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Re: dangerous cleverness? ppc int<->float conversions, subreg
- To: Joern Rennecke <amylaar at onetel dot net dot uk>
- Subject: Re: dangerous cleverness? ppc int<->float conversions, subreg
- From: Jan Hubicka <jh at suse dot cz>
- Date: Sat, 27 Oct 2001 14:43:28 +0200
- Cc: Zack Weinberg <zack at codesourcery dot com>, Richard Henderson <rth at redhat dot com>, gcc at gcc dot gnu dot org
- References: <20011026122447.G14501@codesourcery.com> <200110270125.CAA25058@meolyon.local>
> Zack Weinberg wrote:
> > On Thu, Oct 25, 2001 at 04:29:45PM +0100, Joern Rennecke wrote:
> > > in elf flags or similar? FWIW the SH gas alrweady has to do this, to keep
> > ... keep what?
> keep sh3e and sh-dsp opcodes apart.
> > In addition to the block move issue, I need to figure out how to fix
> > the old varargs implementation and sjlj eh so they don't touch
> > floating point registers unless absolutely necessary. Clues in that
> > direction would be appreciated too.
> For the old varargs implementation, you could always use statement
> expressions in the macor definitions, and call magic builtin functions
> when a floating point argument is used; you can then have the compiler
> set a flag when the magic builtin is seen. And then you'd still have to
> track when an entire va_list is passed.
What I am doing on x86_64 is to save SSA (floating point) registers to special
alias set. Then when there are no references to that set, the compiler
manages to remove the stores as dead itself.