[libc] add cpu feature flags for SVE/SVE2/MOPS

[SchrodingerZhu]

Add in SVE/SVE2/MOPS features for aarch64 cpus. These features may be interesting for future memory/math routines.

SVE/SVE2 are now being accepted in more implementations:

❯ echo | clang-21 -dM -E - -march=native | grep -i ARM_FEAT
#define __ARM_FEATURE_ATOMICS 1
#define __ARM_FEATURE_BF16 1
#define __ARM_FEATURE_BF16_SCALAR_ARITHMETIC 1
#define __ARM_FEATURE_BF16_VECTOR_ARITHMETIC 1
#define __ARM_FEATURE_BTI 1
#define __ARM_FEATURE_CLZ 1
#define __ARM_FEATURE_COMPLEX 1
#define __ARM_FEATURE_CRC32 1
#define __ARM_FEATURE_DIRECTED_ROUNDING 1
#define __ARM_FEATURE_DIV 1
#define __ARM_FEATURE_DOTPROD 1
#define __ARM_FEATURE_FMA 1
#define __ARM_FEATURE_FP16_SCALAR_ARITHMETIC 1
#define __ARM_FEATURE_FP16_VECTOR_ARITHMETIC 1
#define __ARM_FEATURE_FRINT 1
#define __ARM_FEATURE_IDIV 1
#define __ARM_FEATURE_JCVT 1
#define __ARM_FEATURE_LDREX 0xF
#define __ARM_FEATURE_MATMUL_INT8 1
#define __ARM_FEATURE_NUMERIC_MAXMIN 1
#define __ARM_FEATURE_PAUTH 1
#define __ARM_FEATURE_QRDMX 1
#define __ARM_FEATURE_RCPC 1
#define __ARM_FEATURE_SVE 1
#define __ARM_FEATURE_SVE2 1
#define __ARM_FEATURE_SVE_BF16 1
#define __ARM_FEATURE_SVE_MATMUL_INT8 1
#define __ARM_FEATURE_SVE_VECTOR_OPERATORS 2
#define __ARM_FEATURE_UNALIGNED 1

MOPS is another set of extension for string operations, but may not be generally available for now:

❯ echo | clang-21 -dM -E - -march=armv9.2a+mops | grep -i MOPS
#define __ARM_FEATURE_MOPS 1

[llvmbot]

@llvm/pr-subscribers-libc

Author: Schrodinger ZHU Yifan (SchrodingerZhu)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/166884.diff

5 Files Affected:

• (modified) libc/cmake/modules/LLVMLibCCheckCpuFeatures.cmake (+1-1)
• (added) libc/cmake/modules/cpu_features/check_MOPS.cpp (+7)
• (added) libc/cmake/modules/cpu_features/check_SVE.cpp (+7)
• (added) libc/cmake/modules/cpu_features/check_SVE2.cpp (+7)
• (modified) libc/src/__support/macros/properties/cpu_features.h (+12)

diff --git a/libc/cmake/modules/LLVMLibCCheckCpuFeatures.cmake b/libc/cmake/modules/LLVMLibCCheckCpuFeatures.cmake
index c09d4751d3907..d76f3b16b30ec 100644
--- a/libc/cmake/modules/LLVMLibCCheckCpuFeatures.cmake
+++ b/libc/cmake/modules/LLVMLibCCheckCpuFeatures.cmake
@@ -9,7 +9,7 @@ if(LIBC_TARGET_ARCHITECTURE_IS_X86_64)
   set(ALL_CPU_FEATURES SSE2 SSE4_2 AVX AVX2 AVX512F AVX512BW FMA)
   set(LIBC_COMPILE_OPTIONS_NATIVE -march=native)
 elseif(LIBC_TARGET_ARCHITECTURE_IS_AARCH64)
-  set(ALL_CPU_FEATURES "FullFP16")
+  set(ALL_CPU_FEATURES FullFP16 MOPS SVE SVE2)
   set(LIBC_COMPILE_OPTIONS_NATIVE -mcpu=native)
 endif()
 
diff --git a/libc/cmake/modules/cpu_features/check_MOPS.cpp b/libc/cmake/modules/cpu_features/check_MOPS.cpp
new file mode 100644
index 0000000000000..bf5d392242b44
--- /dev/null
+++ b/libc/cmake/modules/cpu_features/check_MOPS.cpp
@@ -0,0 +1,7 @@
+#include "src/__support/macros/properties/cpu_features.h"
+
+#ifndef LIBC_TARGET_CPU_HAS_MOPS
+#error unsupported
+#endif
+
+
diff --git a/libc/cmake/modules/cpu_features/check_SVE.cpp b/libc/cmake/modules/cpu_features/check_SVE.cpp
new file mode 100644
index 0000000000000..0ae4b4dcf3558
--- /dev/null
+++ b/libc/cmake/modules/cpu_features/check_SVE.cpp
@@ -0,0 +1,7 @@
+#include "src/__support/macros/properties/cpu_features.h"
+
+#ifndef LIBC_TARGET_CPU_HAS_SVE
+#error unsupported
+#endif
+
+
diff --git a/libc/cmake/modules/cpu_features/check_SVE2.cpp b/libc/cmake/modules/cpu_features/check_SVE2.cpp
new file mode 100644
index 0000000000000..b46d1ac421267
--- /dev/null
+++ b/libc/cmake/modules/cpu_features/check_SVE2.cpp
@@ -0,0 +1,7 @@
+#include "src/__support/macros/properties/cpu_features.h"
+
+#ifndef LIBC_TARGET_CPU_HAS_SVE2
+#error unsupported
+#endif
+
+
diff --git a/libc/src/__support/macros/properties/cpu_features.h b/libc/src/__support/macros/properties/cpu_features.h
index fc6099ca6ccc5..1fe20d9b23a34 100644
--- a/libc/src/__support/macros/properties/cpu_features.h
+++ b/libc/src/__support/macros/properties/cpu_features.h
@@ -18,6 +18,18 @@
 #define LIBC_TARGET_CPU_HAS_FULLFP16
 #endif
 
+#if defined(__ARM_FEATURE_SVE)
+#define LIBC_TARGET_CPU_HAS_SVE
+#endif
+
+#if defined(__ARM_FEATURE_SVE2)
+#define LIBC_TARGET_CPU_HAS_SVE2
+#endif
+
+#if defined(__ARM_FEATURE_MOPS)
+#define LIBC_TARGET_CPU_HAS_MOPS
+#endif
+
 #if defined(__SSE2__)
 #define LIBC_TARGET_CPU_HAS_SSE2
 #define LIBC_TARGET_CPU_HAS_FPU_FLOAT

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[Andarwinux]

Just for reference, Arm's latest C1 series CPUs support MOPS, but according to Arm's Software Developer Errata Notice, MOPS might cause performance degradation. may need dispatch like FSRM.

4043997
FEAT_MOPS instructions might cause performance degradation

[SchrodingerZhu]

Just for reference, Arm's latest C1 series CPUs support MOPS, but according to Arm's Software Developer Errata Notice, MOPS might cause performance degradation. may need dispatch like FSRM.

4043997

FEAT_MOPS instructions might cause performance degradation

Got it. Thank you for the info!

Currently it is really just a feature flag. When we are going to use it, we could either look for ways to dispatch it or just leave it as a config flag.