Rename ValueRequiresCast to ShouldOptimizeCast, to better reflect
what it does. Enhance it to return false to optimizing vector
sign extensions from vector comparisions, which is the idiom used
to get a splatted vector for a vector comparison.
Doing this breaks vector-casts.ll, add some compensating
transformations to handle the important case they cover without
depending on this canonicalization.
This fixes rdar://7434900 a serious pessimization of vector compares.
llvm-svn: 95855
diff --git a/llvm/lib/Transforms/InstCombine/InstCombine.h b/llvm/lib/Transforms/InstCombine/InstCombine.h
index 5367900..09accb6 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombine.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombine.h
@@ -199,11 +199,12 @@
SmallVectorImpl<Value*> &NewIndices);
Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI);
- /// ValueRequiresCast - Return true if the cast from "V to Ty" actually
- /// results in any code being generated. It does not require codegen if V is
- /// simple enough or if the cast can be folded into other casts.
- bool ValueRequiresCast(Instruction::CastOps opcode,const Value *V,
- const Type *Ty);
+ /// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually
+ /// results in any code being generated and is interesting to optimize out. If
+ /// the cast can be eliminated by some other simple transformation, we prefer
+ /// to do the simplification first.
+ bool ShouldOptimizeCast(Instruction::CastOps opcode,const Value *V,
+ const Type *Ty);
Instruction *visitCallSite(CallSite CS);
bool transformConstExprCastCall(CallSite CS);