diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp')
-rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp index 9c2bc34..48ab0eb 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp @@ -435,6 +435,15 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) { if (Instruction *Result = commonCastTransforms(CI)) return Result; + // Test if the trunc is the user of a select which is part of a + // minimum or maximum operation. If so, don't do any more simplification. + // Even simplifying demanded bits can break the canonical form of a + // min/max. + Value *LHS, *RHS; + if (SelectInst *SI = dyn_cast<SelectInst>(CI.getOperand(0))) + if (matchSelectPattern(SI, LHS, RHS) != SPF_UNKNOWN) + return nullptr; + // See if we can simplify any instructions used by the input whose sole // purpose is to compute bits we don't care about. if (SimplifyDemandedInstructionBits(CI)) |