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Re: lower subreg optimization


On Tue, Apr 06, 2010 at 11:55:01AM -0700, Ian Lance Taylor wrote:
> Nathan Froyd <froydnj@codesourcery.com> writes:
> > Compiling anything that uses doubles on powerpc e500v2 produces awful
> > code due in part to lower-subregs (the register allocator doesn't help,
> > either, but that's a different story).
> 
> I doubt that a target hook is required to avoid this.  Perhaps
> simple_move_operand should reject a mode changing subreg when the two
> modes are !MODE_TIEABLE_P.

Ah, thanks for the pointer. I'll try poking at that.

> This code is sort of weird, though; why the conversion from DImode to
> DFmode?

Welcome to the wonderful world of e500, which has floating-point
instructions operating on the general purpose registers.

-Nathan


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