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author | David Majnemer <david.majnemer@gmail.com> | 2014-06-19 07:14:33 +0000 |
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committer | David Majnemer <david.majnemer@gmail.com> | 2014-06-19 07:14:33 +0000 |
commit | 6c2e8874b0f1fd993a17ad27c8348ae531cd5464 (patch) | |
tree | 07ebc42227db705656a73d014f0bdd931c190af7 /lib | |
parent | 179bb4e0eef028baf4015a12f962964739d3b542 (diff) | |
download | llvm-6c2e8874b0f1fd993a17ad27c8348ae531cd5464.tar.gz llvm-6c2e8874b0f1fd993a17ad27c8348ae531cd5464.tar.bz2 llvm-6c2e8874b0f1fd993a17ad27c8348ae531cd5464.tar.xz |
InstCombine: Stop two transforms dueling
InstCombineMulDivRem has:
// Canonicalize (X+C1)*CI -> X*CI+C1*CI.
InstCombineAddSub has:
// W*X + Y*Z --> W * (X+Z) iff W == Y
These two transforms could fight with each other if C1*CI would not fold
away to something simpler than a ConstantExpr mul.
The InstCombineMulDivRem transform only acted on ConstantInts until
r199602 when it was changed to operate on all Constants in order to
let it fire on ConstantVectors.
To fix this, make this transform more careful by checking to see if we
actually folded away C1*CI.
This fixes PR20079.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211258 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
-rw-r--r-- | lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 9996ebc2e7..497c0b49ab 100644 --- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -203,8 +203,11 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) { Value *X; Constant *C1; if (match(Op0, m_OneUse(m_Add(m_Value(X), m_Constant(C1))))) { - Value *Add = Builder->CreateMul(X, Op1); - return BinaryOperator::CreateAdd(Add, Builder->CreateMul(C1, Op1)); + Value *Mul = Builder->CreateMul(C1, Op1); + // Only go forward with the transform if C1*CI simplifies to a tidier + // constant. + if (!match(Mul, m_Mul(m_Value(), m_Value()))) + return BinaryOperator::CreateAdd(Builder->CreateMul(X, Op1), Mul); } } } |