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Implement the following xforms:

Browse Source 
(X-Y)-X --> -Y
A + (B - A) --> B
(B - A) + A --> B


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21138 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-04-07 17:14:51 +00:00
parent 7c52702201
commit 7edc8c223e
1 changed files with 18 additions and 3 deletions
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21
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -629,6 +629,17 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
// X + X --> X << 1
if (I.getType()->isInteger()) {
if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
if (Instruction *RHSI = dyn_cast<Instruction>(RHS)) {
if (RHSI->getOpcode() == Instruction::Sub)
if (LHS == RHSI->getOperand(1)) // A + (B - A) --> B
return ReplaceInstUsesWith(I, RHSI->getOperand(0));
}
if (Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
if (LHSI->getOpcode() == Instruction::Sub)
if (RHS == LHSI->getOperand(1)) // (B - A) + A --> B
return ReplaceInstUsesWith(I, LHSI->getOperand(0));
}
}
// -A + B --> B - A
@ -640,6 +651,7 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
if (Value *V = dyn_castNegVal(RHS))
return BinaryOperator::createSub(LHS, V);
ConstantInt *C2;
if (Value *X = dyn_castFoldableMul(LHS, C2)) {
if (X == RHS) // X*C + X --> X * (C+1)
@ -851,13 +863,16 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
}
}
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
if (Op0I->getOpcode() == Instruction::Add)
if (!Op0->getType()->isFloatingPoint()) {
if (!Op0->getType()->isFloatingPoint())
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
if (Op0I->getOpcode() == Instruction::Add) {
if (Op0I->getOperand(0) == Op1) // (Y+X)-Y == X
return ReplaceInstUsesWith(I, Op0I->getOperand(1));
else if (Op0I->getOperand(1) == Op1) // (X+Y)-Y == X
return ReplaceInstUsesWith(I, Op0I->getOperand(0));
} else if (Op0I->getOpcode() == Instruction::Sub) {
if (Op0I->getOperand(0) == Op1) // (X-Y)-X == -Y
return BinaryOperator::createNeg(Op0I->getOperand(1), I.getName());
}
ConstantInt *C1;