[llvm] [InstCombine] Fold umax(nuw_mul(x, C0), x + 1) into (x == 0 ? 1 : nuw_mul(x, C0)) (PR #123468)

[via llvm-commits]

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@@ -1847,6 +1847,37 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
         return CastInst::Create(Instruction::ZExt, NarrowMaxMin, II->getType());
       }
     }
+    // If C0 is not 0:
+    //   umax(nuw_shl(x, C0), x + 1) -> x == 0 ? 1 : nuw_shl(x, C0)
+    // If C0 is not 0 or 1:
+    //   umax(nuw_mul(x, C0), x + 1) -> x == 0 ? 1 : nuw_mul(x, C0)
+    ConstantInt *C0;
+    bool isShl = false;
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Ruhung wrote:

Removed isShl cause it is redundant.

https://github.com/llvm/llvm-project/pull/123468