Re: [PATCH] PR66870 PowerPC64 Enable gold linker with split stack

["Lynn A. Boger" <laboger@linux.vnet.ibm.com>]

I will make the changes Ian suggested to gospec.c and was
planning to fix the sed string in gcc/configure.ac as David suggested.

I need some feedback on whether to enable the gold linker at
all for split stack on platforms other than Power in gcc/configure.ac.
I don't know if there are gold linker versions that should be verified for
non-Power platforms.  My first patch only enabled it on Power and that
  is what I think should be done.  Those who would like to use gold
with split stack for other platforms can enable it under the appropriate
conditions.

On 09/15/2015 01:18 PM, David Edelsohn wrote:
> On Thu, Aug 27, 2015 at 5:00 PM, Lynn A. Boger
> <laboger@linux.vnet.ibm.com> wrote:
>> Here is an updated patch, with a summary of the differences from my previous
>> patch:
>>
>> - In my previous patch gcc configure was verifying the gold linker even if
>> it was the
>> default linker, but that is not necessary since in that case -fuse-ld=gold
>> does not
>> need to be set.  Gold version checking is now only done if the alternate
>> linker is gold
>> and the default linker is not.
>> - The STACK_SPLIT_STACK spec define found in gcc/gcc.c now adds
>> -fuse-ld=gold
>> if the gcc configure determines the alternate gold linker has split stack
>> support.
>> - A case statement is now used in gcc configure to verify the gold version,
>> to make it
>> easier for other platforms to add their checks if necessary.  I don't know
>> if other
>> platforms require this checking; Matthias' patch did not check the version.
>> For powerpc64
>> big and little endian we have to check the gold linker version because the
>> split
>> stack support was added recently and older gold linkers won't work.
>> - The version checking of the gold linker was removed from the libgo
>> configure
>>   since gcc configure has already decided if it is correct.
>> - TARGET_CAN_SPLIT_STACK_64BIT is now defined in sysv4.h if the glibc
>> version
>> is correct for split stack for powerpc64 big and little endian. This define
>> is used in
>> go/gospec.c in the same way that TARGET_CAN_SPLIT_STACK is used now but,
>>   additionally verifies that it is a 64 bit compile.  This is necessary
>> because split
>> stack support is not available for ppc 32 bit big endian in gcc or the gold
>> linker.
>>
>> Bootstrapped and tested on x86_64, ppc64le, ppc64 (ran m32, m64 tests)
>>
>>
>> 2015-08-27    Lynn Boger <laboger@linux.vnet.ibm.com>
>>
>> gcc/
>>           PR target/66870
>>           config/rs6000/sysv4.h:  Define TARGET_CAN_SPLIT_STACK_64BIT
>>           based on LIBC version.
>>           config.in:  Set up HAVE_GOLD_ALTERNATE.
>>           configure.ac:  Define HAVE_GOLD_ALTERNATE if the version of the
>> gold
>>           linker supports split stack.
>>           configure: Regenerate.
>>           gcc.c:  Add -fuse-ld=gold to STACK_SPLIT_SPEC if
>> HAVE_GOLD_ALTERNATE
>>           is defined.
>>           go/gospec.c:  (lang_specific_driver):  Use
>> TARGET_CAN_SPLIT_STACK_64BIT
>>           to control setting of fsplit-stack and u,pthread_create options for
>> 64 bit
>>           compiles.
> I don't have authority to approve for most of the patch.
>
> I noticed that the test for Gold version number is different than a
> similar test in another part of configure.  And the sed pattern seems
> to be too restrictive -- it fails to extract a version number for my
> tests with Gold in a few different Linux distros.  This should be
> addressed instead of silently misidentifying split stack support in
> some distros.
>
> - David
>
>