Hi! On Wed, Apr 25, 2018 at 11:28:44AM -0500, Kelvin Nilsen wrote: > >>> 4. Remove descriptions of built-in function that do not belong in this > >>> section because the > >>> built-in functions are generic (not specific to PowerPC): > >>> __builtin_fabsq, > >>> __builtin_copysignq, __builtin_infq, __builtin_huge_valq, > >>> __builtin_nanq, > >>> __builtin_nansq, __builtin_sqrtf128, __builtin_fmaf128. > > > > Are these described in a generic place, then? I don't see it? > > > >> +@node Low-Level PowerPC Built-in Functions Available on all Targets > >> +@subsubsection Low-Level PowerPC Built-in Functions Available on all > >> Targets > > Regarding your question about "q functions", the existing gcc.pdf document > is a bit confusing. Here's what I can figure out. > > The following are mentioned only in "Section 6.59.33: x86 Built-in Functions" > > __float128 __builtin_fabsq (__float128) > __float128 __builtin_copysignq (__float128, __float128) > __float128 __builtin_infq (void) > __float128 __builtin_huge_valq (void) > __float128 __builtin_nanq (void) > __float128 __builtin_nansq (void) > > As far as I can tell, these should not be documented as specific to x86, but > should be documented as generic across all platforms. This is an issue > outside > the realm of PowerPC maintenance. > > If we want to preserve mention of these "q" functions, I would recommend > changing the text that introduces them. Currently, it says: > > "Previous versions of GCC supported some 'q' builtins for IEEE 128-bit > floating point. These functions are now mapped into the equivalent > 'f128' builtin functions."
I think that is a bit confusing, especially if you are not familiar with those builtins already. > If the description of these built-ins is not moved to a more generic context, > I would prefer to replace this section with something like: > > The following functions, which are also supported on x86 targets, are > supported > if the -mfloat128 option is specified: > > __float128 __builtin_fabsq (__float128) > __float128 __builtin_copysignq (__float128, __float128) > __float128 __builtin_infq (void) > __float128 __builtin_huge_valq (void) > __float128 __builtin_nanq (void) > __float128 __builtin_nansq (void) That looks fine. > Regarding your question about f128 functions, these are "supposed to be" > documented in "Section 6.58: Other Built-in Functions Provided by GCC". > Search for the phrase "corresponding to the TS 18661-3 functions". We > should add "__builtin_sqrtf128 and builtin_fmaf128 to the list of functions > described this way. These may not be the only omissions. Should we push > for fixing this documentation in Section 6.58 instead of keeping it in > the PowerPC section? Well, are they supported on other targets? > It is difficult to find the official TS 18661-3 document, and > I'm not sure where to look for a list of which of the functions are > currently implemented by gcc. I found this "diff" document, which provides > some hints. Given that this standard is not easily accessible, perhaps the > generic built-in documentation should provide a little more information? > > See http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1945.pdf That is the document I use. See other mail for other resources :-) Segher
