On Tue, 2005-05-10 at 08:26 -0400, Jakub Jelinek wrote:
> On Tue, May 10, 2005 at 02:19:32PM +0200, Ralf Ertzinger wrote:
> > On Tue, May 10, 2005 at 08:12:35AM -0400, Build System wrote:
> >
> > > - on x86 and x86_64, use -msse and -msse2 to accomodate newer compilers
> >
> > Not that I want to revive the whole .i386.rpm vs. i686.rpm discussion,
> > but... how does gcc handle these flags? Does it build alternative
> > code for processors that do not have these features? Or does the binary
> > not run on anything below PII or compatible?
>
> The way it is done in current rawhide's GIMP is definitely wrong.
> %ifarch %ix86 x86_64
> CFLAGS="%optflags -msse -msse2" CXXFLAGS="%optflags -msse -msse2" \
> %endif
> %configure \
>
> a) on x86-64 this is unnecessary, all x86-64's have -msse2 by default
> b) -msse2 implies -msse
ACK
> c) if you use -msse2 in CFLAGS for all files, you can't run the latest
> GIMP on e.g. Pentium2, or pre-x86_64 AMD chips.
> -msse2 should be ONLY used on sources that have SSE/SSE2 stuff in it,
> and GIMP should make sure that no routine from those sources will be
> ever called on pre-SSE2 chips
According to the gcc man page, you need to use "-mfpmath=sse" if you
want to get SSE/SSE2 instructions generated from FP code. As I
understand the manpage, "-msse" and the like only _enable_ its use in
inline assembler code. GIMP does check whether MMX/SSE etc. are
available when starting and only uses the optimized code paths if
possible.
Nils
--
Nils Philippsen / Red Hat / nphilipp@xxxxxxxxxx
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." -- B. Franklin, 1759
PGP fingerprint: C4A8 9474 5C4C ADE3 2B8F 656D 47D8 9B65 6951 3011
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