Add support for Arm FHM (#102)

* Add support for Arm FHM

Co-authored-by: Developer-Ecosystem-Engineering <65677710+Developer-Ecosystem-Engineering@users.noreply.github.com>

5 files changed, 29 insertions, 0 deletions

diff --git a/include/cpuinfo.h b/include/cpuinfo.h
index e7ce9ed..e3d7b08 100644
--- a/include/cpuinfo.h
+++ b/include/cpuinfo.h
@@ -1474,6 +1474,7 @@ static inline bool cpuinfo_has_x86_sha(void) {
 		bool dot;
 		bool jscvt;
 		bool fcma;
+		bool fhm;
 
 		bool aes;
 		bool sha1;
@@ -1727,6 +1728,14 @@ static inline bool cpuinfo_has_arm_neon_fp16_arith(void) {
 	#endif
 }
 
+static inline bool cpuinfo_has_arm_fhm(void) {
+	#if CPUINFO_ARCH_ARM || CPUINFO_ARCH_ARM64
+		return cpuinfo_isa.fhm;
+	#else
+		return false;
+	#endif
+}
+
 static inline bool cpuinfo_has_arm_neon_dot(void) {
 	#if CPUINFO_ARCH_ARM || CPUINFO_ARCH_ARM64
 		return cpuinfo_isa.dot;
diff --git a/src/arm/linux/aarch64-isa.c b/src/arm/linux/aarch64-isa.c
index 9019949..44a8f4d 100644
--- a/src/arm/linux/aarch64-isa.c
+++ b/src/arm/linux/aarch64-isa.c
@@ -138,5 +138,8 @@ void cpuinfo_arm64_linux_decode_isa_from_proc_cpuinfo(
 	if (features2 & (CPUINFO_ARM_LINUX_FEATURE2_BF16 | CPUINFO_ARM_LINUX_FEATURE2_SVEBF16)) {
 		isa->bf16 = true;
 	}
+	if (features & CPUINFO_ARM_LINUX_FEATURE_ASIMDFHM) {
+		isa->fhm = true;
+	}
 }
 
diff --git a/src/arm/linux/cpuinfo.c b/src/arm/linux/cpuinfo.c
index bc98c14..817da12 100644
--- a/src/arm/linux/cpuinfo.c
+++ b/src/arm/linux/cpuinfo.c
@@ -287,6 +287,10 @@ static void parse_features(
 					#if CPUINFO_ARCH_ARM64
 						processor->features |= CPUINFO_ARM_LINUX_FEATURE_ASIMDRDM;
 					#endif
+				} else if (memcmp(feature_start, "asimdfhm", feature_length) == 0) {
+					#if CPUINFO_ARCH_ARM64
+						processor->features |= CPUINFO_ARM_LINUX_FEATURE_ASIMDFHM;
+					#endif
 #if CPUINFO_ARCH_ARM
 				} else if (memcmp(feature_start, "fastmult", feature_length) == 0) {
 					processor->features |= CPUINFO_ARM_LINUX_FEATURE_FASTMULT;
diff --git a/src/arm/mach/init.c b/src/arm/mach/init.c
index 3ced773..244d530 100644
--- a/src/arm/mach/init.c
+++ b/src/arm/mach/init.c
@@ -408,6 +408,17 @@ void cpuinfo_arm_mach_init(void) {
 		cpuinfo_isa.i8mm = true;
 	}
 
+	const uint32_t has_feat_fhm = get_sys_info_by_name("hw.optional.arm.FEAT_FHM");
+	if (has_feat_fhm != 0) {
+		cpuinfo_isa.fhm = true;
+	} else {
+		// Prior to iOS 15, use 'hw.optional.armv8_2_fhm'
+		const uint32_t has_feat_fhm_legacy = get_sys_info_by_name("hw.optional.armv8_2_fhm");
+		if (has_feat_fhm_legacy != 0) {
+			cpuinfo_isa.fhm = true;
+		}
+	}
+
 	uint32_t num_clusters = 1;
 	for (uint32_t i = 0; i < mach_topology.cores; i++) {
 		cores[i] = (struct cpuinfo_core) {
diff --git a/tools/isa-info.c b/tools/isa-info.c
index 1b8f81c..da61e50 100644
--- a/tools/isa-info.c
+++ b/tools/isa-info.c
@@ -144,6 +144,7 @@ int main(int argc, char** argv) {
 		printf("\tNEON FP16 arithmetics: %s\n", cpuinfo_has_arm_neon_fp16_arith() ? "yes" : "no");
 		printf("\tNEON complex: %s\n", cpuinfo_has_arm_fcma() ? "yes" : "no");
 		printf("\tNEON dot product: %s\n", cpuinfo_has_arm_neon_dot() ? "yes" : "no");
+		printf("\tNEON VFMLAL/VFMLSL: %s\n", cpuinfo_has_arm_fhm() ? "yes" : "no");
 
 	printf("Cryptography extensions:\n");
 		printf("\tAES: %s\n", cpuinfo_has_arm_aes() ? "yes" : "no");
@@ -157,6 +158,7 @@ int main(int argc, char** argv) {
 		printf("\tARM v8.1 atomics: %s\n", cpuinfo_has_arm_atomics() ? "yes" : "no");
 		printf("\tARM v8.1 SQRDMLxH: %s\n", cpuinfo_has_arm_neon_rdm() ? "yes" : "no");
 		printf("\tARM v8.2 FP16 arithmetics: %s\n", cpuinfo_has_arm_fp16_arith() ? "yes" : "no");
+		printf("\tARM v8.2 FHM: %s\n", cpuinfo_has_arm_fhm() ? "yes" : "no");
 		printf("\tARM v8.2 BF16: %s\n", cpuinfo_has_arm_bf16() ? "yes" : "no");
 		printf("\tARM v8.3 dot product: %s\n", cpuinfo_has_arm_neon_dot() ? "yes" : "no");
 		printf("\tARM v8.3 JS conversion: %s\n", cpuinfo_has_arm_jscvt() ? "yes" : "no");