http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51821
Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |NEW
AssignedTo|ebotcazou at gcc dot |unassigned at gcc dot
|gnu.org |gnu.org
--- Comment #15 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2012-01-12
13:20:01 UTC ---
> Please look into "peep2_insn_data[from].live_before" array and
> "peep2_insn_data[from+1].live_before". You will see that the difference is
> only in ax register. This array is set with df_simulate_one_insn_forwards,
> and this particular function indeed clears set hard registers when REG_UNUSED
> note is found (this is OK for live analysis).
I did and saw exactly that. The problem is that I missed the REG_UNUSED note
for edx among the 3 other notes (and also that you specifically mentioned it in
the comment #9). OK, DF appears to be correct here, or at least consistent.
> and since the difference between live registers before/after the insn is only
> ax register, the loop claims others (including dx reg) as "available". The
> calculation, which register is _NOT_CLOBBERED_ by the pattern from "live"
> information is thus not enough, we have to look into the pattern and mark all
> hard registers that are set or clobbered as _NOT_AVAILABLE_ in the register
> set.
Yes, this seems to be the correct approach.
