[llvm] r250269 - [X86] Update CPU detection to only enable XSAVE features if the OS has enabled them and the saving of YMM state. This seems to be consistent with gcc behavior.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Wed Oct 14 00:37:42 2015
New Revision: 250269

URL: http://llvm.org/viewvc/llvm-project?rev=250269&view=rev
Log:
[X86] Update CPU detection to only enable XSAVE features if the OS has enabled them and the saving of YMM state. This seems to be consistent with gcc behavior.

Modified:
    llvm/trunk/lib/Support/Host.cpp

Modified: llvm/trunk/lib/Support/Host.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Host.cpp?rev=250269&r1=250268&r2=250269&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Host.cpp (original)
+++ llvm/trunk/lib/Support/Host.cpp Wed Oct 14 00:37:42 2015
@@ -769,20 +769,22 @@ bool sys::getHostCPUFeatures(StringMap<b
   Features["movbe"]  = (ECX >> 22) & 1;
   Features["popcnt"] = (ECX >> 23) & 1;
   Features["aes"]    = (ECX >> 25) & 1;
-  Features["xsave"]  = (ECX >> 26) & 1;
   Features["rdrnd"]  = (ECX >> 30) & 1;
 
   // If CPUID indicates support for XSAVE, XRESTORE and AVX, and XGETBV
   // indicates that the AVX registers will be saved and restored on context
   // switch, then we have full AVX support.
-  bool HasAVX = ((ECX >> 27) & 1) && ((ECX >> 28) & 1) &&
-                !GetX86XCR0(&EAX, &EDX) && ((EAX & 0x6) == 0x6);
-  Features["avx"]    = HasAVX;
-  Features["fma"]    = HasAVX && (ECX >> 12) & 1;
-  Features["f16c"]   = HasAVX && (ECX >> 29) & 1;
+  bool HasAVXSave = ((ECX >> 27) & 1) && ((ECX >> 28) & 1) &&
+                    !GetX86XCR0(&EAX, &EDX) && ((EAX & 0x6) == 0x6);
+  Features["avx"]    = HasAVXSave;
+  Features["fma"]    = HasAVXSave && (ECX >> 12) & 1;
+  Features["f16c"]   = HasAVXSave && (ECX >> 29) & 1;
+
+  // Only enable XSAVE if OS has enabled support for saving YMM state.
+  Features["xsave"]  = HasAVXSave && (ECX >> 26) & 1;
 
   // AVX512 requires additional context to be saved by the OS.
-  bool HasAVX512Save = HasAVX && ((EAX & 0xe0) == 0xe0);
+  bool HasAVX512Save = HasAVXSave && ((EAX & 0xe0) == 0xe0);
 
   unsigned MaxExtLevel;
   GetX86CpuIDAndInfo(0x80000000, &MaxExtLevel, &EBX, &ECX, &EDX);
@@ -792,15 +794,15 @@ bool sys::getHostCPUFeatures(StringMap<b
   Features["lzcnt"]  = HasExtLeaf1 && ((ECX >>  5) & 1);
   Features["sse4a"]  = HasExtLeaf1 && ((ECX >>  6) & 1);
   Features["prfchw"] = HasExtLeaf1 && ((ECX >>  8) & 1);
-  Features["xop"]    = HasAVX && HasExtLeaf1 && ((ECX >> 11) & 1);
-  Features["fma4"]   = HasAVX && HasExtLeaf1 && ((ECX >> 16) & 1);
+  Features["xop"]    = HasExtLeaf1 && ((ECX >> 11) & 1) && HasAVXSave;
+  Features["fma4"]   = HasExtLeaf1 && ((ECX >> 16) & 1) && HasAVXSave;
   Features["tbm"]    = HasExtLeaf1 && ((ECX >> 21) & 1);
 
   bool HasLeaf7 = MaxLevel >= 7 &&
                   !GetX86CpuIDAndInfoEx(0x7, 0x0, &EAX, &EBX, &ECX, &EDX);
 
   // AVX2 is only supported if we have the OS save support from AVX.
-  Features["avx2"]     = HasAVX && HasLeaf7 && (EBX >>  5) & 1;
+  Features["avx2"]     = HasAVXSave && HasLeaf7 && ((EBX >>  5) & 1);
 
   Features["fsgsbase"] = HasLeaf7 && ((EBX >>  0) & 1);
   Features["bmi"]      = HasLeaf7 && ((EBX >>  3) & 1);
@@ -820,13 +822,13 @@ bool sys::getHostCPUFeatures(StringMap<b
   Features["avx512bw"] = HasLeaf7 && ((EBX >> 30) & 1) && HasAVX512Save;
   Features["avx512vl"] = HasLeaf7 && ((EBX >> 31) & 1) && HasAVX512Save;
 
-
   bool HasLeafD = MaxLevel >= 0xd &&
     !GetX86CpuIDAndInfoEx(0xd, 0x1, &EAX, &EBX, &ECX, &EDX);
 
-  Features["xsaveopt"] = Features["xsave"] && HasLeafD && ((EAX >> 0) & 1);
-  Features["xsavec"]   = Features["xsave"] && HasLeafD && ((EAX >> 1) & 1);
-  Features["xsaves"]   = Features["xsave"] && HasLeafD && ((EAX >> 3) & 1);
+  // Only enable XSAVE if OS has enabled support for saving YMM state.
+  Features["xsaveopt"] = HasAVXSave && HasLeafD && ((EAX >> 0) & 1);
+  Features["xsavec"]   = HasAVXSave && HasLeafD && ((EAX >> 1) & 1);
+  Features["xsaves"]   = HasAVXSave && HasLeafD && ((EAX >> 3) & 1);
 
   return true;
 }