Lazy deopt without code patching.

runtime/vm/stub_code_arm.cc

Index: runtime/vm/stub_code_arm.cc
diff --git a/runtime/vm/stub_code_arm.cc b/runtime/vm/stub_code_arm.cc
index 3bcf173ba07b6f33928c539493773cb1e531c585..fa370caa6509ef49d5dbcf59243ae58e14bdbb3d 100644
--- a/runtime/vm/stub_code_arm.cc
+++ b/runtime/vm/stub_code_arm.cc
@@ -522,7 +522,7 @@ static void GenerateDeoptimizationSequence(Assembler* assembler,
   __ CallRuntime(kDeoptimizeMaterializeRuntimeEntry, 0);
   // Result tells stub how many bytes to remove from the expression stack
   // of the bottom-most frame. They were used as materialization arguments.
-  __ Pop(R1);
+  __ Pop(R2);
   if (kind == kLazyDeoptFromReturn) {
     __ Pop(R0);  // Restore result.
   } else if (kind == kLazyDeoptFromThrow) {
@@ -531,34 +531,32 @@ static void GenerateDeoptimizationSequence(Assembler* assembler,
   }
   __ LeaveStubFrame();
   // Remove materialization arguments.
-  __ add(SP, SP, Operand(R1, ASR, kSmiTagSize));
+  __ add(SP, SP, Operand(R2, ASR, kSmiTagSize));
   __ Ret();
 }
 
 
-// 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, -CallPattern::DeoptCallPatternLengthInBytes());
   // Push zap value instead of CODE_REG for lazy deopt.
   __ LoadImmediate(IP, 0xf1f1f1f1);
   __ Push(IP);
+  // 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, -CallPattern::DeoptCallPatternLengthInBytes());
   // Push zap value instead of CODE_REG for lazy deopt.
   __ LoadImmediate(IP, 0xf1f1f1f1);
   __ Push(IP);
+  // 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);
 }