diff --git a/llvm/lib/Support/Host.cpp b/llvm/lib/Support/Host.cpp
--- a/llvm/lib/Support/Host.cpp
+++ b/llvm/lib/Support/Host.cpp
@@ -1027,7 +1027,15 @@
   const unsigned AVXBits = (1 << 27) | (1 << 28);
   bool HasAVX = ((ECX & AVXBits) == AVXBits) && !getX86XCR0(&EAX, &EDX) &&
                 ((EAX & 0x6) == 0x6);
+#if defined(__APPLE__)
+  // Darwin lazily saves the AVX512 context on first use: trust that the OS will
+  // save the AVX512 context if we use AVX512 instructions, even the bit is not
+  // set right now.
+  bool HasAVX512Save = true;
+#else
+  // AVX512 requires additional context to be saved by the OS.
   bool HasAVX512Save = HasAVX && ((EAX & 0xe0) == 0xe0);
+#endif
 
   if (HasAVX)
     setFeature(X86::FEATURE_AVX);
@@ -1364,8 +1372,15 @@
   // switch, then we have full AVX support.
   bool HasAVXSave = ((ECX >> 27) & 1) && ((ECX >> 28) & 1) &&
                     !getX86XCR0(&EAX, &EDX) && ((EAX & 0x6) == 0x6);
+#if defined(__APPLE__)
+  // Darwin lazily saves the AVX512 context on first use: trust that the OS will
+  // save the AVX512 context if we use AVX512 instructions, even the bit is not
+  // set right now.
+  bool HasAVX512Save = true;
+#else
   // AVX512 requires additional context to be saved by the OS.
   bool HasAVX512Save = HasAVXSave && ((EAX & 0xe0) == 0xe0);
+#endif
 
   Features["avx"]   = HasAVXSave;
   Features["fma"]   = ((ECX >> 12) & 1) && HasAVXSave;