[PATCH] D141211: Add an AArch64 DAG combine to eliminate redundant truncates feeding into DUPLANE32 operations.

[Owen Anderson via Phabricator via llvm-commits]

resistor created this revision.
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Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D141211

Files:
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/test/CodeGen/AArch64/trunc-v1i64.ll


Index: llvm/test/CodeGen/AArch64/trunc-v1i64.ll
===================================================================
--- llvm/test/CodeGen/AArch64/trunc-v1i64.ll
+++ llvm/test/CodeGen/AArch64/trunc-v1i64.ll
@@ -21,7 +21,7 @@
 
 define <2 x i32> @test_v1i32_1(<1 x i64> %in0) {
 ; CHECK-LABEL: test_v1i32_1:
-; CHECK: xtn v0.2s, v0.2d
+; CHECK-NOT: xtn
 ; CHECK-NEXT: dup v0.2s, v0.s[0]
   %1 = shufflevector <1 x i64> %in0, <1 x i64> undef, <2 x i32> <i32 undef, i32 0>
   %2 = trunc <2 x i64> %1 to <2 x i32>
Index: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -21228,6 +21228,29 @@
   return DAG.getNode(ISD::OR, DL, VT, Sel, SelInv);
 }
 
+static SDValue performDupLane32Combine(SDNode *N, SelectionDAG &DAG) {
+  SDValue Insert = N->getOperand(0);
+  if (Insert.getOpcode() != ISD::INSERT_SUBVECTOR) return SDValue();
+  if (!Insert.getOperand(0).isUndef()) return SDValue();
+
+  uint64_t IdxDupLane = N->getConstantOperandVal(1);
+  uint64_t IdxInsert = Insert.getConstantOperandVal(2);
+  if (IdxInsert != 0 || IdxDupLane != 0) return SDValue();
+
+  SDValue Truncate = Insert.getOperand(1);
+  if (Truncate.getOpcode() != ISD::TRUNCATE) return SDValue();
+
+  EVT InsertVT = Insert.getValueType();
+  EVT WideVT = Truncate.getOperand(0).getValueType();
+  if (InsertVT.getSizeInBits() != WideVT.getSizeInBits()) return SDValue();
+
+  SDLoc DL(N);
+  SDValue Bitcast =
+      DAG.getNode(ISD::BITCAST, DL, InsertVT, Truncate.getOperand(0));
+  return DAG.getNode(AArch64ISD::DUPLANE32, DL, N->getValueType(0), Bitcast,
+                     N->getOperand(1));
+}
+
 static SDValue performDupLane128Combine(SDNode *N, SelectionDAG &DAG) {
   EVT VT = N->getValueType(0);
 
@@ -21353,6 +21376,8 @@
     return performCSELCombine(N, DCI, DAG);
   case AArch64ISD::DUP:
     return performDUPCombine(N, DCI);
+  case AArch64ISD::DUPLANE32:
+    return performDupLane32Combine(N, DAG);
   case AArch64ISD::DUPLANE128:
     return performDupLane128Combine(N, DAG);
   case AArch64ISD::NVCAST:


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