| Message ID | 8f106efb5581e875ad121e7e9fe2280a@optimitech.com |
|---|---|
| State | New |
| Headers | show |
| Series | Add --disable-tm-clone-registry libgcc configure option. | expand |
On Wed, Jun 12, 2019 at 5:57 PM <ilia.diachkov@optimitech.com> wrote: > This patch adds libgcc configuration option to disable TM clone > registry. This option helps to reduce code size for embedded targets > which do not need transactional memory support. This looks OK to me. It is worth pointing out that ARM already ships compilers built this way, but they didn't bother adding a configure option. They just override Makefile variables in their build scripts. I think this is much cleaner as a documented configure option. One issue here is that I don't know the transactional memory support well enough to know what harm comes when we drop the tm clone registry support. Perhaps a change should be made to the compiler to disable the transactional memory support, or some subset of it. Maybe Aldy can comment on that? The intent here is to only use this for size constrained embedded targets (e.g. newlib-nano targets), and such targets are very unlikely to ever want transactional memory support. But someone might accidentally use this configure option with an x86_64-linux toolchain, and then get confusing transactional memory failures, and we might want to try to prevent that before it happens. Jim
On Thu, Jun 20, 2019 at 12:50 PM Jim Wilson <jimw@sifive.com> wrote: > This looks OK to me. It is worth pointing out that ARM already ships > compilers built this way, but they didn't bother adding a configure > option. They just override Makefile variables in their build scripts. > I think this is much cleaner as a documented configure option. It has been a week, and no one else commented on this, so I went ahead and committed it, with the regenerated configure. Jim
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi index 29d0470..1a0e8c7 100644 --- a/gcc/doc/install.texi +++ b/gcc/doc/install.texi @@ -1284,6 +1284,11 @@ assumptions made by the configure test are incorrect. Specify that the target does not support TLS. This is an alias for @option{--enable-tls=no}. +@item --disable-tm-clone-registry +Disable TM clone registry in libgcc. It is enabled in libgcc by default. +This option helps to reduce code size for embedded targets which do +not use transactional memory. + @item --with-cpu=@var{cpu} @itemx --with-cpu-32=@var{cpu} @itemx --with-cpu-64=@var{cpu} diff --git a/libgcc/Makefile.in b/libgcc/Makefile.in index fb77881..189f9ff 100644 --- a/libgcc/Makefile.in +++ b/libgcc/Makefile.in @@ -259,6 +259,8 @@ PICFLAG = @PICFLAG@ CET_FLAGS = @CET_FLAGS@ +USE_TM_CLONE_REGISTRY = @use_tm_clone_registry@ + # Defined in libgcc2.c, included only in the static library. LIB2FUNCS_ST = _eprintf __gcc_bcmp @@ -299,7 +301,7 @@ CRTSTUFF_CFLAGS = -O2 $(GCC_CFLAGS) $(INCLUDES) $(MULTILIB_CFLAGS) -g0 \ $(NO_PIE_CFLAGS) -finhibit-size-directive -fno-inline -fno-exceptions \ -fno-zero-initialized-in-bss -fno-toplevel-reorder -fno-tree-vectorize \ -fbuilding-libgcc -fno-stack-protector $(FORCE_EXPLICIT_EH_REGISTRY) \ - $(INHIBIT_LIBC_CFLAGS) + $(INHIBIT_LIBC_CFLAGS) $(USE_TM_CLONE_REGISTRY) # Extra flags to use when compiling crt{begin,end}.o. CRTSTUFF_T_CFLAGS = diff --git a/libgcc/configure.ac b/libgcc/configure.ac index 5f11455..b1b90d2 100644 --- a/libgcc/configure.ac +++ b/libgcc/configure.ac @@ -261,6 +261,16 @@ fi ]) AC_SUBST([force_explicit_eh_registry]) +AC_ARG_ENABLE([tm-clone-registry], +[ --disable-tm-clone-registry disable TM clone registry], +[ +use_tm_clone_registry= +if test "$enable_tm_clone_registry" = no; then + use_tm_clone_registry=-DUSE_TM_CLONE_REGISTRY=0 +fi +]) +AC_SUBST([use_tm_clone_registry]) + AC_LIB_PROG_LD_GNU AC_MSG_CHECKING([for thread model used by GCC])
Hello, This patch adds libgcc configuration option to disable TM clone registry. This option helps to reduce code size for embedded targets which do not need transactional memory support. Tested on x86_64 and riscv64-unknown-elf-gcc, the last is with the option enabled. If the change is Ok with you, please commit it since I have no write access to gcc repository. Best regards, Ilia. libgcc/ChangeLog: * Makefile.in: Add @use_tm_clone_registry@. * configure: Regenerate. * configure.ac: Add --disable-tm-clone-registry option. gcc/ChangeLog: * doc/install.texi: Document --disable-tm-clone-registry.