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

src/macro-assembler-arm.cc

Index: src/macro-assembler-arm.cc
===================================================================
--- src/macro-assembler-arm.cc	(revision 544)
+++ src/macro-assembler-arm.cc	(working copy)
@@ -648,8 +648,8 @@
 
 
 void MacroAssembler::CheckAccessGlobalProxy(Register holder_reg,
-                                          Register scratch,
-                                          Label* miss) {
+                                            Register scratch,
+                                            Label* miss) {
   Label same_contexts;
 
   ASSERT(!holder_reg.is(scratch));
@@ -671,10 +671,15 @@
 
   // 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.
@@ -684,12 +689,19 @@
 
   // 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));
   }