Testing for _XCR_XFEATURE_ENABLED_MASK instead of a specific MSVC version because...

[oota-llvm.git] / lib / Support / Host.cpp

diff --git a/lib/Support/Host.cpp b/lib/Support/Host.cpp
index c353cc6887aa90a66f742e8749137241ad200d49..27c99c89aeee059af03f1556e6c52ad52803a10f 100644 (file)
--- a/lib/Support/Host.cpp
+++ b/lib/Support/Host.cpp
@@ -112,17 +112,19 @@ static bool GetX86CpuIDAndInfo(unsigned value, unsigned *rEAX,
 #endif
 }
 
-static bool OSHasAVXSupport() {\r
-#if defined( __GNUC__ ) && \\r
-    (__GNUC__ > 4 || __GNUC__ == 4 && __GNUC_MINOR__ >= 4)\r
-  int rEAX, rEDX;\r
-  __asm__ ("xgetbv" : "=a" (rEAX), "=d" (rEDX) : "c" (0)); \r
-#elif defined(_MSC_VER)\r
-  unsigned long long rEAX = _xgetbv(_XCR_XFEATURE_ENABLED_MASK);\r
-#else\r
-  int rEAX = 0; // Ensures we return false\r
-#endif\r
-  return (rEAX & 6) == 6;\r
+static bool OSHasAVXSupport() {
+#if defined(__GNUC__)
+  // Check xgetbv; this uses a .byte sequence instead of the instruction
+  // directly because older assemblers do not include support for xgetbv and
+  // there is no easy way to conditionally compile based on the assembler used.
+  int rEAX, rEDX;
+  __asm__ (".byte 0x0f, 0x01, 0xd0" : "=a" (rEAX), "=d" (rEDX) : "c" (0));
+#elif defined(_MSC_FULL_VER) && defined(_XCR_XFEATURE_ENABLED_MASK)
+  unsigned long long rEAX = _xgetbv(_XCR_XFEATURE_ENABLED_MASK);
+#else
+  int rEAX = 0; // Ensures we return false
+#endif
+  return (rEAX & 6) == 6;
 }
 
 static void DetectX86FamilyModel(unsigned EAX, unsigned &Family,
@@ -149,8 +151,9 @@ std::string sys::getHostCPUName() {
   bool HasSSE3 = (ECX & 0x1);
   // If CPUID indicates support for XSAVE, XRESTORE and AVX, and XGETBV 
   // indicates that the AVX registers will be saved and restored on context
-  // switch, when we have full AVX support.
-  bool HasAVX = (ECX & ((1 << 28) | (1 << 27))) != 0 && OSHasAVXSupport();
+  // switch, then we have full AVX support.
+  const unsigned AVXBits = (1 << 27) | (1 << 28);
+  bool HasAVX = ((ECX & AVXBits) == AVXBits) && OSHasAVXSupport();
   GetX86CpuIDAndInfo(0x80000001, &EAX, &EBX, &ECX, &EDX);
   bool Em64T = (EDX >> 29) & 0x1;