Warn at start when using AVX build of Bun without AVX support (#6242)

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

1 files changed, 28 insertions, 1 deletions

diff --git a/src/bun.js/bindings/c-bindings.cpp b/src/bun.js/bindings/c-bindings.cpp
index ff4c8c4e7..f53ff52cc 100644
--- a/src/bun.js/bindings/c-bindings.cpp
+++ b/src/bun.js/bindings/c-bindings.cpp
@@ -1,4 +1,5 @@
 // when we don't want to use @cInclude, we can just stick wrapper functions here
+#include "root.h"
 #include <sys/resource.h>
 #include <cstdint>
 #include <unistd.h>
@@ -6,6 +7,32 @@
 #include <sys/stat.h>
 #include <sys/signal.h>
 
+#if CPU(X86_64)
+#include <cstring>
+#include <cpuid.h>
+
+extern "C" void bun_warn_avx_missing(const char* url)
+{
+    __builtin_cpu_init();
+    if (__builtin_cpu_supports("avx")) {
+        return;
+    }
+
+    static constexpr const char* str = "warn: CPU lacks AVX support, strange crashes may occur. Reinstall Bun or use *-baseline build:\n  ";
+    const size_t len = strlen(str);
+
+    char buf[512];
+    strcpy(buf, str);
+    strcpy(buf + len, url);
+    strcpy(buf + len + strlen(url), "\n\0");
+    write(STDERR_FILENO, buf, strlen(buf));
+}
+#else
+extern "C" void bun_warn_avx_missing(char* url)
+{
+}
+#endif
+
 extern "C" int32_t get_process_priority(uint32_t pid)
 {
     return getpriority(PRIO_PROCESS, pid);
@@ -48,4 +75,4 @@ extern "C" ssize_t bun_sysconf__SC_CLK_TCK()
 #else
     return 0;
 #endif
-}
\ No newline at end of file
+}