| Message ID | 5152B9FB.1090103@net-b.de |
|---|---|
| State | New |
| Headers | show |
On Wed, Mar 27, 2013 at 10:20:59AM +0100, Tobias Burnus wrote: > (The email below was only sent to gcc-patches@; I now also CC > fortran@ - sorry for the full quote) > > Regarding the below patch: I think it does not work as-is for > Unicode strings (UCS4, character(kind=4)), where each character is 4 > bytes wide and a space does not consist of sequences of four ' '. > I did not know about that. We could use wmemchr when sizeof(wchar_t)==4. where should I put that? > > Regarding Thomas' patch:* I would also think that memcmp should work > for kind=4 characters; one then needs to multiply the length by the > byte-size. (Actually, for kind==1, one could check the excess > characters in the generated code via memchr as done in Ondřej's > patch.) > > > However, looking at intrinsics/string_intrinsics{,_inc}.c, I see > that we don't use MEMCMP for UCS4 either - but some a hand-written > function. I think that could also be replaced by the normal memcmp > (or did I miss some fine print?). A possible patch would be to > replace > #define MEMCMP memcmp_char4 > by > #define MEMCMP(a,b,c) memcmp(a,b,4*(c)) > and delete the memcmp_char4 function. > Or use wmemcmp. > > Tobias > > * http://gcc.gnu.org/ml/fortran/2013-03/msg00142.html >
diff --git a/libgfortran/intrinsics/string_intrinsics_inc.c b/libgfortran/intrinsics/string_intrinsics_inc.c index a1f86b5..9eb0613 100644 --- a/libgfortran/intrinsics/string_intrinsics_inc.c +++ b/libgfortran/intrinsics/string_intrinsics_inc.c @@ -107,16 +107,15 @@ compare_string (gfc_charlen_type len1, const CHARTYPE *s1, res = 1; } - while (len--) + s = memchr (s, ' ', len); + if (!s) + return 0; + if (*s != ' ') { - if (*s != ' ') - { - if (*s > ' ') - return res; - else - return -res; - } - s++; + if (*s > ' ') + return res; + else + return -res; }
(The email below was only sent to gcc-patches@; I now also CC fortran@ - sorry for the full quote) Regarding the below patch: I think it does not work as-is for Unicode strings (UCS4, character(kind=4)), where each character is 4 bytes wide and a space does not consist of sequences of four ' '. Regarding Thomas' patch:* I would also think that memcmp should work for kind=4 characters; one then needs to multiply the length by the byte-size. (Actually, for kind==1, one could check the excess characters in the generated code via memchr as done in Ondřej's patch.) However, looking at intrinsics/string_intrinsics{,_inc}.c, I see that we don't use MEMCMP for UCS4 either - but some a hand-written function. I think that could also be replaced by the normal memcmp (or did I miss some fine print?). A possible patch would be to replace #define MEMCMP memcmp_char4 by #define MEMCMP(a,b,c) memcmp(a,b,4*(c)) and delete the memcmp_char4 function. Tobias * http://gcc.gnu.org/ml/fortran/2013-03/msg00142.html -------- Original Message -------- Subject: [Patch, fortran] optimize string comparison Date: Wed, 27 Mar 2013 09:35:57 +0100 From: Ondřej Bílka <neleai@seznam.cz> To: gcc-patches@gcc.gnu.org Hi, as I looked to compare_string I discovered that it could be optimized. This speeds up case when strings are equal but we must check padding where checking it byte by byte is suboptimal. Ondra 2013-03-27 Ondřej Bílka <neleai@seznam.cz> * libgfortran/intrinsics/string_intrinsics_inc.c (compare_string): Optimize. return 0;