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Re: [patch][rfc] Hookize SMALL_REGISTER_CLASSES, make SSE register classes not small


On Wed, Dec 10, 2008 at 2:38 AM, Michael Meissner
<meissner@linux.vnet.ibm.com> wrote:
> Back when I was at AMD, I often times thought about making
> SMALL_REGISTER_CLASSES false for x86_64 bit (where you have more registers),
> but I never got around to doing it.

We tried it at SuSE a couple of years ago.  It does not work.  There
are too many instructions that require special registers. But the SSE
instructions don't have special requirements.

That's exactly why I decided to try to make SMALL_REGISTER_CLASSES
depend no machine mode.  It's a safe bet that the compiler doesn't
have to walk on eggs for a register in an SSE mode (and
AFAIU-the-x86_64-instruction-set, also not for 64-bit integer
instructions?).

Gr.
Steven


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