[clang] - Add missing builtin name to AtomicExpr JSON dump

As a side effect, introduce AtomicExpr::getOpAsString() to dump the
AtomicOp string representation.

This is a recommit with the ranges unchecked to cope with
platform-specific values.

Differential Revision: https://reviews.llvm.org/D158558

clang/include/clang/AST/Expr.h

@@ -6480,6 +6480,15 @@ class AtomicExpr : public Expr {
   QualType getValueType() const;
 
   AtomicOp getOp() const { return Op; }
+  StringRef getOpAsString() const {
+    switch (Op) {
+#define BUILTIN(ID, TYPE, ATTRS)
+#define ATOMIC_BUILTIN(ID, TYPE, ATTRS)                                        \
+  case AO##ID:                                                                 \
+    return #ID;
+#include "clang/Basic/Builtins.def"
+    }
+  }
   unsigned getNumSubExprs() const { return NumSubExprs; }
 
   Expr **getSubExprs() { return reinterpret_cast<Expr **>(SubExprs); }

clang/include/clang/AST/JSONNodeDumper.h

@@ -285,6 +285,7 @@ class JSONNodeDumper
   void VisitBinaryOperator(const BinaryOperator *BO);
   void VisitCompoundAssignOperator(const CompoundAssignOperator *CAO);
   void VisitMemberExpr(const MemberExpr *ME);
+  void VisitAtomicExpr(const AtomicExpr *AE);
   void VisitCXXNewExpr(const CXXNewExpr *NE);
   void VisitCXXDeleteExpr(const CXXDeleteExpr *DE);
   void VisitCXXThisExpr(const CXXThisExpr *TE);

clang/lib/AST/JSONNodeDumper.cpp

@@ -1179,6 +1179,10 @@ void JSONNodeDumper::VisitBlockDecl(const BlockDecl *D) {
   attributeOnlyIfTrue("capturesThis", D->capturesCXXThis());
 }
 
+void JSONNodeDumper::VisitAtomicExpr(const AtomicExpr *AE) {
+  JOS.attribute("name", AE->getOpAsString());
+}
+
 void JSONNodeDumper::VisitObjCEncodeExpr(const ObjCEncodeExpr *OEE) {
   JOS.attribute("encodedType", createQualType(OEE->getEncodedType()));
 }

clang/test/AST/ast-dump-atomic-json.c

@@ -0,0 +1,60 @@
+// RUN: %clang_cc1 -triple x86_64-pc-linux -Wno-unused-value -ast-dump=json %s | FileCheck %s
+
+int foo(int * ptr) {
+  return __atomic_load_n(ptr, __ATOMIC_SEQ_CST);
+}
+
+// NOTE: CHECK lines have *not* been autogenerated by gen_ast_dump_json_test.py
+// as its output is not portable for AtomicExpr across platforms. Instead rely
+// on loose CHECKS.
+
+
+// CHECK-NOT: {{^}}Dumping
+// CHECK:  "kind": "AtomicExpr",
+// CHECK:  "type": {
+// CHECK:   "qualType": "int"
+// CHECK:  },
+// CHECK:  "valueCategory": "prvalue",
+// CHECK:  "name": "__atomic_load_n",
+// CHECK:  "inner": [
+// CHECK:   {
+// CHECK:    "id": "0x{{.*}}",
+// CHECK:    "kind": "ImplicitCastExpr",
+// CHECK:    },
+// CHECK:    "type": {
+// CHECK:     "qualType": "int *"
+// CHECK:    },
+// CHECK:    "valueCategory": "prvalue",
+// CHECK:    "castKind": "LValueToRValue",
+// CHECK:    "inner": [
+// CHECK:     {
+// CHECK:      "id": "0x{{.*}}",
+// CHECK:      "kind": "DeclRefExpr",
+// CHECK:      },
+// CHECK:      "type": {
+// CHECK:       "qualType": "int *"
+// CHECK:      },
+// CHECK:      "valueCategory": "lvalue",
+// CHECK:      "referencedDecl": {
+// CHECK:       "id": "0x{{.*}}",
+// CHECK:       "kind": "ParmVarDecl",
+// CHECK:       "name": "ptr",
+// CHECK:       "type": {
+// CHECK:        "qualType": "int *"
+// CHECK:       }
+// CHECK:      }
+// CHECK:     }
+// CHECK:    ]
+// CHECK:   },
+// CHECK:   {
+// CHECK:    "id": "0x{{.*}}",
+// CHECK:    "kind": "IntegerLiteral",
+// CHECK:    },
+// CHECK:    "type": {
+// CHECK:     "qualType": "int"
+// CHECK:    },
+// CHECK:    "valueCategory": "prvalue",
+// CHECK:    "value": "5"
+// CHECK:   }
+// CHECK:  ]
+// CHECK: }