[llvm] [RISCV] Reverse (add x, (zext c)) back to (select c, (add x, 1), x) (PR #87236)

[Luke Lau via llvm-commits]

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@@ -52,12 +52,60 @@ class RISCVCodeGenPrepare : public FunctionPass,
   }
 
   bool visitInstruction(Instruction &I) { return false; }
+  bool visitBinaryOperator(BinaryOperator &BO);
   bool visitAnd(BinaryOperator &BO);
   bool visitIntrinsicInst(IntrinsicInst &I);
 };
 
 } // end anonymous namespace
 
+/// InstCombine will canonicalize selects of binary ops where the identity is
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lukel97 wrote:

Just seemed like the right place to put it since it's undoing an InstCombine transform. I don't think there should be any issue doing it as a DAG combine. Would that be preferred?

https://github.com/llvm/llvm-project/pull/87236