First two codegen tests passing on SIMMIPS

runtime/vm/stub_code_mips.cc

Index: runtime/vm/stub_code_mips.cc
===================================================================
--- runtime/vm/stub_code_mips.cc	(revision 20729)
+++ runtime/vm/stub_code_mips.cc	(working copy)
@@ -5,6 +5,11 @@
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_MIPS)
 
+#include "vm/assembler.h"
+#include "vm/code_generator.h"
+#include "vm/dart_entry.h"
+#include "vm/instructions.h"
+#include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 
 #define __ assembler->
@@ -66,8 +71,123 @@
 }
 
 
+// Called when invoking Dart code from C++ (VM code).
+// Input parameters:
+//   RA : points to return address.
+//   A0 : entrypoint of the Dart function to call.
+//   A1 : arguments descriptor array.
+//   A2 : arguments array.
+//   A3 : new context containing the current isolate pointer.
 void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
-  __ Unimplemented("InvokeDartCode stub");
+  // Save frame pointer coming in.
+  __ EnterStubFrame();
+
+  // Save new context and C++ ABI callee-saved registers.
+  const intptr_t kNewContextOffset =
+      -(1 + kAbiPreservedCpuRegCount) * kWordSize;
+
+  __ addiu(SP, SP, Immediate(-(3 + kAbiPreservedCpuRegCount) * kWordSize));
+  for (int i = S0; i <= S7; i++) {
+    Register r = static_cast<Register>(i);
+    __ sw(r, Address(SP, (i - S0 + 3) * kWordSize));
+  }
+  __ sw(A3, Address(SP, 2 * kWordSize));
+
+  // The new Context structure contains a pointer to the current Isolate
+  // structure. Cache the Context pointer in the CTX register so that it is
+  // available in generated code and calls to Isolate::Current() need not be
+  // done. The assumption is that this register will never be clobbered by
+  // compiled or runtime stub code.
+
+  // Cache the new Context pointer into CTX while executing Dart code.
+  __ lw(CTX, Address(A3, VMHandles::kOffsetOfRawPtrInHandle));
+
+  // Load Isolate pointer from Context structure into temporary register R8.
+  __ lw(T2, FieldAddress(CTX, Context::isolate_offset()));
+
+  // Save the top exit frame info. Use R5 as a temporary register.
+  // StackFrameIterator reads the top exit frame info saved in this frame.
+  __ lw(S5, Address(T2, Isolate::top_exit_frame_info_offset()));
+  __ LoadImmediate(T0, 0);
+  __ sw(T0, Address(T2, Isolate::top_exit_frame_info_offset()));
+
+  // Save the old Context pointer. Use S4 as a temporary register.
+  // Note that VisitObjectPointers will find this saved Context pointer during
+  // GC marking, since it traverses any information between SP and
+  // FP - kExitLinkOffsetInEntryFrame.
+  // EntryFrame::SavedContext reads the context saved in this frame.
+  __ lw(S4, Address(T2, Isolate::top_context_offset()));
+
+  // The constants kSavedContextOffsetInEntryFrame and
+  // kExitLinkOffsetInEntryFrame must be kept in sync with the code below.
+  __ sw(S5, Address(SP, 1 * kWordSize));
+  __ sw(S4, Address(SP, 0 * kWordSize));
+
+  // after the call, The stack pointer is restored to this location.
+  // Pushed A3, S0-7, S4, S5 = 11.
+  const intptr_t kSavedContextOffsetInEntryFrame = -11 * kWordSize;
+
+  // Load arguments descriptor array into S4, which is passed to Dart code.
+  __ lw(S4, Address(A1, VMHandles::kOffsetOfRawPtrInHandle));
+
+  // Load number of arguments into S5.
+  __ lw(S5, FieldAddress(S4, ArgumentsDescriptor::count_offset()));
+  __ SmiUntag(S5);
+
+  // Compute address of 'arguments array' data area into A2.
+  __ lw(A2, Address(A2, VMHandles::kOffsetOfRawPtrInHandle));
+  __ addiu(A2, A2, Immediate(Array::data_offset() - kHeapObjectTag));
+
+  // Set up arguments for the Dart call.
+  Label push_arguments;
+  Label done_push_arguments;
+
+  __ beq(S5, ZR, &done_push_arguments);  // check if there are arguments.
+  __ LoadImmediate(A1, 0);
+  __ Bind(&push_arguments);
+  __ lw(A3, Address(A2));
+  __ Push(A3);
+  __ addiu(A2, A2, Immediate(kWordSize));
+  __ addiu(A1, A1, Immediate(1));
+  __ subu(T0, A1, S5);
+  __ bltz(T0, &push_arguments);
+
+  __ Bind(&done_push_arguments);
+
+
+  // Call the Dart code entrypoint.
+  __ jalr(A0);  // S4 is the arguments descriptor array.
+
+  // Read the saved new Context pointer.
+  __ lw(CTX, Address(FP, kNewContextOffset));
+  __ lw(CTX, Address(CTX, VMHandles::kOffsetOfRawPtrInHandle));
+
+  // Get rid of arguments pushed on the stack.
+  __ addiu(SP, FP, Immediate(kSavedContextOffsetInEntryFrame));
+
+  // Load Isolate pointer from Context structure into CTX. Drop Context.
+  __ lw(CTX, FieldAddress(CTX, Context::isolate_offset()));
+
+  // Restore the saved Context pointer into the Isolate structure.
+  // Uses S4 as a temporary register for this.
+  // Restore the saved top exit frame info back into the Isolate structure.
+  // Uses S5 as a temporary register for this.
+  __ lw(S4, Address(SP, 0 * kWordSize));
+  __ lw(S5, Address(SP, 1 * kWordSize));
+  __ sw(S4, Address(CTX, Isolate::top_context_offset()));
+  __ sw(S5, Address(CTX, Isolate::top_exit_frame_info_offset()));
+
+  // Restore C++ ABI callee-saved registers.
+  for (int i = S0; i <= S7; i++) {
+    Register r = static_cast<Register>(i);
+    __ lw(r, Address(SP, (i - S0 + 3) * kWordSize));
+  }
+  __ lw(A3, Address(SP));
+  __ addiu(SP, SP, Immediate((3 + kAbiPreservedCpuRegCount) * kWordSize));
+
+  // Restore the frame pointer and return.
+  __ LeaveStubFrame();
+  __ Ret();
 }