Re: [Valgrind-developers] can I force IRSB to be acyclic?

[Konstantin S. <kon...@gm...>]

On Tue, Apr 27, 2010 at 7:46 PM, Julian Seward <js...@ac...> wrote:
> On Tuesday 27 April 2010, Konstantin Serebryany wrote:
>> Below is a dump of IRSB.
>> Just look at these statements:
>>    ------ IMark(0x4C1C3A4, 4) ------
>> ...
>>    if (t20) goto {Boring} 0x4C1C3B4:I64
>>    goto {Boring} 0x4C1C3A4:I64
>>
>> As you can see, this IRSB represents a loop (label 0x4C1C3A4).
>
> Yes.
>
>> I want valgrind to never create such IRSBs with a loop (but instead break
>> them into several SBs).
>> Is that possible?
>
> Uh .. I'm still confused.  Mostly because I can't see how you can
> guarantee to avoid making IRSBs which have a conditional branch
> back to the start.  For example, consider the translation of
> "rep movsb"; we have to create a straight line block of IR which
> jumps back to the start.
>
> Can you show an IR example which illustrates what you mean?
> eg, what does the IR that you want look like, for this example?


Consider an SB which looks like this:

BB1:
L:
  code;
goto L;

Can valgrind create two SBs for this case?
BB1:
L:
  code;
goto L1

BB2:
L1:
  goto L


--kcc

>
> J
>