On Mon, Feb 28, 2005 at 12:43:35PM +0000, Joern RENNECKE wrote:
> Well, even then, using of the cold section can increase the hot section
> size, depending on target, and for some
> targets the maximum supported distance of the cold section.
>
> For SH, using the cold section, you get (for non-PIC):
>
> L2: mov.l 0f,rn
> jmp @rn
> nop
> .balign 4
> 0: .long L3
>
> .coldsection:
> L3: mov.l 0f,rn
> jmp @rn
> mov #0,rn
> .balign 4
> 0: .long L1
>
> I.e. 10 to 12 bytes each in in hot and cold sections.
>
> Without the cold section, you need only 4 bytes:
> L2: bra L1
> mov #0,rn
>
> Note also, that in order to avoid the condjump-around-jump syndrome, L2 has
> to be within about +-256 bytes of the condjump.
> Should I do custom basic block reordering in machine_dependent_reorg to
> clean up
> the turds of hot and cold partitioning?
Its nothing SH specific, this particular example I'd say results in bigger code
in hot section on almost all arches.
The hot&cold partitioning patch simply must have some low bounds on how big
a cold BB must be if moving it to cold partition is worthwhile.
Jakub
