ARM: Implement OSR infrastructure.

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 4179872d0ce83b5e85630e7de27fedcc20caed8b..38209b4a01ab519a02e85c53018bb00a09d6e4fc 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -3867,7 +3867,19 @@ void LCodeGen::DoStackCheck(LStackCheck* instr) {
 
 
 void LCodeGen::DoOsrEntry(LOsrEntry* instr) {
-  Abort("DoOsrEntry unimplemented.");
+  // This is a pseudo-instruction that ensures that the environment here is
+  // properly registered for deoptimization and records the assembler's PC
+  // offset.
+  LEnvironment* environment = instr->environment();
+  environment->SetSpilledRegisters(instr->SpilledRegisterArray(),
+                                   instr->SpilledDoubleRegisterArray());
+
+  // If the environment were already registered, we would have no way of
+  // backpatching it with the spill slot operands.
+  ASSERT(!environment->HasBeenRegistered());
+  RegisterEnvironmentForDeoptimization(environment);
+  ASSERT(osr_pc_offset_ == -1);
+  osr_pc_offset_ = masm()->pc_offset();
 }