Export of internal Abseil changes

--
e1c30aa6d6bb25987916d3ec39245c6d4a2a93ea by Derek Mauro <dmauro@google.com>:

Only build the non-stub implementation of RandenHwAes when
accelerated AES can be detected by compiler-set flags.

This removes the case where the full RandenHwAes is built when
only ABSL_RANDOM_INTERNAL_AES_DISPATCH is true.

This also removes the case where ARM crypto is enabled through
the crypto directive. This directive doesn't appear to reliably
work when used with arm_neon.h. As far as I can tell, the crypto
directive is only meant to work with crypto instructions in
handwritten asm. For this to work with arm_neon.h, it appears
several hacks are needed, including overriding some compiler-set
defines.

PiperOrigin-RevId: 392948948
GitOrigin-RevId: e1c30aa6d6bb25987916d3ec39245c6d4a2a93ea
Change-Id: Ie97e26f0204c8a86f72d2f38a59181f1ef578418

absl/random/internal/BUILD.bazel

@@ -626,7 +626,7 @@ cc_test(
     name = "randen_hwaes_test",
     size = "small",
     srcs = ["randen_hwaes_test.cc"],
-    copts = ABSL_TEST_COPTS,
+    copts = ABSL_TEST_COPTS + ABSL_RANDOM_RANDEN_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     tags = ABSL_RANDOM_NONPORTABLE_TAGS,
     deps = [

absl/random/internal/randen_hwaes.cc

@@ -30,43 +30,13 @@
 // ABSL_RANDEN_HWAES_IMPL indicates whether this file will contain
 // a hardware accelerated implementation of randen, or whether it
 // will contain stubs that exit the process.
-#if defined(ABSL_ARCH_X86_64) || defined(ABSL_ARCH_X86_32)
-// The platform.h directives are sufficient to indicate whether
-// we should build accelerated implementations for x86.
-#if (ABSL_HAVE_ACCELERATED_AES || ABSL_RANDOM_INTERNAL_AES_DISPATCH)
-#define ABSL_RANDEN_HWAES_IMPL 1
-#endif
-#elif defined(ABSL_ARCH_PPC)
-// The platform.h directives are sufficient to indicate whether
-// we should build accelerated implementations for PPC.
-//
-// NOTE: This has mostly been tested on 64-bit Power variants,
-// and not embedded cpus such as powerpc32-8540
 #if ABSL_HAVE_ACCELERATED_AES
+// The following plaforms have implemented RandenHwAws.
+#if defined(ABSL_ARCH_X86_64) || defined(ABSL_ARCH_X86_32) || \
+    defined(ABSL_ARCH_PPC) || defined(ABSL_ARCH_ARM) ||       \
+    defined(ABSL_ARCH_AARCH64)
 #define ABSL_RANDEN_HWAES_IMPL 1
 #endif
-#elif defined(ABSL_ARCH_ARM) || defined(ABSL_ARCH_AARCH64)
-// ARM is somewhat more complicated. We might support crypto natively...
-#if ABSL_HAVE_ACCELERATED_AES || \
-    (defined(__ARM_NEON) && defined(__ARM_FEATURE_CRYPTO))
-#define ABSL_RANDEN_HWAES_IMPL 1
-
-#elif ABSL_RANDOM_INTERNAL_AES_DISPATCH && !defined(__APPLE__) && \
-    (defined(__GNUC__) && __GNUC__ > 4 || __GNUC__ == 4 && __GNUC_MINOR__ > 9)
-// ...or, on GCC, we can use an ASM directive to
-// instruct the assember to allow crypto instructions.
-#define ABSL_RANDEN_HWAES_IMPL 1
-#define ABSL_RANDEN_HWAES_IMPL_CRYPTO_DIRECTIVE 1
-#endif
-#else
-// HWAES is unsupported by these architectures / platforms:
-//   __myriad2__
-//   __mips__
-//
-// Other architectures / platforms are unknown.
-//
-// See the Abseil documentation on supported macros at:
-// https://abseil.io/docs/cpp/platforms/macros
 #endif
 
 #if !defined(ABSL_RANDEN_HWAES_IMPL)
@@ -192,22 +162,6 @@ inline ABSL_TARGET_CRYPTO void SwapEndian(absl::uint128* state) {
 
 #elif defined(ABSL_ARCH_ARM) || defined(ABSL_ARCH_AARCH64)
 
-// This asm directive will cause the file to be compiled with crypto extensions
-// whether or not the cpu-architecture supports it.
-#if ABSL_RANDEN_HWAES_IMPL_CRYPTO_DIRECTIVE
-asm(".arch_extension  crypto\n");
-
-// Override missing defines.
-#if !defined(__ARM_NEON)
-#define __ARM_NEON 1
-#endif
-
-#if !defined(__ARM_FEATURE_CRYPTO)
-#define __ARM_FEATURE_CRYPTO 1
-#endif
-
-#endif
-
 // Rely on the ARM NEON+Crypto advanced simd types, defined in <arm_neon.h>.
 // uint8x16_t is the user alias for underlying __simd128_uint8_t type.
 // http://infocenter.arm.com/help/topic/com.arm.doc.ihi0073a/IHI0073A_arm_neon_intrinsics_ref.pdf