Remember all deopt reasons in ic_data, not just the last one.

runtime/vm/stub_code_arm64.cc

 // Copyright (c) 2014, 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"
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
@@ skipping 727 matching lines @@
   __ Stop("GenerateOptimizedUsageCounterIncrement");
 }
 
 
 // Loads function into 'temp_reg'.
 void StubCode::GenerateUsageCounterIncrement(Assembler* assembler,
                                              Register temp_reg) {
   Register ic_reg = R5;
   Register func_reg = temp_reg;
   ASSERT(temp_reg == R6);
-  __ LoadFieldFromOffset(func_reg, ic_reg, ICData::function_offset());
+  __ LoadFieldFromOffset(func_reg, ic_reg, ICData::owner_offset());
   __ LoadFieldFromOffset(R7, func_reg, Function::usage_counter_offset());
   __ AddImmediate(R7, R7, 1, PP);
   __ StoreFieldToOffset(R7, func_reg, Function::usage_counter_offset());
 }
 
 
 // Generate inline cache check for 'num_args'.
 //  LR: return address.
 //  R5: inline cache data object.
 // Control flow:
 // - If receiver is null -> jump to IC miss.
 // - If receiver is Smi -> load Smi class.
 // - If receiver is not-Smi -> load receiver's class.
 // - Check if 'num_args' (including receiver) match any IC data group.
 // - Match found -> jump to target.
 // - Match not found -> jump to IC miss.
 void StubCode::GenerateNArgsCheckInlineCacheStub(
     Assembler* assembler,
     intptr_t num_args,
     const RuntimeEntry& handle_ic_miss) {
   ASSERT(num_args > 0);
 #if defined(DEBUG)
   { Label ok;
-    // Check that the IC data array has NumberOfArgumentsChecked() == num_args.
-    // 'num_args_tested' is stored as an untagged int.
-    __ LoadFieldFromOffset(R6, R5, ICData::num_args_tested_offset());
+    // Check that the IC data array has NumArgsTested() == num_args.
+    // 'NumArgsTested' is stored in the least significant bits of 'state_bits'.
+    __ LoadFromOffset(R6, R5, ICData::state_bits_offset() - kHeapObjectTag,
+                      kUnsignedWord);
+    ASSERT(ICData::NumArgsTestedShift() == 0);  // No shift needed.
+    __ andi(R6, R6, ICData::NumArgsTestedMask());
     __ CompareImmediate(R6, num_args, PP);
     __ b(&ok, EQ);
     __ Stop("Incorrect stub for IC data");
     __ Bind(&ok);
   }
 #endif  // DEBUG
 
   // Check single stepping.
   Label not_stepping;
   __ LoadFieldFromOffset(R6, CTX, Context::isolate_offset());
@@ skipping 218 matching lines @@
 
 void StubCode::GenerateMegamorphicCallStub(Assembler* assembler) {
   __ Stop("GenerateMegamorphicCallStub");
 }
 
 
 void StubCode::GenerateZeroArgsUnoptimizedStaticCallStub(Assembler* assembler) {
   GenerateUsageCounterIncrement(assembler, R6);
 #if defined(DEBUG)
   { Label ok;
-    // Check that the IC data array has NumberOfArgumentsChecked() == 0.
-    // 'num_args_tested' is stored as an untagged int.
-    __ LoadFieldFromOffset(R6, R5, ICData::num_args_tested_offset());
+    // Check that the IC data array has NumArgsTested() == 0.
+    // 'NumArgsTested' is stored in the least significant bits of 'state_bits'.
+    __ LoadFromOffset(R6, R5, ICData::state_bits_offset() - kHeapObjectTag,
+                      kUnsignedWord);
+    ASSERT(ICData::NumArgsTestedShift() == 0);  // No shift needed.
+    __ andi(R6, R6, ICData::NumArgsTestedMask());
     __ CompareImmediate(R6, 0, PP);
     __ b(&ok, EQ);
     __ Stop("Incorrect IC data for unoptimized static call");
     __ Bind(&ok);
   }
 #endif  // DEBUG
 
   // Check single stepping.
   Label not_stepping;
   __ LoadFieldFromOffset(R6, CTX, Context::isolate_offset());
@@ skipping 214 matching lines @@
 
 
 void StubCode::GenerateOptimizedIdenticalWithNumberCheckStub(
     Assembler* assembler) {
   __ Stop("GenerateOptimizedIdenticalWithNumberCheckStub");
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64