
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@ -73,7 +74,6 @@ namespace {
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Instruction *visitCastInst(CastInst &CI);
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Instruction *visitPHINode(PHINode &PN);
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Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
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Instruction *visitMemAccessInst(MemAccessInst &MAI);
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// visitInstruction - Specify what to return for unhandled instructions...
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Instruction *visitInstruction(Instruction &I) { return 0; }
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@ -84,8 +84,6 @@ namespace {
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Instruction *InstCombiner::visitNot(UnaryOperator &I) {
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if (I.use_empty()) return 0; // Don't fix dead instructions...
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// not (not X) = X
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if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(0)))
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if (Op->getOpcode() == Instruction::Not) {
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@ -119,7 +117,6 @@ static inline Value *dyn_castNegInst(Value *V) {
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}
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Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
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if (I.use_empty()) return 0; // Don't fix dead add instructions...
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bool Changed = SimplifyBinOp(I);
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Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
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@ -162,7 +159,6 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
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}
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Instruction *InstCombiner::visitSub(BinaryOperator &I) {
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if (I.use_empty()) return 0; // Don't fix dead add instructions...
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Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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if (Op0 == Op1) { // sub X, X -> 0
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@ -199,7 +195,6 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
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}
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Instruction *InstCombiner::visitMul(BinaryOperator &I) {
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if (I.use_empty()) return 0; // Don't fix dead instructions...
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bool Changed = SimplifyBinOp(I);
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Value *Op1 = I.getOperand(0);
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@ -229,8 +224,6 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
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Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
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if (I.use_empty()) return 0; // Don't fix dead instructions...
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// div X, 1 == X
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if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1)))
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if (RHS->equalsInt(1)) {
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@ -243,8 +236,6 @@ Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
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Instruction *InstCombiner::visitRem(BinaryOperator &I) {
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if (I.use_empty()) return 0; // Don't fix dead instructions...
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// rem X, 1 == 0
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if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1)))
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if (RHS->equalsInt(1)) {
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@ -274,7 +265,6 @@ static Constant *getMaxValue(const Type *Ty) {
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Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
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if (I.use_empty()) return 0; // Don't fix dead instructions...
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bool Changed = SimplifyBinOp(I);
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Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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@ -299,7 +289,6 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
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Instruction *InstCombiner::visitOr(BinaryOperator &I) {
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if (I.use_empty()) return 0; // Don't fix dead instructions...
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bool Changed = SimplifyBinOp(I);
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Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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@ -324,7 +313,6 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
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Instruction *InstCombiner::visitXor(BinaryOperator &I) {
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if (I.use_empty()) return 0; // Don't fix dead instructions...
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bool Changed = SimplifyBinOp(I);
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Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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@ -355,7 +343,6 @@ static bool isTrueWhenEqual(Instruction &I) {
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}
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Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
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if (I.use_empty()) return 0; // Don't fix dead instructions...
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bool Changed = SimplifyBinOp(I);
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// setcc X, X
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@ -379,7 +366,6 @@ Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
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Instruction *InstCombiner::visitShiftInst(Instruction &I) {
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if (I.use_empty()) return 0; // Don't fix dead instructions...
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assert(I.getOperand(1)->getType() == Type::UByteTy);
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Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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@ -438,11 +424,9 @@ static inline bool isEliminableCastOfCast(const CastInst &CI,
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// CastInst simplification
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//
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Instruction *InstCombiner::visitCastInst(CastInst &CI) {
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if (CI.use_empty()) return 0; // Don't fix dead instructions...
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// If the user is casting a value to the same type, eliminate this cast
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// instruction...
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if (CI.getType() == CI.getOperand(0)->getType() && !CI.use_empty()) {
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if (CI.getType() == CI.getOperand(0)->getType()) {
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AddUsesToWorkList(CI); // Add all modified instrs to worklist
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CI.replaceAllUsesWith(CI.getOperand(0));
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return &CI;
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@ -467,8 +451,6 @@ Instruction *InstCombiner::visitCastInst(CastInst &CI) {
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// PHINode simplification
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//
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Instruction *InstCombiner::visitPHINode(PHINode &PN) {
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if (PN.use_empty()) return 0; // Don't fix dead instructions...
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// If the PHI node only has one incoming value, eliminate the PHI node...
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if (PN.getNumIncomingValues() == 1) {
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AddUsesToWorkList(PN); // Add all modified instrs to worklist
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@ -481,60 +463,43 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
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Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
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// Is it getelementptr %P, uint 0
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// Is it 'getelementptr %P, uint 0' or 'getelementptr %P'
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// If so, eliminate the noop.
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if (GEP.getNumOperands() == 2 && !GEP.use_empty() &&
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GEP.getOperand(1) == Constant::getNullValue(Type::UIntTy)) {
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if ((GEP.getNumOperands() == 2 &&
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GEP.getOperand(1) == Constant::getNullValue(Type::UIntTy)) ||
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GEP.getNumOperands() == 1) {
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AddUsesToWorkList(GEP); // Add all modified instrs to worklist
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GEP.replaceAllUsesWith(GEP.getOperand(0));
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return &GEP;
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}
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return visitMemAccessInst(GEP);
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}
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// Combine Indices - If the source pointer to this mem access instruction is a
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// getelementptr instruction, combine the indices of the GEP into this
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// instruction
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//
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Instruction *InstCombiner::visitMemAccessInst(MemAccessInst &MAI) {
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return 0; // DISABLE FOLDING. GEP is now the only MAI!
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GetElementPtrInst *Src =
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dyn_cast<GetElementPtrInst>(MAI.getPointerOperand());
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if (!Src) return 0;
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std::vector<Value *> Indices;
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// Combine Indices - If the source pointer to this getelementptr instruction
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// is a getelementptr instruction, combine the indices of the two
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// getelementptr instructions into a single instruction.
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//
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if (GetElementPtrInst *Src =
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dyn_cast<GetElementPtrInst>(GEP.getPointerOperand())) {
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std::vector<Value *> Indices;
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// Only special case we have to watch out for is pointer arithmetic on the
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// 0th index of MAI.
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unsigned FirstIdx = MAI.getFirstIndexOperandNumber();
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if (FirstIdx == MAI.getNumOperands() ||
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(FirstIdx == MAI.getNumOperands()-1 &&
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MAI.getOperand(FirstIdx) == ConstantUInt::get(Type::UIntTy, 0))) {
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// Replace the index list on this MAI with the index on the getelementptr
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Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
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} else if (*MAI.idx_begin() == ConstantUInt::get(Type::UIntTy, 0)) {
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// Otherwise we can do the fold if the first index of the GEP is a zero
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Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
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Indices.insert(Indices.end(), MAI.idx_begin()+1, MAI.idx_end());
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// Can we combine the two pointer arithmetics offsets?
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if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
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isa<Constant>(GEP.getOperand(1))) {
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// Replace the index list on this GEP with the index on the getelementptr
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Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
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Indices[0] = *cast<Constant>(Src->getOperand(1)) +
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*cast<Constant>(GEP.getOperand(1));
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assert(Indices[0] != 0 && "Constant folding of uint's failed!?");
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} else if (*GEP.idx_begin() == ConstantUInt::get(Type::UIntTy, 0)) {
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// Otherwise we can do the fold if the first index of the GEP is a zero
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Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
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Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
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}
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if (!Indices.empty())
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return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
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}
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if (Indices.empty()) return 0; // Can't do the fold?
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switch (MAI.getOpcode()) {
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case Instruction::GetElementPtr:
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return new GetElementPtrInst(Src->getOperand(0), Indices, MAI.getName());
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case Instruction::Load:
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return new LoadInst(Src->getOperand(0), Indices, MAI.getName());
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case Instruction::Store:
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return new StoreInst(MAI.getOperand(0), Src->getOperand(0), Indices);
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default:
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assert(0 && "Unknown memaccessinst!");
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break;
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}
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abort();
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return 0;
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}
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@ -549,31 +514,34 @@ bool InstCombiner::runOnFunction(Function &F) {
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WorkList.pop_back();
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// Now that we have an instruction, try combining it to simplify it...
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Instruction *Result = visit(*I);
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if (Result) {
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if (Instruction *Result = visit(*I)) {
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++NumCombined;
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// Should we replace the old instruction with a new one?
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if (Result != I) {
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// Instructions can end up on the worklist more than once. Make sure
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// we do not process an instruction that has been deleted.
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std::vector<Instruction*>::iterator It = std::find(WorkList.begin(),
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WorkList.end(), I);
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while (It != WorkList.end()) {
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It = WorkList.erase(It);
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It = std::find(It, WorkList.end(), I);
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}
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WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
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WorkList.end());
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ReplaceInstWithInst(I, Result);
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} else {
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// FIXME:
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// FIXME:
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// FIXME: This should DCE the instruction to simplify the cases above.
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// FIXME:
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// FIXME:
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BasicBlock::iterator II = I;
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// If the instruction was modified, it's possible that it is now dead.
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// if so, remove it.
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if (dceInstruction(II)) {
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// Instructions may end up in the worklist more than once. Erase them
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// all.
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WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
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WorkList.end());
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Result = 0;
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}
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}
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WorkList.push_back(Result);
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AddUsesToWorkList(*Result);
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if (Result) {
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WorkList.push_back(Result);
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AddUsesToWorkList(*Result);
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}
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Changed = true;
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}
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}
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