Date: Wed, 5 Jan 2011 09:28:30 -0500 From: John Baldwin <jhb@freebsd.org> To: Dimitry Andric <dim@freebsd.org> Cc: svn-src-head@freebsd.org, Alexander Best <arundel@freebsd.org>, Gleb Kurtsou <gleb.kurtsou@gmail.com>, src-committers@freebsd.org, svn-src-all@freebsd.org Subject: Re: svn commit: r216977 - in head/libexec/rtld-elf: amd64 i386 Message-ID: <201101050928.30748.jhb@freebsd.org> In-Reply-To: <4D2473C6.40102@FreeBSD.org> References: <201101042051.p04KpSGk054564@svn.freebsd.org> <201101050759.50877.jhb@freebsd.org> <4D2473C6.40102@FreeBSD.org>
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On Wednesday, January 05, 2011 8:36:06 am Dimitry Andric wrote: > On 2011-01-05 13:59, John Baldwin wrote: > >> Why not to add NO_HWFLOAT knob (or similar) into makefile > >> infrastructure. And set CFLAGS accordingly, depending on CC, arch, etc. > >> These flags are getting rather common in tree. > > > > It strikes me that we really want clang/gcc to have some sort of > > '-mno-hwfloat' so we don't keep having to add new flags in the future. > > This is not just about floats, clang can also use SSE/AVX instructions > for e.g. memset(), memcpy() and the like, or even for structure > assignments. Yes, but the thing that all these extensions have in common is that they use FPU state (i.e. subject to DNA traps, managed via *SAVE and *RSTOR, etc.) and that is the problem with using them in boot code or rtld. What I would want a -mno-hwfloat flag to do is to disable use of anything that would require working FPU state handling. -- John Baldwin
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