Index: llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp =================================================================== --- llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp +++ llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp @@ -963,6 +963,8 @@ int X86TTIImpl::getVectorInstrCost(unsigned Opcode, Type *Val, unsigned Index) { assert(Val->isVectorTy() && "This must be a vector type"); + Type *ScalarType = Val->getScalarType(); + if (Index != -1U) { // Legalize the type. std::pair LT = TLI->getTypeLegalizationCost(DL, Val); @@ -976,11 +978,17 @@ Index = Index % Width; // Floating point scalars are already located in index #0. - if (Val->getScalarType()->isFloatingPointTy() && Index == 0) + if (ScalarType->isFloatingPointTy() && Index == 0) return 0; } - return BaseT::getVectorInstrCost(Opcode, Val, Index); + // Add to the base cost if we know that the extracted element of a vector is + // destined to be moved to and used in the integer register file. + int RegisterFileMoveCost = 0; + if (Opcode == Instruction::ExtractElement && ScalarType->isPointerTy()) + RegisterFileMoveCost = 1; + + return BaseT::getVectorInstrCost(Opcode, Val, Index) + RegisterFileMoveCost; } int X86TTIImpl::getScalarizationOverhead(Type *Ty, bool Insert, bool Extract) { Index: llvm/trunk/test/Transforms/LoopVectorize/X86/cost-model.ll =================================================================== --- llvm/trunk/test/Transforms/LoopVectorize/X86/cost-model.ll +++ llvm/trunk/test/Transforms/LoopVectorize/X86/cost-model.ll @@ -39,3 +39,44 @@ for.end: ; preds = %for.body ret void } + +; This function uses a stride that is generally too big to benefit from vectorization without +; really good support for a gather load. We were not computing an accurate cost for the +; vectorization and subsequent scalarization of the pointer induction variables. + +define float @PR27826(float* nocapture readonly %a, float* nocapture readonly %b, i32 %n) { +; CHECK-LABEL: @PR27826( +; CHECK-NOT: <4 x float> +; CHECK-NOT: <8 x float> +; CHECK: ret float %s.0.lcssa + +entry: + %cmp = icmp sgt i32 %n, 0 + br i1 %cmp, label %preheader, label %for.end + +preheader: + %t0 = sext i32 %n to i64 + br label %for + +for: + %indvars.iv = phi i64 [ 0, %preheader ], [ %indvars.iv.next, %for ] + %s.02 = phi float [ 0.0, %preheader ], [ %add4, %for ] + %arrayidx = getelementptr inbounds float, float* %a, i64 %indvars.iv + %t1 = load float, float* %arrayidx, align 4 + %arrayidx3 = getelementptr inbounds float, float* %b, i64 %indvars.iv + %t2 = load float, float* %arrayidx3, align 4 + %add = fadd fast float %t1, %s.02 + %add4 = fadd fast float %add, %t2 + %indvars.iv.next = add nuw nsw i64 %indvars.iv, 8 + %cmp1 = icmp slt i64 %indvars.iv.next, %t0 + br i1 %cmp1, label %for, label %loopexit + +loopexit: + %add4.lcssa = phi float [ %add4, %for ] + br label %for.end + +for.end: + %s.0.lcssa = phi float [ 0.0, %entry ], [ %add4.lcssa, %loopexit ] + ret float %s.0.lcssa +} +