tree c37dcefa7f2c7cf03da033752a497934764636aa
parent a94c267787df4ac0517456231ebc7be40442895f
author David Benjamin <davidben@google.com> 1640810077 -0500
committer Adam Langley <agl@google.com> 1641580913 +0000

Simplify __ARM_ARCH__ definition.

OpenSSL's assembly files have a few places where we condition code on
__ARM_ARCH__, the minimum target ARM revision. It currently only
controls some pre-ARMv7 code. This symbol has, from what I can tell, the
same semantics as __ARM_ARCH, defined in Arm C Language Extensions, and
added in GCC 4.8 and Clang 3.2:
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=9e94a7fc5ab770928b9e6a2b74e292d35b4c94da;hp=25bab91e017eb1d6d93117f3da96fa9b43703190
https://github.com/llvm/llvm-project/commit/e98c4dbd1ef783b04f0d8276847076fb79a804e8

Those are over nine years old, so drop all the fallback code. Also fix
arm_arch.h to be includable on non-ARM platforms. Some tools expect all
public headers to be cleanly includable and arm_arch.h being "public"
was getting in the way (see cl/416881417).

Interestingly, arm_arch.h previously only computed __ARM_ARCH__ for
__GNUC__ and Clang doesn't define __GNUC__ on Windows. That means we
actually weren't defining __ARM_ARCH__ for Windows. But none of the
aarch64 assembly has __ARM_ARCH__-gated code, so it works out. If it
ever does, that CL smooths that over. I've gated the
__ARM_(MAX_)_ARCH__ bits on __ASSEMBLER__ to avoid breaking no-asm
Windows/aarch64 builds on MSVC. There aren't any uses in C.

Update-Note: ARM assembly now requires the compiler define __ARM_ARCH.
This is not expected to break Clang or GCC from the last 8 or 9 years.

Change-Id: Id45e95406edeecf8dda11dce9e82418516e9de1f
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/50849
Reviewed-by: Adam Langley <agl@google.com>