[X86] Move integer hadd/hsub formation into a helper function shared by combineAdd and combineSub.

There was a lot of duplicate code here for checking the VT and
subtarget. Moving it into a helper avoids that.

It also fixes a bug that combineAdd reused Op0/Op1 after a call
to isHorizontalBinOp may have changed it. The new helper function
has its own local version of Op0/Op1 that aren't shared by other
code.

Fixes PR46455.

Reviewed By: spatel, bkramer

Differential Revision: https://reviews.llvm.org/D83971

Author: topperc

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -47606,6 +47606,30 @@ static SDValue matchPMADDWD_2(SelectionDAG &DAG, SDValue N0, SDValue N1,
                           PMADDBuilder);
 }
 
+static SDValue combineAddOrSubToHADDorHSUB(SDNode *N, SelectionDAG &DAG,
+                                           const X86Subtarget &Subtarget) {
+  EVT VT = N->getValueType(0);
+  SDValue Op0 = N->getOperand(0);
+  SDValue Op1 = N->getOperand(1);
+  bool IsAdd = N->getOpcode() == ISD::ADD;
+  assert((IsAdd || N->getOpcode() == ISD::SUB) && "Wrong opcode");
+
+  if ((VT == MVT::v8i16 || VT == MVT::v4i32 || VT == MVT::v16i16 ||
+       VT == MVT::v8i32) &&
+      Subtarget.hasSSSE3() &&
+      isHorizontalBinOp(Op0, Op1, DAG, Subtarget, IsAdd)) {
+    auto HOpBuilder = [IsAdd](SelectionDAG &DAG, const SDLoc &DL,
+                              ArrayRef<SDValue> Ops) {
+      return DAG.getNode(IsAdd ? X86ISD::HADD : X86ISD::HSUB,
+                         DL, Ops[0].getValueType(), Ops);
+    };
+    return SplitOpsAndApply(DAG, Subtarget, SDLoc(N), VT, {Op0, Op1},
+                            HOpBuilder);
+  }
+
+  return SDValue();
+}
+
 static SDValue combineAdd(SDNode *N, SelectionDAG &DAG,
                           TargetLowering::DAGCombinerInfo &DCI,
                           const X86Subtarget &Subtarget) {
@@ -47619,17 +47643,8 @@ static SDValue combineAdd(SDNode *N, SelectionDAG &DAG,
     return MAdd;
 
   // Try to synthesize horizontal adds from adds of shuffles.
-  if ((VT == MVT::v8i16 || VT == MVT::v4i32 || VT == MVT::v16i16 ||
-       VT == MVT::v8i32) &&
-      Subtarget.hasSSSE3() &&
-      isHorizontalBinOp(Op0, Op1, DAG, Subtarget, true)) {
-    auto HADDBuilder = [](SelectionDAG &DAG, const SDLoc &DL,
-                          ArrayRef<SDValue> Ops) {
-      return DAG.getNode(X86ISD::HADD, DL, Ops[0].getValueType(), Ops);
-    };
-    return SplitOpsAndApply(DAG, Subtarget, SDLoc(N), VT, {Op0, Op1},
-                            HADDBuilder);
-  }
+  if (SDValue V = combineAddOrSubToHADDorHSUB(N, DAG, Subtarget))
+    return V;
 
   // If vectors of i1 are legal, turn (add (zext (vXi1 X)), Y) into
   // (sub Y, (sext (vXi1 X))).
@@ -47802,18 +47817,8 @@ static SDValue combineSub(SDNode *N, SelectionDAG &DAG,
   }
 
   // Try to synthesize horizontal subs from subs of shuffles.
-  EVT VT = N->getValueType(0);
-  if ((VT == MVT::v8i16 || VT == MVT::v4i32 || VT == MVT::v16i16 ||
-       VT == MVT::v8i32) &&
-      Subtarget.hasSSSE3() &&
-      isHorizontalBinOp(Op0, Op1, DAG, Subtarget, false)) {
-    auto HSUBBuilder = [](SelectionDAG &DAG, const SDLoc &DL,
-                          ArrayRef<SDValue> Ops) {
-      return DAG.getNode(X86ISD::HSUB, DL, Ops[0].getValueType(), Ops);
-    };
-    return SplitOpsAndApply(DAG, Subtarget, SDLoc(N), VT, {Op0, Op1},
-                            HSUBBuilder);
-  }
+  if (SDValue V = combineAddOrSubToHADDorHSUB(N, DAG, Subtarget))
+    return V;
 
   // Try to create PSUBUS if SUB's argument is max/min
   if (SDValue V = combineSubToSubus(N, DAG, Subtarget))

llvm/test/CodeGen/X86/pr46455.ll

@@ -8,12 +8,13 @@ define void @EntryModule(i8** %buffer_table) {
 ; CHECK-NEXT:    movq (%rdi), %rax
 ; CHECK-NEXT:    movq 24(%rdi), %rcx
 ; CHECK-NEXT:    vcmpneqps (%rax), %ymm0, %ymm0
-; CHECK-NEXT:    vandps {{.*}}(%rip){1to4}, %xmm0, %xmm1
-; CHECK-NEXT:    vpermilps {{.*#+}} xmm2 = xmm1[2,3,0,1]
-; CHECK-NEXT:    vpermilps {{.*#+}} xmm3 = xmm1[3,1,2,3]
-; CHECK-NEXT:    vpaddd %xmm3, %xmm2, %xmm2
-; CHECK-NEXT:    vpsubd %xmm0, %xmm1, %xmm0
-; CHECK-NEXT:    vpaddd %xmm2, %xmm0, %xmm0
+; CHECK-NEXT:    vpsrld $31, %xmm0, %xmm1
+; CHECK-NEXT:    vpshufd {{.*#+}} xmm2 = xmm1[1,1,2,3]
+; CHECK-NEXT:    vpshufd {{.*#+}} xmm3 = xmm1[2,3,0,1]
+; CHECK-NEXT:    vpshufd {{.*#+}} xmm1 = xmm1[3,1,2,3]
+; CHECK-NEXT:    vpaddd %xmm1, %xmm3, %xmm1
+; CHECK-NEXT:    vpsubd %xmm0, %xmm2, %xmm0
+; CHECK-NEXT:    vpaddd %xmm1, %xmm0, %xmm0
 ; CHECK-NEXT:    vmovd %xmm0, (%rcx)
 ; CHECK-NEXT:    vzeroupper
 ; CHECK-NEXT:    retq