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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2019-03-11 23:39:15 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2019-04-04 16:01:10 +0700
commite3fd0b0e93a7b49a2f26640633fb2643c460ff4a (patch)
tree56a9c07a5330c18e39e9b53b39a7c5acbd91713c
parent8260f23616c1a2a4e609f989a195fba7690a42ca (diff)
downloadglibc-e3fd0b0e93a7b49a2f26640633fb2643c460ff4a.tar.gz
wcsmbs: Add wcscpy loop unroll option
This allows an architecture to use the old generic implementation and also set explicit loop unrolling. Checked on aarch64-linux-gnu. * include/loop_unroll.h: New file. * wcsmbs/wcscpy (__wcscpy): Add option to use loop unrolling besides generic implementation.
-rw-r--r--ChangeLog6
-rw-r--r--include/loop_unroll.h78
-rw-r--r--wcsmbs/wcscpy.c19
3 files changed, 103 insertions, 0 deletions
diff --git a/ChangeLog b/ChangeLog
index b5c13e8954..89558b0ea7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -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)