Fix LLVM C API for DataLayout

We removed access to the DataLayout on the TargetMachine and
deprecated the C API function LLVMGetTargetMachineData() in r243114.
However the way I tried to be backward compatible was broken: I
changed the wrapper of the TargetMachine to be a structure that
includes the DataLayout as well. However the TargetMachine is also
wrapped by the ExecutionEngine, in the more classic way. A client
using the TargetMachine wrapped by the ExecutionEngine and trying
to get the DataLayout would break.

It seems tricky to solve the problem completely in the C API
implementation. This patch tries to address this backward
compatibility in a more lighter way in the C++ API. The C API is
restored in its original state and the removed C++ API is
reintroduced, but privately. The C API is friended to the
TargetMachine and should be the only consumer for this API.

Reviewers: ributzka

Differential Revision: http://reviews.llvm.org/D12263

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 245916

llvm/include/llvm/Target/TargetMachine.h

@@ -59,6 +59,13 @@ class PassManagerBase;
 }
 using legacy::PassManagerBase;
 
+extern "C" {
+// This function from the C API is deprecated. We still supports it using a
+// private method on the TargetMachine for now. But it needs to be friended and
+// so we forward declare it here.
+LLVMTargetDataRef LLVMGetTargetMachineData(LLVMTargetMachineRef T);
+}
+
 //===----------------------------------------------------------------------===//
 ///
 /// Primary interface to the complete machine description for the target
@@ -103,6 +110,12 @@ protected: // Can only create subclasses.
 
   unsigned RequireStructuredCFG : 1;
 
+  /// This API is here to support the C API, deprecated in 3.7 release.
+  /// This should never be used outside of legacy existing client.
+  const DataLayout &getDataLayout() const { return DL; }
+  friend struct LLVMOpaqueTargetData * ::LLVMGetTargetMachineData(
+      LLVMTargetMachineRef T);
+
 public:
   mutable TargetOptions Options;
 

llvm/lib/Target/TargetMachineC.cpp

@@ -32,25 +32,14 @@
 
 using namespace llvm;
 
-
-// The TargetMachine uses to offer access to a DataLayout member. This is reflected
-// in the C API. For backward compatibility reason, this structure allows to keep
-// a DataLayout member accessible to C client that have a handle to a
-// LLVMTargetMachineRef.
-struct LLVMOpaqueTargetMachine {
-  std::unique_ptr<TargetMachine> Machine;
-  DataLayout DL;
-};
-
-
 static TargetMachine *unwrap(LLVMTargetMachineRef P) {
-  return P->Machine.get();
+  return reinterpret_cast<TargetMachine *>(P);
 }
 static Target *unwrap(LLVMTargetRef P) {
   return reinterpret_cast<Target*>(P);
 }
 static LLVMTargetMachineRef wrap(const TargetMachine *P) {
-  return new LLVMOpaqueTargetMachine{ std::unique_ptr<TargetMachine>(const_cast<TargetMachine*>(P)),  P->createDataLayout() };
+  return reinterpret_cast<LLVMTargetMachineRef>(const_cast<TargetMachine *>(P));
 }
 static LLVMTargetRef wrap(const Target * P) {
   return reinterpret_cast<LLVMTargetRef>(const_cast<Target*>(P));
@@ -79,16 +68,16 @@ LLVMTargetRef LLVMGetTargetFromName(const char *Name) {
 LLVMBool LLVMGetTargetFromTriple(const char* TripleStr, LLVMTargetRef *T,
                                  char **ErrorMessage) {
   std::string Error;
-  
+
   *T = wrap(TargetRegistry::lookupTarget(TripleStr, Error));
-  
+
   if (!*T) {
     if (ErrorMessage)
       *ErrorMessage = strdup(Error.c_str());
 
     return 1;
   }
-  
+
   return 0;
 }
 
@@ -155,10 +144,7 @@ LLVMTargetMachineRef LLVMCreateTargetMachine(LLVMTargetRef T,
     CM, OL));
 }
 
-
-void LLVMDisposeTargetMachine(LLVMTargetMachineRef T) {
-  delete T;
-}
+void LLVMDisposeTargetMachine(LLVMTargetMachineRef T) { delete unwrap(T); }
 
 LLVMTargetRef LLVMGetTargetMachineTarget(LLVMTargetMachineRef T) {
   const Target* target = &(unwrap(T)->getTarget());
@@ -180,9 +166,9 @@ char* LLVMGetTargetMachineFeatureString(LLVMTargetMachineRef T) {
   return strdup(StringRep.c_str());
 }
 
-/// @deprecated: see "struct LLVMOpaqueTargetMachine" description above
+/** Deprecated: use LLVMGetDataLayout(LLVMModuleRef M) instead. */
 LLVMTargetDataRef LLVMGetTargetMachineData(LLVMTargetMachineRef T) {
-  return wrap(&T->DL);
+  return wrap(&unwrap(T)->getDataLayout());
 }
 
 void LLVMSetTargetMachineAsmVerbosity(LLVMTargetMachineRef T,