[PATCH] D156963: [X86] Workaround possible CPUID bug in Sandy Bridge.

[Craig Topper via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG2a5e3f4c6c2c: [X86] Workaround possible CPUID bug in Sandy Bridge. (authored by craig.topper).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D156963/new/

https://reviews.llvm.org/D156963

Files:
  compiler-rt/lib/builtins/cpu_model.c
  llvm/lib/TargetParser/Host.cpp


Index: llvm/lib/TargetParser/Host.cpp
===================================================================
--- llvm/lib/TargetParser/Host.cpp
+++ llvm/lib/TargetParser/Host.cpp
@@ -1259,8 +1259,11 @@
   if (HasLeaf7 && ((EDX >> 8) & 1) && HasAVX512Save)
     setFeature(X86::FEATURE_AVX512VP2INTERSECT);
 
+  // EAX from subleaf 0 is the maximum subleaf supported. Some CPUs don't
+  // return all 0s for invalid subleaves so check the limit.
   bool HasLeaf7Subleaf1 =
-      MaxLeaf >= 7 && !getX86CpuIDAndInfoEx(0x7, 0x1, &EAX, &EBX, &ECX, &EDX);
+      HasLeaf7 && EAX >= 1 &&
+      !getX86CpuIDAndInfoEx(0x7, 0x1, &EAX, &EBX, &ECX, &EDX);
   if (HasLeaf7Subleaf1 && ((EAX >> 5) & 1) && HasAVX512Save)
     setFeature(X86::FEATURE_AVX512BF16);
 
@@ -1768,8 +1771,11 @@
   Features["avx512fp16"] = HasLeaf7 && ((EDX >> 23) & 1) && HasAVX512Save;
   Features["amx-tile"]   = HasLeaf7 && ((EDX >> 24) & 1) && HasAMXSave;
   Features["amx-int8"]   = HasLeaf7 && ((EDX >> 25) & 1) && HasAMXSave;
+  // EAX from subleaf 0 is the maximum subleaf supported. Some CPUs don't
+  // return all 0s for invalid subleaves so check the limit.
   bool HasLeaf7Subleaf1 =
-      MaxLevel >= 7 && !getX86CpuIDAndInfoEx(0x7, 0x1, &EAX, &EBX, &ECX, &EDX);
+      HasLeaf7 && EAX >= 1 &&
+      !getX86CpuIDAndInfoEx(0x7, 0x1, &EAX, &EBX, &ECX, &EDX);
   Features["sha512"]     = HasLeaf7Subleaf1 && ((EAX >> 0) & 1);
   Features["sm3"]        = HasLeaf7Subleaf1 && ((EAX >> 1) & 1);
   Features["sm4"]        = HasLeaf7Subleaf1 && ((EAX >> 2) & 1);
Index: compiler-rt/lib/builtins/cpu_model.c
===================================================================
--- compiler-rt/lib/builtins/cpu_model.c
+++ compiler-rt/lib/builtins/cpu_model.c
@@ -771,8 +771,11 @@
   if (HasLeaf7 && ((EDX >> 8) & 1) && HasAVX512Save)
     setFeature(FEATURE_AVX512VP2INTERSECT);
 
+  // EAX from subleaf 0 is the maximum subleaf supported. Some CPUs don't
+  // return all 0s for invalid subleaves so check the limit.
   bool HasLeaf7Subleaf1 =
-      MaxLeaf >= 0x7 && !getX86CpuIDAndInfoEx(0x7, 0x1, &EAX, &EBX, &ECX, &EDX);
+      HasLeaf7 && EAX >= 1 &&
+      !getX86CpuIDAndInfoEx(0x7, 0x1, &EAX, &EBX, &ECX, &EDX);
   if (HasLeaf7Subleaf1 && ((EAX >> 5) & 1) && HasAVX512Save)
     setFeature(FEATURE_AVX512BF16);
 


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