| Message ID | 20140530210219.GE17544@kam.mff.cuni.cz |
|---|---|
| State | New |
| Headers | show |
Honza, With the patch, I cannot bootstrap. I am concerned about the much greater frequency of AIX linker warnings about branch not followed by no-op after your patch. GCC may bootstrap only because it links libstdc++ statically. If your patch is too aggressive in its effort to remove PLT calls, it may be breaking shared library support on AIX. Previously there were a few recursive libstdc++ calls that binds_local_p() asserted were bound locally to functions declared global. I hope that cross-module calls have not been incorrectly analyzed as local. Thanks, David On Fri, May 30, 2014 at 5:02 PM, Jan Hubicka <hubicka@ucw.cz> 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 > > 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
David Edelsohn <dje.gcc@gmail.com> writes: > Honza, > > With the patch, I cannot bootstrap. I think it was meant to be: place_block_symbol (target); rather than: place_block_symbol (symbol); I.e. we need to place "target" before copying its offset. Thanks, Richard
This leads to bootstrap errors like:
In file included from
/tmp/20140531/powerpc-ibm-aix7.1.0.0/libstdc++-v3/include/backward/strstream:54:0,
from
/nasfarm/edelsohn/src/src/libstdc++-v3/src/c++98/strstream.cc:44:
/tmp/20140531/powerpc-ibm-aix7.1.0.0/libstdc++-v3/include/istream: In
constructor 'std::istrstream::istrstream(char*)':
/tmp/20140531/powerpc-ibm-aix7.1.0.0/libstdc++-v3/include/istream:94:32:
internal compiler error: in place_block_symbol, at varasm.c:7067
: _M_gcount(streamsize(0))
^
On Sat, May 31, 2014 at 3:42 AM, Richard Sandiford
<rdsandiford@googlemail.com> wrote:
> David Edelsohn <dje.gcc@gmail.com> writes:
>> Honza,
>>
>> With the patch, I cannot bootstrap.
>
> I think it was meant to be:
>
> place_block_symbol (target);
>
> rather than:
>
> place_block_symbol (symbol);
>
> I.e. we need to place "target" before copying its offset.
>
> Thanks,
> Richard
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; }