From 2eeaa9282e4f2eab4bcd97084dbcce31dc0ba824 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers3@gmail.com>
Date: Sat, 10 Oct 2020 23:02:50 -0700
Subject: [PATCH] lib/arm/cpu_features: recognize the crc32 feature

If support for CRC32 instructions is detected, set
ARM_CPU_FEATURE_CRC32.  Also define
COMPILER_SUPPORTS_CRC32_TARGET_INTRINSICS when appropriate, and update
run_tests.sh to toggle the crc32 feature for testing.
---
 common/common_defs.h   |  3 +++
 common/compiler_gcc.h  | 14 ++++++++++++++
 lib/arm/cpu_features.c |  5 +++++
 lib/arm/cpu_features.h |  1 +
 tools/run_tests.sh     |  2 +-
 5 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/common/common_defs.h b/common/common_defs.h
index dcfcbfa..d56c5cf 100644
--- a/common/common_defs.h
+++ b/common/common_defs.h
@@ -152,6 +152,9 @@ typedef size_t machine_word_t;
 #ifndef COMPILER_SUPPORTS_PMULL_TARGET_INTRINSICS
 #  define COMPILER_SUPPORTS_PMULL_TARGET_INTRINSICS 0
 #endif
+#ifndef COMPILER_SUPPORTS_CRC32_TARGET_INTRINSICS
+#  define COMPILER_SUPPORTS_CRC32_TARGET_INTRINSICS 0
+#endif
 
 /* _aligned_attribute(n) - declare that the annotated variable, or variables of
  * the annotated type, are to be aligned on n-byte boundaries */
diff --git a/common/compiler_gcc.h b/common/compiler_gcc.h
index 4b3b449..0bda3a5 100644
--- a/common/compiler_gcc.h
+++ b/common/compiler_gcc.h
@@ -119,6 +119,20 @@
 #      elif __has_builtin(__builtin_neon_vmull_p64) || !defined(__clang__)
 #        define COMPILER_SUPPORTS_PMULL_TARGET_INTRINSICS 1
 #      endif
+#    endif
+
+     /*
+      * Determine whether CRC32 intrinsics are supported.
+      *
+      * With gcc r274827 or later (gcc 10.1+, 9.3+, or 8.4+), or with clang,
+      * they work as expected.  (Well, not quite.  There's still a bug, but we
+      * have to work around it later when including arm_acle.h.)
+      */
+#    if GCC_PREREQ(10, 1) || \
+        (GCC_PREREQ(9, 3) && !GCC_PREREQ(10, 0)) || \
+        (GCC_PREREQ(8, 4) && !GCC_PREREQ(9, 0)) || \
+        (defined(__clang__) && __has_builtin(__builtin_arm_crc32b))
+#      define COMPILER_SUPPORTS_CRC32_TARGET_INTRINSICS 1
 #    endif
 
 #  endif /* __arm__ || __aarch64__ */
diff --git a/lib/arm/cpu_features.c b/lib/arm/cpu_features.c
index c4556a3..60b1be3 100644
--- a/lib/arm/cpu_features.c
+++ b/lib/arm/cpu_features.c
@@ -95,6 +95,7 @@ out:
 static const struct cpu_feature arm_cpu_feature_table[] = {
 	{ARM_CPU_FEATURE_NEON,		"neon"},
 	{ARM_CPU_FEATURE_PMULL,		"pmull"},
+	{ARM_CPU_FEATURE_CRC32,		"crc32"},
 };
 
 void setup_cpu_features(void)
@@ -111,12 +112,16 @@ void setup_cpu_features(void)
 		features |= ARM_CPU_FEATURE_NEON;
 	if (hwcap2 & (1 << 1))	/* HWCAP2_PMULL */
 		features |= ARM_CPU_FEATURE_PMULL;
+	if (hwcap2 & (1 << 4))	/* HWCAP2_CRC32 */
+		features |= ARM_CPU_FEATURE_CRC32;
 #else
 	STATIC_ASSERT(sizeof(long) == 8);
 	if (hwcap & (1 << 1))	/* HWCAP_ASIMD */
 		features |= ARM_CPU_FEATURE_NEON;
 	if (hwcap & (1 << 4))	/* HWCAP_PMULL */
 		features |= ARM_CPU_FEATURE_PMULL;
+	if (hwcap & (1 << 7))	/* HWCAP_CRC32 */
+		features |= ARM_CPU_FEATURE_CRC32;
 #endif
 
 	disable_cpu_features_for_testing(&features, arm_cpu_feature_table,
diff --git a/lib/arm/cpu_features.h b/lib/arm/cpu_features.h
index a491436..69d7235 100644
--- a/lib/arm/cpu_features.h
+++ b/lib/arm/cpu_features.h
@@ -20,6 +20,7 @@
 
 #define ARM_CPU_FEATURE_NEON		0x00000001
 #define ARM_CPU_FEATURE_PMULL		0x00000002
+#define ARM_CPU_FEATURE_CRC32		0x00000004
 
 #define ARM_CPU_FEATURES_KNOWN		0x80000000
 
diff --git a/tools/run_tests.sh b/tools/run_tests.sh
index b1b3c7e..59e11c8 100755
--- a/tools/run_tests.sh
+++ b/tools/run_tests.sh
@@ -149,7 +149,7 @@ native_build_and_test() {
 			features=(avx512bw avx2 avx bmi2 pclmul sse2)
 			;;
 		arm*|aarch*)
-			features=(pmull neon)
+			features=(crc32 pmull neon)
 			;;
 		esac
 	fi