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InstCombine: Turn urem to bitwise-and more often

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Use isKnownToBeAPowerOfTwo in visitUrem so that we may more aggressively
fold away urem instructions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181661 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2013-05-11 09:01:28 +00:00
parent d84ccfaf50
commit a8ccefc0a3
2 changed files with 53 additions and 22 deletions
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22
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
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@ -1027,31 +1027,13 @@ Instruction *InstCombiner::visitURem(BinaryOperator &I) {
if (Instruction *common = commonIRemTransforms(I))
return common;
// X urem C^2 -> X and C-1
{ const APInt *C;
if (match(Op1, m_Power2(C)))
return BinaryOperator::CreateAnd(Op0,
ConstantInt::get(I.getType(), *C-1));
}
// Turn A % (C << N), where C is 2^k, into A & ((C << N)-1)
if (match(Op1, m_Shl(m_Power2(), m_Value()))) {
// X urem Y -> X and Y-1, where Y is a power of 2,
if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/true)) {
Constant *N1 = Constant::getAllOnesValue(I.getType());
Value *Add = Builder->CreateAdd(Op1, N1);
return BinaryOperator::CreateAnd(Op0, Add);
}
// urem X, (select Cond, 2^C1, 2^C2) -->
// select Cond, (and X, C1-1), (and X, C2-1)
// when C1&C2 are powers of two.
{ Value *Cond; const APInt *C1, *C2;
if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) {
Value *TrueAnd = Builder->CreateAnd(Op0, *C1-1, Op1->getName()+".t");
Value *FalseAnd = Builder->CreateAnd(Op0, *C2-1, Op1->getName()+".f");
return SelectInst::Create(Cond, TrueAnd, FalseAnd);
}
}
// (zext A) urem (zext B) --> zext (A urem B)
if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))