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Simplify __ARM_ARCH__ definition.

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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
e98c4dbd1e

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>
This commit is contained in:
David Benjamin 2021-12-29 15:34:37 -05:00 committed by Adam Langley
parent a94c267787
commit d80f17d5c9
1 changed files with 25 additions and 43 deletions
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68
include/openssl/arm_arch.h
View File

@ -53,49 +53,12 @@
#ifndef OPENSSL_HEADER_ARM_ARCH_H
#define OPENSSL_HEADER_ARM_ARCH_H
#if !defined(__ARM_ARCH__)
# if defined(__CC_ARM)
# define __ARM_ARCH__ __TARGET_ARCH_ARM
# if defined(__BIG_ENDIAN)
# define __ARMEB__
# else
# define __ARMEL__
# endif
# elif defined(__GNUC__)
# if defined(__aarch64__)
# define __ARM_ARCH__ 8
// Why doesn't gcc define __ARM_ARCH__? Instead it defines
// bunch of below macros. See all_architectires[] table in
// gcc/config/arm/arm.c. On a side note it defines
// __ARMEL__/__ARMEB__ for little-/big-endian.
# elif defined(__ARM_ARCH)
# define __ARM_ARCH__ __ARM_ARCH
# elif defined(__ARM_ARCH_8A__)
# define __ARM_ARCH__ 8
# elif defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) || \
defined(__ARM_ARCH_7R__)|| defined(__ARM_ARCH_7M__) || \
defined(__ARM_ARCH_7EM__)
# define __ARM_ARCH__ 7
# elif defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) || \
defined(__ARM_ARCH_6K__)|| defined(__ARM_ARCH_6M__) || \
defined(__ARM_ARCH_6Z__)|| defined(__ARM_ARCH_6ZK__) || \
defined(__ARM_ARCH_6T2__)
# define __ARM_ARCH__ 6
# elif defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5T__) || \
defined(__ARM_ARCH_5E__)|| defined(__ARM_ARCH_5TE__) || \
defined(__ARM_ARCH_5TEJ__)
# define __ARM_ARCH__ 5
# elif defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__)
# define __ARM_ARCH__ 4
# else
# error "unsupported ARM architecture"
# endif
# endif
#endif
// arm_arch.h contains symbols used by ARM assembly, and the C code that calls
// it. It is included as a public header to simplify the build, but is not
// intended for external use.
// Even when building for 32-bit ARM, support for aarch64 crypto instructions
// will be included.
#define __ARM_MAX_ARCH__ 8
#if defined(__ARMEL__) || defined(_M_ARM) || defined(__AARCH64EL__) || \
defined(_M_ARM64)
// ARMV7_NEON is true when a NEON unit is present in the current CPU.
#define ARMV7_NEON (1 << 0)
@ -117,6 +80,23 @@
#if defined(__ASSEMBLER__)
// We require the ARM assembler provide |__ARM_ARCH| from Arm C Language
// Extensions (ACLE). This is supported in GCC 4.8+ and Clang 3.2+. MSVC does
// not implement ACLE, but we require Clang's assembler on Windows.
#if !defined(__ARM_ARCH)
#error "ARM assembler must define __ARM_ARCH"
#endif
// __ARM_ARCH__ is used by OpenSSL assembly to determine the minimum target ARM
// version.
//
// TODO(davidben): Switch the assembly to use |__ARM_ARCH| directly.
#define __ARM_ARCH__ __ARM_ARCH
// Even when building for 32-bit ARM, support for aarch64 crypto instructions
// will be included.
#define __ARM_MAX_ARCH__ 8
// Support macros for
// - Armv8.3-A Pointer Authentication and
// - Armv8.5-A Branch Target Identification
@ -233,6 +213,8 @@
.popsection;
#endif
#endif /* defined __ASSEMBLER__ */
#endif // __ASSEMBLER__
#endif // __ARMEL__ || _M_ARM || __AARCH64EL__ || _M_ARM64
#endif // OPENSSL_HEADER_ARM_ARCH_H