MIPS: Fix DIRECT_API_CALL_NEW and DIRECT_GETTER_CALL_NEW call.

src/mips/simulator-mips.cc

Index: src/mips/simulator-mips.cc
diff --git a/src/mips/simulator-mips.cc b/src/mips/simulator-mips.cc
index 18e78a5abda9921a281763a1d4899281c7b1ecfc..baf042c3b2191d0db70fd7e22b25228ff120f26f 100644
--- a/src/mips/simulator-mips.cc
+++ b/src/mips/simulator-mips.cc
@@ -1387,12 +1387,19 @@ typedef double (*SimulatorRuntimeFPIntCall)(double darg0, int32_t arg0);
 
 // This signature supports direct call in to API function native callback
 // (refer to InvocationCallback in v8.h).
+// NOTE: the O32 abi requires a0 to hold a special pointer when returning a
+// struct from the function (which is currently the case). This means we pass
+// the first argument in a1 instead of a0.
 typedef v8::Handle<v8::Value> (*SimulatorRuntimeDirectApiCall)(int32_t arg0);
+// Here, we pass the first argument in a0, because this function
+// does not return a struct.
 typedef void (*SimulatorRuntimeDirectApiCallNew)(int32_t arg0);
 
 // This signature supports direct call to accessor getter callback.
+// See comment at SimulatorRuntimeDirectApiCall.
 typedef v8::Handle<v8::Value> (*SimulatorRuntimeDirectGetterCall)(int32_t arg0,
                                                                   int32_t arg1);
+// See comment at SimulatorRuntimeDirectApiCallNew.
 typedef void (*SimulatorRuntimeDirectGetterCallNew)(int32_t arg0,
                                                     int32_t arg1);
 
@@ -1542,40 +1549,50 @@ void Simulator::SoftwareInterrupt(Instruction* instr) {
     } else if (
         redirection->type() == ExternalReference::DIRECT_API_CALL ||
         redirection->type() == ExternalReference::DIRECT_API_CALL_NEW) {
-      // See DirectCEntryStub::GenerateCall for explanation of register usage.
-      if (::v8::internal::FLAG_trace_sim) {
-        PrintF("Call to host function at %p args %08x\n",
-            reinterpret_cast<void*>(external), arg1);
-      }
       if (redirection->type() == ExternalReference::DIRECT_API_CALL) {
+        // See comment at type definition of SimulatorRuntimeDirectApiCall
+        // for explanation of register usage.
+        if (::v8::internal::FLAG_trace_sim) {
+          PrintF("Call to host function at %p args %08x\n",
+              reinterpret_cast<void*>(external), arg1);
+        }
         SimulatorRuntimeDirectApiCall target =
             reinterpret_cast<SimulatorRuntimeDirectApiCall>(external);
         v8::Handle<v8::Value> result = target(arg1);
         *(reinterpret_cast<int*>(arg0)) = reinterpret_cast<int32_t>(*result);
         set_register(v0, arg0);
       } else {
+        if (::v8::internal::FLAG_trace_sim) {
+          PrintF("Call to host function at %p args %08x\n",
+              reinterpret_cast<void*>(external), arg0);
+        }
         SimulatorRuntimeDirectApiCallNew target =
             reinterpret_cast<SimulatorRuntimeDirectApiCallNew>(external);
-        target(arg1);
+        target(arg0);
       }
     } else if (
         redirection->type() == ExternalReference::DIRECT_GETTER_CALL ||
         redirection->type() == ExternalReference::DIRECT_GETTER_CALL_NEW) {
-      // See DirectCEntryStub::GenerateCall for explanation of register usage.
-      if (::v8::internal::FLAG_trace_sim) {
-        PrintF("Call to host function at %p args %08x %08x\n",
-            reinterpret_cast<void*>(external), arg1, arg2);
-      }
       if (redirection->type() == ExternalReference::DIRECT_GETTER_CALL) {
+        // See comment at type definition of SimulatorRuntimeDirectGetterCall
+        // for explanation of register usage.
+        if (::v8::internal::FLAG_trace_sim) {
+          PrintF("Call to host function at %p args %08x %08x\n",
+              reinterpret_cast<void*>(external), arg1, arg2);
+        }
         SimulatorRuntimeDirectGetterCall target =
             reinterpret_cast<SimulatorRuntimeDirectGetterCall>(external);
         v8::Handle<v8::Value> result = target(arg1, arg2);
         *(reinterpret_cast<int*>(arg0)) = reinterpret_cast<int32_t>(*result);
         set_register(v0, arg0);
       } else {
+        if (::v8::internal::FLAG_trace_sim) {
+          PrintF("Call to host function at %p args %08x %08x\n",
+              reinterpret_cast<void*>(external), arg0, arg1);
+        }
         SimulatorRuntimeDirectGetterCallNew target =
             reinterpret_cast<SimulatorRuntimeDirectGetterCallNew>(external);
-        target(arg1, arg2);
+        target(arg0, arg1);
       }
     } else {
       SimulatorRuntimeCall target =