>
> gcc/ChangeLog:
>
> * tree-ssa-loop-split.c (split_loop): Fix incorrect probability.
> (do_split_loop_on_cond): Likewise.
> ---
> gcc/tree-ssa-loop-split.c | 25 ++++++++++++++++---------
> 1 file changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/gcc/tree-ssa-loop-split.c b/gcc/tree-ssa-loop-split.c
> index 3f6ad046623..d30782888f3 100644
> --- a/gcc/tree-ssa-loop-split.c
> +++ b/gcc/tree-ssa-loop-split.c
> @@ -575,7 +575,11 @@ split_loop (class loop *loop1)
> stmts2);
> tree cond = build2 (guard_code, boolean_type_node, guard_init, border);
> if (!initial_true)
> - cond = fold_build1 (TRUTH_NOT_EXPR, boolean_type_node, cond);
> + cond = fold_build1 (TRUTH_NOT_EXPR, boolean_type_node, cond);
> +
> + edge true_edge = EDGE_SUCC (bbs[i], 0)->flags & EDGE_TRUE_VALUE
> + ? EDGE_SUCC (bbs[i], 0)
> + : EDGE_SUCC (bbs[i], 1);
>
> /* Now version the loop, placing loop2 after loop1 connecting
> them, and fix up SSA form for that. */
> @@ -583,10 +587,10 @@ split_loop (class loop *loop1)
> basic_block cond_bb;
>
> class loop *loop2 = loop_version (loop1, cond, &cond_bb,
> - profile_probability::always (),
> - profile_probability::always (),
> - profile_probability::always (),
> - profile_probability::always (),
> + true_edge->probability,
> + true_edge->probability.invert (),
> + true_edge->probability,
> + true_edge->probability.invert (),
> true);
As discussed yesterday, for loop of form
for (...)
if (cond)
cond = something();
else
something2
Split as
loop1:
for (...)
if (true)
cond = something();
if (!cond)
break
else
something2 ();
loop2:
for (...)
if (false)
cond = something();
else
something2 ();
If "if (cond)" has probability p, you want to scale loop1 by p
and loop2 by 1-p as your patch does, but you need to exclude the basic
blocks guarded by the condition.
One way is to break out loop_version and implement it inline, other
option (perhaps leading to less code duplication) is to add argument listing
basic blocks that should not be scaled, which would be set to both arms
of the if.
Are there other profile patches of your I should look at?
Honza
> gcc_assert (loop2);
>
> @@ -1486,10 +1490,10 @@ do_split_loop_on_cond (struct loop *loop1, edge
> invar_branch)
> initialize_original_copy_tables ();
>
> struct loop *loop2 = loop_version (loop1, boolean_true_node, NULL,
> - profile_probability::always (),
> - profile_probability::never (),
> - profile_probability::always (),
> - profile_probability::always (),
> + invar_branch->probability.invert (),
> + invar_branch->probability,
> + invar_branch->probability.invert (),
> + invar_branch->probability,
> true);
> if (!loop2)
> {
> @@ -1530,6 +1534,9 @@ do_split_loop_on_cond (struct loop *loop1, edge
> invar_branch)
> to_loop1->flags |= true_invar ? EDGE_FALSE_VALUE : EDGE_TRUE_VALUE;
> to_loop2->flags |= true_invar ? EDGE_TRUE_VALUE : EDGE_FALSE_VALUE;
>
> + to_loop1->probability = invar_branch->probability.invert ();
> + to_loop2->probability = invar_branch->probability;
> +
> /* Due to introduction of a control flow edge from loop1 latch to loop2
> pre-header, we should update PHIs in loop2 to reflect this connection
> between loop1 and loop2. */
> --
> 2.27.0.90.geebb51ba8c
>
