Re: [PATCH] Fixes tree-loop-distribute-patterns issues

[Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>]

On 20-06-2013 14:58, Roland McGrath wrote:
> Thanks, that is much closer.
> [...] Please change the configure check so that it tests the
> syntax that we actually use.
>
> The libc-symbols.h definition also needs clear comments about its purpose
> and appropriate uses, as I mentioned before.

Fixed both.

>
> [...]
>
> Further, I think we should apply the macro to every simple_* function in
> every string/ test (not just the ones we know today have an issue).  But
> that could be a separate follow-up patch if you prefer.

I'll create a follow-up patch for such modification.

>
>
> Thanks,
> Roland
>
Thanks for the review, below is the version with the aforementioned revision.

---

2013-06-20  Adhemerval Zanella  <azanella@linux.vnet.ibm.com>

	* config.h.in (HAVE_CC_INHIBIT_LOOP_TO_LIBCALL): New define.
	* configure.in (libc_cv_cc_loop_to_function): Check if compiler
	accepts -fno-tree-loop-distribute-patterns.
	* include/libc-symbols.h (inhibit_loop_to_libcall): New macro.
	* string/memmove.c (MEMMOVE): Disable loop transformation to avoid
	recursive call.
	* string/memset.c (memset): Likewise.
	* string/test-memmove.c (simple_memmove): Disable loop transformation
	to library calls.
	* string/test-memset.c (simple_memset): Likewise.
	* benchtests/bench-memmove.c (simple_memmove): Likewise.
	* benchtests/bench-memset.c (simple_memset): Likewise.
	* configure: Regenerated.

--

diff --git a/benchtests/bench-memmove.c b/benchtests/bench-memmove.c
index dccde5d..8925606 100644
--- a/benchtests/bench-memmove.c
+++ b/benchtests/bench-memmove.c
@@ -46,6 +46,7 @@ IMPL (memmove, 1)
 #endif
 
 char *
+inhibit_loop_to_libcall
 simple_memmove (char *dst, const char *src, size_t n)
 {
   char *ret = dst;
diff --git a/benchtests/bench-memset.c b/benchtests/bench-memset.c
index 92e34f0..ea29cf3 100644
--- a/benchtests/bench-memset.c
+++ b/benchtests/bench-memset.c
@@ -63,6 +63,7 @@ builtin_memset (char *s, int c, size_t n)
 #endif
 
 char *
+inhibit_loop_to_libcall
 simple_memset (char *s, int c, size_t n)
 {
   char *r = s, *end = s + n;
diff --git a/config.h.in b/config.h.in
index 8c2479e..b5c6f16 100644
--- a/config.h.in
+++ b/config.h.in
@@ -69,6 +69,9 @@
 /* Define if the compiler supports __builtin_memset.  */
 #undef	HAVE_BUILTIN_MEMSET
 
+/* Define if compiler accepts -ftree-loop-distribute-patterns.  */
+#undef  HAVE_CC_INHIBIT_LOOP_TO_LIBCALL
+
 /* Define if the regparm attribute shall be used for local functions
    (gcc on ix86 only).  */
 #undef	USE_REGPARMS
diff --git a/configure b/configure
index 09d8336..12fd05a 100755
diff --git a/configure.in b/configure.in
index 8b11081..1dc8e6f 100644
--- a/configure.in
+++ b/configure.in
@@ -1964,6 +1964,25 @@ if test -n "$submachine"; then
 fi
 AC_SUBST(libc_cv_cc_submachine)
 
+AC_CACHE_CHECK(if $CC accepts -fno-tree-loop-distribute-patterns with \
+__attribute__ ((__optimize__)), libc_cv_cc_loop_to_function, [dnl
+cat > conftest.c <<EOF
+void
+__attribute__ ((__optimize__ ("-fno-tree-loop-distribute-patterns")))
+foo (void) {}
+EOF
+libc_cv_cc_loop_to_function=no
+if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS -c
+			    -fno-tree-loop-distribute-patterns conftest.c])
+then
+  libc_cv_cc_loop_to_function=yes
+fi
+rm -f conftest*])
+if test $libc_cv_cc_loop_to_function = yes; then
+  AC_DEFINE(HAVE_CC_INHIBIT_LOOP_TO_LIBCALL)
+fi
+AC_SUBST(libc_cv_cc_loop_to_function)
+
 dnl Check whether we have the gd library available.
 AC_MSG_CHECKING(for libgd)
 if test "$with_gd" != "no"; then
diff --git a/include/libc-symbols.h b/include/libc-symbols.h
index f043ce0..36633fe 100644
--- a/include/libc-symbols.h
+++ b/include/libc-symbols.h
@@ -782,4 +782,14 @@ for linking")
 #define libc_ifunc_hidden_def(name) \
   libc_ifunc_hidden_def1 (__GI_##name, name)
 
+/* 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
+
 #endif /* libc-symbols.h */
diff --git a/string/memmove.c b/string/memmove.c
index 9dcd2f1..ec61e28 100644
--- a/string/memmove.c
+++ b/string/memmove.c
@@ -41,6 +41,7 @@
 #endif
 
 rettype
+inhibit_loop_to_libcall
 MEMMOVE (a1, a2, len)
      a1const void *a1;
      a2const void *a2;
diff --git a/string/memset.c b/string/memset.c
index 868be53..74b5409 100644
--- a/string/memset.c
+++ b/string/memset.c
@@ -21,6 +21,7 @@
 #undef memset
 
 void *
+inhibit_loop_to_libcall
 memset (dstpp, c, len)
      void *dstpp;
      int c;
diff --git a/string/test-memmove.c b/string/test-memmove.c
index 4ec55b2..94576a2 100644
--- a/string/test-memmove.c
+++ b/string/test-memmove.c
@@ -47,6 +47,7 @@ IMPL (memmove, 1)
 #endif
 
 char *
+inhibit_loop_to_libcall
 simple_memmove (char *dst, const char *src, size_t n)
 {
   char *ret = dst;
diff --git a/string/test-memset.c b/string/test-memset.c
index 9981fce..72a390e 100644
--- a/string/test-memset.c
+++ b/string/test-memset.c
@@ -64,6 +64,7 @@ builtin_memset (char *s, int c, size_t n)
 #endif
 
 char *
+inhibit_loop_to_libcall
 simple_memset (char *s, int c, size_t n)
 {
   char *r = s, *end = s + n;