On Tue, Jul 21, 2020 at 8:24 PM Maciej W. Rozycki <ma...@wdc.com> wrote:
>
> Complement commit b932f770f70d ("x86_64 frame unwind info"), SVN r46374,
> <https://gcc.gnu.org/ml/gcc-patches/2001-10/msg00860.html>, and replace
> `-fexceptions -fnon-call-exceptions' with `-fasynchronous-unwind-tables'
> in LIB2_DIVMOD_FUNCS compilation flags so as to provide unwind tables
> for the affected functions while not pulling the unwinder proper, which
> is not required here.
>
> Remove the ARM overrides accordingly, retaining the hook infrastructure
> however, and make the ARM test case a generic one.You're changing arm files only so CCing arm maintainers. Richard. > Beyond saving program space it fixes a RISC-V glibc build error due to > unsatisfied `malloc' and `free' references from the unwinder causing > link errors with `ld.so' where libgcc has been built at -O0. > --- > Hi, > > As discussed: <https://gcc.gnu.org/pipermail/gcc/2020-July/233120.html>. > > This has been regression-tested with all the GCC compiler testsuites with > the `x86_64-linux' native configuration, which in particular means the > moved ARM test case scored the UNSUPPORTED result. I have no access to a > non-Linux configuration right now, so I cannot verify this test case, but > in principle I expect it to work across the relevant targets (and the > irrelevant ones can be excluded as they are discovered). > > OK to apply then? It may make sense to backport this fix too to the > active release branches; please let me know if to do so. > > NB the original commit referred appears to contain more than just the > corresponding mailing list posting; it looks like several patches were > folded together before comitting, so this is as good as you can get. > > Maciej > --- > gcc/testsuite/gcc.dg/div64-unwinding.c | 25 > +++++++++++++++++++++++++ > gcc/testsuite/gcc.target/arm/div64-unwinding.c | 25 > ------------------------- > libgcc/Makefile.in | 2 +- > libgcc/config/arm/t-bpabi | 5 ----- > libgcc/config/arm/t-netbsd-eabi | 5 ----- > 5 files changed, 26 insertions(+), 36 deletions(-) > > gcc-libgcc-divmod-asynchronous-unwind-tables.diff > Index: gcc/gcc/testsuite/gcc.dg/div64-unwinding.c > =================================================================== > --- /dev/null > +++ gcc/gcc/testsuite/gcc.dg/div64-unwinding.c > @@ -0,0 +1,25 @@ > +/* Performing a 64-bit division should not pull in the unwinder. */ > + > +/* { dg-do run { target { { ! *-*-linux* } && { ! *-*-uclinux* } } } } */ > +/* { dg-skip-if "load causes weak symbol resolution" { vxworks_kernel } } */ > +/* { 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); > +} > Index: gcc/gcc/testsuite/gcc.target/arm/div64-unwinding.c > =================================================================== > --- gcc.orig/gcc/testsuite/gcc.target/arm/div64-unwinding.c > +++ /dev/null > @@ -1,25 +0,0 @@ > -/* Performing a 64-bit division should not pull in the unwinder. */ > - > -/* { dg-do run { target { { ! *-*-linux* } && { ! *-*-uclinux* } } } } */ > -/* { dg-skip-if "load causes weak symbol resolution" { vxworks_kernel } } */ > -/* { 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); > -} > Index: gcc/libgcc/Makefile.in > =================================================================== > --- gcc.orig/libgcc/Makefile.in > +++ gcc/libgcc/Makefile.in > @@ -533,7 +533,7 @@ 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 > +LIB2_DIVMOD_EXCEPTION_FLAGS := -fasynchronous-unwind-tables > endif > > # Build LIB2_DIVMOD_FUNCS. > Index: gcc/libgcc/config/arm/t-bpabi > =================================================================== > --- gcc.orig/libgcc/config/arm/t-bpabi > +++ gcc/libgcc/config/arm/t-bpabi > @@ -13,8 +13,3 @@ LIB2ADDEH = $(srcdir)/config/arm/unwind- > > # Add the BPABI names. > SHLIB_MAPFILES += $(srcdir)/config/arm/libgcc-bpabi.ver > - > -# 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 > Index: gcc/libgcc/config/arm/t-netbsd-eabi > =================================================================== > --- gcc.orig/libgcc/config/arm/t-netbsd-eabi > +++ gcc/libgcc/config/arm/t-netbsd-eabi > @@ -11,8 +11,3 @@ LIB2ADDEH = > > # Add the BPABI names. > SHLIB_MAPFILES += $(srcdir)/config/arm/libgcc-bpabi.ver > - > -# 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
