Use constants from the frame at OSR entry.

runtime/vm/flow_graph_compiler_x64.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 1039 matching lines @@
     __ movq(new_pp, Address(new_pc, -object_pool_pc_dist - offset));
     AddCurrentDescriptor(PcDescriptors::kEntryPatch,
                          Isolate::kNoDeoptId,
                          0);  // No token position.
   }
   __ Comment("Enter frame");
   if (flow_graph().IsCompiledForOsr()) {
     intptr_t extra_slots = StackSize()
         - flow_graph().num_stack_locals()
         - flow_graph().num_copied_params();
-    ASSERT(extra_slots >= 0);
     __ EnterOsrFrame(extra_slots * kWordSize, new_pp, new_pc);
   } else {
     ASSERT(StackSize() >= 0);
     __ EnterDartFrameWithInfo(StackSize() * kWordSize, new_pp, new_pc);
   }
 }
 
 
 void FlowGraphCompiler::CompileGraph() {
   InitCompiler();
@@ skipping 768 matching lines @@
   __ movups(reg, Address(RSP, 0));
   __ AddImmediate(RSP, Immediate(kFpuRegisterSize), PP);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64