diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp index c69b305dfa7..d8166de6c33 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp @@ -622,11 +622,8 @@ Instruction *InstCombiner::visitShl(BinaryOperator &I) { return BinaryOperator::CreateAnd(X, ConstantInt::get(Ty, Mask)); } - // Be careful about hiding shl instructions behind bit masks. They are used - // to represent multiplies by a constant, and it is important that simple - // arithmetic expressions are still recognizable by scalar evolution. - // The inexact versions are deferred to DAGCombine, so we don't hide shl - // behind a bit mask. + // FIXME: we do not yet transform non-exact shr's. The backend (DAGCombine) + // needs a few fixes for the rotate pattern recognition first. const APInt *ShOp1; if (match(Op0, m_Exact(m_Shr(m_Value(X), m_APInt(ShOp1))))) { unsigned ShrAmt = ShOp1->getZExtValue(); |
