Reapply "Lazy deopt without code patching."

runtime/vm/stub_code_arm64.cc

Index: runtime/vm/stub_code_arm64.cc
diff --git a/runtime/vm/stub_code_arm64.cc b/runtime/vm/stub_code_arm64.cc
index 1eebe2586cade37075a41b50899a951cb5f27633..fdcf3a70eb86eefbe0b055f5fdd83e3bc23e03e6 100644
--- a/runtime/vm/stub_code_arm64.cc
+++ b/runtime/vm/stub_code_arm64.cc
@@ -557,29 +557,27 @@ static void GenerateDeoptimizationSequence(Assembler* assembler,
 }
 
 
-// LR: return address + call-instruction-size
 // R0: result, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
-  // Correct return address to point just after the call that is being
-  // deoptimized.
-  __ AddImmediate(LR, LR, -CallPattern::kDeoptCallLengthInBytes);
   // Push zap value instead of CODE_REG for lazy deopt.
   __ LoadImmediate(TMP, 0xf1f1f1f1);
   __ Push(TMP);
+  // Return address for "call" to deopt stub.
+  __ LoadImmediate(LR, 0xe1e1e1e1);
+  __ ldr(CODE_REG, Address(THR, Thread::lazy_deopt_from_return_stub_offset()));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromReturn);
 }
 
 
-// LR: return address + call-instruction-size
 // R0: exception, must be preserved
 // R1: stacktrace, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromThrowStub(Assembler* assembler) {
-  // Correct return address to point just after the call that is being
-  // deoptimized.
-  __ AddImmediate(LR, LR, -CallPattern::kDeoptCallLengthInBytes);
   // Push zap value instead of CODE_REG for lazy deopt.
   __ LoadImmediate(TMP, 0xf1f1f1f1);
   __ Push(TMP);
+  // Return address for "call" to deopt stub.
+  __ LoadImmediate(LR, 0xe1e1e1e1);
+  __ ldr(CODE_REG, Address(THR, Thread::lazy_deopt_from_throw_stub_offset()));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromThrow);
 }