- ip register cannot be used when accessing large constants in the instructio...

src/macro-assembler-arm.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 630 matching lines @@
   ASSERT(object == holder);
   ASSERT(object->IsJSGlobalProxy() || !object->IsAccessCheckNeeded());
   if (object->IsJSGlobalProxy()) {
     CheckAccessGlobalProxy(reg, scratch, miss);
   }
   return reg;
 }
 
 
 void MacroAssembler::CheckAccessGlobalProxy(Register holder_reg,
-                                          Register scratch,
-                                          Label* miss) {
+                                            Register scratch,
+                                            Label* miss) {
   Label same_contexts;
 
   ASSERT(!holder_reg.is(scratch));
   ASSERT(!holder_reg.is(ip));
   ASSERT(!scratch.is(ip));
 
   // Load current lexical context from the stack frame.
   ldr(scratch, MemOperand(fp, StandardFrameConstants::kContextOffset));
   // In debug mode, make sure the lexical context is set.
   if (kDebug) {
     cmp(scratch, Operand(0));
     Check(ne, "we should not have an empty lexical context");
   }
 
   // Load the global context of the current context.
   int offset = Context::kHeaderSize + Context::GLOBAL_INDEX * kPointerSize;
   ldr(scratch, FieldMemOperand(scratch, offset));
   ldr(scratch, FieldMemOperand(scratch, GlobalObject::kGlobalContextOffset));
 
   // Check the context is a global context.
   if (FLAG_debug_code) {
+    // TODO(119): avoid push(holder_reg)/pop(holder_reg)
+    // Cannot use ip as a temporary in this verification code. Due to the fact
+    // that ip is clobbered as part of cmp with an object Operand.
+    push(holder_reg);  // Temporarily save holder on the stack.
     // Read the first word and compare to the global_context_map.
-    ldr(ip, FieldMemOperand(scratch, HeapObject::kMapOffset));
-    cmp(ip, Operand(Factory::global_context_map()));
+    ldr(holder_reg, FieldMemOperand(scratch, HeapObject::kMapOffset));
+    cmp(holder_reg, Operand(Factory::global_context_map()));
     Check(eq, "JSGlobalObject::global_context should be a global context.");
+    pop(holder_reg);  // Restore holder.
   }
 
   // Check if both contexts are the same.
   ldr(ip, FieldMemOperand(holder_reg, JSGlobalProxy::kContextOffset));
   cmp(scratch, Operand(ip));
   b(eq, &same_contexts);
 
   // Check the context is a global context.
   if (FLAG_debug_code) {
-    cmp(ip, Operand(Factory::null_value()));
+    // TODO(119): avoid push(holder_reg)/pop(holder_reg)
+    // Cannot use ip as a temporary in this verification code. Due to the fact
+    // that ip is clobbered as part of cmp with an object Operand.
+    push(holder_reg);  // Temporarily save holder on the stack.
+    mov(holder_reg, ip);  // Move ip to its holding place.
+    cmp(holder_reg, Operand(Factory::null_value()));
     Check(ne, "JSGlobalProxy::context() should not be null.");
 
-    ldr(ip, FieldMemOperand(ip, HeapObject::kMapOffset));
-    cmp(ip, Operand(Factory::global_context_map()));
+    ldr(holder_reg, FieldMemOperand(holder_reg, HeapObject::kMapOffset));
+    cmp(holder_reg, Operand(Factory::global_context_map()));
     Check(eq, "JSGlobalObject::global_context should be a global context.");
+    // Restore ip is not needed. ip is reloaded below.
+    pop(holder_reg);  // Restore holder.
     // Restore ip to holder's context.
     ldr(ip, FieldMemOperand(holder_reg, JSGlobalProxy::kContextOffset));
   }
 
   // Check that the security token in the calling global object is
   // compatible with the security token in the receiving global
   // object.
   int token_offset = Context::kHeaderSize +
                      Context::SECURITY_TOKEN_INDEX * kPointerSize;
 
@@ skipping 159 matching lines @@
 #endif
   mov(r0, Operand(p0));
   push(r0);
   mov(r0, Operand(Smi::FromInt(p1 - p0)));
   push(r0);
   CallRuntime(Runtime::kAbort, 2);
   // will not return here
 }
 
 } }  // namespace v8::internal