Reapply "Initial implementation of on-stack replacement (OSR)."

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 12cfe2d0a32fce9d193a126c1e0216e1581ce4fb..c0e5a6536e8bf9d8f4ad7b218970e1e8a8d5cb3b 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -22,6 +22,7 @@
 #include "vm/datastream.h"
 #include "vm/debugger.h"
 #include "vm/deopt_instructions.h"
+#include "vm/disassembler.h"
 #include "vm/double_conversion.h"
 #include "vm/exceptions.h"
 #include "vm/flow_graph_builder.h"
@@ -7292,6 +7293,7 @@ const char* PcDescriptors::KindAsStr(intptr_t index) const {
     case PcDescriptors::kClosureCall:   return "closure-call ";
     case PcDescriptors::kReturn:        return "return       ";
     case PcDescriptors::kRuntimeCall:   return "runtime-call ";
+    case PcDescriptors::kOsrEntry:      return "osr-entry    ";
     case PcDescriptors::kOther:         return "other        ";
   }
   UNREACHABLE();
@@ -7999,6 +8001,13 @@ void Code::SetStaticCallTargetCodeAt(uword pc, const Code& code) const {
 }
 
 
+void Code::Disassemble() const {
+  const Instructions& instr = Instructions::Handle(instructions());
+  uword start = instr.EntryPoint();
+  Disassembler::Disassemble(start, start + instr.size(), comments());
+}
+
+
 const Code::Comments& Code::comments() const  {
   Comments* comments = new Code::Comments(Array::Handle(raw_ptr()->comments_));
   return *comments;
@@ -8151,6 +8160,18 @@ uword Code::GetPcForDeoptId(intptr_t deopt_id, PcDescriptors::Kind kind) const {
 }
 
 
+intptr_t Code::GetDeoptIdForOsr(uword pc) const {
+  const PcDescriptors& descriptors = PcDescriptors::Handle(pc_descriptors());
+  for (intptr_t i = 0; i < descriptors.Length(); ++i) {
+    if ((descriptors.PC(i) == pc) &&
+        (descriptors.DescriptorKind(i) == PcDescriptors::kOsrEntry)) {
+      return descriptors.DeoptId(i);
+    }
+  }
+  return Isolate::kNoDeoptId;
+}
+
+
 const char* Code::ToCString() const {
   const char* kFormat = "Code entry:%p";
   intptr_t len = OS::SNPrint(NULL, 0, kFormat, EntryPoint()) + 1;