Changed basic cost of store operation on X86
Store operation takes 2 UOps on X86 processors. The exact cost calculation affects several optimization passes including loop unroling.
This change compensates performance degradation caused by https://reviews.llvm.org/D34458 and shows improvements on some benchmarks.
Differential Revision: https://reviews.llvm.org/D35888
llvm-svn: 311285
diff --git a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
index 2f44d61..6c73a68 100644
--- a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
+++ b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
@@ -2113,6 +2113,21 @@
return X86TTIImpl::getIntImmCost(Imm, Ty);
}
+unsigned X86TTIImpl::getUserCost(const User *U,
+ ArrayRef<const Value *> Operands) {
+ if (isa<StoreInst>(U)) {
+ Value *Ptr = U->getOperand(1);
+ // Store instruction with index and scale costs 2 Uops.
+ // Check the preceding GEP to identify non-const indices.
+ if (auto GEP = dyn_cast<GetElementPtrInst>(Ptr)) {
+ if (!all_of(GEP->indices(), [](Value *V) { return isa<Constant>(V); }))
+ return TTI::TCC_Basic * 2;
+ }
+ return TTI::TCC_Basic;
+ }
+ return BaseT::getUserCost(U, Operands);
+}
+
// Return an average cost of Gather / Scatter instruction, maybe improved later
int X86TTIImpl::getGSVectorCost(unsigned Opcode, Type *SrcVTy, Value *Ptr,
unsigned Alignment, unsigned AddressSpace) {
diff --git a/llvm/lib/Target/X86/X86TargetTransformInfo.h b/llvm/lib/Target/X86/X86TargetTransformInfo.h
index fc63eff..dc18403 100644
--- a/llvm/lib/Target/X86/X86TargetTransformInfo.h
+++ b/llvm/lib/Target/X86/X86TargetTransformInfo.h
@@ -102,6 +102,8 @@
int getIntImmCost(const APInt &Imm, Type *Ty);
+ unsigned getUserCost(const User *U, ArrayRef<const Value *> Operands);
+
int getIntImmCost(unsigned Opcode, unsigned Idx, const APInt &Imm, Type *Ty);
int getIntImmCost(Intrinsic::ID IID, unsigned Idx, const APInt &Imm,
Type *Ty);