> Am 01.09.2024 um 06:07 schrieb Andrew Pinski <quic_apin...@quicinc.com>:
>
> While working on a phiopt patch, it was noticed that
> SLSR would leave around some unused ssa names. Let's
> add simple_dce_from_worklist usage to SLSR to remove
> the dead statements. This should give a small improvemnent
> for passes afterwards.
>
> Boostrapped and tested on x86_64.
Ok
Richard
> gcc/ChangeLog:
>
> PR tree-optimization/116554
> * gimple-ssa-strength-reduction.cc: Include tree-ssa-dce.h.
> (replace_mult_candidate): Add sdce_worklist argument, mark
> the rhs1/rhs2 for maybe dceing.
> (replace_unconditional_candidate): Add sdce_worklist argument,
> Update call to replace_mult_candidate.
> (replace_conditional_candidate): Add sdce_worklist argument,
> update call to replace_mult_candidate.
> (replace_uncond_cands_and_profitable_phis): Add sdce_worklist argument,
> update call to replace_conditional_candidate,
> replace_unconditional_candidate, and
> replace_uncond_cands_and_profitable_phis.
> (replace_one_candidate): Add sdce_worklist argument, mark
> the orig_rhs1/orig_rhs2 for maybe dceing.
> (replace_profitable_candidates): Add sdce_worklist argument,
> update call to replace_one_candidate and replace_profitable_candidates.
> (analyze_candidates_and_replace): Call simple_dce_from_worklist and
> update calls to replace_profitable_candidates, and
> replace_uncond_cands_and_profitable_phis.
>
> Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
> ---
> gcc/gimple-ssa-strength-reduction.cc | 59 +++++++++++++++++++---------
> 1 file changed, 41 insertions(+), 18 deletions(-)
>
> diff --git a/gcc/gimple-ssa-strength-reduction.cc
> b/gcc/gimple-ssa-strength-reduction.cc
> index 1cb3625c7eb..39cd9339c77 100644
> --- a/gcc/gimple-ssa-strength-reduction.cc
> +++ b/gcc/gimple-ssa-strength-reduction.cc
> @@ -56,6 +56,7 @@ along with GCC; see the file COPYING3. If not see
> #include "tree-affine.h"
> #include "tree-eh.h"
> #include "builtins.h"
> +#include "tree-ssa-dce.h"
>
> /* Information about a strength reduction candidate. Each statement
> in the candidate table represents an expression of one of the
> @@ -2126,7 +2127,8 @@ cand_already_replaced (slsr_cand_t c)
> replace_conditional_candidate. */
>
> static void
> -replace_mult_candidate (slsr_cand_t c, tree basis_name, offset_int bump)
> +replace_mult_candidate (slsr_cand_t c, tree basis_name, offset_int bump,
> + auto_bitmap &sdce_worklist)
> {
> tree target_type = TREE_TYPE (gimple_assign_lhs (c->cand_stmt));
> enum tree_code cand_code = gimple_assign_rhs_code (c->cand_stmt);
> @@ -2193,6 +2195,11 @@ replace_mult_candidate (slsr_cand_t c, tree
> basis_name, offset_int bump)
> if (cand_code != NEGATE_EXPR) {
> rhs1 = gimple_assign_rhs1 (c->cand_stmt);
> rhs2 = gimple_assign_rhs2 (c->cand_stmt);
> + /* Mark the 2 original rhs for maybe DCEing. */
> + if (TREE_CODE (rhs1) == SSA_NAME)
> + bitmap_set_bit (sdce_worklist, SSA_NAME_VERSION (rhs1));
> + if (TREE_CODE (rhs2) == SSA_NAME)
> + bitmap_set_bit (sdce_worklist, SSA_NAME_VERSION (rhs2));
> }
> if (cand_code != NEGATE_EXPR
> && ((operand_equal_p (rhs1, basis_name, 0)
> @@ -2237,7 +2244,7 @@ replace_mult_candidate (slsr_cand_t c, tree basis_name,
> offset_int bump)
> folded value ((i - i') * S) is referred to here as the "bump." */
>
> static void
> -replace_unconditional_candidate (slsr_cand_t c)
> +replace_unconditional_candidate (slsr_cand_t c, auto_bitmap &sdce_worklist)
> {
> slsr_cand_t basis;
>
> @@ -2247,7 +2254,8 @@ replace_unconditional_candidate (slsr_cand_t c)
> basis = lookup_cand (c->basis);
> offset_int bump = cand_increment (c) * wi::to_offset (c->stride);
>
> - replace_mult_candidate (c, gimple_assign_lhs (basis->cand_stmt), bump);
> + replace_mult_candidate (c, gimple_assign_lhs (basis->cand_stmt), bump,
> + sdce_worklist);
> }
>
> /* Return the index in the increment vector of the given INCREMENT,
> @@ -2507,7 +2515,8 @@ create_phi_basis (slsr_cand_t c, gimple *from_phi, tree
> basis_name,
> basis. */
>
> static void
> -replace_conditional_candidate (slsr_cand_t c)
> +replace_conditional_candidate (slsr_cand_t c, auto_bitmap &sdce_worklist)
> +
> {
> tree basis_name, name;
> slsr_cand_t basis;
> @@ -2527,7 +2536,7 @@ replace_conditional_candidate (slsr_cand_t c)
> /* Replace C with an add of the new basis phi and a constant. */
> offset_int bump = c->index * wi::to_offset (c->stride);
>
> - replace_mult_candidate (c, name, bump);
> + replace_mult_candidate (c, name, bump, sdce_worklist);
> }
>
> /* Recursive helper function for phi_add_costs. SPREAD is a measure of
> @@ -2608,7 +2617,8 @@ phi_add_costs (gimple *phi, slsr_cand_t c, int
> one_add_cost)
> so, replace the candidate and introduce the compensation code. */
>
> static void
> -replace_uncond_cands_and_profitable_phis (slsr_cand_t c)
> +replace_uncond_cands_and_profitable_phis (slsr_cand_t c,
> + auto_bitmap &sdce_worklist)
> {
> if (phi_dependent_cand_p (c))
> {
> @@ -2643,17 +2653,19 @@ replace_uncond_cands_and_profitable_phis (slsr_cand_t
> c)
> }
>
> if (cost <= COST_NEUTRAL)
> - replace_conditional_candidate (c);
> + replace_conditional_candidate (c, sdce_worklist);
> }
> }
> else
> - replace_unconditional_candidate (c);
> + replace_unconditional_candidate (c, sdce_worklist);
>
> if (c->sibling)
> - replace_uncond_cands_and_profitable_phis (lookup_cand (c->sibling));
> + replace_uncond_cands_and_profitable_phis (lookup_cand (c->sibling),
> + sdce_worklist);
>
> if (c->dependent)
> - replace_uncond_cands_and_profitable_phis (lookup_cand (c->dependent));
> + replace_uncond_cands_and_profitable_phis (lookup_cand (c->dependent),
> + sdce_worklist);
> }
>
> /* Count the number of candidates in the tree rooted at C that have
> @@ -3675,7 +3687,8 @@ replace_rhs_if_not_dup (enum tree_code new_code, tree
> new_rhs1, tree new_rhs2,
> is the rhs1 to use in creating the add/subtract. */
>
> static void
> -replace_one_candidate (slsr_cand_t c, unsigned i, tree basis_name)
> +replace_one_candidate (slsr_cand_t c, unsigned i, tree basis_name,
> + auto_bitmap &sdce_worklist)
> {
> gimple *stmt_to_print = NULL;
> tree orig_rhs1, orig_rhs2;
> @@ -3693,6 +3706,12 @@ replace_one_candidate (slsr_cand_t c, unsigned i, tree
> basis_name)
> if (!orig_rhs2)
> return;
>
> + /* Mark the 2 original rhs for maybe DCEing. */
> + if (TREE_CODE (orig_rhs1) == SSA_NAME)
> + bitmap_set_bit (sdce_worklist, SSA_NAME_VERSION (orig_rhs1));
> + if (TREE_CODE (orig_rhs2) == SSA_NAME)
> + bitmap_set_bit (sdce_worklist, SSA_NAME_VERSION (orig_rhs2));
> +
> if (dump_file && (dump_flags & TDF_DETAILS))
> {
> fputs ("Replacing: ", dump_file);
> @@ -3835,7 +3854,7 @@ replace_one_candidate (slsr_cand_t c, unsigned i, tree
> basis_name)
> an increment if such has been shown to be profitable. */
>
> static void
> -replace_profitable_candidates (slsr_cand_t c)
> +replace_profitable_candidates (slsr_cand_t c, auto_bitmap &sdce_worklist)
> {
> if (!cand_already_replaced (c))
> {
> @@ -3872,23 +3891,23 @@ replace_profitable_candidates (slsr_cand_t c)
>
> /* Replace C with an add of the new basis phi and the
> increment. */
> - replace_one_candidate (c, i, name);
> + replace_one_candidate (c, i, name, sdce_worklist);
> }
> }
> else
> {
> slsr_cand_t basis = lookup_cand (c->basis);
> tree basis_name = gimple_assign_lhs (basis->cand_stmt);
> - replace_one_candidate (c, i, basis_name);
> + replace_one_candidate (c, i, basis_name, sdce_worklist);
> }
> }
> }
>
> if (c->sibling)
> - replace_profitable_candidates (lookup_cand (c->sibling));
> + replace_profitable_candidates (lookup_cand (c->sibling), sdce_worklist);
>
> if (c->dependent)
> - replace_profitable_candidates (lookup_cand (c->dependent));
> + replace_profitable_candidates (lookup_cand (c->dependent),
> sdce_worklist);
> }
>
> /* Analyze costs of related candidates in the candidate vector,
> @@ -3899,6 +3918,7 @@ analyze_candidates_and_replace (void)
> {
> unsigned i;
> slsr_cand_t c;
> + auto_bitmap simple_dce_worklist;
>
> /* Each candidate that has a null basis and a non-null
> dependent is the root of a tree of related statements.
> @@ -3932,7 +3952,8 @@ analyze_candidates_and_replace (void)
> compensation code it requires is offset by the strength
> reduction savings. */
> else if (TREE_CODE (c->stride) == INTEGER_CST)
> - replace_uncond_cands_and_profitable_phis (first_dep);
> + replace_uncond_cands_and_profitable_phis (first_dep,
> + simple_dce_worklist);
>
> /* When the stride is an SSA name, it may still be profitable
> to replace some or all of the dependent candidates, depending
> @@ -3969,7 +3990,7 @@ analyze_candidates_and_replace (void)
> dump_incr_vec ();
>
> /* Perform the replacements. */
> - replace_profitable_candidates (first_dep);
> + replace_profitable_candidates (first_dep, simple_dce_worklist);
> free (incr_vec);
> }
> }
> @@ -3977,6 +3998,8 @@ analyze_candidates_and_replace (void)
> /* For conditional candidates, we may have uncommitted insertions
> on edges to clean up. */
> gsi_commit_edge_inserts ();
> +
> + simple_dce_from_worklist (simple_dce_worklist);
> }
>
> namespace {
> --
> 2.43.0
>
