[llvm] [DAG][X86] Use pattern matching to simplify PSADBW+ADD combine (PR #147637)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: woruyu (woruyu)

<details>
<summary>Changes</summary>

### Summary

This patch refactors the add(psadbw(x, 0), psadbw(y, 0)) -> psadbw(x + y, 0) combine to use SelectionDAG::sd_match and SDPatternMatch matchers instead of manually checking opcodes and operands.

---
Full diff: https://github.com/llvm/llvm-project/pull/147637.diff


1 Files Affected:

- (modified) llvm/lib/Target/X86/X86ISelLowering.cpp (+9-11) 


``````````diff
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index fd617f7062313..9baa51ea36a86 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -57867,22 +57867,20 @@ static SDValue combineAdd(SDNode *N, SelectionDAG &DAG,
     }
   }
 
+  SDValue X, Y;
+
   // add(psadbw(X,0),psadbw(Y,0)) -> psadbw(add(X,Y),0)
   // iff X and Y won't overflow.
-  if (Op0.getOpcode() == X86ISD::PSADBW && Op1.getOpcode() == X86ISD::PSADBW &&
-      ISD::isBuildVectorAllZeros(Op0.getOperand(1).getNode()) &&
-      ISD::isBuildVectorAllZeros(Op1.getOperand(1).getNode())) {
-    if (DAG.willNotOverflowAdd(false, Op0.getOperand(0), Op1.getOperand(0))) {
-      MVT OpVT = Op0.getOperand(1).getSimpleValueType();
-      SDValue Sum =
-          DAG.getNode(ISD::ADD, DL, OpVT, Op0.getOperand(0), Op1.getOperand(0));
-      return DAG.getNode(X86ISD::PSADBW, DL, VT, Sum,
-                         getZeroVector(OpVT, Subtarget, DAG, DL));
-    }
+  if (sd_match(Op0, m_c_BinOp(X86ISD::PSADBW, m_Value(X), m_Zero())) &&
+      sd_match(Op1, m_c_BinOp(X86ISD::PSADBW, m_Value(Y), m_Zero())) &&
+      DAG.willNotOverflowAdd(/*IsSigned=*/false, X, Y)) {
+    MVT OpVT = X.getSimpleValueType();
+    SDValue Sum = DAG.getNode(ISD::ADD, DL, OpVT, X, Y);
+    return DAG.getNode(X86ISD::PSADBW, DL, VT, Sum,
+                       getZeroVector(OpVT, Subtarget, DAG, DL));
   }
 
   if (VT.isVector()) {
-    SDValue X, Y;
     EVT BoolVT = EVT::getVectorVT(*DAG.getContext(), MVT::i1,
                                   VT.getVectorElementCount());
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/147637