diff --git a/clang/include/clang/Interpreter/Interpreter.h b/clang/include/clang/Interpreter/Interpreter.h
--- a/clang/include/clang/Interpreter/Interpreter.h
+++ b/clang/include/clang/Interpreter/Interpreter.h
@@ -14,6 +14,7 @@
 #ifndef LLVM_CLANG_INTERPRETER_INTERPRETER_H
 #define LLVM_CLANG_INTERPRETER_INTERPRETER_H
 
+#include "clang/AST/Decl.h"
 #include "clang/Interpreter/PartialTranslationUnit.h"
 
 #include "clang/AST/GlobalDecl.h"
@@ -49,6 +50,7 @@
   std::unique_ptr<llvm::orc::ThreadSafeContext> TSCtx;
   std::unique_ptr<IncrementalParser> IncrParser;
   std::unique_ptr<IncrementalExecutor> IncrExecutor;
+  Expr *RuntimeInterface = nullptr;
 
   Interpreter(std::unique_ptr<CompilerInstance> CI, llvm::Error &Err);
 
@@ -60,14 +62,7 @@
   const llvm::orc::LLJIT *getExecutionEngine() const;
   llvm::Expected<PartialTranslationUnit &> Parse(llvm::StringRef Code);
   llvm::Error Execute(PartialTranslationUnit &T);
-  llvm::Error ParseAndExecute(llvm::StringRef Code) {
-    auto PTU = Parse(Code);
-    if (!PTU)
-      return PTU.takeError();
-    if (PTU->TheModule)
-      return Execute(*PTU);
-    return llvm::Error::success();
-  }
+  llvm::Error ParseAndExecute(llvm::StringRef Code);
 
   /// Undo N previous incremental inputs.
   llvm::Error Undo(unsigned N = 1);
@@ -85,6 +80,14 @@
   /// file.
   llvm::Expected<llvm::JITTargetAddress>
   getSymbolAddressFromLinkerName(llvm::StringRef LinkerName) const;
+
+  llvm::Expected<Expr *> CaptureExpr(TranslationUnitDecl &TU);
+
+  bool FindRuntimeInterface();
+
+  Expr *SynthesizeCall(clang::Expr *E);
+
+  llvm::Expected<PartialTranslationUnit &> GenPTU(clang::Expr *E);
 };
 } // namespace clang
 
diff --git a/clang/include/clang/Interpreter/Value.h b/clang/include/clang/Interpreter/Value.h
new file mode 100644
--- /dev/null
+++ b/clang/include/clang/Interpreter/Value.h
@@ -0,0 +1,59 @@
+//===--- Interpreter.h - Incremental Compiation and Execution---*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the class that used to represent a value in incremental
+// C++.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_INTERPRETER_VALUE_H
+#define LLVM_CLANG_INTERPRETER_VALUE_H
+
+#include "llvm/Support/Compiler.h"
+
+namespace llvm {
+class raw_ostream;
+
+} // namespace llvm
+
+namespace clang {
+
+class Interpreter;
+class QualType;
+
+class LLVM_EXTERNAL_VISIBILITY Value {
+  union Storage {
+    int Int;
+  };
+
+public:
+  enum class Kind { Char, Int, Float, Double, Unspecified };
+
+  explicit Value(void *Type) : OpaqueType(Type) {}
+
+  template <typename T> static Value Create(void *Type, T Val);
+
+  // Interpreter *getInterpreter() const { return Interp; }
+  bool isValid() const { return ValueKind != Kind::Unspecified; }
+  Kind getKind() const { return ValueKind; }
+
+  void setKind(Kind K) { ValueKind = K; }
+  clang::QualType getType() const;
+  void print(llvm::raw_ostream &Out) const;
+  void dump() const;
+
+private:
+  // Interpreter *Interp;
+  // QualType, stored as void* to reduce dependencies.
+  void *OpaqueType;
+  Storage Data;
+  Kind ValueKind = Kind::Unspecified;
+};
+
+} // namespace clang
+#endif
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -435,6 +435,10 @@
   /// a statement expression and builds a suitable expression statement.
   StmtResult handleExprStmt(ExprResult E, ParsedStmtContext StmtCtx);
 
+  /// A flag that indicate if we run into something that need to pretty print.
+  /// Note this should only be used in incremental C++ (clang-repl).
+  bool PrettyPrintMode = false;
+
 public:
   Parser(Preprocessor &PP, Sema &Actions, bool SkipFunctionBodies);
   ~Parser() override;
@@ -455,6 +459,17 @@
     return Actions.getObjCDeclContext();
   }
 
+  bool isPrettyPrintMode() const {
+    assert(PP.isIncrementalProcessingEnabled() &&
+           "This should only be used in incremental C++");
+    return PrettyPrintMode;
+  }
+  void setPrettyPrintMode(bool Mode = true) {
+    assert(PP.isIncrementalProcessingEnabled() &&
+           "This should only be used in incremental C++");
+    PrettyPrintMode = Mode;
+  }
+
   // Type forwarding.  All of these are statically 'void*', but they may all be
   // different actual classes based on the actions in place.
   typedef OpaquePtr<DeclGroupRef> DeclGroupPtrTy;
@@ -1058,7 +1073,8 @@
   /// If the next token is not a semicolon, this emits the specified diagnostic,
   /// or, if there's just some closing-delimiter noise (e.g., ')' or ']') prior
   /// to the semicolon, consumes that extra token.
-  bool ExpectAndConsumeSemi(unsigned DiagID , StringRef TokenUsed = "");
+  bool ExpectAndConsumeSemi(unsigned DiagID, StringRef TokenUsed = "",
+                            bool IsTopExpr = false);
 
   /// The kind of extra semi diagnostic to emit.
   enum ExtraSemiKind {
diff --git a/clang/lib/Interpreter/CMakeLists.txt b/clang/lib/Interpreter/CMakeLists.txt
--- a/clang/lib/Interpreter/CMakeLists.txt
+++ b/clang/lib/Interpreter/CMakeLists.txt
@@ -12,6 +12,8 @@
   IncrementalExecutor.cpp
   IncrementalParser.cpp
   Interpreter.cpp
+  PrettyPrint.cpp
+  Value.cpp
 
   DEPENDS
   intrinsics_gen
diff --git a/clang/lib/Interpreter/IncrementalParser.h b/clang/lib/Interpreter/IncrementalParser.h
--- a/clang/lib/Interpreter/IncrementalParser.h
+++ b/clang/lib/Interpreter/IncrementalParser.h
@@ -16,7 +16,7 @@
 #include "clang/Interpreter/PartialTranslationUnit.h"
 
 #include "clang/AST/GlobalDecl.h"
-
+#include "clang/Parse/Parser.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Error.h"
@@ -32,7 +32,7 @@
 class CompilerInstance;
 class IncrementalAction;
 class Parser;
-
+class Interpreter;
 /// Provides support for incremental compilation. Keeps track of the state
 /// changes between the subsequent incremental input.
 ///
@@ -49,9 +49,6 @@
   /// Consumer to process the produced top level decls. Owned by Act.
   ASTConsumer *Consumer = nullptr;
 
-  /// Counts the number of direct user input lines that have been parsed.
-  unsigned InputCount = 0;
-
   /// List containing every information about every incrementally parsed piece
   /// of code.
   std::list<PartialTranslationUnit> PTUs;
@@ -68,6 +65,8 @@
   /// \c TranslationUnitDecl and \c llvm::Module corresponding to the input.
   llvm::Expected<PartialTranslationUnit &> Parse(llvm::StringRef Input);
 
+  llvm::Expected<PartialTranslationUnit &> Parse(Parser::DeclGroupPtrTy D);
+
   /// Uses the CodeGenModule mangled name cache and avoids recomputing.
   ///\returns the mangled name of a \c GD.
   llvm::StringRef GetMangledName(GlobalDecl GD) const;
@@ -76,8 +75,11 @@
 
   std::list<PartialTranslationUnit> &getPTUs() { return PTUs; }
 
-private:
-  llvm::Expected<PartialTranslationUnit &> ParseOrWrapTopLevelDecl();
+  llvm::Expected<PartialTranslationUnit &>
+  ParseOrWrapTopLevelDecl(Parser::DeclGroupPtrTy SynthesizedDecl = nullptr);
+
+  bool isPrettyPrintMode() const { return P->isPrettyPrintMode(); }
+  void setPrettyPrintMode(bool Mode = true) { P->setPrettyPrintMode(Mode); }
 };
 } // end namespace clang
 
diff --git a/clang/lib/Interpreter/IncrementalParser.cpp b/clang/lib/Interpreter/IncrementalParser.cpp
--- a/clang/lib/Interpreter/IncrementalParser.cpp
+++ b/clang/lib/Interpreter/IncrementalParser.cpp
@@ -19,9 +19,9 @@
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendAction.h"
 #include "clang/FrontendTool/Utils.h"
+#include "clang/Interpreter/Interpreter.h"
 #include "clang/Parse/Parser.h"
 #include "clang/Sema/Sema.h"
-
 #include "llvm/Option/ArgList.h"
 #include "llvm/Support/CrashRecoveryContext.h"
 #include "llvm/Support/Error.h"
@@ -143,7 +143,8 @@
 }
 
 llvm::Expected<PartialTranslationUnit &>
-IncrementalParser::ParseOrWrapTopLevelDecl() {
+IncrementalParser::ParseOrWrapTopLevelDecl(
+    Parser::DeclGroupPtrTy SynthesizedDecl) {
   // Recover resources if we crash before exiting this method.
   Sema &S = CI->getSema();
   llvm::CrashRecoveryContextCleanupRegistrar<Sema> CleanupSema(&S);
@@ -169,14 +170,24 @@
     S.ActOnTranslationUnitScope(P->getCurScope());
   }
 
-  Parser::DeclGroupPtrTy ADecl;
-  Sema::ModuleImportState ImportState;
-  for (bool AtEOF = P->ParseFirstTopLevelDecl(ADecl, ImportState); !AtEOF;
-       AtEOF = P->ParseTopLevelDecl(ADecl, ImportState)) {
-    if (ADecl && !Consumer->HandleTopLevelDecl(ADecl.get()))
-      return llvm::make_error<llvm::StringError>("Parsing failed. "
-                                                 "The consumer rejected a decl",
-                                                 std::error_code());
+  if (SynthesizedDecl) {
+    if (!Consumer->HandleTopLevelDecl(SynthesizedDecl.get())) {
+      return llvm::make_error<llvm::StringError>(
+          "Parsing failed. "
+          "The consumer rejected the synthesized decl",
+          std::error_code());
+    }
+  } else {
+    Parser::DeclGroupPtrTy ADecl;
+    Sema::ModuleImportState ImportState;
+    for (bool AtEOF = P->ParseFirstTopLevelDecl(ADecl, ImportState); !AtEOF;
+         AtEOF = P->ParseTopLevelDecl(ADecl, ImportState)) {
+      if (ADecl && !Consumer->HandleTopLevelDecl(ADecl.get()))
+        return llvm::make_error<llvm::StringError>(
+            "Parsing failed. "
+            "The consumer rejected a decl",
+            std::error_code());
+    }
   }
 
   DiagnosticsEngine &Diags = getCI()->getDiagnostics();
@@ -213,24 +224,31 @@
   return static_cast<CodeGenAction *>(WrappedAct)->getCodeGenerator();
 }
 
-llvm::Expected<PartialTranslationUnit &>
-IncrementalParser::Parse(llvm::StringRef input) {
-  Preprocessor &PP = CI->getPreprocessor();
-  assert(PP.isIncrementalProcessingEnabled() && "Not in incremental mode!?");
-
+static std::unique_ptr<llvm::MemoryBuffer> MakeInputBuf(StringRef Input) {
+  /// Counts the number of direct user input lines that have been parsed.
+  static unsigned InputCount = 0;
   std::ostringstream SourceName;
   SourceName << "input_line_" << InputCount++;
-
   // Create an uninitialized memory buffer, copy code in and append "\n"
-  size_t InputSize = input.size(); // don't include trailing 0
+  size_t InputSize = Input.size(); // don't include trailing 0
+  size_t AllocSize = Input.size() + 1;
+
   // MemBuffer size should *not* include terminating zero
   std::unique_ptr<llvm::MemoryBuffer> MB(
-      llvm::WritableMemoryBuffer::getNewUninitMemBuffer(InputSize + 1,
+      llvm::WritableMemoryBuffer::getNewUninitMemBuffer(AllocSize,
                                                         SourceName.str()));
   char *MBStart = const_cast<char *>(MB->getBufferStart());
-  memcpy(MBStart, input.data(), InputSize);
-  MBStart[InputSize] = '\n';
+  memcpy(MBStart, Input.data(), InputSize);
+  MBStart[AllocSize - 1] = '\n';
+  return MB;
+}
 
+llvm::Expected<PartialTranslationUnit &>
+IncrementalParser::Parse(llvm::StringRef input) {
+  Preprocessor &PP = CI->getPreprocessor();
+  assert(PP.isIncrementalProcessingEnabled() && "Not in incremental mode!?");
+
+  std::unique_ptr<llvm::MemoryBuffer> MB = MakeInputBuf(input);
   SourceManager &SM = CI->getSourceManager();
 
   // FIXME: Create SourceLocation, which will allow clang to order the overload
@@ -278,6 +296,24 @@
   return PTU;
 }
 
+llvm::Expected<PartialTranslationUnit &>
+IncrementalParser::Parse(Parser::DeclGroupPtrTy D) {
+  llvm::Expected<PartialTranslationUnit &> PTUOrErr =
+      ParseOrWrapTopLevelDecl(D);
+  if (!PTUOrErr) {
+    return PTUOrErr.takeError();
+  }
+  if (CodeGenerator *CG = getCodeGen(Act.get())) {
+    std::unique_ptr<llvm::Module> M(CG->ReleaseModule());
+    CG->StartModule("incr_module_" + std::to_string(PTUs.size()),
+                    M->getContext());
+
+    PTUOrErr.get().TheModule = std::move(M);
+  }
+
+  return PTUOrErr;
+}
+
 void IncrementalParser::CleanUpPTU(PartialTranslationUnit &PTU) {
   TranslationUnitDecl *MostRecentTU = PTU.TUPart;
   TranslationUnitDecl *FirstTU = MostRecentTU->getFirstDecl();
diff --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -15,8 +15,9 @@
 
 #include "IncrementalExecutor.h"
 #include "IncrementalParser.h"
-
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/Expr.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/CodeGen/ModuleBuilder.h"
 #include "clang/CodeGen/ObjectFilePCHContainerOperations.h"
@@ -27,10 +28,15 @@
 #include "clang/Driver/Tool.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/TextDiagnosticBuffer.h"
+#include "clang/Interpreter/PartialTranslationUnit.h"
 #include "clang/Lex/PreprocessorOptions.h"
+#include "clang/Sema/DeclSpec.h"
+#include "clang/Sema/Lookup.h"
+#include "clang/Sema/Sema.h"
 
 #include "llvm/IR/Module.h"
 #include "llvm/Support/Errc.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Host.h"
 
 using namespace clang;
@@ -235,6 +241,34 @@
   return llvm::Error::success();
 }
 
+llvm::Error Interpreter::ParseAndExecute(llvm::StringRef Code) {
+  auto PTU = Parse(Code);
+  if (!PTU)
+    return PTU.takeError();
+  if (IncrParser->isPrettyPrintMode()) {
+    IncrParser->setPrettyPrintMode(false);
+
+    // Capture the expression we want to print.
+    auto ExprOrErr = CaptureExpr(*PTU->TUPart);
+    if (!ExprOrErr)
+      return ExprOrErr.takeError();
+    // Synthesize a CallExpr to `__InterpreterPrettyPrint`.
+    clang::Expr *E = SynthesizeCall(ExprOrErr.get());
+    // Generate a PartialTranslationUnit from the CallExpr.
+    llvm::Expected<clang::PartialTranslationUnit &> SynthesizedPTUOrErr =
+        GenPTU(E);
+    if (!SynthesizedPTUOrErr)
+      return SynthesizedPTUOrErr.takeError();
+
+    if (SynthesizedPTUOrErr->TheModule)
+      return Execute(*SynthesizedPTUOrErr);
+    return llvm::Error::success();
+  }
+  if (PTU->TheModule)
+    return Execute(*PTU);
+  return llvm::Error::success();
+}
+
 llvm::Expected<llvm::JITTargetAddress>
 Interpreter::getSymbolAddress(GlobalDecl GD) const {
   if (!IncrExecutor)
@@ -283,3 +317,79 @@
   }
   return llvm::Error::success();
 }
+
+llvm::Expected<Expr *> Interpreter::CaptureExpr(TranslationUnitDecl &TU) {
+  for (auto *D : TU.decls()) {
+    if (const auto *S = llvm::dyn_cast<clang::TopLevelStmtDecl>(D)) {
+      if (const auto *E = llvm::dyn_cast<clang::Expr>(S->getStmt())) {
+        return const_cast<Expr *>(E);
+      }
+    }
+  }
+  return llvm::make_error<llvm::StringError>("Can not capture any Expr*!",
+                                             std::error_code());
+}
+
+llvm::Expected<PartialTranslationUnit &> Interpreter::GenPTU(clang::Expr *E) {
+  Sema &S = getCompilerInstance()->getSema();
+  SmallVector<Decl *, 2> DeclsInGroup;
+  DeclsInGroup.push_back(S.ActOnTopLevelStmtDecl(E));
+  Sema::DeclGroupPtrTy DeclGroupPtr = S.BuildDeclaratorGroup(DeclsInGroup);
+  return IncrParser->Parse(DeclGroupPtr);
+}
+
+static constexpr llvm::StringRef MagicRuntimeInterface =
+    "__InterpreterPrettyPrint";
+
+bool Interpreter::FindRuntimeInterface() {
+  if (RuntimeInterface)
+    return true;
+
+  Sema &S = getCompilerInstance()->getSema();
+  ASTContext &Ctx = S.getASTContext();
+  LookupResult R(S, &Ctx.Idents.get(MagicRuntimeInterface), SourceLocation(),
+                 Sema::LookupOrdinaryName, Sema::ForVisibleRedeclaration);
+  S.LookupQualifiedName(R, Ctx.getTranslationUnitDecl());
+  if (R.empty()) {
+    return false;
+  }
+  CXXScopeSpec CSS;
+  RuntimeInterface = S.BuildDeclarationNameExpr(CSS, R, /*ADL=*/false).get();
+  return true;
+}
+
+static IntegerLiteral *IntegerLiteralExpr(ASTContext &C, uintptr_t Ptr) {
+  const llvm::APInt Addr(8 * sizeof(void *), Ptr);
+  return IntegerLiteral::Create(C, Addr, C.getUIntPtrType(), SourceLocation());
+}
+
+static Expr *CStyleCastPtrExpr(Sema *S, QualType Ty, Expr *E) {
+  ASTContext &Ctx = S->getASTContext();
+  if (!Ty->isPointerType())
+    Ty = Ctx.getPointerType(Ty);
+
+  TypeSourceInfo *TSI = Ctx.getTrivialTypeSourceInfo(Ty, SourceLocation());
+  Expr *Result =
+      S->BuildCStyleCastExpr(SourceLocation(), TSI, SourceLocation(), E).get();
+  assert(Result && "Cannot create CStyleCastPtrExpr");
+  return Result;
+}
+
+static Expr *CStyleCastPtrExpr(Sema *S, QualType Ty, uintptr_t Ptr) {
+  ASTContext &Ctx = S->getASTContext();
+  return CStyleCastPtrExpr(S, Ty, IntegerLiteralExpr(Ctx, Ptr));
+}
+
+Expr *Interpreter::SynthesizeCall(clang::Expr *E) {
+  Sema &S = getCompilerInstance()->getSema();
+  if (!FindRuntimeInterface()) {
+    llvm_unreachable("We can't find the runtime iterface for pretty print!");
+  }
+  Expr *TypeArg = CStyleCastPtrExpr(&S, S.getASTContext().VoidPtrTy,
+                                    (uintptr_t)E->getType().getAsOpaquePtr());
+  llvm::SmallVector<Expr *, 2> Args = {TypeArg, E};
+  ExprResult Result = S.ActOnCallExpr(/*Scope=*/nullptr, RuntimeInterface,
+                                      E->getBeginLoc(), Args, E->getEndLoc());
+  assert(!Result.isInvalid() && "Failed to generate the CallExpr!");
+  return Result.get();
+}
diff --git a/clang/lib/Interpreter/PrettyPrint.cpp b/clang/lib/Interpreter/PrettyPrint.cpp
new file mode 100644
--- /dev/null
+++ b/clang/lib/Interpreter/PrettyPrint.cpp
@@ -0,0 +1,10 @@
+#include "clang/Interpreter/Value.h"
+#include "llvm/Support/Compiler.h"
+
+using namespace clang;
+
+LLVM_EXTERNAL_VISIBILITY void __InterpreterPrettyPrint(void *OpaqueType,
+                                                       int Val) {
+
+  Value::Create(OpaqueType, Val).dump();
+}
diff --git a/clang/lib/Interpreter/Value.cpp b/clang/lib/Interpreter/Value.cpp
new file mode 100644
--- /dev/null
+++ b/clang/lib/Interpreter/Value.cpp
@@ -0,0 +1,23 @@
+#include "clang/Interpreter/Value.h"
+#include "clang/AST/Type.h"
+#include "llvm/Support/raw_os_ostream.h"
+
+using namespace clang;
+
+template <> Value Value::Create(void *Type, int Val) {
+  Value V(Type);
+  V.setKind(Value::Kind::Int);
+  V.Data.Int = Val;
+  return V;
+}
+
+QualType Value::getType() const {
+  return QualType::getFromOpaquePtr(OpaqueType);
+}
+
+void Value::print(llvm::raw_ostream &Out) const {
+  Out << "[" << getType().getAsString() << "]: ";
+  Out << Data.Int << "\n";
+}
+
+void Value::dump() const { print(llvm::outs()); }
diff --git a/clang/lib/Parse/ParseStmt.cpp b/clang/lib/Parse/ParseStmt.cpp
--- a/clang/lib/Parse/ParseStmt.cpp
+++ b/clang/lib/Parse/ParseStmt.cpp
@@ -541,9 +541,9 @@
     // Recover parsing as a case statement.
     return ParseCaseStatement(StmtCtx, /*MissingCase=*/true, Expr);
   }
-
   // Otherwise, eat the semicolon.
-  ExpectAndConsumeSemi(diag::err_expected_semi_after_expr);
+  ExpectAndConsumeSemi(diag::err_expected_semi_after_expr, /*TokenUsed=*/"",
+                       StmtCtx == ParsedStmtContext::SubStmt);
   return handleExprStmt(Expr, StmtCtx);
 }
 
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -153,10 +153,20 @@
   return true;
 }
 
-bool Parser::ExpectAndConsumeSemi(unsigned DiagID, StringRef TokenUsed) {
+bool Parser::ExpectAndConsumeSemi(unsigned DiagID, StringRef TokenUsed,
+                                  bool IsTopExpr) {
   if (TryConsumeToken(tok::semi))
     return false;
 
+  // If this is in the incremental C++ mode, then it means we need to pretty
+  // print this expression. Thus, let's pretend we have this semi and continue
+  // parsing.
+  if (PP.isIncrementalProcessingEnabled() && IsTopExpr &&
+      DiagID == diag::err_expected_semi_after_expr) {
+    setPrettyPrintMode();
+    return false;
+  }
+
   if (Tok.is(tok::code_completion)) {
     handleUnexpectedCodeCompletionToken();
     return false;
diff --git a/clang/test/Interpreter/pretty-print.cpp b/clang/test/Interpreter/pretty-print.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Interpreter/pretty-print.cpp
@@ -0,0 +1,11 @@
+// RUN: clang-repl "int i = 10;" 'extern "C" int printf(const char*,...);' \
+// RUN:            'auto r1 = printf("i = %d\n", i);' | FileCheck --check-prefix=CHECK-DRIVER %s
+// UNSUPPORTED: system-aix
+// CHECK-DRIVER: i = 10
+// RUN: cat %s | clang-repl | FileCheck %s
+int x = 42;
+x
+// CHECK: [int]: 42
+x + 42
+// CHECK-NEXT: [int]: 84
+%quit
diff --git a/clang/tools/clang-repl/CMakeLists.txt b/clang/tools/clang-repl/CMakeLists.txt
--- a/clang/tools/clang-repl/CMakeLists.txt
+++ b/clang/tools/clang-repl/CMakeLists.txt
@@ -12,6 +12,7 @@
   )
 
 clang_target_link_libraries(clang-repl PRIVATE
+  clangAST
   clangBasic
   clangFrontend
   clangInterpreter
diff --git a/clang/tools/clang-repl/ClangRepl.cpp b/clang/tools/clang-repl/ClangRepl.cpp
--- a/clang/tools/clang-repl/ClangRepl.cpp
+++ b/clang/tools/clang-repl/ClangRepl.cpp
@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/AST/Decl.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendDiagnostic.h"
@@ -18,6 +19,8 @@
 #include "llvm/ExecutionEngine/Orc/LLJIT.h"
 #include "llvm/LineEditor/LineEditor.h"
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/ManagedStatic.h" // llvm_shutdown
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/TargetSelect.h" // llvm::Initialize*
@@ -65,6 +68,18 @@
   return (Errs || HasError) ? EXIT_FAILURE : EXIT_SUCCESS;
 }
 
+static void DeclareMagicFunctions(clang::Interpreter &Interp) {
+  llvm::ArrayRef<llvm::StringRef> MagicFunctions = {
+      "void __InterpreterPrettyPrint(void*, char);",
+      "void __InterpreterPrettyPrint(void*, int);",
+      "void __InterpreterPrettyPrint(void*, float);",
+      "void __InterpreterPrettyPrint(void*, double);",
+  };
+  for (llvm::StringRef Function : MagicFunctions) {
+    llvm::cantFail(Interp.ParseAndExecute(Function));
+  }
+}
+
 llvm::ExitOnError ExitOnErr;
 int main(int argc, const char **argv) {
   ExitOnErr.setBanner("clang-repl: ");
@@ -109,13 +124,18 @@
 
   bool HasError = false;
 
+  DeclareMagicFunctions(*Interp);
   if (OptInputs.empty()) {
     llvm::LineEditor LE("clang-repl");
     // FIXME: Add LE.setListCompleter
     while (llvm::Optional<std::string> Line = LE.readLine()) {
-      if (*Line == R"(%quit)")
+      llvm::StringRef Code = *Line;
+      if (Code.empty()) {
+        continue;
+      }
+      if (Code == R"(%quit)")
         break;
-      if (*Line == R"(%undo)") {
+      if (Code == R"(%undo)") {
         if (auto Err = Interp->Undo()) {
           llvm::logAllUnhandledErrors(std::move(Err), llvm::errs(), "error: ");
           HasError = true;
@@ -123,7 +143,7 @@
         continue;
       }
 
-      if (auto Err = Interp->ParseAndExecute(*Line)) {
+      if (auto Err = Interp->ParseAndExecute(Code)) {
         llvm::logAllUnhandledErrors(std::move(Err), llvm::errs(), "error: ");
         HasError = true;
       }