[PATCH, rs6000] -mno-sched-prolog vs .debug_frame

[Richard Henderson <rth at redhat dot com>]

On 07/05/2011 04:30 PM, David Edelsohn wrote:
> On Fri, Jul 1, 2011 at 8:31 PM, Richard Henderson <rth@redhat.com> wrote:
>> The implementation of TARGET_SCHED_PROLOG is incompatible with
>> some coming changes to how dwarf2 cfi is to be generated.
>>
>> Some suggested solutions are:
>>
>>  (1) Remove the option.  Is it really that interesting
>>     beyond -mno-sched-insns2?
>>
>>  (2) Emit blockage insns at the end of the prologue
>>     and the beginning of the epilogue.  That'll prevent
>>     the majority of the changes that scheduling could
>>     introduce.
>>
>>  (3) Emit the prologue and epilogue somewhere after
>>     scheduling and before final.  E.g. md_reorg.
>>
>> I'd be delighted if someone could actually implement one
>> of these changes at some point in the next week, but
>> failing that please weigh in on the preferred solution.
> 
> As we discussed on IRC, (1) with and eventual implementation of (2) are okay.

Implements (2).  I emit the blockage in the expanders and not in
rs6000_emit_{pro,epi}logue because the functions contain several
sets of early-returns.  Putting it here avoids any tricky code
rearrangement.

Tested via cross-compile, and as they say, "what could go wrong?"

Ok?


r~

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