[X86] Attempt to make the Intel core CPU inheritance a little more readable and maintainable

[craig.topper]

Summary

The recently added cooperlake CPU has made our already ugly switch statement even worse. There's a CPU exclusion list around the bf16 feature in the cooper lake block. I worry that we'll have to keep adding new CPUs to that until bf16 intercepts a client space CPU. We have several other exclusion lists in other parts of the switch due to skylakeserver, cascadelake, and cooperlake not having sgx. Another for cannonlake not having clwb but having all other features from skx.

This removes all these special ifs at the cost of some duplication of features and a goto. I've copied all of the skx features into either cannonlake or icelakeclient(for clwb). And pulled sklyakeserver, cascadelake, and cooperlake out of the main inheritance chain into their own chain. At the end of skylakeserver we merge back into the main chain at skylakeclient but below sgx. I think this is at least easier to follow. Do others agree or have alternate suggestions of what to do here? Of course the best answer is probably this should all be in a table somehow.

[craig.topper]

Fix mistake in a comment

[RKSimon]

LGTM - the goto is unfortunate but more maintainable and less confusing then the current state of things

clang/lib/Basic/Targets/X86.cpp

157

Worth adding a comment explaining the AVX512 ISA divergence?

clang/lib/Basic/Targets/X86.cpp

bool X86TargetInfo::initFeatureMap(
 
   case CK_PentiumMMX:
   case CK_Pentium2:
   case CK_K6:
   case CK_WinChipC6:
     setFeatureEnabledImpl(Features, "mmx", true);
     break;
 
+  case CK_Cooperlake:
+    // CPX inherits all CLX features plus AVX512BF16
+    setFeatureEnabledImpl(Features, "avx512bf16", true);
+    LLVM_FALLTHROUGH;
+  case CK_Cascadelake:
+    // CLX inherits all SKX features plus AVX512VNNI
+    setFeatureEnabledImpl(Features, "avx512vnni", true);
+    LLVM_FALLTHROUGH;
+  case CK_SkylakeServer:
+    setFeatureEnabledImpl(Features, "avx512f", true);
+    setFeatureEnabledImpl(Features, "avx512cd", true);
+    setFeatureEnabledImpl(Features, "avx512dq", true);
+    setFeatureEnabledImpl(Features, "avx512bw", true);
+    setFeatureEnabledImpl(Features, "avx512vl", true);
+    setFeatureEnabledImpl(Features, "clwb", true);
+    setFeatureEnabledImpl(Features, "pku", true);
+    goto SkylakeCommon;
+
   case CK_IcelakeServer:
     setFeatureEnabledImpl(Features, "pconfig", true);
     setFeatureEnabledImpl(Features, "wbnoinvd", true);
     LLVM_FALLTHROUGH;
   case CK_IcelakeClient:
     setFeatureEnabledImpl(Features, "vaes", true);
     setFeatureEnabledImpl(Features, "gfni", true);
     setFeatureEnabledImpl(Features, "vpclmulqdq", true);
     setFeatureEnabledImpl(Features, "avx512bitalg", true);
     setFeatureEnabledImpl(Features, "avx512vbmi2", true);
+    setFeatureEnabledImpl(Features, "avx512vnni", true);
     setFeatureEnabledImpl(Features, "avx512vpopcntdq", true);
     setFeatureEnabledImpl(Features, "rdpid", true);
+    setFeatureEnabledImpl(Features, "clwb", true);
     LLVM_FALLTHROUGH;
   case CK_Cannonlake:
-    setFeatureEnabledImpl(Features, "avx512ifma", true);
-    setFeatureEnabledImpl(Features, "avx512vbmi", true);
-    setFeatureEnabledImpl(Features, "sha", true);
-    LLVM_FALLTHROUGH;
-  case CK_Cooperlake:
-    // Cannonlake, IcelakeClient and IcelakeServer have no AVX512BF16 feature
-    if (Kind != CK_Cannonlake && Kind != CK_IcelakeClient &&
-        Kind != CK_IcelakeServer)
-      // CPX inherits all CLX features plus AVX512BF16
-      setFeatureEnabledImpl(Features, "avx512bf16", true);
-    LLVM_FALLTHROUGH;
-  case CK_Cascadelake:
-    //Cannonlake has no VNNI feature inside while Icelake has
-    if (Kind != CK_Cannonlake)
-      // CLK inherits all SKX features plus AVX512_VNNI
-      setFeatureEnabledImpl(Features, "avx512vnni", true);
-    LLVM_FALLTHROUGH;
-  case CK_SkylakeServer:
     setFeatureEnabledImpl(Features, "avx512f", true);
     setFeatureEnabledImpl(Features, "avx512cd", true);
     setFeatureEnabledImpl(Features, "avx512dq", true);
     setFeatureEnabledImpl(Features, "avx512bw", true);
     setFeatureEnabledImpl(Features, "avx512vl", true);
+    setFeatureEnabledImpl(Features, "avx512ifma", true);
+    setFeatureEnabledImpl(Features, "avx512vbmi", true);
     setFeatureEnabledImpl(Features, "pku", true);
-    if (Kind != CK_Cannonlake) // CNL inherits all SKX features, except CLWB
-      setFeatureEnabledImpl(Features, "clwb", true);
+    setFeatureEnabledImpl(Features, "sha", true);
     LLVM_FALLTHROUGH;
   case CK_SkylakeClient:
+    setFeatureEnabledImpl(Features, "sgx", true);
+    // SkylakeServer cores inherits all SKL features, except SGX
+SkylakeCommon:
     setFeatureEnabledImpl(Features, "xsavec", true);
     setFeatureEnabledImpl(Features, "xsaves", true);
     setFeatureEnabledImpl(Features, "mpx", true);
-    if (Kind != CK_SkylakeServer && Kind != CK_Cascadelake &&
-        Kind != CK_Cooperlake)
-      // SKX/CLX/CPX inherits all SKL features, except SGX
-      setFeatureEnabledImpl(Features, "sgx", true);
     setFeatureEnabledImpl(Features, "clflushopt", true);
     setFeatureEnabledImpl(Features, "aes", true);
     LLVM_FALLTHROUGH;
   case CK_Broadwell:
     setFeatureEnabledImpl(Features, "rdseed", true);
     setFeatureEnabledImpl(Features, "adx", true);
     setFeatureEnabledImpl(Features, "prfchw", true);
     LLVM_FALLTHROUGH;