On Wed, Sep 5, 2018 at 2:01 PM Ilya Leoshkevich <i...@linux.ibm.com> wrote:
>
> gcc/ChangeLog:
>
> 2018-09-05 Ilya Leoshkevich <i...@linux.ibm.com>
>
> PR target/80080
> * combine.c (rest_of_handle_combine): Perform jump threading.
>
> gcc/testsuite/ChangeLog:
>
> 2018-09-05 Ilya Leoshkevich <i...@linux.ibm.com>
>
> PR target/80080
> * gcc.target/s390/pr80080-4.c: New test.
> ---
> gcc/combine.c | 10 ++++++++--
> gcc/testsuite/gcc.target/s390/pr80080-4.c | 16 ++++++++++++++++
> 2 files changed, 24 insertions(+), 2 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/s390/pr80080-4.c
>
> diff --git a/gcc/combine.c b/gcc/combine.c
> index a2649b6d5a1..818b4c5b77d 100644
> --- a/gcc/combine.c
> +++ b/gcc/combine.c
> @@ -14960,10 +14960,16 @@ rest_of_handle_combine (void)
> free_dominance_info (CDI_DOMINATORS);
> timevar_push (TV_JUMP);
> rebuild_jump_labels (get_insns ());
> - cleanup_cfg (0);
> - timevar_pop (TV_JUMP);
> }
>
> + /* Combining insns can change basic blocks in a way that they end up
> + containing a single jump_insn. This creates an opportunity to improve
> code
> + with jump threading. */
> + cleanup_cfg (CLEANUP_THREADING);
> +
> + if (rebuild_jump_labels_after_combine)
> + timevar_pop (TV_JUMP);
cleanup_cfg pushes its own timevar so it doesn't make sense to try covering it
with TV_JUMP. And rebuild_jump_labels immediately pushes TV_REBUILD_JUMP.
So I suggest to remove the timevar_push/pop of TV_JUMP here.
No comment in general about the change, maybe we can detect transforms that
make jump-threading viable and conditionalize that properly? Note the only
setter of CLEANUP_THREADING guards it with flag_thread_jumps so maybe better
do it above as well (avoids cost at -O0 for example).
Richard.
> +
> regstat_free_n_sets_and_refs ();
> return 0;
> }
> diff --git a/gcc/testsuite/gcc.target/s390/pr80080-4.c
> b/gcc/testsuite/gcc.target/s390/pr80080-4.c
> new file mode 100644
> index 00000000000..91d31ec7845
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/s390/pr80080-4.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-options "-march=z196 -O2" } */
> +
> +extern void bar(int *mem);
> +
> +void foo4(int *mem)
> +{
> + int oldval = 0;
> + if (!__atomic_compare_exchange_n (mem, (void *) &oldval, 1,
> + 1, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED))
> + {
> + bar (mem);
> + }
> +}
> +
> +/* { dg-final { scan-assembler
> "\n\tlt\t.*\n\tjne\t(\\.L\\d+)\n(.*\n)*\tcs\t.*\n\tber\t%r14\n\\1:\n\tjg\tbar\n"
> } } */
> --
> 2.18.0
>
