Index: lib/Basic/Targets/X86.cpp
===================================================================
--- lib/Basic/Targets/X86.cpp
+++ lib/Basic/Targets/X86.cpp
@@ -830,35 +830,35 @@
     break;
   case CK_Bonnell:
     defineCPUMacros(Builder, "atom");
+    // gcc also defines 'bonnell', but we never have. See comment below.
     break;
   case CK_Silvermont:
     defineCPUMacros(Builder, "slm");
+    // gcc also defines 'silvermont', but we never have. See comment below.
     break;
   case CK_Goldmont:
     defineCPUMacros(Builder, "goldmont");
     break;
   case CK_Nehalem:
   case CK_Westmere:
+    defineCPUMacros(Builder, "corei7");
+    // gcc also defines 'nehalem', but we never have. See comment below.
+    break;
   case CK_SandyBridge:
   case CK_IvyBridge:
   case CK_Haswell:
   case CK_Broadwell:
   case CK_SkylakeClient:
-    // FIXME: Historically, we defined this legacy name, it would be nice to
-    // remove it at some point. We've never exposed fine-grained names for
-    // recent primary x86 CPUs, and we should keep it that way.
-    defineCPUMacros(Builder, "corei7");
-    break;
   case CK_SkylakeServer:
-    defineCPUMacros(Builder, "skx");
-    break;
   case CK_Cannonlake:
+  case CK_KNM:
+    // We don't want to define fine-grained macros for new CPUs going forward.
+    // While at the same time maintaining compatibility with gcc for the ones
+    // we have historically defined.
     break;
   case CK_KNL:
     defineCPUMacros(Builder, "knl");
     break;
-  case CK_KNM:
-    break;
   case CK_Lakemont:
     Builder.defineMacro("__tune_lakemont__");
     break;
Index: test/Preprocessor/predefined-arch-macros.c
===================================================================
--- test/Preprocessor/predefined-arch-macros.c
+++ test/Preprocessor/predefined-arch-macros.c
@@ -427,11 +427,8 @@
 // CHECK_COREI7_AVX_M32: #define __SSSE3__ 1
 // CHECK_COREI7_AVX_M32: #define __XSAVEOPT__ 1
 // CHECK_COREI7_AVX_M32: #define __XSAVE__ 1
-// CHECK_COREI7_AVX_M32: #define __corei7 1
-// CHECK_COREI7_AVX_M32: #define __corei7__ 1
 // CHECK_COREI7_AVX_M32: #define __i386 1
 // CHECK_COREI7_AVX_M32: #define __i386__ 1
-// CHECK_COREI7_AVX_M32: #define __tune_corei7__ 1
 // CHECK_COREI7_AVX_M32: #define i386 1
 // RUN: %clang -march=corei7-avx -m64 -E -dM %s -o - 2>&1 \
 // RUN:     -target i386-unknown-linux \
@@ -454,9 +451,6 @@
 // CHECK_COREI7_AVX_M64: #define __XSAVE__ 1
 // CHECK_COREI7_AVX_M64: #define __amd64 1
 // CHECK_COREI7_AVX_M64: #define __amd64__ 1
-// CHECK_COREI7_AVX_M64: #define __corei7 1
-// CHECK_COREI7_AVX_M64: #define __corei7__ 1
-// CHECK_COREI7_AVX_M64: #define __tune_corei7__ 1
 // CHECK_COREI7_AVX_M64: #define __x86_64 1
 // CHECK_COREI7_AVX_M64: #define __x86_64__ 1
 //
@@ -477,11 +471,8 @@
 // CHECK_CORE_AVX_I_M32: #define __SSSE3__ 1
 // CHECK_CORE_AVX_I_M32: #define __XSAVEOPT__ 1
 // CHECK_CORE_AVX_I_M32: #define __XSAVE__ 1
-// CHECK_CORE_AVX_I_M32: #define __corei7 1
-// CHECK_CORE_AVX_I_M32: #define __corei7__ 1
 // CHECK_CORE_AVX_I_M32: #define __i386 1
 // CHECK_CORE_AVX_I_M32: #define __i386__ 1
-// CHECK_CORE_AVX_I_M32: #define __tune_corei7__ 1
 // CHECK_CORE_AVX_I_M32: #define i386 1
 // RUN: %clang -march=core-avx-i -m64 -E -dM %s -o - 2>&1 \
 // RUN:     -target i386-unknown-linux \
@@ -504,9 +495,6 @@
 // CHECK_CORE_AVX_I_M64: #define __XSAVE__ 1
 // CHECK_CORE_AVX_I_M64: #define __amd64 1
 // CHECK_CORE_AVX_I_M64: #define __amd64__ 1
-// CHECK_CORE_AVX_I_M64: #define __corei7 1
-// CHECK_CORE_AVX_I_M64: #define __corei7__ 1
-// CHECK_CORE_AVX_I_M64: #define __tune_corei7__ 1
 // CHECK_CORE_AVX_I_M64: #define __x86_64 1
 // CHECK_CORE_AVX_I_M64: #define __x86_64__ 1
 //
@@ -533,11 +521,8 @@
 // CHECK_CORE_AVX2_M32: #define __SSSE3__ 1
 // CHECK_CORE_AVX2_M32: #define __XSAVEOPT__ 1
 // CHECK_CORE_AVX2_M32: #define __XSAVE__ 1
-// CHECK_CORE_AVX2_M32: #define __corei7 1
-// CHECK_CORE_AVX2_M32: #define __corei7__ 1
 // CHECK_CORE_AVX2_M32: #define __i386 1
 // CHECK_CORE_AVX2_M32: #define __i386__ 1
-// CHECK_CORE_AVX2_M32: #define __tune_corei7__ 1
 // CHECK_CORE_AVX2_M32: #define i386 1
 // RUN: %clang -march=core-avx2 -m64 -E -dM %s -o - 2>&1 \
 // RUN:     -target i386-unknown-linux \
@@ -566,9 +551,6 @@
 // CHECK_CORE_AVX2_M64: #define __XSAVE__ 1
 // CHECK_CORE_AVX2_M64: #define __amd64 1
 // CHECK_CORE_AVX2_M64: #define __amd64__ 1
-// CHECK_CORE_AVX2_M64: #define __corei7 1
-// CHECK_CORE_AVX2_M64: #define __corei7__ 1
-// CHECK_CORE_AVX2_M64: #define __tune_corei7__ 1
 // CHECK_CORE_AVX2_M64: #define __x86_64 1
 // CHECK_CORE_AVX2_M64: #define __x86_64__ 1
 //
@@ -597,11 +579,8 @@
 // CHECK_BROADWELL_M32: #define __SSSE3__ 1
 // CHECK_BROADWELL_M32: #define __XSAVEOPT__ 1
 // CHECK_BROADWELL_M32: #define __XSAVE__ 1
-// CHECK_BROADWELL_M32: #define __corei7 1
-// CHECK_BROADWELL_M32: #define __corei7__ 1
 // CHECK_BROADWELL_M32: #define __i386 1
 // CHECK_BROADWELL_M32: #define __i386__ 1
-// CHECK_BROADWELL_M32: #define __tune_corei7__ 1
 // CHECK_BROADWELL_M32: #define i386 1
 // RUN: %clang -march=broadwell -m64 -E -dM %s -o - 2>&1 \
 // RUN:     -target i386-unknown-linux \
@@ -632,9 +611,6 @@
 // CHECK_BROADWELL_M64: #define __XSAVE__ 1
 // CHECK_BROADWELL_M64: #define __amd64 1
 // CHECK_BROADWELL_M64: #define __amd64__ 1
-// CHECK_BROADWELL_M64: #define __corei7 1
-// CHECK_BROADWELL_M64: #define __corei7__ 1
-// CHECK_BROADWELL_M64: #define __tune_corei7__ 1
 // CHECK_BROADWELL_M64: #define __x86_64 1
 // CHECK_BROADWELL_M64: #define __x86_64__ 1
 //
@@ -892,9 +868,6 @@
 // CHECK_SKX_M32: #define __XSAVE__ 1
 // CHECK_SKX_M32: #define __i386 1
 // CHECK_SKX_M32: #define __i386__ 1
-// CHECK_SKX_M32: #define __skx 1
-// CHECK_SKX_M32: #define __skx__ 1
-// CHECK_SKX_M32: #define __tune_skx__ 1
 // CHECK_SKX_M32: #define i386 1
 
 // RUN: %clang -march=skylake-avx512 -m64 -E -dM %s -o - 2>&1 \
@@ -936,9 +909,6 @@
 // CHECK_SKX_M64: #define __XSAVE__ 1
 // CHECK_SKX_M64: #define __amd64 1
 // CHECK_SKX_M64: #define __amd64__ 1
-// CHECK_SKX_M64: #define __skx 1
-// CHECK_SKX_M64: #define __skx__ 1
-// CHECK_SKX_M64: #define __tune_skx__ 1
 // CHECK_SKX_M64: #define __x86_64 1
 // CHECK_SKX_M64: #define __x86_64__ 1
 //