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[RFC] hot/cold attributes on labels


The motivation for this feature is to inform the compiler how
it may wish to layout blocks following an asm goto.

Since we can't annotate the asm goto with __builtin_expect,
putting some information onto the label decl itself seems a
reasonable solution.

Note that one needs to use -O2 and not -Os in order to see the
effects of this patch, since bb-reorder does nothing when
optimizing for size -- despite any explicit option enabling block
reordering.  This is probably a bug.  Of course, a size-sensitive
block reordering pass would be Even Cooler.

Comments?


r~

Attachment: d-hotcold-1
Description: Text document


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