[SelectionDAG] Convert to or mask if all insertions are -1

[AZero13]

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

[llvmbot]

@llvm/pr-subscribers-backend-aarch64

@llvm/pr-subscribers-backend-x86

Author: AZero13 (AZero13)

Changes

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

---

Full diff: https://github.com/llvm/llvm-project/pull/138213.diff

3 Files Affected:

• (modified) llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (+13-1)
• (modified) llvm/test/CodeGen/AArch64/vecreduce-and-legalization.ll (+5-11)
• (modified) llvm/test/CodeGen/X86/avx-cvt-3.ll (+2-6)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ea1435c3934be..1645acb9d3fd0 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -22974,7 +22974,6 @@ SDValue DAGCombiner::visitINSERT_VECTOR_ELT(SDNode *N) {
       }
 
       // 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) {
@@ -22987,6 +22986,19 @@ SDValue DAGCombiner::visitINSERT_VECTOR_ELT(SDNode *N) {
                            DAG.getBuildVector(VT, DL, Mask));
       }
 
+      // If all insertions are -1, try to convert to OR mask.
+      if (!LegalOperations && 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);
+        for (unsigned I = 0; I != NumElts; ++I)
+          Mask[I] = Ops[I] ? AllOnes : Zero;
+        return DAG.getNode(ISD::OR, DL, VT, CurVec,
+                           DAG.getBuildVector(VT, DL, Mask));
+      }
+
       // Failed to find a match in the chain - bail.
       break;
     }
diff --git a/llvm/test/CodeGen/AArch64/vecreduce-and-legalization.ll b/llvm/test/CodeGen/AArch64/vecreduce-and-legalization.ll
index 7fa416e0dbcd5..d2f16721e6e47 100644
--- a/llvm/test/CodeGen/AArch64/vecreduce-and-legalization.ll
+++ b/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
diff --git a/llvm/test/CodeGen/X86/avx-cvt-3.ll b/llvm/test/CodeGen/X86/avx-cvt-3.ll
index 87eabd9cb5521..760db4af1f1b4 100644
--- a/llvm/test/CodeGen/X86/avx-cvt-3.ll
+++ b/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

[AZero13]

@RKSimon @arsenm Done!

[topperc]

You can share the loop for both cases by conditionally doing a std::swap of Zero/AllOnes and selecting the opcode.

[AZero13]

Eh, do I want to do that?

Looks more confusing.

[topperc]

Then put the loop in a lambda and pass opcode, AllOnes, and AllZeros as arguments?

[AZero13]

I would but this is a tiny one-line loop. It really is not worth the complexity.

[topperc]

I meant the getNode and getBuildVector too.