Date: Mon, 6 Jan 2020 11:17:44 +0300 (MSK) From: Alexander Monakov <amonakov@...ras.ru> To: musl@...ts.openwall.com Subject: Re: [PATCH] math: move x86_64 fabs, fabsf to C with inline asm On Sun, 5 Jan 2020, Rich Felker wrote: > I'm not sure if "this logic" carries over. fabs is a common operation > (ideally compiler would inline it anyway in the caller, though). > copysign not so much. Indeed, in practice we want compilers to recognize and inline simple math functions, especially on x86 where all float registers are call-clobbered. This makes it moot, except maybe for musl-internal uses like in floatscan.c, but there the right solution is probably to use __builtin_ forms if available. (to be clear: I think musl may not implement math functions in terms of math builtins because it might result in a circular dependency, but using builtins for complex math and higher-level functions like in floatscan.c should be fair game) For functions like sqrt GCC can be changed to default to -fno-math-errno on *-musl targets, as progress on flipping it globally seems slow. > Really I'm not even sure it makes sense to have the asm here at all > for fabs either, but perhaps with the gratuitous stack access in the > older-GCC version it does...? That's why I'm asking, the situation just looks ambiguous to me, I can't deduce the intent and I could imagine arguments both ways. I think I'd prefer a more inclusive playground. Please come up with some policy or guidelines if possible. Alexander
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.