Lithium: avoid registers for constants when possible.

src/arm/lithium-arm.h

Index: src/arm/lithium-arm.h
diff --git a/src/arm/lithium-arm.h b/src/arm/lithium-arm.h
index d81881e6fbbd95c4ecf77e1bbb92ba926d897904..1c95419daf270eb6eba40b1bd740bcfab56ab126 100644
--- a/src/arm/lithium-arm.h
+++ b/src/arm/lithium-arm.h
@@ -2787,6 +2787,9 @@ class LChunkBuilder BASE_EMBEDDED {
   MUST_USE_RESULT LOperand* UseRegisterOrConstant(HValue* value);
   MUST_USE_RESULT LOperand* UseRegisterOrConstantAtStart(HValue* value);
 
+  // An input operand in a constant operand.
+  MUST_USE_RESULT LOperand* UseConstant(HValue* value);
+
   // An input operand in register, stack slot or a constant operand.
   // Will not be moved to a register even if one is freely available.
   MUST_USE_RESULT LOperand* UseAny(HValue* value);