On Wed, Nov 8, 2023 at 4:00 PM Ajit Agarwal <aagar...@linux.ibm.com> wrote:
>
> tree-ssa-loop-ivopts : Add live analysis in regs used in decision making.
>
> Add live anaysis in regs used calculation in decision making of
> selecting ivopts candidates.
>
> 2023-11-08 Ajit Kumar Agarwal <aagar...@linux.ibm.com>
>
> gcc/ChangeLog:
>
> * tree-ssa-loop-ivopts.cc (get_regs_used): New function.
> (determine_set_costs): Call to get_regs_used to use live
> analysis.
> ---
> gcc/tree-ssa-loop-ivopts.cc | 73 +++++++++++++++++++++++++++++++++++--
> 1 file changed, 70 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/tree-ssa-loop-ivopts.cc b/gcc/tree-ssa-loop-ivopts.cc
> index c3336603778..e02fe7d434b 100644
> --- a/gcc/tree-ssa-loop-ivopts.cc
> +++ b/gcc/tree-ssa-loop-ivopts.cc
> @@ -6160,6 +6160,68 @@ ivopts_estimate_reg_pressure (struct ivopts_data
> *data, unsigned n_invs,
> return cost + n_cands;
> }
>
> +/* Return regs used based on live-in and liveout of given ssa variables. */
Please explain how the following code relates to anything like "live
analysis" and
where it uses live-in and live-out. And what "live-in/out of a given
SSA variable"
should be.
Also explain why you are doing this at all. The patch doesn't come
with a testcase
or with any other hint that motivated you.
Richard.
> +static unsigned
> +get_regs_used (tree ssa_name)
> +{
> + unsigned regs_used = 0;
> + gimple *stmt;
> + use_operand_p use;
> + basic_block def_bb = NULL;
> + imm_use_iterator imm_iter;
> +
> + stmt = SSA_NAME_DEF_STMT (ssa_name);
> + if (stmt)
> + {
> + def_bb = gimple_bb (stmt);
> + /* Mark defs in liveout bitmap temporarily. */
> + if (def_bb)
> + regs_used++;
> + }
> + else
> + def_bb = ENTRY_BLOCK_PTR_FOR_FN (cfun);
> +
> + /* An undefined local variable does not need to be very alive. */
> + if (virtual_operand_p (ssa_name)
> + || ssa_undefined_value_p (ssa_name, false))
> + return 0;
> +
> + /* Visit each use of SSA_NAME and if it isn't in the same block as the def,
> + add it to the list of live on entry blocks. */
> + FOR_EACH_IMM_USE_FAST (use, imm_iter, ssa_name)
> + {
> + gimple *use_stmt = USE_STMT (use);
> + basic_block add_block = NULL;
> +
> + if (gimple_code (use_stmt) == GIMPLE_PHI)
> + {
> + /* Uses in PHI's are considered to be live at exit of the SRC block
> + as this is where a copy would be inserted. Check to see if it is
> + defined in that block, or whether its live on entry. */
> + int index = PHI_ARG_INDEX_FROM_USE (use);
> + edge e = gimple_phi_arg_edge (as_a <gphi *> (use_stmt), index);
> + if (e->src != def_bb)
> + add_block = e->src;
> + }
> + else if (is_gimple_debug (use_stmt))
> + continue;
> + else
> + {
> + /* If its not defined in this block, its live on entry. */
> + basic_block use_bb = gimple_bb (use_stmt);
> + if (use_bb != def_bb)
> + add_block = use_bb;
> + }
> +
> + /* If there was a live on entry use, increment register used. */
> + if (add_block)
> + {
> + regs_used++;
> + }
> + }
> + return regs_used;
> +}
> +
> /* For each size of the induction variable set determine the penalty. */
>
> static void
> @@ -6200,15 +6262,20 @@ determine_set_costs (struct ivopts_data *data)
> n++;
> }
>
> + unsigned max = 0;
> EXECUTE_IF_SET_IN_BITMAP (data->relevant, 0, j, bi)
> {
> struct version_info *info = ver_info (data, j);
> -
> if (info->inv_id && info->has_nonlin_use)
> - n++;
> + {
> + tree ssa_name = ssa_name (j);
> + n = get_regs_used (ssa_name);
> + if (n >= max)
> + max = n;
> + }
> }
>
> - data->regs_used = n;
> + data->regs_used = max;
> if (dump_file && (dump_flags & TDF_DETAILS))
> fprintf (dump_file, " regs_used %d\n", n);
>
> --
> 2.39.3
>
>
