jcranmer-intel added a comment. In D136568#3878104 <https://reviews.llvm.org/D136568#3878104>, @Izaron wrote:
> The online documentation > (https://en.cppreference.com/w/cpp/numeric/math/ilogb) says: > > 1. If the correct result is greater than INT_MAX or smaller than INT_MIN, > FE_INVALID is raised. > 2. If arg is ±0, ±∞, or NaN, FE_INVALID is raised. > 3. In all other cases, the result is exact (FE_INEXACT is never raised) and > the current rounding mode is ignored > > The first point seemingly never occur, because llvm's `ilogb` return type is > `int`. > The second point is handled as expected (`APFloatTest.cpp` checks it) FWIW, I would be slightly wary of relying on cppreference as definitive for niche semantic issues like this, although it is correct in this case. C2x is actually pretty well-organized in Annex F, and enumerates most of the corner cases specifically in every function. ================ Comment at: clang/lib/AST/ExprConstant.cpp:12452 + int Ilogb; + if (APFloat::opStatus St = ilogb(F, Ilogb); !isConstantOpStatus(St)) + return false; ---------------- `long double` is `ppc_fp128` on at least some PPC targets, and while I'm not entirely certain of what `ilogb` properly returns in the corner cases of the `ppc_fp128`, I'm not entirely confident that the implementation of `APFloat` is correct in those cases. I'd like someone with PPC background to comment in here. ================ Comment at: clang/test/Sema/constant-builtins-ilogb.cpp:13 + static_assert(!__builtin_constant_p(FUNC(T(Inf)))); \ + static_assert(!__builtin_constant_p(FUNC(T(NegInf)))); + ---------------- Test of smallest subnormal and largest finite number would also be useful. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D136568/new/ https://reviews.llvm.org/D136568 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
