[llvm] [DAG] Fold nested add(add(reduce(a), b), add(reduce(c), d)) (PR #115150)

[David Green via llvm-commits]

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@@ -17107,12 +17129,15 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
                            DAG.getConstantFP(4.0, DL, VT));
       }
     }
+  } // enable-unsafe-fp-math && AllowNewConst
 
+  if (((Options.UnsafeFPMath && Options.NoSignedZerosFPMath) ||
+       (Flags.hasAllowReassociation() && Flags.hasNoSignedZeros()))) {
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davemgreen wrote:

Do you mean do it in another later patch? It felt like a relatively small change, and will only allow the transform a little later after legalization. It can be difficult to test that kind of thing in SDAG.

https://github.com/llvm/llvm-project/pull/115150