1 files changed, 82 insertions, 0 deletions
diff --git a/cmake/utils/CPUUtils.cmake b/cmake/utils/CPUUtils.cmake
new file mode 100644
index 00000000..8ca7683a
--- /dev/null
+++ b/cmake/utils/CPUUtils.cmake
@@ -0,0 +1,82 @@
+include(CheckCSourceRuns)
+
+# Compile + run a probe so we only enable a feature the host CPU
+# actually implements (toolchains accept flags the silicon may lack).
+# Cross-compile without an emulator: feature off.
+function(detect_cpu_feature _result_var _flags _source)
+  set(_save_flags "${CMAKE_REQUIRED_FLAGS}")
+  set(_save_quiet "${CMAKE_REQUIRED_QUIET}")
+  set(CMAKE_REQUIRED_FLAGS "${_save_flags} ${_flags}")
+  set(CMAKE_REQUIRED_QUIET TRUE)
+  if(CMAKE_CROSSCOMPILING AND NOT CMAKE_CROSSCOMPILING_EMULATOR)
+    set(${_result_var} FALSE CACHE INTERNAL
+        "${_result_var} (cross-compile without emulator: off)")
+  else()
+    check_c_source_runs("${_source}" ${_result_var})
+  endif()
+  set(CMAKE_REQUIRED_FLAGS "${_save_flags}")
+  set(CMAKE_REQUIRED_QUIET "${_save_quiet}")
+endfunction()
+
+# x86 PCLMULQDQ + SSE4.1. argc-derived input defeats constant folding;
+# SIGILL handler exits cleanly so the kernel skips the core dump.
+function(detect_pclmul)
+  detect_cpu_feature(_HAVE_PCLMUL "-mpclmul"
+"#include <wmmintrin.h>
+#include <signal.h>
+#include <unistd.h>
+static void on_sigill(int sig) { (void) sig; _exit(1); }
+int main(int argc, char ** argv) {
+        __m128i a;
+        __m128i b;
+        (void) argv;
+        signal(SIGILL, on_sigill);
+        a = _mm_set1_epi32(argc);
+        b = _mm_clmulepi64_si128(a, a, 0);
+        return _mm_cvtsi128_si32(b) & 0;
+}")
+  detect_cpu_feature(_HAVE_SSE41 "-msse4.1"
+"#include <smmintrin.h>
+#include <signal.h>
+#include <unistd.h>
+static void on_sigill(int sig) { (void) sig; _exit(1); }
+int main(int argc, char ** argv) {
+        __m128i a;
+        (void) argv;
+        signal(SIGILL, on_sigill);
+        a = _mm_set1_epi32(argc);
+        return _mm_extract_epi32(a, 0) & 0;
+}")
+  if(_HAVE_PCLMUL AND _HAVE_SSE41)
+    set(HAVE_PCLMUL TRUE CACHE INTERNAL
+        "x86 PCLMUL + SSE4.1 intrinsics available")
+  else()
+    unset(HAVE_PCLMUL CACHE)
+  endif()
+endfunction()
+
+# aarch64 FEAT_PMULL (vmull_p64). Pi 4's BCM2711 accepts +crypto at
+# compile time but lacks the hardware — the runtime probe catches that.
+function(detect_pmull)
+  detect_cpu_feature(_HAVE_PMULL "-march=armv8-a+crypto"
+"#include <arm_neon.h>
+#include <signal.h>
+#include <stdint.h>
+#include <unistd.h>
+static void on_sigill(int sig) { (void) sig; _exit(1); }
+int main(int argc, char ** argv) {
+        poly64_t   a;
+        poly128_t  c;
+        (void) argv;
+        signal(SIGILL, on_sigill);
+        a = (poly64_t) (uint64_t) argc;
+        c = vmull_p64(a, a);
+        return (int) (vgetq_lane_u64((uint64x2_t) c, 0) & 0);
+}")
+  if(_HAVE_PMULL)
+    set(HAVE_PMULL TRUE CACHE INTERNAL
+        "aarch64 PMULL intrinsics available")
+  else()
+    unset(HAVE_PMULL CACHE)
+  endif()
+endfunction()