ARM: Make use of d16-d31 when available.

src/ia32/assembler-ia32.h

Index: src/ia32/assembler-ia32.h
diff --git a/src/ia32/assembler-ia32.h b/src/ia32/assembler-ia32.h
index b1f421ec86730388f2e8d72c1e8b6c1e5b980c2a..1818c9ae24b8baf1c8de10e3b695ef34c7c22668 100644
--- a/src/ia32/assembler-ia32.h
+++ b/src/ia32/assembler-ia32.h
@@ -142,6 +142,8 @@ struct XMMRegister {
   static const int kNumAllocatableRegisters = 7;
   static const int kNumRegisters = 8;
 
+  static int NumAllocatableRegisters() { return kNumAllocatableRegisters; }
+
   static int ToAllocationIndex(XMMRegister reg) {
     ASSERT(reg.code() != 0);
     return reg.code() - 1;