[X86 TTI] Implement LSV hook

[loladiro]

Summary

LSV wants to know the maximum size that can be loaded to a vector register.
On X86, this always matches the maximum register width. Implement this
accordingly and add a test to make sure that LSV can vectorize up to the
maximum permissible width on X86.

[arsenm]

LGTM

[delena]

lib/Target/X86/X86TargetTransformInfo.h

55

Do you use this interface somewhere?

[loladiro]

lib/Target/X86/X86TargetTransformInfo.h

55

LSV (LoadStoreVectorizer) uses it.

[delena]

lib/Target/X86/X86TargetTransformInfo.h

55

Ok. Thanks.

lib/Target/X86/X86TargetTransformInfo.h

public:
   TTI::PopcntSupportKind getPopcntSupport(unsigned TyWidth);
 
   /// @}
 
   /// \name Vector TTI Implementations
   /// @{
 
   unsigned getNumberOfRegisters(bool Vector);
-  unsigned getRegisterBitWidth(bool Vector);
+  unsigned getRegisterBitWidth(bool Vector) const;
+  unsigned getLoadStoreVecRegBitWidth(unsigned AS) const;
   unsigned getMaxInterleaveFactor(unsigned VF);
   int getArithmeticInstrCost(
       unsigned Opcode, Type *Ty,
       TTI::OperandValueKind Opd1Info = TTI::OK_AnyValue,
       TTI::OperandValueKind Opd2Info = TTI::OK_AnyValue,
       TTI::OperandValueProperties Opd1PropInfo = TTI::OP_None,
       TTI::OperandValueProperties Opd2PropInfo = TTI::OP_None,
       ArrayRef<const Value *> Args = ArrayRef<const Value *>());

lib/Target/X86/X86TargetTransformInfo.cpp

unsigned X86TTIImpl::getNumberOfRegisters(bool Vector) {
   if (ST->is64Bit()) {
     if (Vector && ST->hasAVX512())
       return 32;
     return 16;
   }
   return 8;
 }
 
-unsigned X86TTIImpl::getRegisterBitWidth(bool Vector) {
+unsigned X86TTIImpl::getRegisterBitWidth(bool Vector) const {
   if (Vector) {
     if (ST->hasAVX512())
       return 512;
     if (ST->hasAVX())
       return 256;
     if (ST->hasSSE1())
       return 128;
     return 0;
   }
 
   if (ST->is64Bit())
     return 64;
 
   return 32;
 }
 
+unsigned X86TTIImpl::getLoadStoreVecRegBitWidth(unsigned) const {
+  return getRegisterBitWidth(true);
+}
+
 unsigned X86TTIImpl::getMaxInterleaveFactor(unsigned VF) {
   // If the loop will not be vectorized, don't interleave the loop.
   // Let regular unroll to unroll the loop, which saves the overflow
   // check and memory check cost.
   if (VF == 1)
     return 1;
 
   if (ST->isAtom())

test/Transforms/LoadStoreVectorizer/X86/load-width.ll

+; RUN: opt -mtriple=x86_64-unknown-linux-gnu -load-store-vectorizer -mcpu haswell -S -o - %s | FileCheck --check-prefix=CHECK-HSW %s
+; RUN: opt -mtriple=x86_64-unknown-linux-gnu -load-store-vectorizer -mcpu knl -S -o - %s | FileCheck --check-prefix=CHECK-KNL %s
+
+define <8 x double> @loadwidth_insert_extract(double* %ptr) {
+    %a = bitcast double* %ptr to <2 x double> *
+    %b = getelementptr <2 x double>, <2 x double>* %a, i32 1
+    %c = getelementptr <2 x double>, <2 x double>* %a, i32 2
+    %d = getelementptr <2 x double>, <2 x double>* %a, i32 3
+; CHECK-HSW: load <4 x double>
+; CHECK-HSW: load <4 x double>
+; CHECK-HSW-NOT: load
+; CHECK-KNL: load <8 x double>
+; CHECK-KNL-NOT: load
+    %la = load <2 x double>, <2 x double> *%a
+    %lb = load <2 x double>, <2 x double> *%b
+    %lc = load <2 x double>, <2 x double> *%c
+    %ld = load <2 x double>, <2 x double> *%d
+    ; Scalarize everything - Explicitly not a shufflevector to test this code
+    ; path in the LSV
+    %v1 = extractelement <2 x double> %la, i32 0
+    %v2 = extractelement <2 x double> %la, i32 1
+    %v3 = extractelement <2 x double> %lb, i32 0
+    %v4 = extractelement <2 x double> %lb, i32 1
+    %v5 = extractelement <2 x double> %lc, i32 0
+    %v6 = extractelement <2 x double> %lc, i32 1
+    %v7 = extractelement <2 x double> %ld, i32 0
+    %v8 = extractelement <2 x double> %ld, i32 1
+    ; Make a vector again
+    %i1 = insertelement <8 x double> undef, double %v1, i32 0
+    %i2 = insertelement <8 x double> %i1, double %v2, i32 1
+    %i3 = insertelement <8 x double> %i2, double %v3, i32 2
+    %i4 = insertelement <8 x double> %i3, double %v4, i32 3
+    %i5 = insertelement <8 x double> %i4, double %v5, i32 4
+    %i6 = insertelement <8 x double> %i5, double %v6, i32 5
+    %i7 = insertelement <8 x double> %i6, double %v7, i32 6
+    %i8 = insertelement <8 x double> %i7, double %v8, i32 7
+    ret <8 x double> %i8
+}