[llvm] [LoongArch] Refine 256-bit vector_shuffle legalization for LASX (PR #160254)
via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 23 22:06:27 PDT 2025
https://github.com/zhaoqi5 updated https://github.com/llvm/llvm-project/pull/160254
>From 80abdb7318bc7e1ff7bc4ea1f6ff0b1cc4a9813e Mon Sep 17 00:00:00 2001
From: Qi Zhao <zhaoqi01 at loongson.cn>
Date: Tue, 23 Sep 2025 16:02:12 +0800
Subject: [PATCH] [LoongArch] Refine 256-bit vector_shuffle legalization for
LASX
---
.../LoongArch/LoongArchISelLowering.cpp | 73 +++++++++++--------
.../lasx/ir-instruction/fix-xvshuf.ll | 2 +-
.../ir-instruction/shuffle-as-xvrepl128vei.ll | 7 +-
3 files changed, 45 insertions(+), 37 deletions(-)
diff --git a/llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp b/llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp
index 32baa2d111270..9662fec5ef4b9 100644
--- a/llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp
+++ b/llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp
@@ -2060,7 +2060,10 @@ lowerVECTOR_SHUFFLE_XVREPLVEI(const SDLoc &DL, ArrayRef<int> Mask, MVT VT,
const auto &Begin = Mask.begin();
const auto &End = Mask.end();
- unsigned HalfSize = Mask.size() / 2;
+ int HalfSize = Mask.size() / 2;
+
+ if (SplatIndex >= HalfSize)
+ return SDValue();
assert(SplatIndex < (int)Mask.size() && "Out of bounds mask index");
if (fitsRegularPattern<int>(Begin, 1, End - HalfSize, SplatIndex, 0) &&
@@ -2354,7 +2357,7 @@ static SDValue lowerVECTOR_SHUFFLE_XVSHUF(const SDLoc &DL, ArrayRef<int> Mask,
/// cases need to be converted to it for processing.
///
/// This function may modify V1, V2 and Mask
-static void canonicalizeShuffleVectorByLane(
+static bool canonicalizeShuffleVectorByLane(
const SDLoc &DL, MutableArrayRef<int> Mask, MVT VT, SDValue &V1,
SDValue &V2, SelectionDAG &DAG, const LoongArchSubtarget &Subtarget) {
@@ -2378,15 +2381,15 @@ static void canonicalizeShuffleVectorByLane(
preMask = LowLaneTy;
if (std::all_of(Mask.begin() + HalfSize, Mask.end(), [&](int M) {
- return M < 0 || (M >= 0 && M < HalfSize) ||
- (M >= MaskSize && M < MaskSize + HalfSize);
+ return M < 0 || (M >= HalfSize && M < MaskSize) ||
+ (M >= MaskSize + HalfSize && M < MaskSize * 2);
}))
- postMask = HighLaneTy;
+ postMask = LowLaneTy;
else if (std::all_of(Mask.begin() + HalfSize, Mask.end(), [&](int M) {
- return M < 0 || (M >= HalfSize && M < MaskSize) ||
- (M >= MaskSize + HalfSize && M < MaskSize * 2);
+ return M < 0 || (M >= 0 && M < HalfSize) ||
+ (M >= MaskSize && M < MaskSize + HalfSize);
}))
- postMask = LowLaneTy;
+ postMask = HighLaneTy;
// The pre-half of mask is high lane type, and the post-half of mask
// is low lane type, which is closest to the LoongArch instructions.
@@ -2395,7 +2398,7 @@ static void canonicalizeShuffleVectorByLane(
// to the lower 128-bit of vector register, and the low lane of mask
// corresponds the higher 128-bit of vector register.
if (preMask == HighLaneTy && postMask == LowLaneTy) {
- return;
+ return false;
}
if (preMask == LowLaneTy && postMask == HighLaneTy) {
V1 = DAG.getBitcast(MVT::v4i64, V1);
@@ -2449,8 +2452,10 @@ static void canonicalizeShuffleVectorByLane(
*it = *it < 0 ? *it : *it + HalfSize;
}
} else { // cross-lane
- return;
+ return false;
}
+
+ return true;
}
/// Lower VECTOR_SHUFFLE as lane permute and then shuffle (if possible).
@@ -2516,27 +2521,20 @@ static SDValue lower256BitShuffle(const SDLoc &DL, ArrayRef<int> Mask, MVT VT,
assert(Mask.size() % 2 == 0 && "Expected even mask size.");
assert(Mask.size() >= 4 && "Mask size is less than 4.");
- // canonicalize non cross-lane shuffle vector
- SmallVector<int> NewMask(Mask);
- canonicalizeShuffleVectorByLane(DL, NewMask, VT, V1, V2, DAG, Subtarget);
-
APInt KnownUndef, KnownZero;
- computeZeroableShuffleElements(NewMask, V1, V2, KnownUndef, KnownZero);
+ computeZeroableShuffleElements(Mask, V1, V2, KnownUndef, KnownZero);
APInt Zeroable = KnownUndef | KnownZero;
SDValue Result;
// TODO: Add more comparison patterns.
if (V2.isUndef()) {
- if ((Result = lowerVECTOR_SHUFFLE_XVREPLVEI(DL, NewMask, VT, V1, V2, DAG,
+ if ((Result = lowerVECTOR_SHUFFLE_XVREPLVEI(DL, Mask, VT, V1, V2, DAG,
Subtarget)))
return Result;
- if ((Result = lowerVECTOR_SHUFFLE_XVSHUF4I(DL, NewMask, VT, V1, V2, DAG,
+ if ((Result = lowerVECTOR_SHUFFLE_XVSHUF4I(DL, Mask, VT, V1, V2, DAG,
Subtarget)))
return Result;
- if ((Result = lowerVECTOR_SHUFFLE_XVPERM(DL, NewMask, VT, V1, V2, DAG)))
- return Result;
- if ((Result = lowerVECTOR_SHUFFLEAsLanePermuteAndShuffle(DL, NewMask, VT,
- V1, V2, DAG)))
+ if ((Result = lowerVECTOR_SHUFFLE_XVPERM(DL, Mask, VT, V1, V2, DAG)))
return Result;
// TODO: This comment may be enabled in the future to better match the
@@ -2546,24 +2544,39 @@ static SDValue lower256BitShuffle(const SDLoc &DL, ArrayRef<int> Mask, MVT VT,
// It is recommended not to change the pattern comparison order for better
// performance.
- if ((Result = lowerVECTOR_SHUFFLE_XVPACKEV(DL, NewMask, VT, V1, V2, DAG)))
+ if ((Result = lowerVECTOR_SHUFFLE_XVPACKEV(DL, Mask, VT, V1, V2, DAG)))
return Result;
- if ((Result = lowerVECTOR_SHUFFLE_XVPACKOD(DL, NewMask, VT, V1, V2, DAG)))
+ if ((Result = lowerVECTOR_SHUFFLE_XVPACKOD(DL, Mask, VT, V1, V2, DAG)))
return Result;
- if ((Result = lowerVECTOR_SHUFFLE_XVILVH(DL, NewMask, VT, V1, V2, DAG)))
+ if ((Result = lowerVECTOR_SHUFFLE_XVILVH(DL, Mask, VT, V1, V2, DAG)))
return Result;
- if ((Result = lowerVECTOR_SHUFFLE_XVILVL(DL, NewMask, VT, V1, V2, DAG)))
+ if ((Result = lowerVECTOR_SHUFFLE_XVILVL(DL, Mask, VT, V1, V2, DAG)))
return Result;
- if ((Result = lowerVECTOR_SHUFFLE_XVPICKEV(DL, NewMask, VT, V1, V2, DAG)))
+ if ((Result = lowerVECTOR_SHUFFLE_XVPICKEV(DL, Mask, VT, V1, V2, DAG)))
return Result;
- if ((Result = lowerVECTOR_SHUFFLE_XVPICKOD(DL, NewMask, VT, V1, V2, DAG)))
+ if ((Result = lowerVECTOR_SHUFFLE_XVPICKOD(DL, Mask, VT, V1, V2, DAG)))
return Result;
- if ((Result = lowerVECTOR_SHUFFLEAsShift(DL, NewMask, VT, V1, V2, DAG,
- Subtarget, Zeroable)))
+ if ((Result = lowerVECTOR_SHUFFLEAsShift(DL, Mask, VT, V1, V2, DAG, Subtarget,
+ Zeroable)))
return Result;
- if ((Result = lowerVECTOR_SHUFFLEAsByteRotate(DL, NewMask, VT, V1, V2, DAG,
+ if ((Result = lowerVECTOR_SHUFFLEAsByteRotate(DL, Mask, VT, V1, V2, DAG,
Subtarget)))
return Result;
+
+ // canonicalize non cross-lane shuffle vector
+ SmallVector<int> NewMask(Mask);
+ if (canonicalizeShuffleVectorByLane(DL, NewMask, VT, V1, V2, DAG, Subtarget))
+ return lower256BitShuffle(DL, NewMask, VT, V1, V2, DAG, Subtarget);
+
+ // FIXME: Handling the remaining cases earlier can degrade performance
+ // in some situations. Further analysis is required to enable more
+ // effective optimizations.
+ if (V2.isUndef()) {
+ if ((Result = lowerVECTOR_SHUFFLEAsLanePermuteAndShuffle(DL, NewMask, VT,
+ V1, V2, DAG)))
+ return Result;
+ }
+
if (SDValue NewShuffle = widenShuffleMask(DL, NewMask, VT, V1, V2, DAG))
return NewShuffle;
if ((Result = lowerVECTOR_SHUFFLE_XVSHUF(DL, NewMask, VT, V1, V2, DAG)))
diff --git a/llvm/test/CodeGen/LoongArch/lasx/ir-instruction/fix-xvshuf.ll b/llvm/test/CodeGen/LoongArch/lasx/ir-instruction/fix-xvshuf.ll
index 765473ce166df..30539427a1a0a 100644
--- a/llvm/test/CodeGen/LoongArch/lasx/ir-instruction/fix-xvshuf.ll
+++ b/llvm/test/CodeGen/LoongArch/lasx/ir-instruction/fix-xvshuf.ll
@@ -8,7 +8,7 @@ define <4 x double> @shufflevector_v4f64(<4 x double> %a, <4 x double> %b) {
; CHECK-LABEL: shufflevector_v4f64:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: xvpickve.d $xr2, $xr1, 3
-; CHECK-NEXT: xvpermi.d $xr3, $xr0, 78
+; CHECK-NEXT: xvpermi.d $xr3, $xr0, 238
; CHECK-NEXT: xvrepl128vei.d $xr3, $xr3, 1
; CHECK-NEXT: vextrins.d $vr3, $vr2, 16
; CHECK-NEXT: xvpickve.d $xr1, $xr1, 2
diff --git a/llvm/test/CodeGen/LoongArch/lasx/ir-instruction/shuffle-as-xvrepl128vei.ll b/llvm/test/CodeGen/LoongArch/lasx/ir-instruction/shuffle-as-xvrepl128vei.ll
index 935a30a3e54ed..69bb5899e685f 100644
--- a/llvm/test/CodeGen/LoongArch/lasx/ir-instruction/shuffle-as-xvrepl128vei.ll
+++ b/llvm/test/CodeGen/LoongArch/lasx/ir-instruction/shuffle-as-xvrepl128vei.ll
@@ -16,7 +16,6 @@ define <32 x i8> @shufflevector_v32i8(<32 x i8> %a, <32 x i8> %b) {
define <32 x i8> @shufflevector_v32i8_undef(<32 x i8> %a) {
; CHECK-LABEL: shufflevector_v32i8_undef:
; CHECK: # %bb.0:
-; CHECK-NEXT: xvpermi.d $xr0, $xr0, 68
; CHECK-NEXT: xvrepl128vei.b $xr0, $xr0, 1
; CHECK-NEXT: ret
%c = shufflevector <32 x i8> %a, <32 x i8> poison, <32 x i32> <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1,
@@ -39,7 +38,6 @@ define <16 x i16> @shufflevector_v16i16(<16 x i16> %a, <16 x i16> %b) {
define <16 x i16> @shufflevector_v16i16_undef(<16 x i16> %a) {
; CHECK-LABEL: shufflevector_v16i16_undef:
; CHECK: # %bb.0:
-; CHECK-NEXT: xvpermi.d $xr0, $xr0, 68
; CHECK-NEXT: xvrepl128vei.h $xr0, $xr0, 3
; CHECK-NEXT: ret
%c = shufflevector <16 x i16> %a, <16 x i16> poison, <16 x i32> <i32 3, i32 3, i32 3, i32 3, i32 3, i32 3, i32 3, i32 3,
@@ -62,7 +60,6 @@ define <8 x i32> @shufflevector_v8i32(<8 x i32> %a, <8 x i32> %b) {
define <8 x i32> @shufflevector_v8i32_undef(<8 x i32> %a) {
; CHECK-LABEL: shufflevector_v8i32_undef:
; CHECK: # %bb.0:
-; CHECK-NEXT: xvpermi.d $xr0, $xr0, 68
; CHECK-NEXT: xvrepl128vei.w $xr0, $xr0, 2
; CHECK-NEXT: ret
%c = shufflevector <8 x i32> %a, <8 x i32> poison, <8 x i32> <i32 2, i32 2, i32 2, i32 2, i32 8, i32 8, i32 8, i32 8>
@@ -83,7 +80,6 @@ define <4 x i64> @shufflevector_v4i64(<4 x i64> %a, <4 x i64> %b) {
define <4 x i64> @shufflevector_v4i64_undef(<4 x i64> %a) {
; CHECK-LABEL: shufflevector_v4i64_undef:
; CHECK: # %bb.0:
-; CHECK-NEXT: xvpermi.d $xr0, $xr0, 68
; CHECK-NEXT: xvrepl128vei.d $xr0, $xr0, 1
; CHECK-NEXT: ret
%c = shufflevector <4 x i64> %a, <4 x i64> poison, <4 x i32> <i32 1, i32 1, i32 5, i32 5>
@@ -104,7 +100,7 @@ define <8 x float> @shufflevector_v8f32(<8 x float> %a, <8 x float> %b) {
define <8 x float> @shufflevector_v8f32_undef(<8 x float> %a) {
; CHECK-LABEL: shufflevector_v8f32_undef:
; CHECK: # %bb.0:
-; CHECK-NEXT: xvpermi.d $xr0, $xr0, 78
+; CHECK-NEXT: xvpermi.d $xr0, $xr0, 238
; CHECK-NEXT: xvrepl128vei.w $xr0, $xr0, 1
; CHECK-NEXT: ret
%c = shufflevector <8 x float> %a, <8 x float> poison, <8 x i32> <i32 5, i32 5, i32 5, i32 5, i32 9, i32 9, i32 9, i32 9>
@@ -125,7 +121,6 @@ define <4 x double> @shufflevector_v4f64(<4 x double> %a, <4 x double> %b) {
define <4 x double> @shufflevector_v4f64_undef(<4 x double> %a) {
; CHECK-LABEL: shufflevector_v4f64_undef:
; CHECK: # %bb.0:
-; CHECK-NEXT: xvpermi.d $xr0, $xr0, 68
; CHECK-NEXT: xvrepl128vei.d $xr0, $xr0, 0
; CHECK-NEXT: ret
%c = shufflevector <4 x double> %a, <4 x double> poison, <4 x i32> <i32 0, i32 0, i32 7, i32 7>
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