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Correct cost model for vector shift on AVX2 

- After moving logic recognizing vector shift with scalar amount from
  DAG combining into DAG lowering, we declare to customize all vector
  shifts even vector shift on AVX is legal. As a result, the cost model
  needs special tuning to identify these legal cases.

llvm-svn: 177586
This commit is contained in:
Michael Liao 2013-03-20 22:01:10 +00:00
parent 7430382970
commit 70dd7f999d
2 changed files with 77 additions and 0 deletions
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23
llvm/lib/Target/X86/X86TargetTransformInfo.cpp
View File

@ -169,6 +169,29 @@ unsigned X86TTI::getArithmeticInstrCost(unsigned Opcode, Type *Ty) const {
int ISD = TLI->InstructionOpcodeToISD(Opcode);
assert(ISD && "Invalid opcode");
static const CostTblEntry<MVT> AVX2CostTable[] = {
// Shifts on v4i64/v8i32 on AVX2 is legal even though we declare to
// customize them to detect the cases where shift amount is a scalar one.
{ ISD::SHL, MVT::v4i32, 1 },
{ ISD::SRL, MVT::v4i32, 1 },
{ ISD::SRA, MVT::v4i32, 1 },
{ ISD::SHL, MVT::v8i32, 1 },
{ ISD::SRL, MVT::v8i32, 1 },
{ ISD::SRA, MVT::v8i32, 1 },
{ ISD::SHL, MVT::v2i64, 1 },
{ ISD::SRL, MVT::v2i64, 1 },
{ ISD::SHL, MVT::v4i64, 1 },
{ ISD::SRL, MVT::v4i64, 1 },
};
// Look for AVX2 lowering tricks.
if (ST->hasAVX2()) {
int Idx = CostTableLookup<MVT>(AVX2CostTable, array_lengthof(AVX2CostTable),
ISD, LT.second);
if (Idx != -1)
return LT.first * AVX2CostTable[Idx].Cost;
}
static const CostTblEntry<MVT> AVX1CostTable[] = {
// We don't have to scalarize unsupported ops. We can issue two half-sized
// operations and we only need to extract the upper YMM half.

54
llvm/test/Analysis/CostModel/X86/arith.ll
View File

@ -72,3 +72,57 @@ define i32 @fmul(i32 %arg) {
%B = fmul <8 x float> undef, undef
ret i32 undef
}
; AVX: shift
; AVX2: shift
define void @shift() {
; AVX: cost of 2 {{.*}} shl
; AVX2: cost of 1 {{.*}} shl
%A0 = shl <4 x i32> undef, undef
; AVX: cost of 2 {{.*}} shl
; AVX2: cost of 1 {{.*}} shl
%A1 = shl <2 x i64> undef, undef
; AVX: cost of 2 {{.*}} lshr
; AVX2: cost of 1 {{.*}} lshr
%B0 = lshr <4 x i32> undef, undef
; AVX: cost of 2 {{.*}} lshr
; AVX2: cost of 1 {{.*}} lshr
%B1 = lshr <2 x i64> undef, undef
; AVX: cost of 2 {{.*}} ashr
; AVX2: cost of 1 {{.*}} ashr
%C0 = ashr <4 x i32> undef, undef
; AVX: cost of 6 {{.*}} ashr
; AVX2: cost of 6 {{.*}} ashr
%C1 = ashr <2 x i64> undef, undef
ret void
}
; AVX: avx2shift
; AVX2: avx2shift
define void @avx2shift() {
; AVX: cost of 2 {{.*}} shl
; AVX2: cost of 1 {{.*}} shl
%A0 = shl <8 x i32> undef, undef
; AVX: cost of 2 {{.*}} shl
; AVX2: cost of 1 {{.*}} shl
%A1 = shl <4 x i64> undef, undef
; AVX: cost of 2 {{.*}} lshr
; AVX2: cost of 1 {{.*}} lshr
%B0 = lshr <8 x i32> undef, undef
; AVX: cost of 2 {{.*}} lshr
; AVX2: cost of 1 {{.*}} lshr
%B1 = lshr <4 x i64> undef, undef
; AVX: cost of 2 {{.*}} ashr
; AVX2: cost of 1 {{.*}} ashr
%C0 = ashr <8 x i32> undef, undef
; AVX: cost of 12 {{.*}} ashr
; AVX2: cost of 12 {{.*}} ashr
%C1 = ashr <4 x i64> undef, undef
ret void
}