[DAG] visitINSERT_VECTOR_ELT - convert to or mask if all insertions are -1 (llvm#138213)

We did this for 0 and and, but we can do this with or and -1.

Co-authored-by: Simon Pilgrim <[email protected]>

Author: AZero13

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -23018,18 +23018,33 @@ SDValue DAGCombiner::visitINSERT_VECTOR_ELT(SDNode *N) {
             return NewShuffle;
       }
 
-      // If all insertions are zero value, try to convert to AND mask.
-      // TODO: Do this for -1 with OR mask?
-      if (!LegalOperations && llvm::isNullConstant(InVal) &&
-          all_of(Ops, [InVal](SDValue Op) { return !Op || Op == InVal; }) &&
-          count_if(Ops, [InVal](SDValue Op) { return Op == InVal; }) >= 2) {
-        SDValue Zero = DAG.getConstant(0, DL, MaxEltVT);
-        SDValue AllOnes = DAG.getAllOnesConstant(DL, MaxEltVT);
-        SmallVector<SDValue, 8> Mask(NumElts);
-        for (unsigned I = 0; I != NumElts; ++I)
-          Mask[I] = Ops[I] ? Zero : AllOnes;
-        return DAG.getNode(ISD::AND, DL, VT, CurVec,
-                           DAG.getBuildVector(VT, DL, Mask));
+      if (!LegalOperations) {
+        bool IsNull = llvm::isNullConstant(InVal);
+        // We can convert to AND/OR mask if all insertions are zero or -1
+        // respectively.
+        if ((IsNull || llvm::isAllOnesConstant(InVal)) &&
+            all_of(Ops, [InVal](SDValue Op) { return !Op || Op == InVal; }) &&
+            count_if(Ops, [InVal](SDValue Op) { return Op == InVal; }) >= 2) {
+          SDValue Zero = DAG.getConstant(0, DL, MaxEltVT);
+          SDValue AllOnes = DAG.getAllOnesConstant(DL, MaxEltVT);
+          SmallVector<SDValue, 8> Mask(NumElts);
+
+          // Build the mask and return the corresponding DAG node.
+          auto BuildMaskAndNode = [&](SDValue TrueVal, SDValue FalseVal,
+                                      unsigned MaskOpcode) {
+            for (unsigned I = 0; I != NumElts; ++I)
+              Mask[I] = Ops[I] ? TrueVal : FalseVal;
+            return DAG.getNode(MaskOpcode, DL, VT, CurVec,
+                               DAG.getBuildVector(VT, DL, Mask));
+          };
+
+          // If all elements are zero, we can use AND with all ones.
+          if (IsNull)
+            return BuildMaskAndNode(Zero, AllOnes, ISD::AND);
+
+          // If all elements are -1, we can use OR with zero.
+          return BuildMaskAndNode(AllOnes, Zero, ISD::OR);
+        }
       }
 
       // Failed to find a match in the chain - bail.

llvm/test/CodeGen/AArch64/vecreduce-and-legalization.ll

@@ -101,19 +101,13 @@ define i8 @test_v3i8(<3 x i8> %a) nounwind {
 define i8 @test_v9i8(<9 x i8> %a) nounwind {
 ; CHECK-LABEL: test_v9i8:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    mov v1.16b, v0.16b
-; CHECK-NEXT:    mov w8, #-1 // =0xffffffff
-; CHECK-NEXT:    mov v1.b[9], w8
-; CHECK-NEXT:    mov v1.b[10], w8
-; CHECK-NEXT:    mov v1.b[11], w8
-; CHECK-NEXT:    mov v1.b[12], w8
-; CHECK-NEXT:    mov v1.b[13], w8
-; CHECK-NEXT:    mov v1.b[14], w8
-; CHECK-NEXT:    mov v1.b[15], w8
+; CHECK-NEXT:    movi v1.2d, #0xffffff00ffffff00
+; CHECK-NEXT:    fmov x8, d0
+; CHECK-NEXT:    orr v1.16b, v0.16b, v1.16b
 ; CHECK-NEXT:    ext v1.16b, v1.16b, v1.16b, #8
 ; CHECK-NEXT:    and v0.8b, v0.8b, v1.8b
-; CHECK-NEXT:    fmov x8, d0
-; CHECK-NEXT:    and x8, x8, x8, lsr #32
+; CHECK-NEXT:    fmov x9, d0
+; CHECK-NEXT:    and x8, x9, x8, lsr #32
 ; CHECK-NEXT:    and x8, x8, x8, lsr #16
 ; CHECK-NEXT:    lsr x9, x8, #8
 ; CHECK-NEXT:    and w0, w8, w9

llvm/test/CodeGen/X86/avx-cvt-3.ll

@@ -48,17 +48,13 @@ define <8 x float> @sitofp_shuffle_zero_v8i32(<8 x i32> %a0) {
 define <8 x float> @sitofp_insert_allbits_v8i32(<8 x i32> %a0) {
 ; X86-LABEL: sitofp_insert_allbits_v8i32:
 ; X86:       # %bb.0:
-; X86-NEXT:    vxorps %xmm1, %xmm1, %xmm1
-; X86-NEXT:    vcmptrueps %ymm1, %ymm1, %ymm1
-; X86-NEXT:    vblendps {{.*#+}} ymm0 = ymm1[0],ymm0[1],ymm1[2],ymm0[3],ymm1[4,5],ymm0[6,7]
+; X86-NEXT:    vorps {{\.?LCPI[0-9]+_[0-9]+}}, %ymm0, %ymm0
 ; X86-NEXT:    vcvtdq2ps %ymm0, %ymm0
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: sitofp_insert_allbits_v8i32:
 ; X64:       # %bb.0:
-; X64-NEXT:    vxorps %xmm1, %xmm1, %xmm1
-; X64-NEXT:    vcmptrueps %ymm1, %ymm1, %ymm1
-; X64-NEXT:    vblendps {{.*#+}} ymm0 = ymm1[0],ymm0[1],ymm1[2],ymm0[3],ymm1[4,5],ymm0[6,7]
+; X64-NEXT:    vorps {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %ymm0, %ymm0
 ; X64-NEXT:    vcvtdq2ps %ymm0, %ymm0
 ; X64-NEXT:    retq
   %1 = insertelement <8 x i32> %a0, i32 -1, i32 0