Fix variable decl register collision on ARM.

src/arm/full-codegen-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_ARM
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 846 matching lines @@
       globals_->Add(variable->binding_needs_init()
                         ? isolate()->factory()->the_hole_value()
                         : isolate()->factory()->undefined_value(),
                     zone());
       break;
 
     case Variable::PARAMETER:
     case Variable::LOCAL:
       if (hole_init) {
         Comment cmnt(masm_, "[ VariableDeclaration");
-        __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
-        __ str(ip, StackOperand(variable));
+        __ LoadRoot(r0, Heap::kTheHoleValueRootIndex);
+        __ str(r0, StackOperand(variable));

[Dmitry Lomov (no reviews), 2015/03/28 10:41:18]

Actually there are more usages of ip below this, see line 876.
I am a bit surprised that this change fixes anything, since currently variables
that need hole-init are not stack allocated

[Jarin, 2015/03/30 05:54:50]

Well, the test case is not really valid code (it re-assigns a const variable),
so it might well be that we get a bit confused. However, I have verified that
this change "fixes" the regression test.

       }
       break;
 
     case Variable::CONTEXT:
       if (hole_init) {
         Comment cmnt(masm_, "[ VariableDeclaration");
         EmitDebugCheckDeclarationContext(variable);
         __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
         __ str(ip, ContextOperand(cp, variable->index()));

[Benedikt Meurer, 2015/03/29 09:07:04]

As noted by Dmitry, this will also cause trouble if variable->index() is too
big.

[Jarin, 2015/03/30 05:54:50]

Done.

         // No write barrier since the_hole_value is in old space.
         PrepareForBailoutForId(proxy->id(), NO_REGISTERS);
       }
       break;
 
     case Variable::LOOKUP: {
       Comment cmnt(masm_, "[ VariableDeclaration");
       __ mov(r2, Operand(variable->name()));
       // Declaration nodes are always introduced in one of four modes.
       DCHECK(IsDeclaredVariableMode(mode));
@@ skipping 4603 matching lines @@
 
   DCHECK(interrupt_address ==
          isolate->builtins()->OsrAfterStackCheck()->entry());
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM