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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2490 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-05-06 16:49:18 +00:00
parent fa78358a05
commit b35dde1df4
1 changed files with 43 additions and 16 deletions
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59
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -88,33 +88,52 @@ static bool SimplifyBinOp(BinaryOperator *I) {
return false;
}
// dyn_castNegInst - Given a 'sub' instruction, return the RHS of the
// instruction if the LHS is a constant zero (which is the 'negate' form).
//
static inline Value *dyn_castNegInst(Value *V) {
Instruction *I = dyn_cast<Instruction>(V);
if (!I || I->getOpcode() != Instruction::Sub) return 0;
if (I->getOperand(0) == Constant::getNullValue(I->getType()))
return I->getOperand(1);
return 0;
}
Instruction *InstCombiner::visitAdd(BinaryOperator *I) {
if (I->use_empty()) return 0; // Don't fix dead add instructions...
bool Changed = SimplifyBinOp(I);
Value *Op1 = I->getOperand(0);
Value *LHS = I->getOperand(0), *RHS = I->getOperand(1);
// Eliminate 'add int %X, 0'
if (I->getType()->isIntegral() &&
RHS == Constant::getNullValue(I->getType())) {
AddUsesToWorkList(I); // Add all modified instrs to worklist
I->replaceAllUsesWith(LHS);
return I;
}
// -B + A --> A - B
if (Value *V = dyn_castNegInst(LHS))
return BinaryOperator::create(Instruction::Sub, RHS, LHS);
// A + -B --> A - B
if (Value *V = dyn_castNegInst(RHS))
return BinaryOperator::create(Instruction::Sub, LHS, RHS);
// Simplify add instructions with a constant RHS...
if (Constant *Op2 = dyn_cast<Constant>(I->getOperand(1))) {
// Eliminate 'add int %X, 0'
if (I->getType()->isIntegral() && Op2->isNullValue()) {
AddUsesToWorkList(I); // Add all modified instrs to worklist
I->replaceAllUsesWith(Op1);
return I;
}
if (BinaryOperator *IOp1 = dyn_cast<BinaryOperator>(Op1)) {
Changed |= SimplifyBinOp(IOp1);
if (IOp1->getOpcode() == Instruction::Add &&
isa<Constant>(IOp1->getOperand(1))) {
if (Constant *Op2 = dyn_cast<Constant>(RHS)) {
if (BinaryOperator *ILHS = dyn_cast<BinaryOperator>(LHS)) {
if (ILHS->getOpcode() == Instruction::Add &&
isa<Constant>(ILHS->getOperand(1))) {
// Fold:
// %Y = add int %X, 1
// %Z = add int %Y, 1
// into:
// %Z = add int %X, 2
//
if (Constant *Val = *Op2 + *cast<Constant>(IOp1->getOperand(1))) {
I->setOperand(0, IOp1->getOperand(0));
if (Constant *Val = *Op2 + *cast<Constant>(ILHS->getOperand(1))) {
I->setOperand(0, ILHS->getOperand(0));
I->setOperand(1, Val);
return I;
}
@ -142,6 +161,14 @@ Instruction *InstCombiner::visitSub(BinaryOperator *I) {
if (Constant *RHS = *Constant::getNullValue(I->getType()) - *Op2) // 0 - RHS
return BinaryOperator::create(Instruction::Add, Op0, RHS, I->getName());
// If this is a 'C = -B', check to see if 'B = -A', so that C = A...
if (Op0 == Constant::getNullValue(I->getType()))
if (Value *V = dyn_castNegInst(Op1)) {
AddUsesToWorkList(I); // Add all modified instrs to worklist
I->replaceAllUsesWith(V);
return I;
}
return 0;
}