ipa-visibility TLC 2/n
David Edelsohn
dje.gcc@gmail.com
Tue Jun 3 13:53:00 GMT 2014
Honza,
How can we make further progress with the large regression on AIX?
Thanks, David
On Fri, May 30, 2014 at 1:24 PM, David Edelsohn <dje.gcc@gmail.com> wrote:
> 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
>
>
>
> On Fri, May 30, 2014 at 3:20 AM, Richard Sandiford
> <rdsandiford@googlemail.com> wrote:
>> Jan Hubicka <hubicka@ucw.cz> writes:
>>>> Jan Hubicka <hubicka@ucw.cz> writes:
>>>> >> Richard Sandiford wrote the original section anchors implementation,
>>>> >> so he would be a good person to comment about the interaction between
>>>> >> aliases and section anchors.
>>>> >
>>>> > Thanks! Richard, does this patch seem sane?
>>>>
>>>> Looks good to me in principle, but with:
>>>>
>>>> > + struct symtab_node *snode;
>>>> > decl = SYMBOL_REF_DECL (symbol);
>>>> > +
>>>> > + snode = symtab_node (decl);
>>>> > + if (snode->alias)
>>>> > + {
>>>> > + rtx target = DECL_RTL (symtab_alias_ultimate_target
>>>> > (snode)->decl);
>>>> > + SYMBOL_REF_BLOCK_OFFSET (symbol) = SYMBOL_REF_BLOCK_OFFSET
>>>> > (target);
>>>> > + return;
>>>> > + }
>>>>
>>>> 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.
>>
>> 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
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