[llvm] [DAG] foldABSToABD - fallback to value tracking if the (ABS (SUB LHS, RHS)) operands aren't extended (PR #147053)

[David Green via llvm-commits]

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@@ -11402,16 +11402,25 @@ SDValue DAGCombiner::foldABSToABD(SDNode *N, const SDLoc &DL) {
   SDValue AbsOp0 = N->getOperand(0);
   unsigned Opc0 = Op0.getOpcode();
 
-  // Check if the operands of the sub are (zero|sign)-extended.
-  // TODO: Should we use ValueTracking instead?
+  // Check if the operands of the sub are (zero|sign)-extended, otherwise
+  // fallback to ValueTracking.
   if (Opc0 != Op1.getOpcode() ||
       (Opc0 != ISD::ZERO_EXTEND && Opc0 != ISD::SIGN_EXTEND &&
        Opc0 != ISD::SIGN_EXTEND_INREG)) {
     // fold (abs (sub nsw x, y)) -> abds(x, y)
-    // Don't fold this for unsupported types as we lose the NSW handling.
-    if (AbsOp0->getFlags().hasNoSignedWrap() && hasOperation(ISD::ABDS, VT) &&
-        TLI.preferABDSToABSWithNSW(VT)) {
-      SDValue ABD = DAG.getNode(ISD::ABDS, DL, VT, Op0, Op1);
+    if (hasOperation(ISD::ABDS, VT)) {
+      // Don't fold this for unsupported types as we lose the NSW handling.
+      if (TLI.preferABDSToABSWithNSW(VT) &&
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davemgreen wrote:

Could still be a single `if`, if you don't plan to expand them later.

https://github.com/llvm/llvm-project/pull/147053