On 09/08/2021 12:22, Richard Biener wrote:
On Mon, Aug 9, 2021 at 8:52 AM Sebastian Huber
<sebastian.hu...@embedded-brains.de> wrote:
Hello,
I would like to use gcov for a multi-threaded program running on an SMP
machine using a 32-bit SPARC/LEON3 target. This target supports
HAVE_atomic_compare_and_swapsi but not HAVE_atomic_compare_and_swapdi.
Unfortunately we have:
/* Return the type node for gcov_type. */
tree
get_gcov_type (void)
{
scalar_int_mode mode
= smallest_int_mode_for_size (LONG_LONG_TYPE_SIZE > 32 ? 64 : 32);
return lang_hooks.types.type_for_mode (mode, false);
}
The long long type is 64-bit, the get_gcov_type() returns a 64-bit type.
This disables the atomic support in tree_profiling().
For what is the gcov type used? Could we add an option to force it to
32-bit? What would be the consequences?
It's a generic counter used for number of CFG edge traversal tracking.
So I guess if this counter overflows, then you get inconsistent
coverage/profiling information?
Can you not implement 64bit atomic support for 32bit SPARC somehow?
The 32-bit SPARC/LEON3 has only a 32-bit compare and swap instruction
(gcc/config/sparc/sync.md). I don't know how you could implement a
64-bit atomic support using this without spin locks (this is how
libatomic support for RTEMS works).
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