Re: RFA: New pass to delete unexecutable paths in the CFG

[Jeff Law <law@redhat.com>]

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On 11/09/11 15:10, Paolo Bonzini wrote:
> On 11/09/2011 06:53 PM, Jeff Law wrote:
>> My patch totally ignores the other code on the unexecutable path.
>> So we can miss externally visible side effects, if we were to
>> somehow get on the unexecutable path.  But that's the whole
>> point, in a conforming program we can't ever get on the
>> unexecutable path.
> 
> But if a subroutine call never returns, we wouldn't get to the
> undefined behavior in the first place.
Yea, I'd been pondering this aspect as well.  The cases that most
concern me would be aborts and infinite loops.

Stuff like EH is represented in the CFG and the control dependence
stuff would ensure we do the right thing.

I think there are enough unanswered questions that we should defer
this until after 4.7 branches.  Or at the least not have the option on
by default for 4.7, even if the issues raised in the threads are
addressed.


Jeff
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