diff --git a/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.cpp b/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.cpp
index 7caccb48..15c6aba6 100644
--- a/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.cpp
+++ b/Source/JavaScriptCore/assembler/MacroAssemblerX86Common.cpp
@@ -1035,13 +1035,14 @@ void MacroAssemblerX86Common::collectCPUFeatures()
     static std::once_flag onceKey;
     std::call_once(onceKey, [] {
         {
+            __builtin_cpu_init ();
             CPUID cpuid = getCPUID(0x1);
             s_sse3CheckState = (cpuid[2] & (1 << 0)) ? CPUIDCheckState::Set : CPUIDCheckState::Clear;
             s_supplementalSSE3CheckState = (cpuid[2] & (1 << 9)) ? CPUIDCheckState::Set : CPUIDCheckState::Clear;
             s_sse4_1CheckState = (cpuid[2] & (1 << 19)) ? CPUIDCheckState::Set : CPUIDCheckState::Clear;
             s_sse4_2CheckState = (cpuid[2] & (1 << 20)) ? CPUIDCheckState::Set : CPUIDCheckState::Clear;
             s_popcntCheckState = (cpuid[2] & (1 << 23)) ? CPUIDCheckState::Set : CPUIDCheckState::Clear;
-            s_avxCheckState = (cpuid[2] & (1 << 28)) ? CPUIDCheckState::Set : CPUIDCheckState::Clear;
+            s_avxCheckState = (__builtin_cpu_supports ("avx")) ? CPUIDCheckState::Set : CPUIDCheckState::Clear;
         }
 #if OS(DARWIN)
         {
@@ -1057,7 +1058,7 @@ void MacroAssemblerX86Common::collectCPUFeatures()
         {
             CPUID cpuid = getCPUID(0x7);
             s_bmi1CheckState = (cpuid[2] & (1 << 3)) ? CPUIDCheckState::Set : CPUIDCheckState::Clear;
-            s_avx2CheckState = (cpuid[2] & (1 << 5)) ? CPUIDCheckState::Set : CPUIDCheckState::Clear;
+            s_avx2CheckState = (__builtin_cpu_supports ("avx2")) ? CPUIDCheckState::Set : CPUIDCheckState::Clear;
         }
 #endif
         {