[PATCH] D51929: [DAGCombiner] use UADDO to optimize saturated unsigned add

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:7312-7323
+    SDValue Cond0 = N0.getOperand(0), Cond1 = N0.getOperand(1);
+    ISD::CondCode CC = cast<CondCodeSDNode>(N0.getOperand(2))->get();
+
     // select x, y (fcmp lt x, y) -> fminnum x, y
     // select x, y (fcmp gt x, y) -> fmaxnum x, y
     //
     // This is OK if we don't care about what happens if either operand is a
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Seems like some of this can be a preparatory NFC commit?


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Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:7332-7333
+    if (!LegalOperations && TLI.isOperationLegalOrCustom(ISD::UADDO, VT) &&
+        CC == ISD::SETUGT && N0.hasOneUse() && isAllOnesConstant(N1) &&
+        N2.getOpcode() == ISD::ADD && Cond0 == N2.getOperand(0)) {
+      auto *C = dyn_cast<ConstantSDNode>(N2.getOperand(1));
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I feel like this needs a comment with IR example..


https://reviews.llvm.org/D51929