Fix EH handling in PInvoke stubs and remove workaround (#327)

* Fix EH handling in PInvoke stubs and remove workaround

The fix in the JIT is to inline the raw PInvoke call if:
1) We are compiling a PInvoke IL Stub
2) We are compiling using the PInvoke helpers

Author: Fadi Hanna

src/coreclr/src/jit/importer.cpp

@@ -6393,6 +6393,13 @@ bool Compiler::impCanPInvokeInlineCallSite(BasicBlock* block)
     //   jit\jit64\ebvts\mcpp\sources2\ijw\__clrcall\vector_ctor_dtor.02\deldtor_clr.exe
     if (block->hasTryIndex())
     {
+        // This does not apply to the raw pinvoke call that is inside the pinvoke
+        // ILStub. In this case, we have to inline the raw pinvoke call into the stub,
+        // otherwise we would end up with a stub that recursively calls itself, and end
+        // up with a stack overflow.
+        if (opts.jitFlags->IsSet(JitFlags::JIT_FLAG_IL_STUB) && opts.ShouldUsePInvokeHelpers())
+            return true;
+
         return false;
     }
 #endif // _TARGET_64BIT_

src/coreclr/src/tools/crossgen2/ILCompiler.ReadyToRun/IL/Stubs/PInvokeILEmitter.cs

@@ -76,13 +76,6 @@ private void EmitPInvokeCall(PInvokeILCodeStreams ilCodeStreams)
 
         private MethodIL EmitIL()
         {
-            // Temp workaround to disable PInvoke stubs that require marshalling.
-            // https://github.com/dotnet/runtime/issues/248
-            {
-                if (Marshaller.IsMarshallingRequired(_targetMethod))
-                    throw new NotSupportedException();
-            }
-
             if (!_importMetadata.Flags.PreserveSig)
                 throw new NotSupportedException();
 
@@ -95,13 +88,11 @@ private MethodIL EmitIL()
             ILCodeStream unmarshallingCodestream = pInvokeILCodeStreams.UnmarshallingCodestream;
             ILCodeStream cleanupCodestream = pInvokeILCodeStreams.CleanupCodeStream;
 
-            /* Temp workaround: disable EH blocks because of https://github.com/dotnet/runtime/issues/248
-
             // Marshalling is wrapped in a finally block to guarantee cleanup
             ILExceptionRegionBuilder tryFinally = emitter.NewFinallyRegion();
 
             marshallingCodestream.BeginTry(tryFinally);
-            cleanupCodestream.BeginHandler(tryFinally);*/
+            cleanupCodestream.BeginHandler(tryFinally);
 
             // Marshal the arguments
             for (int i = 0; i < _marshallers.Length; i++)
@@ -112,12 +103,11 @@ private MethodIL EmitIL()
             EmitPInvokeCall(pInvokeILCodeStreams);
 
             ILCodeLabel lReturn = emitter.NewCodeLabel();
-            /* Temp workaround: disable EH blocks because of https://github.com/dotnet/runtime/issues/248
             unmarshallingCodestream.Emit(ILOpcode.leave, lReturn);
             unmarshallingCodestream.EndTry(tryFinally);
 
             cleanupCodestream.Emit(ILOpcode.endfinally);
-            cleanupCodestream.EndHandler(tryFinally);*/
+            cleanupCodestream.EndHandler(tryFinally);
 
             cleanupCodestream.EmitLabel(lReturn);