[X86] Change getHostCPUName to report Intel model 0x4e as "skylake" instead of "skylake-avx512". Add the proper 0x55 model for "skylake-avx512".

Summary:
Intel's i5-6300U CPU is reporting to have a model id of 78 (4e).
The Host detection assumes that to be Skylake Xeon (with AVX512 support),
instead of a normal Skylake machine.

Patch by: Valentin Churavy

Reviewers: nalimilan, craig.topper

Subscribers: hfinkel, tkelman, craig.topper, nalimilan, llvm-commits

Differential Revision: https://reviews.llvm.org/D28221

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291084 91177308-0d34-0410-b5e6-96231b3b80d8

Author: topperc

lib/Support/Host.cpp

@@ -475,14 +475,22 @@ getIntelProcessorTypeAndSubtype(unsigned int Family, unsigned int Model,
 
     // Skylake:
     case 0x4e:
-      *Type = INTEL_COREI7; // "skylake-avx512"
-      *Subtype = INTEL_COREI7_SKYLAKE_AVX512;
-      break;
     case 0x5e:
       *Type = INTEL_COREI7; // "skylake"
       *Subtype = INTEL_COREI7_SKYLAKE;
       break;
 
+    // Skylake Xeon:
+    case 0x55:
+      *Type = INTEL_COREI7;
+      // Check that we really have AVX512
+      if (Features & (1 << FEATURE_AVX512)) {
+        *Subtype = INTEL_COREI7_SKYLAKE_AVX512; // "skylake-avx512"
+      } else {
+        *Subtype = INTEL_COREI7_SKYLAKE; // "skylake"
+      }
+      break;
+
     case 0x1c: // Most 45 nm Intel Atom processors
     case 0x26: // 45 nm Atom Lincroft
     case 0x27: // 32 nm Atom Medfield