ipa-visibility TLC 2/n

[Jan Hubicka]

> Honza,
> 
> For example g++.dg/abi/vcall1.C fails at a call in a "localalias"
> function, which jumps to a bad location:
> 
> 
> (gdb) up
> #1  0x100004c0 in B::B() [clone .localalias.2] ()
> (gdb) x/16i $pc-32
>    0x100004a0 <_ZN1BC2Ev+156>:  add     r10,r10,r8
>    0x100004a4 <_ZN1BC2Ev+160>:  mr      r3,r10
>    0x100004a8 <_ZN1BC2Ev+164>:  stw     r2,20(r1)
>    0x100004ac <_ZN1BC2Ev+168>:  lwz     r10,0(r9)
>    0x100004b0 <_ZN1BC2Ev+172>:  lwz     r11,8(r9)
>    0x100004b4 <_ZN1BC2Ev+176>:  mtctr   r10
>    0x100004b8 <_ZN1BC2Ev.localalias.2+180>:     lwz     r2,4(r9)
>    0x100004bc <_ZN1BC2Ev.localalias.2+184>:     bctrl
> => 0x100004c0 <_ZN1BC2Ev.localalias.2+188>:     lwz     r2,20(r1)
>    0x100004c4 <_ZN1BC2Ev.localalias.2+192>:     addi    r1,r31,64
>    0x100004c8 <_ZN1BC2Ev.localalias.2+196>:     lwz     r0,8(r1)
>    0x100004cc <_ZN1BC2Ev.localalias.2+200>:     mtlr    r0
>    0x100004d0 <_ZN1BC2Ev.localalias.2+204>:     lwz     r31,-4(r1)
>    0x100004d4 <_ZN1BC2Ev.localalias.2+208>:     blr

I suppose this is the problem Richard mentioned - the offsets are not computed
by DECL_RTL callback but by place_block. 

> >>> is SYMBOL_REF_BLOCK_OFFSET (target) guaranteed to be valid at this point?
> >>> It looked at face value like you'd need a recursive call to place_block_symbol
> >>> on the target before the copy.
> >>
> >> My reading was that SYMBOL_REF_BLOCK_OFFSET is computed at DECL_RTL
> >> calculation time. But you are right - it is done by validize_mem that
> >> is not done by DECL_RTL.  Shall I just call it on target first?
> >
> > Yeah, sounds like calling place_block_symbol would be safer.

I will test:
Index: varasm.c
===================================================================
--- varasm.c    (revision 211096)
+++ varasm.c    (working copy)
@@ -7094,6 +7094,7 @@
       if (snode->alias)
        {
          rtx target = DECL_RTL (symtab_alias_ultimate_target (snode)->decl);
+         place_block_symbol (symbol);
          SYMBOL_REF_BLOCK_OFFSET (symbol) = SYMBOL_REF_BLOCK_OFFSET (target);
          return;
        }


Honza
> >
> > IIRC, the reason I didn't do it at SET_DECL_RTL time is that some frontends
> > tended to create placeholder decls that for whatever reason ended up with
> > an initial DECL_RTL, then changed the properties of the decl later once
> > more information was known.  (This was all many years ago.)
> >
> > Thanks,
> > Richard