[llvm] [RISCV] Fold subtraction if above threshold to Zbb `minu` (PR #134235)

[Craig Topper via llvm-commits]

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@@ -14895,6 +14895,19 @@ static SDValue performSUBCombine(SDNode *N, SelectionDAG &DAG,
   if (SDValue V = combineSubShiftToOrcB(N, DAG, Subtarget))
     return V;
 
+  if (Subtarget.hasStdExtZbb()) {
+    // fold (sub x, (select (ult x, y), 0, y)) -> (umin x, (sub x, y))
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topperc wrote:

Is there something that prevents this from being

(sub x, (select (uge y, x), y, 0)?

https://github.com/llvm/llvm-project/pull/134235