[llvm] [AArch64][Codegen]Transform saturating smull to sqdmulh (PR #143671)

David Green via llvm-commits llvm-commits at lists.llvm.org
Tue Jul 1 09:23:41 PDT 2025


================
@@ -20918,6 +20928,79 @@ static SDValue performBuildVectorCombine(SDNode *N,
   return SDValue();
 }
 
+// A special combine for the sqdmulh family of instructions.
+// smin( sra ( mul( sext v0, sext v1 ) ), SHIFT_AMOUNT ),
+// SATURATING_VAL ) can be reduced to sext(sqdmulh(...))
+static SDValue trySQDMULHCombine(SDNode *N, SelectionDAG &DAG) {
+
+  if (N->getOpcode() != ISD::TRUNCATE)
----------------
davemgreen wrote:

Edit: You might need a setTargetDAGCombine(ISD::SMIN);

https://github.com/llvm/llvm-project/pull/143671


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