Date: Sat, 31 Dec 2011 21:04:42 -0500 From: David Schultz <das@FreeBSD.ORG> To: Dimitry Andric <dim@FreeBSD.ORG> Cc: svn-src-head@FreeBSD.ORG, svn-src-all@FreeBSD.ORG, src-committers@FreeBSD.ORG Subject: Re: svn commit: r228801 - head Message-ID: <20120101020442.GA94452@zim.MIT.EDU> In-Reply-To: <201112221503.pBMF3m0w021930@svn.freebsd.org> References: <201112221503.pBMF3m0w021930@svn.freebsd.org>
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On Thu, Dec 22, 2011, Dimitry Andric wrote: > Remove -mfancy-math from LIB32CPUFLAGS for amd64. It has been default > for our gcc since more than three years (see r181534, which is also in > stable/9 and stable/8). This flag used to be for the benefit of the old > in-kernel math emulator, which was removed more than eight years ago. Quite the opposite, actually. gcc/freebsd used to be hard-coded to use -mno-fancy-math-387 by default, which was really only appropriate for FPUless x86 chips back when FreeBSD supported them. The makefile setting overrides the old gcc default. The flag isn't "for the benefit of the in-kernel math emulator"; it's actually to reap the benefits of *not* having an in-kernel math emulator! Do you know if clang has the correct default here, or if it picked up trunk gcc's bogus default? It doesn't seem to support the flag to change the behavior, and it seems to default to -mno-fancy-math-387. (The flag should only affect things when -ffast-math is also specified.)
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