[PCH] Support writing BuiltinBitCastExprs to PCHs

[hyd-dev]

Summary

D62825 adds the new BuiltinBitCastExpr, but does not set the Code member of ASTStmtWriter. This is not correct and causes an assertion failue (assert(Code != serialization::STMT_NULL_PTR && "unhandled sub-statement writing AST file")) in ASTStmtWriter::emit() when building PCHs that contain __builtin_bit_cast. This patch adds serialization::EXPR_BUILTIN_BIT_CAST and handles ASTStmtWriter::Code properly.

[hyd-dev]

Format builtin-bit-cast.cpp and make it simpler.

[hyd-dev]

Ping?

[erik.pilkington]

LGTM (after a minor comment), thank you for fixing this!

clang/lib/Serialization/ASTReaderStmt.cpp

3623

PathSize should always be zero, so I think it makes more sense to assert(Record[ASTStmtReader::NumExprFields] == 0); here and remove the PathSize parameter from the BuiltinBitCastExpr constructor.

[hyd-dev]

Address the comment: remove PathSize from BuiltinBitCastExpr's constructor and assert() it == 0.

[hyd-dev]

If this is OK, please commit it with --author "hyd-dev <[e-mail]>". Thanks.

clang/include/clang/AST/ExprCXX.h

 
 public:
   BuiltinBitCastExpr(QualType T, ExprValueKind VK, CastKind CK, Expr *SrcExpr,
                      TypeSourceInfo *DstType, SourceLocation KWLoc,
                      SourceLocation RParenLoc)
       : ExplicitCastExpr(BuiltinBitCastExprClass, T, VK, CK, SrcExpr, 0,
                          DstType),
         KWLoc(KWLoc), RParenLoc(RParenLoc) {}
+  BuiltinBitCastExpr(EmptyShell Empty)
+      : ExplicitCastExpr(BuiltinBitCastExprClass, Empty, 0) {}
 
   SourceLocation getBeginLoc() const LLVM_READONLY { return KWLoc; }
   SourceLocation getEndLoc() const LLVM_READONLY { return RParenLoc; }
 
   static bool classof(const Stmt *T) {
     return T->getStmtClass() == BuiltinBitCastExprClass;
   }
 };
 
 } // namespace clang
 
 #endif // LLVM_CLANG_AST_EXPRCXX_H

clang/include/clang/Serialization/ASTBitCodes.h

enum StmtCode {
       EXPR_CXX_CONST_CAST,
 
       /// A CXXAddrspaceCastExpr record.
       EXPR_CXX_ADDRSPACE_CAST,
 
       /// A CXXFunctionalCastExpr record.
       EXPR_CXX_FUNCTIONAL_CAST,
 
+      /// A BuiltinBitCastExpr record.
+      EXPR_BUILTIN_BIT_CAST,
+
       /// A UserDefinedLiteral record.
       EXPR_USER_DEFINED_LITERAL,
 
       /// A CXXStdInitializerListExpr record.
       EXPR_CXX_STD_INITIALIZER_LIST,
 
       /// A CXXBoolLiteralExpr record.
       EXPR_CXX_BOOL_LITERAL,

clang/lib/Serialization/ASTReaderStmt.cpp

case EXPR_CXX_ADDRSPACE_CAST:
       S = CXXAddrspaceCastExpr::CreateEmpty(Context);
       break;
 
     case EXPR_CXX_FUNCTIONAL_CAST:
       S = CXXFunctionalCastExpr::CreateEmpty(Context,
                        /*PathSize*/ Record[ASTStmtReader::NumExprFields]);
       break;
 
+    case EXPR_BUILTIN_BIT_CAST:
+      assert(Record[ASTStmtReader::NumExprFields] == 0 && "Wrong PathSize!");
+      S = new (Context) BuiltinBitCastExpr(Empty);
+      break;
+
     case EXPR_USER_DEFINED_LITERAL:
       S = UserDefinedLiteral::CreateEmpty(
           Context, /*NumArgs=*/Record[ASTStmtReader::NumExprFields], Empty);
       break;
 
     case EXPR_CXX_STD_INITIALIZER_LIST:
       S = new (Context) CXXStdInitializerListExpr(Empty);
       break;

clang/lib/Serialization/ASTWriterStmt.cpp

void ASTStmtWriter::VisitCXXFunctionalCastExpr(CXXFunctionalCastExpr *E) {
   Record.AddSourceLocation(E->getRParenLoc());
   Code = serialization::EXPR_CXX_FUNCTIONAL_CAST;
 }
 
 void ASTStmtWriter::VisitBuiltinBitCastExpr(BuiltinBitCastExpr *E) {
   VisitExplicitCastExpr(E);
   Record.AddSourceLocation(E->getBeginLoc());
   Record.AddSourceLocation(E->getEndLoc());
+  Code = serialization::EXPR_BUILTIN_BIT_CAST;
 }
 
 void ASTStmtWriter::VisitUserDefinedLiteral(UserDefinedLiteral *E) {
   VisitCallExpr(E);
   Record.AddSourceLocation(E->UDSuffixLoc);
   Code = serialization::EXPR_USER_DEFINED_LITERAL;
 }
 

clang/test/PCH/builtin-bit-cast.cpp

+// RUN: %clang_cc1 -emit-pch -o %t %s
+// RUN: %clang_cc1 -include-pch %t -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+template <class T, class U>
+constexpr T BuiltinBitCastWrapper(const U &Arg) {
+  return __builtin_bit_cast(T, Arg);
+}
+
+#else
+
+int main() {
+  return BuiltinBitCastWrapper<int>(0);
+}
+
+#endif