Optimize out unicode_to_native(), native_to_unicode()

These just return their argument on ASCII platforms, so can get rid of
the function call overhead there.

Thanks to Zefram and Matthew Horsfall for their help in this.

2 files changed, 25 insertions, 2 deletions

diff --git a/lib/utf8.pm b/lib/utf8.pm
index 4980c7c7c3..ed23b61386 100644
--- a/lib/utf8.pm
+++ b/lib/utf8.pm
@@ -2,7 +2,7 @@ package utf8;
 
 $utf8::hint_bits = 0x00800000;
 
-our $VERSION = '1.14';
+our $VERSION = '1.15';
 
 sub import {
     $^H |= $utf8::hint_bits;
@@ -186,6 +186,7 @@ L<Encode>.
 
 =item * C<$unicode = utf8::native_to_unicode($code_point)>
 
+(Since Perl v5.8.0)
 This takes an unsigned integer (which represents the ordinal number of a
 character (or a code point) on the platform the program is being run on) and
 returns its Unicode equivalent value.  Since ASCII platforms natively use the
@@ -195,8 +196,12 @@ platforms it converts from EBCIDC to Unicode.
 A meaningless value will currently be returned if the input is not an unsigned
 integer.
 
+Since Perl v5.22.0, calls to this function are optimized out on ASCII
+platforms, so there is no performance hit in using it there.
+
 =item * C<$native = utf8::unicode_to_native($code_point)>
 
+(Since Perl v5.8.0)
 This is the inverse of C<utf8::native_to_unicode()>, converting the other
 direction.  Again, on ASCII platforms, this returns its input, but on EBCDIC
 platforms it will find the native platform code point, given any Unicode one.
@@ -204,6 +209,9 @@ platforms it will find the native platform code point, given any Unicode one.
 A meaningless value will currently be returned if the input is not an unsigned
 integer.
 
+Since Perl v5.22.0, calls to this function are optimized out on ASCII
+platforms, so there is no performance hit in using it there.
+
 =item * C<$flag = utf8::is_utf8($string)>
 
 (Since Perl 5.8.1)  Test whether I<$string> is marked internally as encoded in
diff --git a/lib/utf8.t b/lib/utf8.t
index 8578444fb8..bf722f3797 100644
--- a/lib/utf8.t
+++ b/lib/utf8.t
@@ -481,7 +481,7 @@ SKIP: {
             use strict;
             my $s = "hlagh";
             my $r = \$s;
-            %s($r);
+            my $dummy = %s($r);
             $$r;
         ], $func;
         my $ret = eval $code or my $error = $@;
@@ -603,6 +603,21 @@ for my $pos (0..5) {
     is($s, "A$utf8_bytes","(pos $pos) str after  U; utf8::encode");
 }
 
+SKIP: {
+    skip("Test only valid on ASCII platform", 1) unless $::IS_ASCII;
+    require Config;
+    skip("Test needs a B module, which is lacking in this Perl", 1)
+        if $Config::Config{'extensions'} !~ /\bB\b/;
+
+    my $out = runperl ( switches => ["-XMO=Concise"],
+                    prog => 'utf8::unicode_to_native(0x41);
+                             utf8::native_to_unicode(0x42)',
+                    stderr => 1 );
+    unlike($out, qr/entersub/,
+            "utf8::unicode_to_native() and native_to_unicode() optimized out");
+}
+
+
 # [perl #119043] utf8::upgrade should not croak on read-only COWs
 for(__PACKAGE__) {
 	eval { utf8::upgrade($_) };