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4 new transformations: 

* X*C + X --> X * (C+1)
  * X + X*C --> X * (C+1)
  * X - X*C --> X * (1-C)
  * X*C - X --> X * (C-1)

llvm-svn: 5592
This commit is contained in:
Chris Lattner 2003-02-18 19:57:07 +00:00
parent 395934091d
commit 57c8d99bbd
1 changed files with 42 additions and 0 deletions
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42
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -146,6 +146,16 @@ static unsigned Log2(uint64_t Val) {
return Count;
}
static inline Value *dyn_castFoldableMul(Value *V) {
if (V->use_size() == 1 && V->getType()->isInteger())
if (Instruction *I = dyn_cast<Instruction>(V))
if (I->getOpcode() == Instruction::Mul)
if (isa<Constant>(I->getOperand(1)))
return I->getOperand(0);
return 0;
}
Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
bool Changed = SimplifyBinOp(I);
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
@ -182,6 +192,22 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
}
}
// X*C + X --> X * (C+1)
if (dyn_castFoldableMul(LHS) == RHS) {
Constant *CP1 = *cast<Constant>(cast<Instruction>(LHS)->getOperand(1)) +
*ConstantInt::get(I.getType(), 1);
assert(CP1 && "Couldn't constant fold C + 1?");
return BinaryOperator::create(Instruction::Mul, RHS, CP1);
}
// X + X*C --> X * (C+1)
if (dyn_castFoldableMul(RHS) == LHS) {
Constant *CP1 = *cast<Constant>(cast<Instruction>(RHS)->getOperand(1)) +
*ConstantInt::get(I.getType(), 1);
assert(CP1 && "Couldn't constant fold C + 1?");
return BinaryOperator::create(Instruction::Mul, LHS, CP1);
}
return Changed ? &I : 0;
}
@ -231,8 +257,24 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
return BinaryOperator::create(Instruction::And, Op0, NewNot);
}
// X - X*C --> X * (1-C)
if (dyn_castFoldableMul(Op1I) == Op0) {
Constant *CP1 = *ConstantInt::get(I.getType(), 1) -
*cast<Constant>(cast<Instruction>(Op1)->getOperand(1));
assert(CP1 && "Couldn't constant fold 1-C?");
return BinaryOperator::create(Instruction::Mul, Op0, CP1);
}
}
// X*C - X --> X * (C-1)
if (dyn_castFoldableMul(Op0) == Op1) {
Constant *CP1 = *cast<Constant>(cast<Instruction>(Op0)->getOperand(1)) -
*ConstantInt::get(I.getType(), 1);
assert(CP1 && "Couldn't constant fold C - 1?");
return BinaryOperator::create(Instruction::Mul, Op1, CP1);
}
return 0;
}