Moves infrequently used debugger code in CheckInlineCachestub.

runtime/vm/stub_code_ia32.cc

 // Copyright (c) 2013, 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_IA32)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 1276 matching lines @@
     __ movl(EBX, FieldAddress(ECX, ICData::state_bits_offset()));
     ASSERT(ICData::NumArgsTestedShift() == 0);  // No shift needed.
     __ andl(EBX, Immediate(ICData::NumArgsTestedMask()));
     __ cmpl(EBX, Immediate(num_args));
     __ j(EQUAL, &ok, Assembler::kNearJump);
     __ Stop("Incorrect stub for IC data");
     __ Bind(&ok);
   }
 #endif  // DEBUG
 
+  Label stepping, done_stepping;
   if (FLAG_enable_debugger) {
     // Check single stepping.
-    Label not_stepping;
     __ movl(EAX, FieldAddress(CTX, Context::isolate_offset()));
     __ movzxb(EAX, Address(EAX, Isolate::single_step_offset()));

[Vyacheslav Egorov (Google), 2014/07/11 23:31:34]

I wonder if single_step were intptr_t would there be any visible performance
improvement from a shorter

testl(Address(...), Immediate(1)); sequence

     __ cmpl(EAX, Immediate(0));
-    __ j(EQUAL, &not_stepping, Assembler::kNearJump);
-
-    __ EnterStubFrame();
-    __ pushl(ECX);
-    __ CallRuntime(kSingleStepHandlerRuntimeEntry, 0);
-    __ popl(ECX);
-    __ LeaveFrame();
-    __ Bind(&not_stepping);
+    __ j(NOT_EQUAL, &stepping);
+    __ Bind(&done_stepping);
   }
 
   // ECX: IC data object (preserved).
   // Load arguments descriptor into EDX.
   __ movl(EDX, FieldAddress(ECX, ICData::arguments_descriptor_offset()));
   // Loop that checks if there is an IC data match.
   Label loop, update, test, found;
   // ECX: IC data object (preserved).
   __ movl(EBX, FieldAddress(ECX, ICData::ic_data_offset()));
   // EBX: ic_data_array with check entries: classes and target functions.
@@ skipping 89 matching lines @@
   __ cmovno(EDI, EAX);
   __ movl(Address(EBX, count_offset), EDI);
 
   __ movl(EAX, Address(EBX, target_offset));
   __ Bind(&call_target_function);
   // EAX: Target function.
   __ movl(EBX, FieldAddress(EAX, Function::instructions_offset()));
   __ addl(EBX, Immediate(Instructions::HeaderSize() - kHeapObjectTag));
   __ jmp(EBX);
   __ int3();
+
+  if (FLAG_enable_debugger) {
+    __ Bind(&stepping);
+    __ EnterStubFrame();
+    __ pushl(ECX);
+    __ CallRuntime(kSingleStepHandlerRuntimeEntry, 0);
+    __ popl(ECX);
+    __ LeaveFrame();
+    __ jmp(&done_stepping);
+  }
 }
 
 
 // Use inline cache data array to invoke the target or continue in inline
 // cache miss handler. Stub for 1-argument check (receiver class).
 //  ECX: Inline cache data object.
 //  TOS(0): Return address.
 // Inline cache data object structure:
 // 0: function-name
 // 1: N, number of arguments checked.
@@ skipping 467 matching lines @@
   const Register temp = ECX;
   __ movl(left, Address(ESP, 2 * kWordSize));
   __ movl(right, Address(ESP, 1 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32