On Fri, Apr 14, 2023 at 10:42 AM Ajit Agarwal via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Hello All:
>
> This patch add heuristics for code sinking opportunities.
> Bootstrapped and regtested for powerpc64-linux-gnu.
>
> Thanks & Regards
> Ajit
>
> tree-ssa-sink: Add heuristics for code sinking.
>
> Add following code sinking heuristics:
>
> 1. from code block dominates the call.
> 2. To Code block have uses inside the function call.
> 3. Loop headers.
> 4. Sinking from code block after call increases register
> pressure.
> 5. Sinking calls.
>
> 2023-04-14 Ajit Kumar Agarwal <aagar...@linux.ibm.com>
>
> gcc/ChangeLog:
>
> * tree-ssa-sink.cc (statement_sink_location): Add heuristics
> for code sinking.
> ---
> gcc/tree-ssa-sink.cc | 33 +++++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/gcc/tree-ssa-sink.cc b/gcc/tree-ssa-sink.cc
> index 87b1d40c174..8de88b259a3 100644
> --- a/gcc/tree-ssa-sink.cc
> +++ b/gcc/tree-ssa-sink.cc
> @@ -465,6 +465,39 @@ statement_sink_location (gimple *stmt, basic_block
> frombb,
> if (sinkbb == frombb)
> return false;
>
> + auto_vec<basic_block> h;
> + h = get_all_dominated_blocks (CDI_DOMINATORS,
> + frombb);
> + bool is_call = false;
> + while (h.length ())
> + {
> + basic_block bb = h.pop ();
> +
> + if (bb == frombb)
> + continue;
> +
> + for (gimple_stmt_iterator gsi = gsi_last_bb (bb); !gsi_end_p
> (gsi);)
> + {
> + gimple *stmt = gsi_stmt (gsi);
> +
> + if (is_gimple_call (stmt))
> + {
> + is_call = true;
> + break;
> + }
> +
> + if (!gsi_end_p (gsi))
> + gsi_prev (&gsi);
> + }
> + }
> +
> + if (!is_gimple_call (stmt)
> + && (gimple_bb (use) != frombb)
> + && !is_gimple_call (use)
> + && dominated_by_p (CDI_DOMINATORS, sinkbb, frombb)
> + && is_call)
> + return false;
> +
Sorry, but this lacks a comment, it doesn't explain why the existing heuristics
are not enough (select_best_block), it repeats dominance computing.
More so it lacks a testcase demonstrating the effect.
Richard.
> if (sinkbb == gimple_bb (use))
> *togsi = gsi_for_stmt (use);
> else
> --
> 2.31.1
>
