Simplify some of the startup code for SubStringStub::Generate.

src/arm/macro-assembler-arm.h

 // Copyright 2012 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 859 matching lines @@
                    SmiCheckType smi_check_type);
 
 
   // Compare the object in a register to a value from the root list.
   // Uses the ip register as scratch.
   void CompareRoot(Register obj, Heap::RootListIndex index);
 
 
   // Load and check the instance type of an object for being a string.
   // Loads the type into the second argument register.
-  // Returns a condition that will be enabled if the object was a string.
+  // Returns a condition that will be enabled if the object was a string
+  // and the passed-in condition passed. If the passed-in condition failed
+  // then flags remain unchanged.
   Condition IsObjectStringType(Register obj,
-                               Register type) {
-    ldr(type, FieldMemOperand(obj, HeapObject::kMapOffset));
-    ldrb(type, FieldMemOperand(type, Map::kInstanceTypeOffset));
-    tst(type, Operand(kIsNotStringMask));
+                               Register type,
+                               Condition cond = al) {
+    ldr(type, FieldMemOperand(obj, HeapObject::kMapOffset), cond);
+    ldrb(type, FieldMemOperand(type, Map::kInstanceTypeOffset), cond);
+    tst(type, Operand(kIsNotStringMask), cond);
     ASSERT_EQ(0, kStringTag);
     return eq;
   }
 
 
   // Generates code for reporting that an illegal operation has
   // occurred.
   void IllegalOperation(int num_arguments);
 
   // Picks out an array index from the hash field.
@@ skipping 283 matching lines @@
   }
 
   // Untag the source value into destination and jump if source is a smi.
   // Souce and destination can be the same register.
   void UntagAndJumpIfSmi(Register dst, Register src, Label* smi_case);
 
   // Untag the source value into destination and jump if source is not a smi.
   // Souce and destination can be the same register.
   void UntagAndJumpIfNotSmi(Register dst, Register src, Label* non_smi_case);
 
-  // Jump the register contains a smi.
+  // Jump if the register contains a smi.
   inline void JumpIfSmi(Register value, Label* smi_label) {
     tst(value, Operand(kSmiTagMask));
     b(eq, smi_label);
   }
   // Jump if either of the registers contain a non-smi.
   inline void JumpIfNotSmi(Register value, Label* not_smi_label) {
     tst(value, Operand(kSmiTagMask));
     b(ne, not_smi_label);
   }
   // Jump if either of the registers contain a non-smi.
@@ skipping 202 matching lines @@
 #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
 #define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_MACRO_ASSEMBLER_ARM_H_