===================================================================
@@ -317,7 +317,7 @@ arm*-*-linux*) # ARM GNU/Linux with EL
tmake_file="${tmake_file} arm/t-arm t-fixedpoint-gnu-prefix"
case ${host} in
arm*-*-linux-*eabi)
- tmake_file="${tmake_file} arm/t-elf arm/t-bpabi arm/t-linux-eabi t-slibgcc-libgcc"
+ tmake_file="${tmake_file} arm/t-elf arm/t-bpabi arm/t-linux-eabi arm/t-divmod-ef t-slibgcc-libgcc"
tm_file="$tm_file arm/bpabi-lib.h"
unwind_header=config/arm/unwind-arm.h
;;
@@ -331,7 +331,7 @@ arm*-*-uclinux*) # ARM ucLinux
tmake_file="${tmake_file} t-fixedpoint-gnu-prefix"
case ${host} in
arm*-*-uclinux*eabi)
- tmake_file="${tmake_file} arm/t-bpabi"
+ tmake_file="${tmake_file} arm/t-bpabi arm/t-divmod-ef"
tm_file="$tm_file arm/bpabi-lib.h"
unwind_header=config/arm/unwind-arm.h
;;
@@ -344,7 +344,7 @@ arm*-*-ecos-elf)
extra_parts="$extra_parts crti.o crtn.o"
;;
arm*-*-eabi* | arm*-*-symbianelf* | arm*-*-rtemseabi*)
- tmake_file="${tmake_file} arm/t-arm arm/t-elf t-fixedpoint-gnu-prefix"
+ tmake_file="${tmake_file} arm/t-arm arm/t-elf arm/t-divmod-ef t-fixedpoint-gnu-prefix"
tm_file="$tm_file arm/bpabi-lib.h"
case ${host} in
arm*-*-eabi* | arm*-*-rtemseabi*)
===================================================================
@@ -497,18 +497,24 @@ libgcc-s-objects += $(patsubst %,%_s$(ob
endif
endif
+ifeq ($(LIB2_DIVMOD_EXCEPTION_FLAGS),)
+# Provide default flags for compiling divmod functions, if they haven't been
+# set already by a target-specific Makefile fragment.
+LIB2_DIVMOD_EXCEPTION_FLAGS := -fexceptions -fnon-call-exceptions
+endif
+
# Build LIB2_DIVMOD_FUNCS.
lib2-divmod-o = $(patsubst %,%$(objext),$(LIB2_DIVMOD_FUNCS))
$(lib2-divmod-o): %$(objext): $(srcdir)/libgcc2.c
$(gcc_compile) -DL$* -c $< \
- -fexceptions -fnon-call-exceptions $(vis_hide)
+ $(LIB2_DIVMOD_EXCEPTION_FLAGS) $(vis_hide)
libgcc-objects += $(lib2-divmod-o)
ifeq ($(enable_shared),yes)
lib2-divmod-s-o = $(patsubst %,%_s$(objext),$(LIB2_DIVMOD_FUNCS))
$(lib2-divmod-s-o): %_s$(objext): $(srcdir)/libgcc2.c
$(gcc_s_compile) -DL$* -c $< \
- -fexceptions -fnon-call-exceptions
+ $(LIB2_DIVMOD_EXCEPTION_FLAGS)
libgcc-s-objects += $(lib2-divmod-s-o)
endif
===================================================================
@@ -0,0 +1,4 @@
+# On ARM, specifying -fnon-call-exceptions will needlessly pull in
+# the unwinder in simple programs which use 64-bit division. Omitting
+# the option is safe.
+LIB2_DIVMOD_EXCEPTION_FLAGS := -fexceptions
===================================================================
@@ -0,0 +1,24 @@
+/* Performing a 64-bit division should not pull in the unwinder. */
+
+/* { dg-do run } */
+/* { dg-options "-O0" } */
+
+#include <stdlib.h>
+
+long long
+foo (long long c, long long d)
+{
+ return c/d;
+}
+
+long long x = 0;
+long long y = 1;
+
+extern int (*_Unwind_RaiseException) (void *) __attribute__((weak));
+
+int main(void)
+{
+ if (&_Unwind_RaiseException != NULL)
+ abort ();;
+ return foo (x, y);
+}
Hi, This (old!) patch avoids uselessly pulling in the unwinder for 64-bit division routines. I last posted it here: http://gcc.gnu.org/ml/gcc-patches/2009-10/msg01618.html Other people have noticed the same issue, e.g.: http://gcc.gnu.org/ml/gcc-help/2011-03/msg00187.html Note that we take special care already for the case where division-by-zero throws an exception: we tailcall the division-by-zero handler at the head of the 64-bit division helper routines, so never create a stack frame which needs to be unwound. On ARM, division by zero can trapped by defining magic __aeabi_[il]div0 functions. See here: http://gcc.gnu.org/ml/gcc-patches/2009-10/msg01661.html Unfortunately, despite that, throwing an exception from the division-by-zero handler functions doesn't appear to work at present -- either with or without the current patch. I'm not intending to tackle that now (see attached program -- which exits with "terminate called after throwing an instance of 'int'" for me). I'm no C++ expert, so I might have done something dumb :-). Anyway: this revised version of the patch removes the strange libgcc Makefile-fragment changes, the equivalent of which have since been incorporated into mainline GCC now anyway, so the patch is somewhat more straightforward than it was previously. The patch allows a trivial program using 64-bit division (on bare metal) to shrink quite considerably: $ arm-none-eabi-size div64 text data bss dec hex filename 13120 2404 276 15800 3db8 div64 $ arm-none-eabi-size div64-unpatched text data bss dec hex filename 20064 2404 276 22744 58d8 div64-unpatched OK to apply? Thanks, Julian ChangeLog libgcc/ * config.host (arm*-*-linux-*eabi, arm*-*-uclinux*eabi) (arm*-*-eabi*, arm*-*-symbianelf*, arm*-*-rtemseabi*): Add arm/t-divmod-ef to tmake_file. * Makefile.in (LIB2_DIVMOD_EXCEPTION_FLAGS): Default to -fexceptions -fnon-call-exceptions if not defined. ($(lib2-divmod-o), $(lib2-divmod-s-o)): Use above. * config/arm/t-divmod-ef: New file. gcc/testsuite/ * gcc.target/arm/div64-unwinding.c: New test.