[PATCH v2, i386]: Fix PR 63538, With -mcmodel=medium .lrodata accesses do not use 64-bit addresses

[Uros Bizjak <ubizjak at gmail dot com>]

On Tue, Nov 4, 2014 at 10:46 AM, Uros Bizjak <ubizjak@gmail.com> wrote:

>> Following patch fixes PR 63538, where the data in the large data
>> section was accessed through 32bit address. The patch unifies places
>> where large data sections are determined and passes all declarations
>> to ix86_in_large_data_p only.
>>
>> The patch fixes the testcase form the PR. Also, the code from several
>> tests involving various -mlarge-data-threshold= settings looks
>> consistent now.

[...]

> We probably want to avoid putting automatic variables (and STRING_CSTs
> ?) to large data section. However, it is important that we use the
> same condition in ix86_encode_section_info and
> x86_64_elf_select_section (and likes), otherwise the data can go into
> large section, while the access to the data will be via limited 32bit
> pointers.
>
> The attached alternative patch rejects automatic variables and
> STRING_CSTs from large data sections. Please note, that it still
> access the data with the correct instructions.

Considering that STRING_CSTs always have TREE_STATIC set, the patch
should allow them, similar to the patch at [1].

Attached is the final patch.

2014-11-04  Uros Bizjak  <ubizjak@gmail.com>

    PR target/63538
    * config/i386/i386.c (in_large_data_p): Reject automatic variables.
    (ix86_encode_section_info): Do not check for non-automatic varibles
    when setting SYMBOL_FLAG_FAR_ADDR flag.
    (x86_64_elf_select_section): Do not check ix86_cmodel here.
    (x86_64_elf_unique_section): Ditto.
    (x86_elf_aligned_common): Emit tab before .largecomm.

testsuite/ChangeLog:

2014-11-03  Uros Bizjak  <ubizjak@gmail.com>

    PR target/63538
    * gcc.target/i386/pr63538.c: New test.

I plan to commit the patch in a couple of days to mainline and 4.9 branch.

[1] https://gcc.gnu.org/ml/gcc-patches/2014-10/msg01963.html

Uros.

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