towlower()/towupper(): reuse tolower()/toupper().

Now <ctype.h> tolower() and toupper() are inlined, we don't need to
duplicate the code in the towlower() and towupper() fast paths to avoid
a function call.

Test: treehugger
Change-Id: Ie9ae78500a3ea253756b8bbb9cc9ea86774ff616

Author: enh-google

libc/bionic/wctype.cpp

@@ -109,23 +109,15 @@ int iswctype_l(wint_t wc, wctype_t char_class, locale_t) {
 }
 
 wint_t towlower(wint_t wc) {
-  if (wc < 0x80) {
-    if (wc >= 'A' && wc <= 'Z') return wc | 0x20;
-    return wc;
-  }
+  if (wc < 0x80) return tolower(wc);
 
   typedef UChar32 (*FnT)(UChar32);
   static auto u_tolower = reinterpret_cast<FnT>(__find_icu_symbol("u_tolower"));
   return u_tolower ? u_tolower(wc) : tolower(wc);
 }
 
 wint_t towupper(wint_t wc) {
-  if (wc < 0x80) {
-    // Using EOR rather than AND makes no difference on arm, but saves an
-    // instruction on arm64.
-    if (wc >= 'a' && wc <= 'z') return wc ^ 0x20;
-    return wc;
-  }
+  if (wc < 0x80) return toupper(wc);
 
   typedef UChar32 (*FnT)(UChar32);
   static auto u_toupper = reinterpret_cast<FnT>(__find_icu_symbol("u_toupper"));