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Re: -fssa kicks butt on alphaev6 ieee floating point code
- To: rth at cygnus dot com (Richard Henderson)
- Subject: Re: -fssa kicks butt on alphaev6 ieee floating point code
- From: Brad Lucier <lucier at popov dot math dot purdue dot edu>
- Date: Thu, 16 Mar 2000 13:37:52 -0500 (EST)
- Cc: lucier at math dot purdue dot edu, gcc at gcc dot gnu dot org, feeley at iro dot umontreal dot ca
- Reply-To: lucier at math dot purdue dot edu
>
> On Thu, Mar 16, 2000 at 10:43:23AM -0500, Brad Lucier wrote:
> > -fssa definitely helps IEEE floating-point register allocation on
> > alphaev6.
>
> It's an accident. What it means is that our register allocator
> really bites.
I disagree completely.
The register allocator cannot deal well with the constraint
that a source operand cannot overlap a destination operand.
Translating the intermediate representation to a canonical
form (which is what translating to SSA and back again does)
to help the register allocator in this case seems a perfectly
reasonable strategy. (Which is why I thought of trying this
in the first place.)
Brad