diff --git a/cmake/modules/AddSwift.cmake b/cmake/modules/AddSwift.cmake
index ade4c55deda8a..3c000b25c20c5 100644
--- a/cmake/modules/AddSwift.cmake
+++ b/cmake/modules/AddSwift.cmake
@@ -722,10 +722,15 @@ endfunction()
 # This is a temporary workaround until it's possible to compile libswift with
 # cmake's builtin swift support.
 function(add_libswift name)
+  set(libswift_compile_options
+      "-target" "x86_64-apple-macosx10.15" # TODO: remove this once #38675 lands.
+      "-Xfrontend" "-validate-tbd-against-ir=none"
+      "-Xfrontend" "-enable-cxx-interop")
+
   if(CMAKE_BUILD_TYPE STREQUAL Debug)
-    set(libswift_compile_options "-g")
+    list(APPEND libswift_compile_options "-g")
   else()
-    set(libswift_compile_options "-O" "-cross-module-optimization")
+    list(APPEND libswift_compile_options "-O" "-cross-module-optimization")
   endif()
 
   set(build_dir ${CMAKE_CURRENT_BINARY_DIR})
diff --git a/include/swift/SIL/SILBridging.h b/include/swift/SIL/SILBridging.h
index 6d02c63d57f57..d0b9aeec633ce 100644
--- a/include/swift/SIL/SILBridging.h
+++ b/include/swift/SIL/SILBridging.h
@@ -15,10 +15,7 @@
 
 #include "BridgedSwiftObject.h"
 #include <stddef.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
+#include <string>
 
 typedef struct {
   const unsigned char * _Nullable data;
@@ -155,17 +152,17 @@ BridgedSlab PassContext_freeSlab(BridgedPassContext passContext,
                                  BridgedSlab slab);
 
 BridgedStringRef SILFunction_getName(BridgedFunction function);
-BridgedStringRef SILFunction_debugDescription(BridgedFunction function);
+std::string SILFunction_debugDescription(BridgedFunction function);
 OptionalBridgedBasicBlock SILFunction_firstBlock(BridgedFunction function);
 OptionalBridgedBasicBlock SILFunction_lastBlock(BridgedFunction function);
 
 BridgedStringRef SILGlobalVariable_getName(BridgedGlobalVar global);
-BridgedStringRef SILGlobalVariable_debugDescription(BridgedGlobalVar global);
+std::string SILGlobalVariable_debugDescription(BridgedGlobalVar global);
 
 OptionalBridgedBasicBlock SILBasicBlock_next(BridgedBasicBlock block);
 OptionalBridgedBasicBlock SILBasicBlock_previous(BridgedBasicBlock block);
 BridgedFunction SILBasicBlock_getFunction(BridgedBasicBlock block);
-BridgedStringRef SILBasicBlock_debugDescription(BridgedBasicBlock block);
+std::string SILBasicBlock_debugDescription(BridgedBasicBlock block);
 OptionalBridgedInstruction SILBasicBlock_firstInst(BridgedBasicBlock block);
 OptionalBridgedInstruction SILBasicBlock_lastInst(BridgedBasicBlock block);
 SwiftInt SILBasicBlock_getNumArguments(BridgedBasicBlock block);
@@ -179,7 +176,7 @@ BridgedValue Operand_getValue(BridgedOperand);
 OptionalBridgedOperand Operand_nextUse(BridgedOperand);
 BridgedInstruction Operand_getUser(BridgedOperand);
 
-BridgedStringRef SILNode_debugDescription(BridgedNode node);
+std::string SILNode_debugDescription(BridgedNode node);
 OptionalBridgedOperand SILValue_firstUse(BridgedValue value);
 BridgedType SILValue_getType(BridgedValue value);
 
@@ -227,8 +224,4 @@ BridgedInstruction SILBuilder_createBuiltinBinaryFunction(
 BridgedInstruction SILBuilder_createCondFail(BridgedInstruction insertionPoint,
           BridgedLocation loc, BridgedValue condition, BridgedStringRef messge);
 
-#ifdef __cplusplus
-} // extern "C"
-#endif
-
 #endif
diff --git a/lib/SIL/Utils/SILBridging.cpp b/lib/SIL/Utils/SILBridging.cpp
index 42261c507b2e6..d15f3f5891705 100644
--- a/lib/SIL/Utils/SILBridging.cpp
+++ b/lib/SIL/Utils/SILBridging.cpp
@@ -15,6 +15,8 @@
 #include "swift/SIL/SILGlobalVariable.h"
 #include "swift/SIL/SILBuilder.h"
 
+#include <string>
+
 using namespace swift;
 
 namespace {
@@ -159,11 +161,12 @@ BridgedStringRef SILFunction_getName(BridgedFunction function) {
   return getBridgedStringRef(castToFunction(function)->getName());
 }
 
-BridgedStringRef SILFunction_debugDescription(BridgedFunction function) {
+std::string SILFunction_debugDescription(BridgedFunction function) {
   std::string str;
   llvm::raw_string_ostream os(str);
   castToFunction(function)->print(os);
-  return getCopiedBridgedStringRef(str, /*removeTrailingNewline*/ true);
+  str.pop_back(); // Remove trailing newline.
+  return str;
 }
 
 OptionalBridgedBasicBlock SILFunction_firstBlock(BridgedFunction function) {
@@ -207,11 +210,12 @@ BridgedFunction SILBasicBlock_getFunction(BridgedBasicBlock block) {
   return {castToBasicBlock(block)->getParent()};
 }
 
-BridgedStringRef SILBasicBlock_debugDescription(BridgedBasicBlock block) {
+std::string SILBasicBlock_debugDescription(BridgedBasicBlock block) {
   std::string str;
   llvm::raw_string_ostream os(str);
   castToBasicBlock(block)->print(os);
-  return getCopiedBridgedStringRef(str, /*removeTrailingNewline*/ true);
+  str.pop_back(); // Remove trailing newline.
+  return str;
 }
 
 OptionalBridgedInstruction SILBasicBlock_firstInst(BridgedBasicBlock block) {
@@ -271,11 +275,12 @@ BridgedBasicBlock SILArgument_getParent(BridgedArgument argument) {
 static_assert(BridgedOperandSize == sizeof(Operand),
               "wrong bridged Operand size");
 
-BridgedStringRef SILNode_debugDescription(BridgedNode node) {
+std::string SILNode_debugDescription(BridgedNode node) {
   std::string str;
   llvm::raw_string_ostream os(str);
   castToSILNode(node)->print(os);
-  return getCopiedBridgedStringRef(str, /*removeTrailingNewline*/ true);
+  str.pop_back(); // Remove trailing newline.
+  return str;
 }
 
 static Operand *castToOperand(BridgedOperand operand) {
@@ -318,11 +323,12 @@ BridgedStringRef SILGlobalVariable_getName(BridgedGlobalVar global) {
   return getBridgedStringRef(castToGlobal(global)->getName());
 }
 
-BridgedStringRef SILGlobalVariable_debugDescription(BridgedGlobalVar global) {
+std::string SILGlobalVariable_debugDescription(BridgedGlobalVar global) {
   std::string str;
   llvm::raw_string_ostream os(str);
   castToGlobal(global)->print(os);
-  return getCopiedBridgedStringRef(str, /*removeTrailingNewline*/ true);
+  str.pop_back(); // Remove trailing newline.
+  return str;
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/libswift/Sources/SIL/BasicBlock.swift b/libswift/Sources/SIL/BasicBlock.swift
index 4e276a0f0d8c0..1190ee46e8494 100644
--- a/libswift/Sources/SIL/BasicBlock.swift
+++ b/libswift/Sources/SIL/BasicBlock.swift
@@ -19,7 +19,7 @@ final public class BasicBlock : ListNode, CustomStringConvertible {
   public var function: Function { SILBasicBlock_getFunction(bridged).function }
 
   public var description: String {
-    SILBasicBlock_debugDescription(bridged).takeString()
+    SILBasicBlock_debugDescription(bridged).string
   }
 
   public var arguments: ArgumentArray { ArgumentArray(block: self) }
diff --git a/libswift/Sources/SIL/Function.swift b/libswift/Sources/SIL/Function.swift
index f39f3719b47fa..0f6b615bb6999 100644
--- a/libswift/Sources/SIL/Function.swift
+++ b/libswift/Sources/SIL/Function.swift
@@ -18,7 +18,7 @@ final public class Function : CustomStringConvertible {
   }
 
   final public var description: String {
-    return SILFunction_debugDescription(bridged).takeString()
+    return SILFunction_debugDescription(bridged).string
   }
 
   public var entryBlock: BasicBlock {
diff --git a/libswift/Sources/SIL/GlobalVariable.swift b/libswift/Sources/SIL/GlobalVariable.swift
index 57124be60da75..d2e2115431add 100644
--- a/libswift/Sources/SIL/GlobalVariable.swift
+++ b/libswift/Sources/SIL/GlobalVariable.swift
@@ -18,7 +18,7 @@ final public class GlobalVariable : CustomStringConvertible {
   }
 
   public var description: String {
-    return SILGlobalVariable_debugDescription(bridged).takeString()
+    return SILGlobalVariable_debugDescription(bridged).string
   }
 
   // TODO: initializer instructions
diff --git a/libswift/Sources/SIL/Instruction.swift b/libswift/Sources/SIL/Instruction.swift
index 9107748b295fc..2bbcfaf132015 100644
--- a/libswift/Sources/SIL/Instruction.swift
+++ b/libswift/Sources/SIL/Instruction.swift
@@ -30,7 +30,7 @@ public class Instruction : ListNode, CustomStringConvertible, Hashable {
   }
 
   final public var description: String {
-    SILNode_debugDescription(bridgedNode).takeString()
+    SILNode_debugDescription(bridgedNode).string
   }
   
   final public var operands: OperandArray {
@@ -132,7 +132,7 @@ public class SingleValueInstruction : Instruction, Value {
 
 public final class MultipleValueInstructionResult : Value {
   final public var description: String {
-    SILNode_debugDescription(bridgedNode).takeString()
+    SILNode_debugDescription(bridgedNode).string
   }
 
   public var definingInstruction: Instruction? {
diff --git a/libswift/Sources/SIL/Utils.swift b/libswift/Sources/SIL/Utils.swift
index 6444c182e2c0c..9b3b7a0e358e2 100644
--- a/libswift/Sources/SIL/Utils.swift
+++ b/libswift/Sources/SIL/Utils.swift
@@ -81,6 +81,15 @@ extension BridgedStringRef {
   }
 }
 
+extension std.__1.string {
+  public var string: String {
+    // TODO: remove this once a new version of Swift is released (and call
+    // c_str() directly).
+    var mutableSelf = self
+    return String(cString: mutableSelf.c_str())
+  }
+}
+
 extension String {
   public func withBridgedStringRef<T>(_ c: (BridgedStringRef) -> T) -> T {
     var str = self
diff --git a/libswift/Sources/SIL/Value.swift b/libswift/Sources/SIL/Value.swift
index 097bbfb58c7d1..d8e2658b9fe13 100644
--- a/libswift/Sources/SIL/Value.swift
+++ b/libswift/Sources/SIL/Value.swift
@@ -20,7 +20,7 @@ public protocol Value : AnyObject, CustomStringConvertible {
 
 extension Value {
   public var description: String {
-    SILNode_debugDescription(bridgedNode).takeString()
+    SILNode_debugDescription(bridgedNode).string
   }
 
   public var uses: UseList {