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From: "joseph at codesourcery dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/106117] Use of option -fexcess-precision for operation-by-operation emulation for _Float16 arithmetics. Date: Tue, 28 Jun 2022 21:14:56 +0000 [thread overview] Message-ID: <bug-106117-4-aN91KhkNET@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-106117-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106117 --- Comment #2 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- "none" was something I mentioned as a possible future argument when originally posting -fexcess-precision <https://gcc.gnu.org/legacy-ml/gcc-patches/2008-11/msg00105.html>. I still think it's the appropriate name for that case. (Doing +-*/ operations on float and then immediately converting back to _Float16 has exactly the same semantics as direct _Float16 arithmetic; float has sufficient precision that no double rounding issues arise; that doesn't apply to fma, however. The effect of excess precision is that e.g. in "a + b + c", the value of a + b with the range and precision of float is what gets added to c; there's no intermediate truncation of a + b to _Float16. But (_Float16)(a + b) + c would have such a truncation, because casts and conversion as if by assignment remove excess range and precision.)
next prev parent reply other threads:[~2022-06-28 21:14 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-06-28 13:17 [Bug c/106117] New: " Zahira.Ammarguellat at intel dot com 2022-06-28 15:04 ` [Bug c/106117] " rjmccall at gmail dot com 2022-06-28 21:14 ` joseph at codesourcery dot com [this message] 2022-06-28 23:44 ` crazylht at gmail dot com 2022-06-29 15:47 ` rjmccall at gmail dot com 2022-06-29 17:34 ` joseph at codesourcery dot com 2022-06-29 17:58 ` rjmccall at gmail dot com 2022-06-29 20:16 ` joseph at codesourcery dot com 2022-06-29 21:31 ` rjmccall at gmail dot com
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