Re: [PATCH] Don't use .gnu.linkonce with COMDAT

["H. J. Lu" <hjl at lucon dot org>]

The patch?


H.J.
On Fri, May 06, 2005 at 05:59:17PM +0100, Julian Brown wrote:
> Hi,
> 
> This is a combination of various patches to make COMDAT groups work 
> better. The first is from the csl-arm branch:
> 
>   http://gcc.gnu.org/ml/gcc-patches/2004-09/msg02497.html
> 
> This stops .gnu.linkonce from being used on targets which have COMDAT 
> groups.
> 
> The next bit is new: rodata sections relating to text sections in COMDAT 
> groups are now put into the same COMDAT group rather than being left 
> stranded. i.e., a function put in a section:
> 
>         .section        .text._Z3fooi,"axG",@progbits,_Z3fooi,comdat
> 
> which generates a jump table for a switch statement, now has that table 
> put into a section:
> 
>         .section        .rodata._Z3fooi,"aG",@progbits,_Z3fooi,comdat
> 
> rather than just .rodata. This fixes testcase 
> g++.old-deja/g++.other/comdat4.C on x86_64 with the above bit applied.
> 
> Thirdly, COMDAT groups have proven buggy on various platforms with 
> various (older) binutils versions. The third part of the patch stops 
> COMDAT groups from being used altogether when the linker version is less 
> than 2.16. This is perhaps slightly too pessimistic (i.e., earlier 
> versions might work OK), but I'm reasonably confident my testing has 
> shown it to be about right. This is based on a patch from H.J. Lu which 
> never seems to have been applied:
> 
>   http://gcc.gnu.org/ml/gcc-patches/2004-09/msg02774.html
> 
> Though the required version has been bumped by several. This will have 
> the effect of disabling COMDAT on some setups where it is currently 
> enabled. I have also renamed the macro HAVE_GAS_COMDAT_GROUP to just 
> HAVE_COMDAT_GROUP to better indicate that it's not just an assembler 
> feature that's being relied on.
> 
> I have run tests on powerpc64-unknown-linux-gnu with c,c++ and 
> x86_64-pc-linux-gnu with c,c++,java,objc, with binutils 2.16, with no 
> regressions.
> 
> OK to apply?
> 
> ChangeLog:
> 
>   * gcc/configure.ac: Set ld_vers_major, ld_vers_minor and ld_vers_patch
>   for GNU linker. Support linker version x.x.x.x.x. Require GNU linker
>   20050308/2.16.0 or newer for comdat group.
>   * gcc/configure: Regenerated.
>   * gcc/config.in: Regenerated.
>   * gcc/varasm.c (default_function_rodata_section): Put .rodata section
>   in COMDAT group when necessary.
>   (default_elf_asm_named_section): Rename HAVE_GAS_COMDAT_GROUP to
>   HAVE_COMDAT_GROUP.
>   (default_unique_section_1): Don't use .gnu.linkonce when COMDAT is
>   available.