From df48e84b5bf0967c1fc397912c109f29475c791b Mon Sep 17 00:00:00 2001 From: Stuart Hastings Date: Tue, 31 May 2011 19:29:55 +0000 Subject: Followup to 132316; accept arbitrary constants, add with a constant, sub with a non-constant. Fix comments, enlarge test case. rdar://problem/6501862 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132348 91177308-0d34-0410-b5e6-96231b3b80d8 --- .../InstCombine/InstCombineMulDivRem.cpp | 25 ++++++++++++++-------- 1 file changed, 16 insertions(+), 9 deletions(-) (limited to 'lib') diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 94b619b203..b860440f60 100644 --- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -136,19 +136,26 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) { } } - // (1 - X) * (-2) -> (x - 1) * 2, for all positive nonzero powers of 2 - // The "* 2" thus becomes a potential shifting opportunity. + // (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. { const APInt & Val = CI->getValue(); const APInt &PosVal = Val.abs(); if (Val.isNegative() && PosVal.isPowerOf2()) { - 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)); + 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)); } } } -- cgit v1.2.3