[llvm] [DAGCombiner][VP] Add DAGCombine for VP_MUL (PR #80105)

[Shao-Ce SUN via llvm-commits]

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@@ -4428,26 +4434,27 @@ SDValue DAGCombiner::visitMUL(SDNode *N) {
 
     // FIXME: If the input is something that is easily negated (e.g. a
     // single-use add), we should put the negate there.
-    return DAG.getNode(ISD::SUB, DL, VT,
-                       DAG.getConstant(0, DL, VT),
-                       DAG.getNode(ISD::SHL, DL, VT, N0,
-                            DAG.getConstant(Log2Val, DL, ShiftVT)));
+    return matcher.getNode(
+        ISD::SUB, DL, VT, DAG.getConstant(0, DL, VT),
+        matcher.getNode(ISD::SHL, DL, VT, N0,
+                        DAG.getConstant(Log2Val, DL, ShiftVT)));
   }
 
   // Attempt to reuse an existing umul_lohi/smul_lohi node, but only if the
   // hi result is in use in case we hit this mid-legalization.
-  for (unsigned LoHiOpc : {ISD::UMUL_LOHI, ISD::SMUL_LOHI}) {
-    if (!LegalOperations || TLI.isOperationLegalOrCustom(LoHiOpc, VT)) {
-      SDVTList LoHiVT = DAG.getVTList(VT, VT);
-      // TODO: Can we match commutable operands with getNodeIfExists?
-      if (SDNode *LoHi = DAG.getNodeIfExists(LoHiOpc, LoHiVT, {N0, N1}))
-        if (LoHi->hasAnyUseOfValue(1))
-          return SDValue(LoHi, 0);
-      if (SDNode *LoHi = DAG.getNodeIfExists(LoHiOpc, LoHiVT, {N1, N0}))
-        if (LoHi->hasAnyUseOfValue(1))
-          return SDValue(LoHi, 0);
+  if (!IsVP)
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sunshaoce wrote:

It's better to wrap this with curly braces.

https://github.com/llvm/llvm-project/pull/80105