Revert "Always build with SSE2 support & display an error if not available"

browser/app/nsBrowserApp.cpp

@@ -40,51 +40,6 @@
 #include "mozilla/Telemetry.h"
 #include "mozilla/WindowsDllBlocklist.h"
 
-#ifdef MOZ_LINUX_SSE2_STARTUP_ERROR
-#include <cpuid.h>
-#include "mozilla/Unused.h"
-
-static bool
-IsSSE2Available()
-{
-  // The rest of the app has been compiled to assume that SSE2 is present
-  // unconditionally, so we can't use the normal copy of SSE.cpp here.
-  // Since SSE.cpp caches the results and we need them only transiently,
-  // instead of #including SSE.cpp here, let's just inline the specific check
-  // that's needed.
-  unsigned int level = 1u;
-  unsigned int eax, ebx, ecx, edx;
-  unsigned int bits = (1u<<26);
-  unsigned int max = __get_cpuid_max(0, nullptr);
-  if (level > max) {
-    return false;
-  }
-  __cpuid_count(level, 0, eax, ebx, ecx, edx);
-  return (edx & bits) == bits;
-}
-
-static const char sSSE2Message[] =
-    "This browser version requires a processor with the SSE2 instruction "
-    "set extension.\n";
-
-__attribute__((constructor))
-static void
-SSE2Check()
-{
-  if (IsSSE2Available()) {
-    return;
-  }
-  // Using write() in order to avoid jemalloc-based buffering. Ignoring return
-  // values, since there isn't much we could do on failure and there is no
-  // point in trying to recover from errors.
-  MOZ_UNUSED(write(STDERR_FILENO,
-                   sSSE2Message,
-                   MOZ_ARRAY_LENGTH(sSSE2Message) - 1));
-  // _exit() instead of exit() to avoid running the usual "at exit" code.
-  _exit(255);
-}
-#endif
-
 #if !defined(MOZ_WIDGET_COCOA) && !defined(MOZ_WIDGET_ANDROID)
 #define MOZ_BROWSER_CAN_BE_CONTENTPROC
 #include "../../ipc/contentproc/plugin-container.cpp"