Setup R10/EDX to be valid Oops before stub calls

runtime/vm/flow_graph_compiler_ia32.cc

Index: runtime/vm/flow_graph_compiler_ia32.cc
diff --git a/runtime/vm/flow_graph_compiler_ia32.cc b/runtime/vm/flow_graph_compiler_ia32.cc
index 1c4bfd359948d0527064635cc41c8ec843f7a3d9..c0b2fa36abfc25c3776d95d3d58af37bd0a64da5 100644
--- a/runtime/vm/flow_graph_compiler_ia32.cc
+++ b/runtime/vm/flow_graph_compiler_ia32.cc
@@ -1183,6 +1183,7 @@ void FlowGraphCompiler::EmitUnoptimizedStaticCall(
     UNIMPLEMENTED();
   }
   ExternalLabel target_label(label_address);
+  __ movl(EDX, Immediate(0));
   __ LoadObject(ECX, ic_data);
   GenerateDartCall(deopt_id,
                    token_pos,
@@ -1190,6 +1191,9 @@ void FlowGraphCompiler::EmitUnoptimizedStaticCall(
                    PcDescriptors::kUnoptStaticCall,
                    locs);
   __ Drop(argument_count);
+#if defined(DEBUG)
+  __ movl(EDX, Immediate(1));  // Garbage that looks like an object.
+#endif
 }
 
 
@@ -1240,6 +1244,7 @@ void FlowGraphCompiler::EmitInstanceCall(ExternalLabel* target_label,
                                          intptr_t token_pos,
                                          LocationSummary* locs) {
   ASSERT(Array::Handle(ic_data.arguments_descriptor()).Length() > 0);
+  __ movl(EDX, Immediate(0));
   __ LoadObject(ECX, ic_data);
   GenerateDartCall(deopt_id,
                    token_pos,
@@ -1247,6 +1252,9 @@ void FlowGraphCompiler::EmitInstanceCall(ExternalLabel* target_label,
                    PcDescriptors::kIcCall,
                    locs);
   __ Drop(argument_count);
+#if defined(DEBUG)
+  __ movl(EDX, Immediate(1));  // Garbage that looks like an object.
+#endif
 }
 
 
@@ -1376,6 +1384,8 @@ void FlowGraphCompiler::EmitEqualityRegRegCompare(Register left,
     if (is_optimizing()) {
       __ call(&StubCode::OptimizedIdenticalWithNumberCheckLabel());
     } else {
+      __ movl(EDX, Immediate(0));
+      __ movl(ECX, Immediate(0));
       __ call(&StubCode::UnoptimizedIdenticalWithNumberCheckLabel());
     }
     if (token_pos != Scanner::kNoSourcePos) {
@@ -1383,6 +1393,13 @@ void FlowGraphCompiler::EmitEqualityRegRegCompare(Register left,
                            Isolate::kNoDeoptId,
                            token_pos);
     }
+#if defined(DEBUG)
+    if (!is_optimizing()) {
+      // Do this *after* adding the pc descriptor!
+      __ movl(EDX, Immediate(1));  // Garbage that looks like an object.
+      __ movl(ECX, Immediate(1));
+    }
+#endif
     // Stub returns result in flags (result of a cmpl, we need ZF computed).
     __ popl(right);
     __ popl(left);