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