diff options
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | include/loop_unroll.h | 78 | ||||
| -rw-r--r-- | wcsmbs/wcscpy.c | 19 |
3 files changed, 103 insertions, 0 deletions
@@ -1,3 +1,9 @@ +2019-04-04 Adhemerval Zanella <adhemerval.zanella@linaro.org> + + * include/loop_unroll.h: New file. + * wcsmbs/wcscpy (__wcscpy): Add option to use loop unrolling + besides generic implementation. + 2019-04-03 DJ Delorie <dj@redhat.com> * time/tst-strftime3.c (tm_to_printed): Disable warning about diff --git a/include/loop_unroll.h b/include/loop_unroll.h new file mode 100644 index 0000000000..d6a84e6c5d --- /dev/null +++ b/include/loop_unroll.h @@ -0,0 +1,78 @@ +/* Macro for explicit loop unrolling. + Copyright (C) 2019 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#ifndef _LOOP_UNROLL_H +#define _LOOP_UNROLL_H + +/* Loop unroll macro to be used for explicit force loop unrolling with a + configurable number of iterations. The idea is to make the loop unrolling + independent of whether the compiler is able to unroll through specific + optimizations options (-funroll-loops or -funroll-all-loops). + + For instance, to implement strcpy with SRC being the source input and + DEST the destination buffer, it is expected the macro to be used in this + way: + + #define ITERATION(index) \ + ({ char c = *str++; *dest++ = c; c != '\0' }) + + while (1) + UNROLL_REPEAT (4, ITERATION) + + The loop will be manually unrolled 4 times. Another option is to do + the index update after the tests: + + #define ITERATION(index) \ + ({ char c = *(str + index); *(dest + index) = c; c != '\0' }) + #define UPDATE(n) \ + str += n; dst += n + + while (1) + UNROLL_REPEAT_UPDATE (4, ITERATION, UPDATE) + + The loop will be manually unrolled 4 times and the SRC and DEST pointers + will be updated only after the last iteration. + + Currently, both macros unroll the loop 8 times at maximum. */ + +#define UNROLL_REPEAT_1(X) if (!X(0)) break; +#define UNROLL_REPEAT_2(X) UNROLL_REPEAT_1 (X) if (!X (1)) break; +#define UNROLL_REPEAT_3(X) UNROLL_REPEAT_2 (X) if (!X (2)) break; +#define UNROLL_REPEAT_4(X) UNROLL_REPEAT_3 (X) if (!X (3)) break; +#define UNROLL_REPEAT_5(X) UNROLL_REPEAT_4 (X) if (!X (4)) break; +#define UNROLL_REPEAT_6(X) UNROLL_REPEAT_5 (X) if (!X (5)) break; +#define UNROLL_REPEAT_7(X) UNROLL_REPEAT_6 (X) if (!X (6)) break; +#define UNROLL_REPEAT_8(X) UNROLL_REPEAT_7 (X) if (!X (7)) break; + +#define UNROLL_EXPAND(...) __VA_ARGS__ + +#define UNROLL_REPEAT__(N, X) UNROLL_EXPAND(UNROLL_REPEAT_ ## N) (X) +#define UNROLL_REPEAT_(N, X) UNROLL_REPEAT__ (N, X) + +#define UNROLL_REPEAT(N, X) \ + (void) ({ \ + UNROLL_REPEAT_ (UNROLL_EXPAND(N), X); \ + }) + +#define UNROLL_REPEAT_UPDATE(N, X, U) \ + (void) ({ \ + UNROLL_REPEAT_ (UNROLL_EXPAND(N), X); \ + UPDATE (N); \ + }) + +#endif diff --git a/wcsmbs/wcscpy.c b/wcsmbs/wcscpy.c index 6fb2969513..36c001f69a 100644 --- a/wcsmbs/wcscpy.c +++ b/wcsmbs/wcscpy.c @@ -17,6 +17,7 @@ <http://www.gnu.org/licenses/>. */ #include <wchar.h> +#include <loop_unroll.h> #ifdef WCSCPY @@ -27,7 +28,25 @@ wchar_t * __wcscpy (wchar_t *dest, const wchar_t *src) { +#ifndef UNROLL_NTIMES return __wmemcpy (dest, src, __wcslen (src) + 1); +#else + /* Some architectures might have costly tail function call (powerpc + for instance) where wmemcpy call overhead for smalls sizes might + be more costly than just unrolling the main loop. */ + wchar_t *wcp = dest; + +#define ITERATION(index) \ + ({ \ + wchar_t c = *src++; \ + *wcp++ = c; \ + c != L'\0'; \ + }) + + while (1) + UNROLL_REPEAT(UNROLL_NTIMES, ITERATION); + return dest; +#endif } #ifndef WCSCPY weak_alias (__wcscpy, wcscpy) |