[i386] Support .lbss etc. sections with Solaris as (PR target/59407)

[Uros Bizjak]

On Thu, Mar 17, 2016 at 11:40 PM, Rainer Orth
<ro@cebitec.uni-bielefeld.de> wrote:
> gcc.target/i386/pr58218.c currently FAILs on 64-bit Solaris/x86 with the
> native assembler:
>
> FAIL: gcc.target/i386/pr58218.c (test for excess errors)
>
> Excess errors:
> Assembler: pr58218.c
>         "/var/tmp//cciHFIO7.s", line 3 : Section attributes do not match
>
>         .section        .lbss,"aw",@nobits
>
> It turns out x86_64 large sections need to marked with a 'h' section
> flag for as.  gas implicitly sets SHF_AMD64_LARGE based on section
> names, but also accepts an 'l' for the same purpose.
>
> The following patch fixes this by using the SECTION_MACH_DEP section
> flag to mark large sections and emit the right flag in
> default_elf_asm_named_section.
>
> Given this comment in output.h
>
> #define SECTION_MACH_DEP 0x4000000      /* subsequent bits reserved for target */
>
> handling only a single SECTION_MACH_DEP can be considered a hack.
> Currently, only one user of SECTION_MACH_DEP (avr) uses more than one
> section flag, so maybe I can get away with this for now.
>
> A full solution would split out the part of
> default_elf_asm_named_section that emits the flags into a new
> default_elf_asm_section_flags which prints the flag string to a stream,
> invoking it either via a macro than be overridden or perhaps a target
> hook (which seems not fully right either since those are object file
> format agnostic and this is just a small part of emitting ELF named
> sections).
>
> The patch has been bootstrapped without regressions on
> i386-pc-solaris2.12 (with both as and gas) and x86_64-pc-linux-gnu.
> This is not a regression, so this may have to wait for GCC 7 stage 1.
>
> Ok for mainline now or then?

I'd rather leave this and subsequent patch for gcc-7 at this point.
The patch touches middle-end, and from the explanation above, it looks
that some discussion with middle-end maintainers (relevant people
CC'd) and their approval  is still needed.

Uros.

> Thanks.
>         Rainer
>
>
> 2016-03-15  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
>
>         PR target/59407
>         * config/i386/i386.c (SECTION_LARGE): Define.
>         (x86_64_elf_select_section): Set it for large data/bss sections.
>         Only clear SECTION_WRITE for .lrodata.
>         (x86_64_elf_section_type_flags): Set SECTION_LARGE for large
>         data/bss sections.
>         * config/i386/sol2.h (MACH_DEP_SECTION_ASM_FLAG): Define.
>         * varasm.c (default_elf_asm_named_section): Grow flagchars.
>         [MACH_DEP_SECTION_ASM_FLAG] Emit MACH_DEP_SECTION_ASM_FLAG for
>         SECTION_MACH_DEP.
>         * doc/tm.texi.in (Sections, MACH_DEP_SECTION_ASM_FLAG): Describe.
>         * doc/tm.texi: Regenerate.
>
>
>
> --
> -----------------------------------------------------------------------------
> Rainer Orth, Center for Biotechnology, Bielefeld University
>