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Re: A few simple DImode improvements
Bernd Schmidt <bernds@codesourcery.com> writes:
> On 06/28/2010 08:05 PM, Ian Lance Taylor wrote:
>
>> It's superfluous for a simple example like this one, but it's not
>> clearly superfluous in all cases. If register 68 here should wind up
>> being allocated to a floating point register which can't be SUBREG'ed,
>> then my concern is that taking a SUBREG is going to make it harder to
>> allocate the register correctly. In other words, the bitmap is not
>> irrelevant; it's a proxy for non-SImode register classes.
>
> That however applies to only one case in which bits can be set in that
> bitmap, the SUBREG case in find_decomposable_subregs. The normal case,
> I think, is that these bits come from occurrences of the reg that are in
> NOT_SIMPLE_MOVE, and I think this is irrelevant here. Do we need to
> keep track of two different bitmaps?
As far as I can see, it's not irrelevant there, because the pseudo might
be used somewhere else in a case which is NOT_SIMPLE_MOVE. E.g., a
floating point addition. What am I missing?
Ian