From 95d7ccb70b9cbd53f1f137c0b2411852c42c122b Mon Sep 17 00:00:00 2001
From: hyd-dev <yd-huang@outlook.com>
Date: Thu, 11 Jun 2020 12:30:16 -0400
Subject: [PATCH] [PCH] Support writing BuiltinBitCastExprs to PCHs

eee944e7f adds the new BuiltinBitCastExpr, but does not set the Code member of
ASTStmtWriter. This is not correct and causes an assertion failue in
ASTStmtWriter::emit() when building PCHs that contain __builtin_bit_cast.  This
commit adds serialization::EXPR_BUILTIN_BIT_CAST and handles
ASTStmtWriter::Code properly.

Differential revision: https://reviews.llvm.org/D80360
---
 clang/include/clang/AST/ExprCXX.h               |  2 ++
 clang/include/clang/Serialization/ASTBitCodes.h |  3 +++
 clang/lib/Serialization/ASTReaderStmt.cpp       |  5 +++++
 clang/lib/Serialization/ASTWriterStmt.cpp       |  1 +
 clang/test/PCH/builtin-bit-cast.cpp             | 19 +++++++++++++++++++
 5 files changed, 30 insertions(+)
 create mode 100644 clang/test/PCH/builtin-bit-cast.cpp

diff --git a/clang/include/clang/AST/ExprCXX.h b/clang/include/clang/AST/ExprCXX.h
index 56b27d5..379f762 100644
--- a/clang/include/clang/AST/ExprCXX.h
+++ b/clang/include/clang/AST/ExprCXX.h
@@ -4821,6 +4821,8 @@ public:
       : 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; }
diff --git a/clang/include/clang/Serialization/ASTBitCodes.h b/clang/include/clang/Serialization/ASTBitCodes.h
index 4008f11..c6f9f1d 100644
--- a/clang/include/clang/Serialization/ASTBitCodes.h
+++ b/clang/include/clang/Serialization/ASTBitCodes.h
@@ -1812,6 +1812,9 @@ public:
       /// A CXXFunctionalCastExpr record.
       EXPR_CXX_FUNCTIONAL_CAST,
 
+      /// A BuiltinBitCastExpr record.
+      EXPR_BUILTIN_BIT_CAST,
+
       /// A UserDefinedLiteral record.
       EXPR_USER_DEFINED_LITERAL,
 
diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
index 5c7bc7a..86895c3 100644
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -3618,6 +3618,11 @@ Stmt *ASTReader::ReadStmtFromStream(ModuleFile &F) {
                        /*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);
diff --git a/clang/lib/Serialization/ASTWriterStmt.cpp b/clang/lib/Serialization/ASTWriterStmt.cpp
index 5e445b6..45cd54f 100644
--- a/clang/lib/Serialization/ASTWriterStmt.cpp
+++ b/clang/lib/Serialization/ASTWriterStmt.cpp
@@ -1655,6 +1655,7 @@ 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) {
diff --git a/clang/test/PCH/builtin-bit-cast.cpp b/clang/test/PCH/builtin-bit-cast.cpp
new file mode 100644
index 0000000..5755ce9
--- /dev/null
+++ b/clang/test/PCH/builtin-bit-cast.cpp
@@ -0,0 +1,19 @@
+// 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
-- 
2.7.4