[llvm] [AMDGPU][SDAG] Legalise v2i32 or/xor/and instructions to make use of 64-bit wide instructions (PR #140694)

[Janek van Oirschot via llvm-commits]

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@@ -3225,29 +3225,51 @@ bool AMDGPUDAGToDAGISel::SelectVOP3ModsImpl(SDValue In, SDValue &Src,
   if (IsCanonicalizing)
     return true;
 
-  unsigned Opc = Src->getOpcode();
+  // v2i32 xor/or/and are legal. A vselect using these instructions as operands
+  // is scalarised into two selects with EXTRACT_VECTOR_ELT operands. Peek
+  // through the extract to the bitwise op.
+  SDValue PeekSrc =
+      Src->getOpcode() == ISD::EXTRACT_VECTOR_ELT ? Src->getOperand(0) : Src;
+  // Convert various sign-bit masks to src mods. Currently disabled for 16-bit
+  // types as the codegen replaces the operand without adding a srcmod.
+  // This is intentionally finding the cases where we are performing float neg
+  // and abs on int types, the goal is not to obtain two's complement neg or
+  // abs.
+  // TODO: Add 16-bit support.
+  unsigned Opc = PeekSrc.getOpcode();
   EVT VT = Src.getValueType();
   if ((Opc != ISD::AND && Opc != ISD::OR && Opc != ISD::XOR) ||
-      (VT != MVT::i32 && VT != MVT::i64))
+      (VT != MVT::i32 && VT != MVT::v2i32 && VT != MVT::i64))
     return true;
 
-  ConstantSDNode *CRHS = dyn_cast<ConstantSDNode>(Src->getOperand(1));
+  ConstantSDNode *CRHS = isConstOrConstSplat(PeekSrc ? PeekSrc->getOperand(1)
+                                                     : Src->getOperand(1));
   if (!CRHS)
     return true;
 
+  auto ReplaceSrc = [&]() -> SDValue {
+    if (Src->getOpcode() != ISD::EXTRACT_VECTOR_ELT)
+      return PeekSrc.getOperand(0);
+
+    SDValue LHS = PeekSrc->getOperand(0);
+    SDValue Index = Src->getOperand(1);
+    return CurDAG->getNode(ISD::EXTRACT_VECTOR_ELT, SDLoc(Src),
+                           Src.getValueType(), LHS, Index);
+  };
+
   // Recognise (xor a, 0x80000000) as NEG SrcMod.
   // Recognise (and a, 0x7fffffff) as ABS SrcMod.
   // Recognise (or a, 0x80000000) as NEG+ABS SrcModifiers.
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JanekvO wrote:

Update the recognise list for v2i32 case?

https://github.com/llvm/llvm-project/pull/140694