[Clang][BPF] Add __BPF_FEATURE_GOTOX (llvm#165456)

Add a macro __BPF_FEATURE_GOTOX for bpf target for cpu v4. So the
developer can easily detect whether insn gotox is supported or not.

Author: yonghong-song

clang/lib/Basic/Targets/BPF.cpp

@@ -75,6 +75,7 @@ void BPFTargetInfo::getTargetDefines(const LangOptions &Opts,
     Builder.defineMacro("__BPF_FEATURE_GOTOL");
     Builder.defineMacro("__BPF_FEATURE_ST");
     Builder.defineMacro("__BPF_FEATURE_LOAD_ACQ_STORE_REL");
+    Builder.defineMacro("__BPF_FEATURE_GOTOX");
   }
 }
 

clang/test/Preprocessor/bpf-predefined-macros.c

@@ -70,6 +70,9 @@ int u;
 #ifdef __BPF_FEATURE_LOAD_ACQ_STORE_REL
 int v;
 #endif
+#ifdef __BPF_FEATURE_GOTOX
+int w;
+#endif
 
 // CHECK: int b;
 // CHECK: int c;
@@ -110,6 +113,7 @@ int v;
 // CPU_V4: int u;
 
 // CPU_V4: int v;
+// CPU_V4: int w;
 
 // CPU_GENERIC: int g;