[X86] combineHorizOpWithShuffle - generalize HOP(SHUFFLE(X),SHUFFLE(Y)) -> SHUFFLE(HOP(X,Y)) fold.

For 128-bit types, generalize the fold to recognise duplicate operands in either shuffle.

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -43366,39 +43366,60 @@ static SDValue combineHorizOpWithShuffle(SDNode *N, SelectionDAG &DAG,
     }
   }
 
-  // Attempt to fold HOP(SHUFFLE(X),SHUFFLE(Y)) -> SHUFFLE(HOP(X,Y)).
+  // Attempt to fold HOP(SHUFFLE(X,Y),SHUFFLE(Z,W)) -> SHUFFLE(HOP()).
   if (VT.is128BitVector() && SrcVT.getScalarSizeInBits() <= 32) {
-    int PostShuffle[4] = {0, 1, 2, 3};
+    // If either/both ops are a shuffle that can scale to v2x64,
+    // then see if we can perform this as a v4x32 post shuffle.
+    SmallVector<SDValue> Ops0, Ops1;
+    SmallVector<int> Mask0, Mask1, ScaledMask0, ScaledMask1;
+    bool IsShuf0 =
+        getTargetShuffleInputs(BC0, Ops0, Mask0, DAG) && !isAnyZero(Mask0) &&
+        scaleShuffleElements(Mask0, 2, ScaledMask0) &&
+        all_of(Ops0, [](SDValue Op) { return Op.getValueSizeInBits() == 128; });
+    bool IsShuf1 =
+        getTargetShuffleInputs(BC1, Ops1, Mask1, DAG) && !isAnyZero(Mask1) &&
+        scaleShuffleElements(Mask1, 2, ScaledMask1) &&
+        all_of(Ops1, [](SDValue Op) { return Op.getValueSizeInBits() == 128; });
+    if (IsShuf0 || IsShuf1) {
+      if (!IsShuf0) {
+        Ops0.assign({BC0});
+        ScaledMask0.assign({0, 1});
+      }
+      if (!IsShuf1) {
+        Ops1.assign({BC1});
+        ScaledMask1.assign({0, 1});
+      }
 
-    // If the op is an unary shuffle that can scale to v2x64,
+      SDValue LHS, RHS;
-    // then we can perform this as a v4x32 post shuffle.
+      int PostShuffle[4] = {-1, -1, -1, -1};
-    auto AdjustOp = [&](SDValue V, int Offset) {
+      auto FindShuffleOpAndIdx = [&](int M, int &Idx, ArrayRef<SDValue> Ops) {
-      SmallVector<SDValue> ShuffleOps;
+        if (M < 0)
-      SmallVector<int> ShuffleMask, ScaledMask;
+          return true;
-      if (!getTargetShuffleInputs(V, ShuffleOps, ShuffleMask, DAG))
+        Idx = M % 2;
-        return SDValue();
+        SDValue Src = Ops[M / 2];
-
+        if (!LHS || LHS == Src) {
-      resolveTargetShuffleInputsAndMask(ShuffleOps, ShuffleMask);
+          LHS = Src;
-      if (isAnyZero(ShuffleMask) || ShuffleOps.size() != 1 ||
+          return true;
-          !ShuffleOps[0].getValueType().is128BitVector() || !V->hasOneUse() ||
+        }
-          !scaleShuffleElements(ShuffleMask, 2, ScaledMask))
+        if (!RHS || RHS == Src) {
-        return SDValue();
+          Idx += 2;
-
+          RHS = Src;
-      PostShuffle[Offset + 0] = ScaledMask[0] < 0 ? -1 : Offset + ScaledMask[0];
+          return true;
-      PostShuffle[Offset + 1] = ScaledMask[1] < 0 ? -1 : Offset + ScaledMask[1];
+        }
-      return ShuffleOps[0];
+        return false;
-    };
+      };
-
+      if (FindShuffleOpAndIdx(ScaledMask0[0], PostShuffle[0], Ops0) &&
-    SDValue Src0 = AdjustOp(BC0, 0);
+          FindShuffleOpAndIdx(ScaledMask0[1], PostShuffle[1], Ops0) &&
-    SDValue Src1 = AdjustOp(BC1, 2);
+          FindShuffleOpAndIdx(ScaledMask1[0], PostShuffle[2], Ops1) &&
-    if (Src0 || Src1) {
+          FindShuffleOpAndIdx(ScaledMask1[1], PostShuffle[3], Ops1)) {
-      Src0 = DAG.getBitcast(SrcVT, Src0 ? Src0 : BC0);
+        LHS = DAG.getBitcast(SrcVT, LHS);
-      Src1 = DAG.getBitcast(SrcVT, Src1 ? Src1 : BC1);
+        RHS = DAG.getBitcast(SrcVT, RHS ? RHS : LHS);
-      MVT ShufVT = VT.isFloatingPoint() ? MVT::v4f32 : MVT::v4i32;
+        MVT ShufVT = VT.isFloatingPoint() ? MVT::v4f32 : MVT::v4i32;
-      SDValue Res = DAG.getNode(Opcode, DL, VT, Src0, Src1);
+        SDValue Res = DAG.getNode(Opcode, DL, VT, LHS, RHS);
-      Res = DAG.getBitcast(ShufVT, Res);
+        Res = DAG.getBitcast(ShufVT, Res);
-      Res = DAG.getVectorShuffle(ShufVT, DL, Res, Res, PostShuffle);
+        Res = DAG.getVectorShuffle(ShufVT, DL, Res, Res, PostShuffle);
-      return DAG.getBitcast(VT, Res);
+        return DAG.getBitcast(VT, Res);
+      }
     }
   }
 

llvm/test/CodeGen/X86/horizontal-sum.ll

@@ -377,7 +377,7 @@ define <8 x i32> @pair_sum_v8i32_v4i32(<4 x i32> %0, <4 x i32> %1, <4 x i32> %2,
 ; SSSE3-SLOW-NEXT:    punpcklqdq {{.*#+}} xmm0 = xmm0[0],xmm2[0]
 ; SSSE3-SLOW-NEXT:    phaddd %xmm7, %xmm6
 ; SSSE3-SLOW-NEXT:    phaddd %xmm6, %xmm6
-; SSSE3-SLOW-NEXT:    pshufd {{.*#+}} xmm1 = xmm6[0,1,3,3]
+; SSSE3-SLOW-NEXT:    pshufd {{.*#+}} xmm1 = xmm6[0,1,1,1]
 ; SSSE3-SLOW-NEXT:    shufps {{.*#+}} xmm2 = xmm2[2,3],xmm1[0,2]
 ; SSSE3-SLOW-NEXT:    movaps %xmm2, %xmm1
 ; SSSE3-SLOW-NEXT:    retq
@@ -475,7 +475,7 @@ define <8 x i32> @pair_sum_v8i32_v4i32(<4 x i32> %0, <4 x i32> %1, <4 x i32> %2,
 ; AVX2-SLOW-NEXT:    vpshufd {{.*#+}} xmm1 = xmm1[2,3,2,3]
 ; AVX2-SLOW-NEXT:    vinserti128 $1, %xmm1, %ymm0, %ymm0
 ; AVX2-SLOW-NEXT:    vphaddd %xmm7, %xmm6, %xmm1
-; AVX2-SLOW-NEXT:    vphaddd %xmm0, %xmm1, %xmm1
+; AVX2-SLOW-NEXT:    vphaddd %xmm1, %xmm1, %xmm1
 ; AVX2-SLOW-NEXT:    vpbroadcastq %xmm1, %ymm1
 ; AVX2-SLOW-NEXT:    vpblendd {{.*#+}} ymm0 = ymm0[0,1,2,3,4,5],ymm1[6,7]
 ; AVX2-SLOW-NEXT:    retq