[David Michael] [PATCH libgcypt 2/2] cipher/poly1305: Fix 32-bit x86 compilation

[Jussi Kivilinna]

On 22.1.2021 19.32, David Michael wrote:
> On Fri, Jan 22, 2021 at 12:18 PM Jussi Kivilinna <jussi.kivilinna at iki.fi> wrote:
>> On 22.1.2021 18.28, David Michael wrote:
>>> On Fri, Jan 22, 2021 at 10:32 AM Jussi Kivilinna <jussi.kivilinna at iki.fi> wrote:
>>>> Hello,
>>>>
>>>> On 22.1.2021 13.21, Werner Koch via Gcrypt-devel wrote:
>>>>> ForwardedMessage.eml / David Michael <fedora.dm0 at gmail.com>:
>>>>>
>>>>> * cipher/poly1305.c [HAVE_COMPATIBLE_GCC_ARM_PLATFORM_AS]: Also
>>>>> conditionalize on whether __arm__ is defined.
>>>>>
>>>>> --
>>>>>
>>>>> When building for i686, configure detects that the assembler can
>>>>> use the different architectures, so it defined everything under the
>>>>> HAVE_COMPATIBLE_GCC_ARM_PLATFORM_AS conditional block.  Since that
>>>>> block is first and the following x86 block only defines UMUL_ADD_32
>>>>> if it's not already defined, the lto-wrapper failed during linking
>>>>> with a pile of "no such instruction: umlal ..." errors.  Gating on
>>>>> __arm__ prevents that initial defintion and fixes the errors.
>>>>>
>>>>
>>>> HAVE_COMPATIBLE_GCC_ARM_PLATFORM_AS should not be defined on x86/i686
>>>> in first place.
>>>
>>> Using i686 GCC has these in config.log:
>>>
>>> #define HAVE_COMPATIBLE_GCC_ARM_PLATFORM_AS 1
>>> #define HAVE_COMPATIBLE_GCC_AARCH64_PLATFORM_AS 1
>>> #define HAVE_COMPATIBLE_GCC_AMD64_PLATFORM_AS 1
>>>
>>>> Problem must be in 'configure.ac' in the HAVE_COMPATIBLE_GCC_ARM_PLATFORM_AS
>>>> check. Does this issue happen with "clang -flto"?
>>>
>>
>> Hm, ok. Maybe the LTO/configure.ac problem manifests itself also with GCC
>> in some system configurations. Does attached patch help?
> 
> Yes, that seems to result in only
> HAVE_COMPATIBLE_GCC_AMD64_PLATFORM_AS being defined for i686, so it
> successfully builds.

Great! That is the same as I have for non-LTO GCC build:

  $ cat config.h|grep COMPATIBLE
  /* #undef HAVE_COMPATIBLE_CC_PPC_ALTIVEC */
  /* #undef HAVE_COMPATIBLE_CC_PPC_ALTIVEC_WITH_CFLAGS */
  /* #undef HAVE_COMPATIBLE_GCC_AARCH64_PLATFORM_AS */
  #define HAVE_COMPATIBLE_GCC_AMD64_PLATFORM_AS 1
  /* #undef HAVE_COMPATIBLE_GCC_ARM_PLATFORM_AS */
  /* #undef HAVE_COMPATIBLE_GCC_WIN64_PLATFORM_AS */

HAVE_COMPATIBLE_GCC_AMD64_PLATFORM_AS check currently has 32-bit
instruction to check that system is x86. Therefore check succeeds
on x86_64 and on (some) i686 systems and that is expected.

-Jussi

> 
> Thanks.
> 
> David
>