Re: PATCH: PR target/59587: cpu_names in i386.c is accessed with wrong index

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Tue, Dec 24, 2013 at 6:55 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Tue, Dec 24, 2013 at 6:50 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
>> On Tue, Dec 24, 2013 at 3:23 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Tue, Dec 24, 2013 at 6:12 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
>>>> On Tue, Dec 24, 2013 at 2:08 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:
>>>>
>>>>> cpu_names in i386.c is only used by ix86_function_specific_print which
>>>>> accesses it with enum processor_type index. But cpu_names is defined as
>>>>> array with enum target_cpu_default index.  This patch adds processor
>>>>> names to processor_target_table and uses processor_target_table instead
>>>>> of cpu_names.  It removes cpu_names and target_cpu_default.  Tested on
>>>>> Linux/x86-64.  OK to install?
>>>>
>>>> Wait a moment,
>>>>
>>>> it looks to me that TARGET_CPU_DEFAULT has to be synchronized with
>>>> const processor_alias_table, so we are able to define various ISA
>>>> extensions by selecting TARGET_CPU_*. The TARGET_CPU_DEFAULT can then
>>>
>>> TARGET_CPU_DEFAULT sets the default -mtune=, not -march=.
>>>
>>>> be used to select extensions in the same way as PROCESSOR_* selects
>>>> tuning for certain processor.
>>>
>>> It has been like this for a long time.  For x86, TARGET_CPU_DEFAULT
>>> isn't defined no matter which configure options are used.  We can
>>> change config.gcc to set TARGET_CPU_DEFAULT to proper PROCESSOR_XXX or
>>> set it to a string "xxx" for processor "xxx".
>>> But GCC driver always passes -march=/-mtune= to toplev.c so that
>>> TARGET_CPU_DEFAULT is normally used.
>
> I meant to say "TARGET_CPU_DEFAULT isn't normally used."
>
>>
>> Let me rethink this a bit, please do not commit the patch.
>>

TARGET_CPU_DEFAULT is left over for 32-bit target before --with-arch=
and --with-cpu= were added.  Today, -mtune=xxx -march=xxx are
always passed to cc1 by GCC driver.  If cc1 is run by hand and
-mtune=xxx -march=xxx aren't passed to cc1, we should do

1. For 64-bit, it should be the same as -mtune=generic -march=x86_64
are passed.
2. For 32-bit, it should be the same as -mtune=cpu -march=cpu are
passed, where "cpu" is the target cpu used to configure GCC,
like i386 in i386-linux, i486 in i486-linux, .... But there is no i786
cpu.  i786 is treated as i686.  If SUBTARGET32_DEFAULT_CPU
is defined, it should be the same -mtune=SUBTARGET32_DEFAULT_CPU
-march=SUBTARGET32_DEFAULT_CPU.

Here is the patch to implement this.


-- 
H.J.
--
2013-12-24   H.J. Lu  <hongjiu.lu@intel.com>

    PR target/59587
    * configure.ac (target_cpu_default): Defined to PROCESSOR_XXX
    for i[34567]86 targets.
    * configure: Regenerated.
    * config/i386/i386.c (SUBTARGET32_DEFAULT_CPU): Use
    TARGET_CPU_DEFAULT if it is defined.
    (struct ptt): Add a field for processor name.
    (processor_target_table): Sync with processor_type.  Add processor
    names.
    (cpu_names): Removed.
    (ix86_option_override_internal): Default x_ix86_tune_string
    to processor_target_table[TARGET_CPU_DEFAULT].name for 32-bit
    if it is defined.  Otherwise, default to "generic".
    (ix86_function_specific_print): Use processor_target_table
    to print arch and tune names.
    * config/i386/i386.h (TARGET_CPU_DEFAULT): Removed.
    (target_cpu_default): Likewise.
    (processor_type): Reordered.

Attachment: gcc-cpu-2.patch
Description: Text document