Re: Bug compiling the C version of memset with gcc -O3

[Alexander Holler <holler at ahsoftware dot de>]

Am 08.12.2013 03:40, schrieb Alexander Holler:

> I've stumbled over bug compiling newlib 2.0 for ARM with gcc and -O3.

I've attached a quickly done patch which fixed the issue here. Please
not that this patch still needs some love from someone (see the line
containing "hack" in the patch) as I haven't changed configure and
possible existing tests.

It's unlikely that I will post another (better) version of this patch,
but maybe someone else wants to do that. An example how it could look
like can be found here:

http://sourceware.org/ml/libc-alpha/2013-06/msg00734.html

Regards,

Alexander Holler

diff -Naur newlib-2.0.0.orig/newlib/libc/string/memmove.c newlib-2.0.0/newlib/libc/string/memmove.c
--- newlib-2.0.0.orig/newlib/libc/string/memmove.c	2010-09-22 05:15:07.000000000 +0200
+++ newlib-2.0.0/newlib/libc/string/memmove.c	2013-12-08 05:17:00.450248311 +0100
@@ -40,6 +40,22 @@
 #include <stddef.h>
 #include <limits.h>
 
+/* hack because currently I don't want to fiddle with autoconf */
+#define HAVE_CC_INHIBIT_LOOP_TO_LIBCALL
+
+/*
+   Taken from glibc:
+   Add the compiler optimization to inhibit loop transformation to library
+   calls.  This is used to avoid recursive calls in memset and memmove
+   default implementations.
+*/
+#ifdef HAVE_CC_INHIBIT_LOOP_TO_LIBCALL
+# define inhibit_loop_to_libcall \
+  __attribute__ ((__optimize__ ("-fno-tree-loop-distribute-patterns")))
+#else
+# define inhibit_loop_to_libcall
+#endif
+
 /* Nonzero if either X or Y is not aligned on a "long" boundary.  */
 #define UNALIGNED(X, Y) \
   (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
@@ -55,6 +71,7 @@
 
 /*SUPPRESS 20*/
 _PTR
+inhibit_loop_to_libcall
 _DEFUN (memmove, (dst_void, src_void, length),
 	_PTR dst_void _AND
 	_CONST _PTR src_void _AND
diff -Naur newlib-2.0.0.orig/newlib/libc/string/memset.c newlib-2.0.0/newlib/libc/string/memset.c
--- newlib-2.0.0.orig/newlib/libc/string/memset.c	2008-05-27 20:44:40.000000000 +0200
+++ newlib-2.0.0/newlib/libc/string/memset.c	2013-12-08 05:16:27.830247253 +0100
@@ -35,11 +35,28 @@
 
 #include <string.h>
 
+/* hack because currently I don't want to fiddle with autoconf */
+#define HAVE_CC_INHIBIT_LOOP_TO_LIBCALL
+
+/*
+   Taken from glibc:
+   Add the compiler optimization to inhibit loop transformation to library
+   calls.  This is used to avoid recursive calls in memset and memmove
+   default implementations.
+*/
+#ifdef HAVE_CC_INHIBIT_LOOP_TO_LIBCALL
+# define inhibit_loop_to_libcall \
+  __attribute__ ((__optimize__ ("-fno-tree-loop-distribute-patterns")))
+#else
+# define inhibit_loop_to_libcall
+#endif
+
 #define LBLOCKSIZE (sizeof(long))
 #define UNALIGNED(X)   ((long)X & (LBLOCKSIZE - 1))
 #define TOO_SMALL(LEN) ((LEN) < LBLOCKSIZE)
 
 _PTR
+inhibit_loop_to_libcall
 _DEFUN (memset, (m, c, n),
 	_PTR m _AND
 	int c _AND