aaron.ballman added a comment. In D155546#4521383 <https://reviews.llvm.org/D155546#4521383>, @tbaeder wrote:
> In D155546#4510691 <https://reviews.llvm.org/D155546#4510691>, @aaron.ballman > wrote: > >> I'd like to see test coverage for treatment of NaNs. According to the C23 >> standard, a quiet NaN is treated as missing data for fmax and fmin; so if >> there's a quiet NaN and a numeric value, the numeric value it's what's >> returned. > > Isn't this always the case? > > constexpr float qNan = __builtin_nan(""); > > constexpr float min = __builtin_fmin(qNan, 1); > static_assert(min == 1); > constexpr float min2 = __builtin_fmin(1, qNan); > static_assert(min2 == 1); > > works already. I believe it generally is always true, but it's good to have the test coverage. > It's not yet clear to me what happens when any of these functions encounter a > signaling NaN at compile time. CC @hubert.reinterpretcast @jcranmer-intel > @rsmith I asked some members of the C floating point study group and it turns out signaling NaN is a bit weirder than I had realized. Basically, a signal should be raised during any "mathematical operation" unless the operation is explicitly defined to *not* raise the signal or the implementation defines that it doesn't signal under those circumstances. e.g., float some_float_nan(); // Produces a signaling NaN of float type double d = some_float_nan(); // Subject to F.3p4, might signal, might not float f = some_float_nan(); // Also subject to F.3p4 sizeof(some_float_nan()); // No signal, unevaluated operand isnan(some_float_nan()); // No signal, allowed explicitly by standard some_float_nan() + 12; // Signals (void)some_float_nan(); // No signal, no mathematical operation (int)some_float_nan(); // Subject to Annex F, might or might not signal Also, translation-time initialization with SNAN macros don’t convert to a quiet NaN (which is the return value for the default handling of the signal due to a signaling NaN operand of a runtime conversion). Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D155546/new/ https://reviews.llvm.org/D155546 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
