[PATCH] D133850: [AArch64] Improve codegen for "trunc <4 x i64> to <4 x i8>" for all cases

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Fixes #57502


https://reviews.llvm.org/D133850

Files:
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/test/CodeGen/AArch64/pr57502.ll


Index: llvm/test/CodeGen/AArch64/pr57502.ll
===================================================================
--- llvm/test/CodeGen/AArch64/pr57502.ll
+++ llvm/test/CodeGen/AArch64/pr57502.ll
@@ -6,9 +6,8 @@
 define void @trunc(ptr %addr, <4 x i64> %input) {
 ; CHECK-LABEL: trunc:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    xtn v1.2s, v1.2d
-; CHECK-NEXT:    xtn v0.2s, v0.2d
-; CHECK-NEXT:    uzp1 v0.4h, v0.4h, v1.4h
+; CHECK-NEXT:    uzp1 v0.4s, v0.4s, v1.4s
+; CHECK-NEXT:    xtn v0.4h, v0.4s
 ; CHECK-NEXT:    addv h0, v0.4h
 ; CHECK-NEXT:    fmov w8, s0
 ; CHECK-NEXT:    strb w8, [x0]
Index: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -17576,6 +17576,30 @@
     }
   }
 
+  // uzp1(trunc v1, trunc v2) => trunc(uzp1 v1, v2)
+  if (Op0.getOpcode() == ISD::BITCAST && Op1.getOpcode() == ISD::BITCAST &&
+      Op0.getOperand(0).getOpcode() == ISD::TRUNCATE &&
+      Op1.getOperand(0).getOpcode() == ISD::TRUNCATE) {
+
+    SDValue OrigOp0 = Op0.getOperand(0).getOperand(0);
+    SDValue OrigOp1 = Op1.getOperand(0).getOperand(0);
+    EVT CastResultType = MVT::Other;
+
+    if (OrigOp0.getValueType().getSimpleVT().SimpleTy == MVT::v2i64)
+      CastResultType = MVT::v4i32;
+
+    if (CastResultType != MVT::Other) {
+      SDValue BitCastResult0 =
+          DAG.getNode(ISD::BITCAST, DL, CastResultType, OrigOp0);
+      SDValue BitCastResult1 =
+          DAG.getNode(ISD::BITCAST, DL, CastResultType, OrigOp1);
+
+      SDValue ConcatResult = DAG.getNode(AArch64ISD::UZP1, DL, CastResultType,
+                                         BitCastResult0, BitCastResult1);
+      return DAG.getNode(ISD::TRUNCATE, DL, ResVT, ConcatResult);
+    }
+  }
+
   return SDValue();
 }
 


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