[clang] [clang] Implement __builtin_{clzg,ctzg} (PR #83431)

[Eli Friedman via cfe-commits]

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@@ -3157,7 +3177,15 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     if (Result->getType() != ResultType)
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efriedma-quic wrote:

I was more thinking of the opposite: we don't need to make the result of the clz defined if we're not using it.

https://github.com/llvm/llvm-project/pull/83431