[llvm] [RISC-V][ISel] Remove redundant czero.eqz like 'czero.eqz a0, a0, a0' (PR #90208)

[Zhijin Zeng via llvm-commits]

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@@ -7503,6 +7503,17 @@ SDValue RISCVTargetLowering::lowerSELECT(SDValue Op, SelectionDAG &DAG) const {
       return DAG.getNode(ISD::ADD, DL, VT, CMOV, RHSVal);
     }
 
+    // c = setcc f, 0, seteq
+    // (select c, t, f) -> (or f, (czero_nez t, f))
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zengdage wrote:

Thanks for your suggestion. I have changed the code in `RISCVTargetLowering: : PerformDAGCombine`.  It does get better.

https://github.com/llvm/llvm-project/pull/90208