Re: Add few cases to operand_equal_p

[Jan Hubicka <hubicka@ucw.cz>]

> > Will do if we agree on having this.
> > 
> > I know you would like ipa-icf to keep original bodies and use them for 
> > inlining declaring alias sets to be function local.  This is wrong plan.  
> > Consder:
> > 
> > void t(int *ptr)
> > {
> >   *ptr=1;
> > }
> > 
> > int a(int *ptr1, int *ptr2)
> > {
> >   int a = *ptr1;
> >   t(ptr2)
> >   return a+*ptr1;
> > }
> > 
> > long b(long *ptr1, int *ptr2)
> > {
> >   int a = *ptr1;
> >   t(ptr2)
> >   return a+*ptr1;
> > }
> > 
> > here aliasing leads to the two options to be optimizer differently:
> > a:
> > .LFB1:  
> >         .cfi_startproc
> >         movl    4(%esp), %edx
> >         movl    8(%esp), %ecx
> >         movl    (%edx), %eax
> >         movl    $1, (%ecx)
> >         addl    (%edx), %eax
> >         ret
> >         .cfi_endproc
> > b:
> > .LFB2:  
> >         .cfi_startproc
> >         movl    4(%esp), %eax
> >         movl    8(%esp), %edx
> >         movl    (%eax), %eax
> >         movl    $1, (%edx)
> >         addl    %eax, %eax
> >         ret
> >         .cfi_endproc
> > 
> > however with -fno-early-inlining the functions look identical (modulo alias
> > sets) at ipa-icf time.  If we merged a/b, we could get wrong code for a
> > even though no inlining of a or b happens.
> 
> First of all the return types don't agree so the testcase is bogus.

With -m32 they are types_compatible_p because they are of same size.
> 
> > So either we match the alias sets or we need to verify that the alias sets
> > permit precisely the same set of optimizations with taking possible inlining
> > into account.
> 
> Hmm, but then what makes ICF of a and b _with_ early inlining fail with
> -fno-tree-fre1?  The casts from *ptr1 to int in the 'long' case.

Dereferencing *ptr1 that has different alias set in each function.
> 
> So I think I need to see a real testcase and then I'll show you
> even with no inlining after ICF you get wrong-code thus it is a bug
> in ICF ;)

I added the inline only to make it clear that the loads won't be optimized
at early optimization time.
long a(int *ptr1, int *ptr2)
{
  int a = *ptr1;
  *ptr2=1;
  return a+*ptr1;
}

long b(long *ptr1, int *ptr2)
{
  int a = *ptr1;
  *ptr2=1;
  return a+*ptr1;
}

with -fno-tree-fre may be more real

a (int * ptr1, int * ptr2)
{
  int a;
  int D.1380;
  long int D.1379;
  int _4;
  long int _5;

  <bb 2>:
  a_2 = *ptr1_1(D);
  *ptr2_3(D) = 1;
  _4 = *ptr1_1(D);
  _5 = _4 + a_2;

<L0>:
  return _5;

}

;; Function b (b, funcdef_no=1, decl_uid=1375, cgraph_uid=1)

b (long int * ptr1, int * ptr2)
{
  int a;
  long int D.1383;
  long int D.1382;
  long int _4;
  long int _5;

  <bb 2>:
  a_2 = *ptr1_1(D);
  *ptr2_3(D) = 1;
  _4 = *ptr1_1(D);
  _5 = _4 + a_2;

<L0>:
  return _5;

}


> 
> > I also do not believe that TBAA should be function local.  I believe it is
> > useful to propagate stuff interprocedurally, like ipa-prop could be able to
> > propagate this:
> > 
> > long *ptr1;
> > int *ptr2;
> > t(int *ptr)
> > {
> >   return *ptr;
> > }
> > wrap(int *ptr)
> > {
> >  *ptr1=1;
> > }
> > call()
> > {
> >   return wrap (*ptr2);
> > }
> > 
> > and we could have ipa-reference style pass that collect alias sets 
> > read/written by a function and uses it during local optimization to 
> > figure out if there is a true dependence between function call and 
> > memory store.
> 
> Sure, but after ICF there is no IPA propagation...
Doesn't matter if you propagate before or after ICF. If you do before, ICF
would need to match/merge the alias set in optimization summary to be sure that
the functions are same.

Honza
> 
> Richard.
> 
> -- 
> Richard Biener <rguenther@suse.de>
> SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Dilip Upmanyu, Graham Norton, HRB 21284 (AG Nuernberg)