[cfe-dev] Handling of builtin_constant_p

[陳韋任 via cfe-dev]

`grep -r "builtin_constant_p"` under tool/clang shows some hints. For
example, check VisitConditionalOperator if you want.

HTH,
chenwj

2017-10-27 11:22 GMT+08:00 Bharathi Seshadri via cfe-dev <
cfe-dev at lists.llvm.org>:

> Hi,
>
> I'm trying to understand where __builtin_constant_p is folded in the
> front-end. It appears to be handled differently when placed in an if
> condition or in a conditional expression.
>
> In the example below, I see that it is folded in
> CodeGenFunction::EmitBuiltinExpr() in CGBuiltin.cpp
> int x = __builtin_constant_p(100);
>
> But for cases like the ones below, it appears to be folded much
> earlier and it doesn't reach EmitBuiltinExpr().
>
> int x = __builtin_constant_p(100)? 10: 20;
>
> if (__builtin_constant_p(100)) { ... }
>
> Any pointers on what functions to look up for the above case would be
> very helpful.
>
> Thanks,
> Bharathi
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-- 
Wei-Ren Chen (陳韋任)
Homepage: https://people.cs.nctu.edu.tw/~chenwj
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