llvm dev - Jun 2012 - [LLVMdev] Instruction Cleanup Questions

I am working on cleaning up some PPC code generation. Two questions:

1. Which pass is responsible for cleaning up self-moves:
   0x00000000100057c0 <+208>:   mr      r3,r3

2. Which pass is responsible for cleaning up unconditional jumps that
should be fall-throughs:
   0x0000000010005d88 <+1688>:  b       0x10005d8c <._Z11sfoo+1692>
   0x0000000010005d8c <+1692>:  ld r3,-32056(r2)

Maybe there are no such passes, but these things appear in optimized
code, and I'm trying to figure out why.

Thanks in advance,
Hal

-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory

On Wed, Jun 6, 2012 at 10:37 PM, Hal Finkel <hfinkel at anl.gov> wrote:
> I am working on cleaning up some PPC code generation. Two questions:
>
> 1. Which pass is responsible for cleaning up self-moves:
>   0x00000000100057c0 <+208>:   mr      r3,r3
>
> 2. Which pass is responsible for cleaning up unconditional jumps that
> should be fall-throughs:
>   0x0000000010005d88 <+1688>:  b       0x10005d8c
<._Z11sfoo+1692>
>   0x0000000010005d8c <+1692>:  ld r3,-32056(r2)
>
This should be handled by the MachineBlockPlacement (among others). Do you
have a reduced est case?
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Hi Hal,

On 07/06/2012 09:57, Chandler Carruth wrote:
> On Wed, Jun 6, 2012 at 10:37 PM, Hal Finkel <hfinkel at anl.gov 
> <mailto:hfinkel at anl.gov>> wrote:
>
>     I am working on cleaning up some PPC code generation. Two questions:
>
>     1. Which pass is responsible for cleaning up self-moves:
>       0x00000000100057c0 <+208>:   mr      r3,r3
>
and the RA should eliminate trivial copies.
>
>     2. Which pass is responsible for cleaning up unconditional jumps that
>     should be fall-throughs:
>       0x0000000010005d88 <+1688>:  b       0x10005d8c
<._Z11sfoo+1692>
>       0x0000000010005d8c <+1692>:  ld r3,-32056(r2)
>
>
> This should be handled by the MachineBlockPlacement (among others). Do 
> you have a reduced est case?
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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On Thu, 7 Jun 2012 00:57:20 -0700
Chandler Carruth <chandlerc at google.com> wrote:
> On Wed, Jun 6, 2012 at 10:37 PM, Hal Finkel <hfinkel at anl.gov>
wrote:
> 
> > I am working on cleaning up some PPC code generation. Two questions:
> >
> > 1. Which pass is responsible for cleaning up self-moves:
> >   0x00000000100057c0 <+208>:   mr      r3,r3
> >
> > 2. Which pass is responsible for cleaning up unconditional jumps
> > that should be fall-throughs:
> >   0x0000000010005d88 <+1688>:  b       0x10005d8c
<._Z11sfoo+1692>
> >   0x0000000010005d8c <+1692>:  ld r3,-32056(r2)
> >
> 
> This should be handled by the MachineBlockPlacement (among others).
> Do you have a reduced est case?
Chandler,

Thanks for the pointer! It turns out that this was a problem only in
the context of a local modification (and I could fix it by fixing
AnalyzeBranch and friends). That triggered other problems, but that's
another story...

 -Hal

-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory