void added a comment. In D54355#1328786 <https://reviews.llvm.org/D54355#1328786>, @jyknight wrote:
> In D54355#1328557 <https://reviews.llvm.org/D54355#1328557>, @void wrote: > > > The issue is that "`n`" is expecting an immediate value, but the result of > > the ternary operator isn't calculated by the front-end, because it doesn't > > "know" that the evaluation of `__builtin_constant_p` shouldn't be delayed > > (it being compiled at `-O0`). I suspect that this issue will also happen > > with the "`i`" constraint. > > > Indeed. We _do_ actually already know that in clang too, however -- clang > already knows that "n" requires an immediate, and does constant expression > evaluation for it, e.g. to expand constexpr functions. Grep for > "requiresImmediateConstant". I guess it's just not hooked up to the __b_c_p > correctly, though. > > (Note, as a workaround, you could use `|` instead of `||`, or put the > expression as the value of an enumeration constant). I looked at `requiresImmediateConstant`, but when I set it for `n` and `i` things broke all over the place. I sent out a patch for review. It's limited to `-O0`, since we can compile with optimizations without complaint. And there may be instances where it's necessary: inline void foo(int x) { asm("" : : "n" (__builtin_constant_p(n) ? 1 : -1)); } void bar() { foo(37); } Repository: rC Clang CHANGES SINCE LAST ACTION https://reviews.llvm.org/D54355/new/ https://reviews.llvm.org/D54355 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
