[build, libgo, libstdc++] Build libgo with -Wa,-nH if possible (PR go/78978)

[Rainer Orth]

Hi Ian,

> On Thu, Jan 5, 2017 at 1:20 AM, Rainer Orth <ro@cebitec.uni-bielefeld.de> wrote:
>> As could have been expected, the static libgo.a causes the same problem
>> with hardware capabilities on Solaris/x86 as was solved for libgo.so
>> with
>>
>>         https://gcc.gnu.org/ml/gcc-patches/2016-12/msg00726.html
>>
>> Instead of trying to pass -mclear-hwcap with -static-libgo, it was
>> deemed easier to solve both problems the same way and disable hwcaps
>> support in the assembler in the first place.
>>
>> This has already been done in libstdc++, so I've moved the corresponding
>> autoconf macro to config/hwcaps.m4 and adapted it to set HWCAP_CFLAGS
>> instead of HWCAP_FLAGS to better differntiate from HWCAP_LDFLAGS.
>> Everything else is straightforward, I believe.
>>
>> Bootstrapped without regressions on i386-pc-solaris2.1[02] with as/ld
>> (where as supports -nH) and sparc-sun-solaris2.12 with as/ld (where as
>> doesn't, or rather it's called -hwcap={1|0}), and the libgo
>> runtime/pprof failure is gone.
>>
>> Ok for mainline?
>>
>> Once approved, how should we proceed with checking?  Ian, will you take
>> care of the libgo part once the rest is in?
>
> This patch is OK.  Yes, please commit the config and libstdc++
> portions.  Then I will commit the libgo portions to the external repo
> and mirror them in.  Thanks.

done, thanks.  While preparing the partial commit, I noticed that I'd
created the libgo part of the patch on top of a tree that contained a
workaround for PR go/64900.

Here's the libgo part again, this time on top of a vanilla tree.

	Rainer

-- 
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Rainer Orth, Center for Biotechnology, Bielefeld University


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