add vulcan support to gas

[Virendra Pathak <virendra dot pathak at broadcom dot com>]

Hi binutils group,

We have a patch for adding -mcpu=vulcan support to gas.
Broadcom's Vulcan is a armv8-a aarch64 served based processor.
We have also got company wide FSF agreement for contributing to
binutils project.

However, recently I read on this group that now gcc does not pass
-mcpu flag to binutils. GCC now passes -march flag to binutils.
I verified this by compiling a simple hello world inspecting the
assembler flags.
[https://gcc.gnu.org/ml/gcc-patches/2015-08/msg01106.html]
[https://sourceware.org/ml/binutils/2015-08/msg00169.html]

Keeping this in mind, do we still need to add -mcpu=vulcan support to
gas, given that many armv8-a vendors have done it?
Kindly guide me on this.

Please also find the patch (-mcpu=vulcan) attached with this mail for review.
Tested the patch with aarch64-linux-gnu cross build,
aarch64-unknown-linux-gnu native build and make check (ld,gdb,gas,binutils).
Also verified the new option via command line.

Thanks for your time.


gas/ChangeLog:
* config/tc-aarch64.c (aarch64_cpus): Add vulcan.
* doc/c-aarch64.texi : Document that vulcan is a valid processor name


with regards,
Virendra Pathak

Attachment: 0001-aarch64-add-vulcan-support-to-gas.patch.txt
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