[llvm] 4c22990 - [TTI] Add X86 target specific version of getPointersChainCost.

[Valery N Dmitriev via llvm-commits]

Author: Valery N Dmitriev
Date: 2023-03-16T10:26:50-07:00
New Revision: 4c2299003fe1910f729180f3e5e434045e533974

URL: https://github.com/llvm/llvm-project/commit/4c2299003fe1910f729180f3e5e434045e533974
DIFF: https://github.com/llvm/llvm-project/commit/4c2299003fe1910f729180f3e5e434045e533974.diff

LOG: [TTI] Add X86 target specific version of getPointersChainCost.

When all the pointers are off the same base address and have known
distances to each other these differences can be encoded into displacements
in x86 arch. So the only cost that matters is cost of the base GEP.

Differential Revision: https://reviews.llvm.org/D146102

Added: 
    

Modified: 
    llvm/lib/Target/X86/X86TargetTransformInfo.cpp
    llvm/lib/Target/X86/X86TargetTransformInfo.h
    llvm/test/Transforms/SLPVectorizer/X86/remark_horcost.ll
    llvm/test/Transforms/SLPVectorizer/X86/remark_not_all_parts.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
index 4e6acf4a1020a..fb05dc0e96cce 100644
--- a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
+++ b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
@@ -4899,6 +4899,23 @@ X86TTIImpl::getMaskedMemoryOpCost(unsigned Opcode, Type *SrcTy, Align Alignment,
   return Cost + LT.first;
 }
 
+InstructionCost X86TTIImpl::getPointersChainCost(
+    ArrayRef<const Value *> Ptrs, const Value *Base,
+    const TTI::PointersChainInfo &Info, TTI::TargetCostKind CostKind) {
+  if (Info.isSameBase() && Info.isKnownStride()) {
+    // If all the pointers have known stride all the 
diff erences are translated
+    // into constants. X86 memory addressing allows encoding it into
+    // displacement. So we just need to take the base GEP cost.
+    if (const auto *BaseGEP = dyn_cast<GetElementPtrInst>(Base)) {
+      SmallVector<const Value *> Indices(BaseGEP->indices());
+      return getGEPCost(BaseGEP->getSourceElementType(),
+                        BaseGEP->getPointerOperand(), Indices, CostKind);
+    }
+    return TTI::TCC_Free;
+  }
+  return BaseT::getPointersChainCost(Ptrs, Base, Info, CostKind);
+}
+
 InstructionCost X86TTIImpl::getAddressComputationCost(Type *Ty,
                                                       ScalarEvolution *SE,
                                                       const SCEV *Ptr) {

diff  --git a/llvm/lib/Target/X86/X86TargetTransformInfo.h b/llvm/lib/Target/X86/X86TargetTransformInfo.h
index 41f7095c8787d..6893b86056d23 100644
--- a/llvm/lib/Target/X86/X86TargetTransformInfo.h
+++ b/llvm/lib/Target/X86/X86TargetTransformInfo.h
@@ -177,6 +177,10 @@ class X86TTIImpl : public BasicTTIImplBase<X86TTIImpl> {
                                          Align Alignment,
                                          TTI::TargetCostKind CostKind,
                                          const Instruction *I);
+  InstructionCost getPointersChainCost(ArrayRef<const Value *> Ptrs,
+                                       const Value *Base,
+                                       const TTI::PointersChainInfo &Info,
+                                       TTI::TargetCostKind CostKind);
   InstructionCost getAddressComputationCost(Type *PtrTy, ScalarEvolution *SE,
                                             const SCEV *Ptr);
 

diff  --git a/llvm/test/Transforms/SLPVectorizer/X86/remark_horcost.ll b/llvm/test/Transforms/SLPVectorizer/X86/remark_horcost.ll
index d79c08763be8a..f657477ce8e52 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/remark_horcost.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/remark_horcost.ll
@@ -86,7 +86,7 @@ for.body:                                         ; preds = %for.body, %entry
   ; YAML-NEXT: Function:        foo
   ; YAML-NEXT: Args:
   ; YAML-NEXT:   - String:          'Stores SLP vectorized with cost '
-  ; YAML-NEXT:   - Cost:            '-14'
+  ; YAML-NEXT:   - Cost:            '-5'
   ; YAML-NEXT:   - String:          ' and with tree size '
   ; YAML-NEXT:   - TreeSize:        '4'
 

diff  --git a/llvm/test/Transforms/SLPVectorizer/X86/remark_not_all_parts.ll b/llvm/test/Transforms/SLPVectorizer/X86/remark_not_all_parts.ll
index 21a8654ef03b0..0a2cc76d2e25d 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/remark_not_all_parts.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/remark_not_all_parts.ll
@@ -62,7 +62,7 @@ for.body:                                         ; preds = %for.body, %entry
   ; YAML-NEXT: Function:        foo
   ; YAML-NEXT: Args:
   ; YAML-NEXT:   - String:          'Stores SLP vectorized with cost '
-  ; YAML-NEXT:   - Cost:            '-4'
+  ; YAML-NEXT:   - Cost:            '-1'
   ; YAML-NEXT:   - String:          ' and with tree size '
   ; YAML-NEXT:   - TreeSize:        '4'