svn commit: r216977 - in head/libexec/rtld-elf: amd64 i386

[John Baldwin]

On Wednesday, January 05, 2011 7:19:10 am Gleb Kurtsou wrote:
> On (05/01/2011 01:16), Alexander Best wrote:
> > On Tue Jan  4 11, Dimitry Andric wrote:
> > > Author: dim
> > > Date: Tue Jan  4 20:51:28 2011
> > > New Revision: 216977
> > > URL: http://svn.freebsd.org/changeset/base/216977
> > > 
> > > Log:
> > >   On amd64 and i386, tell the compiler to refrain from generating SSE,
> > >   3DNow, MMX and floating point instructions in rtld-elf.
> > >   
> > >   Otherwise, _rtld_bind() (and whatever it calls) could possibly clobber
> > >   function arguments that are passed in SSE/3DNow/MMX/FP registers,
> > >   usually floating point values.  This can happen, for example, when clang
> > >   generates SSE code for memset() or memcpy() calls.
> > 
> > the sorting order for these flags seems to be:
> > 
> > -mno-mmx -mno-3dnow -mno-sse -mno-sse2 -mno-sse3
> > 
> > see 'grep -R "\-no-sse" /usr/src'. maybe the sorting order should stay
> > consistent?
> > 
> > also what's the status of clang? will these flags make sure that newer
> > cpu extension won't be activated? i checked
> > contrib/llvm/tools/clang/include/clang/Driver/Options.td
> > and clang has support for:
> > 
> > -m3dnowa
> > -mssse3
> > -msse4a
> > -msse4
> > -msse4_1
> > -msse4_2
> > -maes
> > -mavx
> > 
> > since these extensions only get set in a hand full of files maybe special
> > cases for CC == clang can be added.
> 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.

-- 
John Baldwin