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| author | Nadav Rotem <nrotem@apple.com> | 2012-08-30 11:23:20 +0000 |
|---|---|---|
| committer | Nadav Rotem <nrotem@apple.com> | 2012-08-30 11:23:20 +0000 |
| commit | 639570c3117aaabb0c97b34a9bf05d09f8903ef4 (patch) | |
| tree | a844659e4411dc7c722bc16c130f349d5d0667b4 /lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | |
| parent | c4a32e6596f3974a6c00322db1f5f31ea448bd58 (diff) | |
| download | llvm-639570c3117aaabb0c97b34a9bf05d09f8903ef4.tar.gz llvm-639570c3117aaabb0c97b34a9bf05d09f8903ef4.tar.bz2 llvm-639570c3117aaabb0c97b34a9bf05d09f8903ef4.tar.xz | |
It is illegal to transform (sdiv (ashr X c1) c2) -> (sdiv x (2^c1 * c2)),
because C always rounds towards zero.
Thanks Dirk and Ben.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162899 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/InstCombine/InstCombineMulDivRem.cpp')
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 10 |
1 files changed, 0 insertions, 10 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 2119115ca7..003dc55a03 100644 --- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -543,16 +543,6 @@ Instruction *InstCombiner::visitSDiv(BinaryOperator &I) { ConstantExpr::getNeg(RHS)); } - // Sdiv ((Ashl x, C1) , C2) -> x / (C2 * 1<<C1); - if (ConstantInt *C2 = dyn_cast<ConstantInt>(Op1)) { - Value *X; - ConstantInt *C1; - if (match(Op0, m_AShr(m_Value(X), m_ConstantInt(C1)))) { - APInt NC = C2->getValue().shl(C1->getLimitedValue(C1->getBitWidth()-1)); - return BinaryOperator::CreateSDiv(X, Builder->getInt(NC)); - } - } - // If the sign bits of both operands are zero (i.e. we can prove they are // unsigned inputs), turn this into a udiv. if (I.getType()->isIntegerTy()) { |