On Tue, May 22, 2018 at 11:37 PM Bill Schmidt <wschm...@linux.ibm.com>
wrote:
> Hi,
> PR85712 shows where an existing test case fails in the SLSR pass because
> the code is flawed that cleans up alternative interpretations (CAND_ADD
> versus CAND_MULT, for example) after a replacement. This patch fixes the
> flaw by ensuring that we always visit all interpretations, not just
> subsequent ones in the next_interp chain. I found six occurrences of
> this mistake in the code.
> Bootstrapped and tested on powerpc64le-linux-gnu with no regressions.
> No new test case is added since the failure occurs on an existing test
> in the test suite. Is this okay for trunk, and for backports to all
> supported branches after some burn-in time?
OK and Yes for the backports.
Thanks,
Richard.
> Thanks,
> Bill
> 2018-05-22 Bill Schmidt <wschm...@linux.ibm.com>
> * gimple-ssa-strength-reduction.c (struct slsr_cand_d): Add
> first_interp field.
> (alloc_cand_and_find_basis): Initialize first_interp field.
> (slsr_process_mul): Modify first_interp field.
> (slsr_process_add): Likewise.
> (slsr_process_cast): Modify first_interp field for each new
> interpretation.
> (slsr_process_copy): Likewise.
> (dump_candidate): Dump first_interp field.
> (replace_mult_candidate): Process all interpretations, not just
> subsequent ones.
> (replace_rhs_if_not_dup): Likewise.
> (replace_one_candidate): Likewise.
> Index: gcc/gimple-ssa-strength-reduction.c
> ===================================================================
> --- gcc/gimple-ssa-strength-reduction.c (revision 260484)
> +++ gcc/gimple-ssa-strength-reduction.c (working copy)
> @@ -266,6 +266,10 @@ struct slsr_cand_d
> of a statement. */
> cand_idx next_interp;
> + /* Index of the first candidate record in a chain for the same
> + statement. */
> + cand_idx first_interp;
> +
> /* Index of the basis statement S0, if any, in the candidate vector.
*/
> cand_idx basis;
> @@ -686,6 +690,7 @@ alloc_cand_and_find_basis (enum cand_kind kind, gi
> c->kind = kind;
> c->cand_num = cand_vec.length () + 1;
> c->next_interp = 0;
> + c->first_interp = c->cand_num;
> c->dependent = 0;
> c->sibling = 0;
> c->def_phi = kind == CAND_MULT ? find_phi_def (base) : 0;
> @@ -1261,6 +1266,7 @@ slsr_process_mul (gimple *gs, tree rhs1, tree rhs2
> is the stride and RHS2 is the base expression. */
> c2 = create_mul_ssa_cand (gs, rhs2, rhs1, speed);
> c->next_interp = c2->cand_num;
> + c2->first_interp = c->cand_num;
> }
> else if (TREE_CODE (rhs2) == INTEGER_CST)
> {
> @@ -1498,7 +1504,10 @@ slsr_process_add (gimple *gs, tree rhs1, tree rhs2
> {
> c2 = create_add_ssa_cand (gs, rhs2, rhs1, false, speed);
> if (c)
> - c->next_interp = c2->cand_num;
> + {
> + c->next_interp = c2->cand_num;
> + c2->first_interp = c->cand_num;
> + }
> else
> add_cand_for_stmt (gs, c2);
> }
> @@ -1621,6 +1630,8 @@ slsr_process_cast (gimple *gs, tree rhs1, bool spe
> if (base_cand && base_cand->kind != CAND_PHI)
> {
> + slsr_cand_t first_cand = NULL;
> +
> while (base_cand)
> {
> /* Propagate all data from the base candidate except the type,
> @@ -1635,6 +1646,12 @@ slsr_process_cast (gimple *gs, tree rhs1, bool spe
> base_cand->index,
base_cand->stride,
> ctype, base_cand->stride_type,
> savings);
> + if (!first_cand)
> + first_cand = c;
> +
> + if (first_cand != c)
> + c->first_interp = first_cand->cand_num;
> +
> if (base_cand->next_interp)
> base_cand = lookup_cand (base_cand->next_interp);
> else
> @@ -1657,6 +1674,7 @@ slsr_process_cast (gimple *gs, tree rhs1, bool spe
> c2 = alloc_cand_and_find_basis (CAND_MULT, gs, rhs1, 0,
> integer_one_node, ctype, sizetype,
0);
> c->next_interp = c2->cand_num;
> + c2->first_interp = c->cand_num;
> }
> /* Add the first (or only) interpretation to the statement-candidate
> @@ -1681,6 +1699,8 @@ slsr_process_copy (gimple *gs, tree rhs1, bool spe
> if (base_cand && base_cand->kind != CAND_PHI)
> {
> + slsr_cand_t first_cand = NULL;
> +
> while (base_cand)
> {
> /* Propagate all data from the base candidate. */
> @@ -1693,6 +1713,12 @@ slsr_process_copy (gimple *gs, tree rhs1, bool spe
> base_cand->index,
base_cand->stride,
> base_cand->cand_type,
> base_cand->stride_type, savings);
> + if (!first_cand)
> + first_cand = c;
> +
> + if (first_cand != c)
> + c->first_interp = first_cand->cand_num;
> +
> if (base_cand->next_interp)
> base_cand = lookup_cand (base_cand->next_interp);
> else
> @@ -1717,6 +1743,7 @@ slsr_process_copy (gimple *gs, tree rhs1, bool spe
> integer_one_node, TREE_TYPE (rhs1),
> sizetype, 0);
> c->next_interp = c2->cand_num;
> + c2->first_interp = c->cand_num;
> }
> /* Add the first (or only) interpretation to the statement-candidate
> @@ -1887,8 +1914,9 @@ dump_candidate (slsr_cand_t c)
> print_generic_expr (dump_file, c->cand_type);
> fprintf (dump_file, "\n basis: %d dependent: %d sibling: %d\n",
> c->basis, c->dependent, c->sibling);
> - fprintf (dump_file, " next-interp: %d dead-savings: %d\n",
> - c->next_interp, c->dead_savings);
> + fprintf (dump_file,
> + " next-interp: %d first-interp: %d dead-savings: %d\n",
> + c->next_interp, c->first_interp, c->dead_savings);
> if (c->def_phi)
> fprintf (dump_file, " phi: %d\n", c->def_phi);
> fputs ("\n", dump_file);
> @@ -2147,14 +2175,13 @@ replace_mult_candidate (slsr_cand_t c, tree basis_
> tree lhs = gimple_assign_lhs (c->cand_stmt);
> gassign *copy_stmt = gimple_build_assign (lhs, basis_name);
> gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt);
> - slsr_cand_t cc = c;
> + slsr_cand_t cc = lookup_cand (c->first_interp);
> gimple_set_location (copy_stmt, gimple_location (c->cand_stmt));
> gsi_replace (&gsi, copy_stmt, false);
> - c->cand_stmt = copy_stmt;
> - while (cc->next_interp)
> + while (cc)
> {
> - cc = lookup_cand (cc->next_interp);
> cc->cand_stmt = copy_stmt;
> + cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
> }
> if (dump_file && (dump_flags & TDF_DETAILS))
> stmt_to_print = copy_stmt;
> @@ -2181,14 +2208,13 @@ replace_mult_candidate (slsr_cand_t c, tree basis_
> else
> {
> gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt);
> - slsr_cand_t cc = c;
> + slsr_cand_t cc = lookup_cand (c->first_interp);
> gimple_assign_set_rhs_with_ops (&gsi, code, basis_name,
bump_tree);
> update_stmt (gsi_stmt (gsi));
> - c->cand_stmt = gsi_stmt (gsi);
> - while (cc->next_interp)
> + while (cc)
> {
> - cc = lookup_cand (cc->next_interp);
> cc->cand_stmt = gsi_stmt (gsi);
> + cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
> }
> if (dump_file && (dump_flags & TDF_DETAILS))
> stmt_to_print = gsi_stmt (gsi);
> @@ -3597,14 +3623,13 @@ replace_rhs_if_not_dup (enum tree_code new_code, t
> || !operand_equal_p (new_rhs2, old_rhs1, 0))))
> {
> gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt);
> - slsr_cand_t cc = c;
> + slsr_cand_t cc = lookup_cand (c->first_interp);
> gimple_assign_set_rhs_with_ops (&gsi, new_code, new_rhs1,
new_rhs2);
> update_stmt (gsi_stmt (gsi));
> - c->cand_stmt = gsi_stmt (gsi);
> - while (cc->next_interp)
> + while (cc)
> {
> - cc = lookup_cand (cc->next_interp);
> cc->cand_stmt = gsi_stmt (gsi);
> + cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
> }
> if (dump_file && (dump_flags & TDF_DETAILS))
> @@ -3709,14 +3734,13 @@ replace_one_candidate (slsr_cand_t c, unsigned i,
> || !operand_equal_p (rhs2, orig_rhs2, 0))
> {
> gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt);
> - slsr_cand_t cc = c;
> + slsr_cand_t cc = lookup_cand (c->first_interp);
> gimple_assign_set_rhs_with_ops (&gsi, MINUS_EXPR, basis_name,
rhs2);
> update_stmt (gsi_stmt (gsi));
> - c->cand_stmt = gsi_stmt (gsi);
> - while (cc->next_interp)
> + while (cc)
> {
> - cc = lookup_cand (cc->next_interp);
> cc->cand_stmt = gsi_stmt (gsi);
> + cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
> }
> if (dump_file && (dump_flags & TDF_DETAILS))
> @@ -3736,14 +3760,13 @@ replace_one_candidate (slsr_cand_t c, unsigned i,
> {
> gassign *copy_stmt = gimple_build_assign (lhs, basis_name);
> gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt);
> - slsr_cand_t cc = c;
> + slsr_cand_t cc = lookup_cand (c->first_interp);
> gimple_set_location (copy_stmt, gimple_location (c->cand_stmt));
> gsi_replace (&gsi, copy_stmt, false);
> - c->cand_stmt = copy_stmt;
> - while (cc->next_interp)
> + while (cc)
> {
> - cc = lookup_cand (cc->next_interp);
> cc->cand_stmt = copy_stmt;
> + cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
> }
> if (dump_file && (dump_flags & TDF_DETAILS))
> @@ -3753,14 +3776,13 @@ replace_one_candidate (slsr_cand_t c, unsigned i,
> {
> gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt);
> gassign *cast_stmt = gimple_build_assign (lhs, NOP_EXPR,
basis_name);
> - slsr_cand_t cc = c;
> + slsr_cand_t cc = lookup_cand (c->first_interp);
> gimple_set_location (cast_stmt, gimple_location (c->cand_stmt));
> gsi_replace (&gsi, cast_stmt, false);
> - c->cand_stmt = cast_stmt;
> - while (cc->next_interp)
> + while (cc)
> {
> - cc = lookup_cand (cc->next_interp);
> cc->cand_stmt = cast_stmt;
> + cc = cc->next_interp ? lookup_cand (cc->next_interp) : NULL;
> }
> if (dump_file && (dump_flags & TDF_DETAILS))
