> From: Christophe Lyon <christophe.l...@linaro.org>
> Date: Tue, 3 Oct 2023 15:20:39 +0200
> Maybe we need a new variant of dg-require-thread-fence ?
Yes: many of the dg-require-thread-fence users need
something stronger. Tested arm-eabi together with the next
patch (2/2) with
RUNTESTFLAGS=--target_board=arm-sim/-mthumb/-march=armv6s-m/-mtune=cortex-m0/-mfloat-abi=soft/-mfpu=auto\
conformance.exp=29_atomics/\*
(Incidentally, in the patch context is seen
dg-require-atomic-builtins which is a misnomer: it should
rather be named "dg-require-lock-atomic-builtins-free".)
Ok to commit?
-- >8 --
Some targets (armv6) support inline atomic load and store,
i.e. dg-require-thread-fence matches, but not atomic like
atomic exchange. This directive will replace uses of
dg-require-thread-fence where an atomic exchange operation
is actually used.
* testsuite/lib/dg-options.exp (dg-require-atomic-exchange): New proc.
* testsuite/lib/libstdc++.exp (check_v3_target_atomic_exchange): Ditto.
---
libstdc++-v3/testsuite/lib/dg-options.exp | 9 ++++++
libstdc++-v3/testsuite/lib/libstdc++.exp | 35 +++++++++++++++++++++++
2 files changed, 44 insertions(+)
diff --git a/libstdc++-v3/testsuite/lib/dg-options.exp
b/libstdc++-v3/testsuite/lib/dg-options.exp
index 84ad0c65330b..b13c2f244c63 100644
--- a/libstdc++-v3/testsuite/lib/dg-options.exp
+++ b/libstdc++-v3/testsuite/lib/dg-options.exp
@@ -133,6 +133,15 @@ proc dg-require-thread-fence { args } {
return
}
+proc dg-require-atomic-exchange { args } {
+ if { ![ check_v3_target_atomic_exchange ] } {
+ upvar dg-do-what dg-do-what
+ set dg-do-what [list [lindex ${dg-do-what} 0] "N" "P"]
+ return
+ }
+ return
+}
+
proc dg-require-atomic-builtins { args } {
if { ![ check_v3_target_atomic_builtins ] } {
upvar dg-do-what dg-do-what
diff --git a/libstdc++-v3/testsuite/lib/libstdc++.exp
b/libstdc++-v3/testsuite/lib/libstdc++.exp
index 608056e5068e..481f81711074 100644
--- a/libstdc++-v3/testsuite/lib/libstdc++.exp
+++ b/libstdc++-v3/testsuite/lib/libstdc++.exp
@@ -1221,6 +1221,41 @@ proc check_v3_target_thread_fence { } {
}]
}
+proc check_v3_target_atomic_exchange { } {
+ return [check_v3_target_prop_cached et_atomic_exchange {
+ global cxxflags
+ global DEFAULT_CXXFLAGS
+
+ # Set up and link a C++11 test program that depends
+ # on atomic exchange be available for "int".
+ set src atomic_exchange[pid].cc
+
+ set f [open $src "w"]
+ puts $f "
+ int i, j, k;
+ int main() {
+ __atomic_exchange (&i, &j, &k, __ATOMIC_SEQ_CST);
+ return 0;
+ }"
+ close $f
+
+ set cxxflags_saved $cxxflags
+ set cxxflags "$cxxflags $DEFAULT_CXXFLAGS -Werror -std=gnu++11"
+
+ set lines [v3_target_compile $src /dev/null executable ""]
+ set cxxflags $cxxflags_saved
+ file delete $src
+
+ if [string match "" $lines] {
+ # No error message, linking succeeded.
+ return 1
+ } else {
+ verbose "check_v3_target_atomic_exchange: compilation failed" 2
+ return 0
+ }
+ }]
+}
+
# Return 1 if atomics_bool and atomic_int are always lock-free, 0 otherwise.
proc check_v3_target_atomic_builtins { } {
return [check_v3_target_prop_cached et_atomic_builtins {
--
2.30.2
>
> Thanks,
>
> Christophe
>
>
> Ok to commit?
> >
> > -- >8 --
> > Make __atomic_test_and_set consistent with other __atomic_ and __sync_
> > builtins: call a matching library function instead of emitting
> > non-atomic code when the target has no direct insn support.
> >
> > There's special-case code handling targetm.atomic_test_and_set_trueval
> > != 1 trying a modified maybe_emit_sync_lock_test_and_set. Previously,
> > if that worked but its matching emit_store_flag_force returned NULL,
> > we'd segfault later on. Now that the caller handles NULL, gcc_assert
> > here instead.
> >
> > While the referenced PR:s are ARM-specific, the issue is general.
> >
> > PR target/107567
> > PR target/109166
> > * builtins.cc (expand_builtin) <case BUILT_IN_ATOMIC_TEST_AND_SET>:
> > Handle failure from expand_builtin_atomic_test_and_set.
> > * optabs.cc (expand_atomic_test_and_set): When all attempts fail to
> > generate atomic code through target support, return NULL
> > instead of emitting non-atomic code. Also, for code handling
> > targetm.atomic_test_and_set_trueval != 1, gcc_assert result
> > from calling emit_store_flag_force instead of returning NULL.
> > ---
> > gcc/builtins.cc | 5 ++++-
> > gcc/optabs.cc | 22 +++++++---------------
> > 2 files changed, 11 insertions(+), 16 deletions(-)
> >
> > diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> > index 6e4274bb2a4e..40dfd36a3197 100644
> > --- a/gcc/builtins.cc
> > +++ b/gcc/builtins.cc
> > @@ -8387,7 +8387,10 @@ expand_builtin (tree exp, rtx target, rtx
> > subtarget, machine_mode mode,
> > break;
> >
> > case BUILT_IN_ATOMIC_TEST_AND_SET:
> > - return expand_builtin_atomic_test_and_set (exp, target);
> > + target = expand_builtin_atomic_test_and_set (exp, target);
> > + if (target)
> > + return target;
> > + break;
> >
> > case BUILT_IN_ATOMIC_CLEAR:
> > return expand_builtin_atomic_clear (exp);
> > diff --git a/gcc/optabs.cc b/gcc/optabs.cc
> > index 8b96f23aec05..e1898da22808 100644
> > --- a/gcc/optabs.cc
> > +++ b/gcc/optabs.cc
> > @@ -7080,25 +7080,17 @@ expand_atomic_test_and_set (rtx target, rtx mem,
> > enum memmodel model)
> > /* Recall that the legacy lock_test_and_set optab was allowed to do
> > magic
> > things with the value 1. Thus we try again without trueval. */
> > if (!ret && targetm.atomic_test_and_set_trueval != 1)
> > - ret = maybe_emit_sync_lock_test_and_set (subtarget, mem, const1_rtx,
> > model);
> > -
> > - /* Failing all else, assume a single threaded environment and simply
> > - perform the operation. */
> > - if (!ret)
> > {
> > - /* If the result is ignored skip the move to target. */
> > - if (subtarget != const0_rtx)
> > - emit_move_insn (subtarget, mem);
> > + ret = maybe_emit_sync_lock_test_and_set (subtarget, mem,
> > const1_rtx, model);
> >
> > - emit_move_insn (mem, trueval);
> > - ret = subtarget;
> > + if (ret)
> > + {
> > + /* Rectify the not-one trueval. */
> > + ret = emit_store_flag_force (target, NE, ret, const0_rtx, mode,
> > 0, 1);
> > + gcc_assert (ret);
> > + }
> > }
> >
> > - /* Recall that have to return a boolean value; rectify if trueval
> > - is not exactly one. */
> > - if (targetm.atomic_test_and_set_trueval != 1)
> > - ret = emit_store_flag_force (target, NE, ret, const0_rtx, mode, 0, 1);
> > -
> > return ret;
> > }
> >
> > --
> > 2.30.2
> >
> >
>
