diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 25 |
1 files changed, 9 insertions, 16 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index b860440f600..94b619b2037 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -136,26 +136,19 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) { } } - // (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n - // (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n - // The "* (2**n)" thus becomes a potential shifting opportunity. + // (1 - X) * (-2) -> (x - 1) * 2, for all positive nonzero powers of 2 + // The "* 2" thus becomes a potential shifting opportunity. { const APInt & Val = CI->getValue(); const APInt &PosVal = Val.abs(); if (Val.isNegative() && PosVal.isPowerOf2()) { - Value *X = 0, *Y = 0; - ConstantInt *C1 = 0; - if (Op0->hasOneUse() && - (match(Op0, m_Sub(m_Value(Y), m_Value(X)))) || - (match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1))))) { - Value *Sub; - if (C1) // Matched ADD of constant, negate both operands: - Sub = Builder->CreateSub(Builder->CreateNeg(C1), Y, "subc"); - else // Matched SUB, swap operands: - Sub = Builder->CreateSub(X, Y, "suba"); - return - BinaryOperator::CreateMul(Sub, - ConstantInt::get(X->getType(), PosVal)); + Value *X = 0; + if (match(Op0, m_Sub(m_One(), m_Value(X)))) { + // ConstantInt::get(Op0->getType(), 2); + Value *Sub = Builder->CreateSub(X, ConstantInt::get(X->getType(), 1), + "dec1"); + return BinaryOperator::CreateMul(Sub, ConstantInt::get(X->getType(), + PosVal)); } } } |
