shylie/llvm-project
1
0
Fork 0
Code Issues Pull Requests Actions 6 Packages Projects Releases Wiki Activity

[X86] canonicalizeLaneShuffleWithRepeatedOps - avoid folding vperm2x128(vpshufd(load()),undef) -> vpshufd(vperm2x128(load(),undef)) (#178675)

Browse Source 
There's no benefit to letting vperm2x128 handle the fold in an unary
shuffle and llvm-mca assumes there's an extra register dependency, which
confuses analysis.

Fixes #178632
This commit is contained in:
Simon Pilgrim 2026-01-29 15:52:09 +00:00 committed by GitHub
parent 7deea9db70
commit 91dad7e7ca
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
2 changed files with 20 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -42646,9 +42646,10 @@ static SDValue canonicalizeShuffleWithOp(SDValue N, SelectionDAG &DAG,
}
/// Attempt to fold vpermf128(op(),op()) -> op(vpermf128(),vpermf128()).
static SDValue canonicalizeLaneShuffleWithRepeatedOps(SDValue V,
SelectionDAG &DAG,
const SDLoc &DL) {
static SDValue
canonicalizeLaneShuffleWithRepeatedOps(SDValue V, SelectionDAG &DAG,
const SDLoc &DL,
const X86Subtarget &Subtarget) {
assert(V.getOpcode() == X86ISD::VPERM2X128 && "Unknown lane shuffle");
MVT VT = V.getSimpleValueType();
@ -42679,10 +42680,15 @@ static SDValue canonicalizeLaneShuffleWithRepeatedOps(SDValue V,
break;
}
[[fallthrough]];
case X86ISD::PSHUFD:
// Don't prefer a folded vpermf128 to a folded pshufd/vpermilp.
if ((Src1.isUndef() || Src0.getOperand(1) == Src1.getOperand(1)) &&
X86::mayFoldLoad(Src0.getOperand(0), Subtarget))
break;
[[fallthrough]];
case X86ISD::VSHLI:
case X86ISD::VSRLI:
case X86ISD::VSRAI:
case X86ISD::PSHUFD:
if (Src1.isUndef() || Src0.getOperand(1) == Src1.getOperand(1)) {
SDValue LHS = Src0.getOperand(0);
SDValue RHS = Src1.isUndef() ? Src1 : Src1.getOperand(0);
@ -43219,7 +43225,8 @@ static SDValue combineTargetShuffle(SDValue N, const SDLoc &DL,
}
// Fold vperm2x128(op(),op()) -> op(vperm2x128(),vperm2x128()).
if (SDValue Res = canonicalizeLaneShuffleWithRepeatedOps(N, DAG, DL))
if (SDValue Res =
canonicalizeLaneShuffleWithRepeatedOps(N, DAG, DL, Subtarget))
return Res;
// Fold vperm2x128 subvector shuffle with an inner concat pattern.

16
llvm/test/CodeGen/X86/merge-consecutive-loads-256.ll
View File

@ -129,8 +129,8 @@ define <4 x double> @merge_4f64_f64_45zz(ptr %ptr) nounwind uwtable noinline ssp
define <4 x double> @merge_v4f64_f64_3210(ptr %ptr) nounwind uwtable noinline ssp {
; AVX1-LABEL: merge_v4f64_f64_3210:
; AVX1: # %bb.0:
; AVX1-NEXT: vperm2f128 {{.*#+}} ymm0 = mem[2,3,0,1]
; AVX1-NEXT: vshufpd {{.*#+}} ymm0 = ymm0[1,0,3,2]
; AVX1-NEXT: vpermilpd {{.*#+}} ymm0 = mem[1,0,3,2]
; AVX1-NEXT: vperm2f128 {{.*#+}} ymm0 = ymm0[2,3,0,1]
; AVX1-NEXT: retq
;
; AVX2-LABEL: merge_v4f64_f64_3210:
@ -146,8 +146,8 @@ define <4 x double> @merge_v4f64_f64_3210(ptr %ptr) nounwind uwtable noinline ss
; X86-AVX-LABEL: merge_v4f64_f64_3210:
; X86-AVX: # %bb.0:
; X86-AVX-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-AVX-NEXT: vperm2f128 {{.*#+}} ymm0 = mem[2,3,0,1]
; X86-AVX-NEXT: vshufpd {{.*#+}} ymm0 = ymm0[1,0,3,2]
; X86-AVX-NEXT: vpermilpd {{.*#+}} ymm0 = mem[1,0,3,2]
; X86-AVX-NEXT: vperm2f128 {{.*#+}} ymm0 = ymm0[2,3,0,1]
; X86-AVX-NEXT: retl
%ptr0 = getelementptr inbounds double, ptr %ptr, i64 3
%ptr1 = getelementptr inbounds double, ptr %ptr, i64 2
@ -421,8 +421,8 @@ define <8 x float> @merge_8f32_f32_1u3u5zu8(ptr %ptr) nounwind uwtable noinline
define <8 x float> @merge_8f32_f32_76543210(ptr %ptr) nounwind uwtable noinline ssp {
; AVX1-LABEL: merge_8f32_f32_76543210:
; AVX1: # %bb.0:
; AVX1-NEXT: vperm2f128 {{.*#+}} ymm0 = mem[2,3,0,1]
; AVX1-NEXT: vshufps {{.*#+}} ymm0 = ymm0[3,2,1,0,7,6,5,4]
; AVX1-NEXT: vpermilps {{.*#+}} ymm0 = mem[3,2,1,0,7,6,5,4]
; AVX1-NEXT: vperm2f128 {{.*#+}} ymm0 = ymm0[2,3,0,1]
; AVX1-NEXT: retq
;
; AVX2-LABEL: merge_8f32_f32_76543210:
@ -440,8 +440,8 @@ define <8 x float> @merge_8f32_f32_76543210(ptr %ptr) nounwind uwtable noinline
; X86-AVX-LABEL: merge_8f32_f32_76543210:
; X86-AVX: # %bb.0:
; X86-AVX-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-AVX-NEXT: vperm2f128 {{.*#+}} ymm0 = mem[2,3,0,1]
; X86-AVX-NEXT: vshufps {{.*#+}} ymm0 = ymm0[3,2,1,0,7,6,5,4]
; X86-AVX-NEXT: vpermilps {{.*#+}} ymm0 = mem[3,2,1,0,7,6,5,4]
; X86-AVX-NEXT: vperm2f128 {{.*#+}} ymm0 = ymm0[2,3,0,1]
; X86-AVX-NEXT: retl
%ptr0 = getelementptr inbounds float, ptr %ptr, i64 7
%ptr1 = getelementptr inbounds float, ptr %ptr, i64 6