Add transform_to_exit_first_loop_alt 2015-03-27 Tom de Vries PR tree-optimization/65443 * tree-parloops.c (replace_imm_uses, replace_uses_in_bb_by) (replace_uses_in_bbs_by, transform_to_exit_first_loop_alt) (try_transform_to_exit_first_loop_alt): New function. (transform_to_exit_first_loop): Use try_transform_to_exit_first_loop_alt. * gcc.dg/parloops-exit-first-loop-alt-2.c: New test. * gcc.dg/parloops-exit-first-loop-alt-3.c: New test. * gcc.dg/parloops-exit-first-loop-alt.c: New test. * testsuite/libgomp.c/parloops-exit-first-loop-alt-2.c: New test. * testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c: New test. * testsuite/libgomp.c/parloops-exit-first-loop-alt.c: New test. --- .../gcc.dg/parloops-exit-first-loop-alt-2.c | 27 ++ .../gcc.dg/parloops-exit-first-loop-alt-3.c | 26 ++ .../gcc.dg/parloops-exit-first-loop-alt.c | 27 ++ gcc/tree-parloops.c | 344 ++++++++++++++++++++- .../libgomp.c/parloops-exit-first-loop-alt-2.c | 48 +++ .../libgomp.c/parloops-exit-first-loop-alt-3.c | 29 ++ .../libgomp.c/parloops-exit-first-loop-alt.c | 48 +++ 7 files changed, 538 insertions(+), 11 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-2.c create mode 100644 gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-3.c create mode 100644 gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt.c create mode 100644 libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-2.c create mode 100644 libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c create mode 100644 libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c diff --git a/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-2.c b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-2.c new file mode 100644 index 0000000..a4d6cb2 --- /dev/null +++ b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-2.c @@ -0,0 +1,27 @@ +/* { dg-do compile } */ +/* { dg-require-effective-target pthread } */ +/* { dg-options "-O2 -ftree-parallelize-loops=2 -fdump-tree-parloops" } */ + +#define N 1000 + +unsigned int a[N]; +unsigned int b[N]; +unsigned int c[N]; + +void __attribute__((noclone,noinline)) +f (unsigned int n) +{ + int i; + + for (i = 0; i < N; ++i) + c[i] = a[i] + b[i]; +} + +/* Three times three array accesses: + - three in f._loopfn.0 + - three in the parallel + - three in the low iteration count loop + Crucially, none for a peeled off last iteration following the parallel. */ +/* { dg-final { scan-tree-dump-times "(?n)\\\[i" 9 "parloops" } } */ + +/* { dg-final { cleanup-tree-dump "parloops" } } */ diff --git a/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-3.c b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-3.c new file mode 100644 index 0000000..c7ab51f88 --- /dev/null +++ b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-3.c @@ -0,0 +1,26 @@ +/* { dg-do compile } */ +/* { dg-require-effective-target pthread } */ +/* { dg-options "-O2 -ftree-parallelize-loops=2 -fdump-tree-parloops" } */ + +unsigned int *a; + +unsigned int __attribute__((noclone,noinline)) +f (unsigned int n) +{ + int i; + unsigned int sum = 1; + + for (i = 0; i < n; ++i) + sum += a[i]; + + return sum; +} + +/* Three array accesses: + - one in f._loopfn.0 + - one in the parallel + - one in the low iteration count loop + Crucially, none for a peeled off last iteration following the parallel. */ +/* { dg-final { scan-tree-dump-times "(?n)\\\* 4" 3 "parloops" } } */ + +/* { dg-final { cleanup-tree-dump "parloops" } } */ diff --git a/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt.c b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt.c new file mode 100644 index 0000000..42ca3ac --- /dev/null +++ b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt.c @@ -0,0 +1,27 @@ +/* { dg-do compile } */ +/* { dg-require-effective-target pthread } */ +/* { dg-options "-O2 -ftree-parallelize-loops=2 -fdump-tree-parloops" } */ + +#define N 1000 + +unsigned int a[N]; +unsigned int b[N]; +unsigned int c[N]; + +void __attribute__((noclone,noinline)) +f (unsigned int n) +{ + int i; + + for (i = 0; i < n; ++i) + c[i] = a[i] + b[i]; +} + +/* Three times three array accesses: + - three in f._loopfn.0 + - three in the parallel + - three in the low iteration count loop + Crucially, none for a peeled off last iteration following the parallel. */ +/* { dg-final { scan-tree-dump-times "(?n)\\\[i" 9 "parloops" } } */ + +/* { dg-final { cleanup-tree-dump "parloops" } } */ diff --git a/gcc/tree-parloops.c b/gcc/tree-parloops.c index fbb9eeb..a60efbe 100644 --- a/gcc/tree-parloops.c +++ b/gcc/tree-parloops.c @@ -1495,17 +1495,327 @@ create_loop_fn (location_t loc) return decl; } -/* Moves the exit condition of LOOP to the beginning of its header, and - duplicates the part of the last iteration that gets disabled to the - exit of the loop. NIT is the number of iterations of the loop - (used to initialize the variables in the duplicated part). - - TODO: the common case is that latch of the loop is empty and immediately - follows the loop exit. In this case, it would be better not to copy the - body of the loop, but only move the entry of the loop directly before the - exit check and increase the number of iterations of the loop by one. - This may need some additional preconditioning in case NIT = ~0. - REDUCTION_LIST describes the reductions in LOOP. */ +/* Replace uses of VAL in iterator IMM_ITER. */ + +static void +replace_imm_uses (tree val, imm_use_iterator *imm_iter) +{ + use_operand_p use_p; + + FOR_EACH_IMM_USE_ON_STMT (use_p, *imm_iter) + SET_USE (use_p, val); +} + +/* Replace uses of NAME by VAL in block BB. */ + +static void +replace_uses_in_bb_by (tree name, tree val, basic_block bb) +{ + gimple use_stmt; + imm_use_iterator imm_iter; + + FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, name) + { + if (gimple_bb (use_stmt) != bb) + continue; + + replace_imm_uses (val, &imm_iter); + } +} + +/* Replace uses of NAME by VAL in blocks BBS. */ + +static void +replace_uses_in_bbs_by (tree name, tree val, bitmap bbs) +{ + gimple use_stmt; + imm_use_iterator imm_iter; + + FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, name) + { + if (!bitmap_bit_p (bbs, gimple_bb (use_stmt)->index)) + continue; + + replace_imm_uses (val, &imm_iter); + } +} + +/* + Do transformation from: + + bb preheader: + ... + goto + + : + ... + if (ivtmp < n) + goto ; + else + goto ; + + : + ivtmp = ivtmp + inc; + goto + + to: + + bb preheader: + ... + goto + + : + ... + goto ; + + : + if (ivtmp < n + 1) + goto ; + else + goto ; + + : + ivtmp = ivtmp + inc; + goto + + Moves the exit condition of LOOP to the beginning of its header. + REDUCTION_LIST describes the reductions in LOOP. BOUND is the new loop + bound. */ + +static void +transform_to_exit_first_loop_alt (struct loop *loop, + reduction_info_table_type *reduction_list, + tree bound) +{ + basic_block header = loop->header; + basic_block latch = loop->latch; + edge exit = single_dom_exit (loop); + basic_block exit_block = exit->dest; + gcond *cond_stmt = as_a (last_stmt (exit->src)); + tree control = gimple_cond_lhs (cond_stmt); + gphi *phi, *nphi; + tree res, new_res, init, inc_res; + + /* Gather the bbs dominated by the exit block. */ + bitmap exit_dominated = BITMAP_ALLOC (NULL); + bitmap_set_bit (exit_dominated, exit_block->index); + vec exit_dominated_vec + = get_dominated_by (CDI_DOMINATORS, exit_block); + + int i; + basic_block dom_bb; + FOR_EACH_VEC_ELT (exit_dominated_vec, i, dom_bb) + bitmap_set_bit (exit_dominated, dom_bb->index); + + exit_dominated_vec.release (); + + /* Create the new_header block. */ + basic_block new_header = split_block_before_cond_jump (exit->src); + edge split_edge = single_pred_edge (new_header); + + /* We could redirect entry to new_header, but we want to keep the phis on + header intact. So we create new_entry here, and remove entry later. */ + edge entry = loop_preheader_edge (loop); + edge new_entry = make_edge (entry->src, new_header, EDGE_FALLTHRU); + new_entry->probability = entry->probability; + + /* We could redirect post_inc_edge to new_header, but we want to keep the phis + on header intact. So we create new_post_inc_edge here, and remove + post_inc_edge later. */ + edge post_inc_edge = single_succ_edge (latch); + edge new_post_inc_edge = make_edge (latch, new_header, EDGE_FALLTHRU); + new_post_inc_edge->probability = REG_BR_PROB_BASE; + + /* Redirect pre_inc_edge to header. */ + edge pre_inc_edge = single_pred_edge (latch); + edge new_latch_edge = redirect_edge_and_branch (pre_inc_edge, header); + + /* Redirect split_edge to latch. */ + redirect_edge_and_branch (split_edge, latch); + + /* Set the new loop bound. */ + gimple_cond_set_rhs (cond_stmt, bound); + + /* Repair the ssa. */ + for (gphi_iterator gsi = gsi_start_phis (header); + !gsi_end_p (gsi); + gsi_next (&gsi)) + { + phi = gsi.phi (); + res = PHI_RESULT (phi); + + /* Create new phi. */ + new_res = copy_ssa_name (res, phi); + nphi = create_phi_node (new_res, new_header); + + /* Set the entry argument of the new phi. */ + init = gimple_phi_arg_def (phi, entry->dest_idx); + add_phi_arg (nphi, init, new_entry, UNKNOWN_LOCATION); + + replace_uses_in_bb_by (res, new_res, new_header); + + /* Set the back argument of the new phi. */ + inc_res = gimple_phi_arg_def (phi, 1 - entry->dest_idx); + add_phi_arg (nphi, inc_res, new_post_inc_edge, UNKNOWN_LOCATION); + + /* Fixup old phi. */ + add_phi_arg (phi, new_res, new_latch_edge, UNKNOWN_LOCATION); + + /* Loop-closed ssa does not hold for virtuals, so we cannot get away with + exit_block only. */ + replace_uses_in_bbs_by (inc_res, new_res, exit_dominated); + + struct reduction_info *red = reduction_phi (reduction_list, phi); + gcc_assert (virtual_operand_p (res) + || res == control + || red != NULL); + + if (red) + { + /* Register the new reduction phi. */ + red->reduc_phi = nphi; + gimple_set_uid (red->reduc_phi, red->reduc_version); + } + } + BITMAP_FREE (exit_dominated); + + /* Register the reduction exit phis. */ + for (gphi_iterator gsi = gsi_start_phis (exit_block); + !gsi_end_p (gsi); + gsi_next (&gsi)) + { + phi = gsi.phi (); + res = PHI_RESULT (phi); + if (virtual_operand_p (res)) + continue; + + tree val = PHI_ARG_DEF_FROM_EDGE (phi, exit); + gimple reduc_phi = SSA_NAME_DEF_STMT (val); + struct reduction_info *red = reduction_phi (reduction_list, reduc_phi); + if (red != NULL) + red->keep_res = phi; + } + + /* We no longer need the phis on the old loop header. Remove replaced + edges. */ + remove_edge (entry); + remove_edge (post_inc_edge); + + /* Fix up loop structure. TODO: Check whether this is sufficient. */ + loop->header = new_header; + + /* Recalculate dominance info. */ + free_dominance_info (CDI_DOMINATORS); + calculate_dominance_info (CDI_DOMINATORS); +} + +/* Tries to moves the exit condition of LOOP to the beginning of its header + without duplication of the loop body. NIT is the number of iterations of the + loop. REDUCTION_LIST describes the reductions in LOOP. Return true if + transformation is successful. */ + +static bool +try_transform_to_exit_first_loop_alt (struct loop *loop, + reduction_info_table_type *reduction_list, + tree nit) +{ + /* Check whether the latch contains a single statement. */ + if (!gimple_seq_singleton_p (bb_seq (loop->latch))) + return true; + + /* Check whether the latch contains the loop iv increment. */ + edge back = single_succ_edge (loop->latch); + edge exit = single_dom_exit (loop); + gcond *cond_stmt = as_a (last_stmt (exit->src)); + tree control = gimple_cond_lhs (cond_stmt); + gphi *phi = as_a (SSA_NAME_DEF_STMT (control)); + tree inc_res = gimple_phi_arg_def (phi, back->dest_idx); + if (gimple_bb (SSA_NAME_DEF_STMT (inc_res)) != loop->latch) + return false; + + /* Check whether there's no code between the loop condition and the latch. */ + if (!single_pred_p (loop->latch) + || single_pred (loop->latch) != exit->src) + return false; + + tree alt_bound = NULL_TREE; + tree nit_type = TREE_TYPE (nit); + + /* Figure out whether nit + 1 overflows. */ + if (TREE_CODE (nit) == INTEGER_CST) + { + if (!tree_int_cst_equal (nit, TYPE_MAXVAL (nit_type))) + { + alt_bound = fold_build2_loc (UNKNOWN_LOCATION, PLUS_EXPR, nit_type, + nit, build_one_cst (nit_type)); + + gcc_assert (TREE_CODE (alt_bound) == INTEGER_CST); + } + else + { + /* Todo: Figure out if we can trigger this, if it's worth to handle + optimally, and if we can handle it optimally. */ + } + } + else + { + gcc_assert (TREE_CODE (nit) == SSA_NAME); + + gimple def = SSA_NAME_DEF_STMT (nit); + + if (def + && is_gimple_assign (def) + && gimple_assign_rhs_code (def) == PLUS_EXPR) + { + tree op1 = gimple_assign_rhs1 (def); + tree op2 = gimple_assign_rhs2 (def); + if (integer_minus_onep (op1)) + alt_bound = op2; + else if (integer_minus_onep (op2)) + alt_bound = op1; + } + + /* There is a number of test-cases for which we don't get an alt_bound + here: they're listed here, with the lhs of the last stmt as the nit: + + libgomp.graphite/force-parallel-1.c: + _21 = (signed long) N_6(D); + _19 = _21 + -1; + _7 = (unsigned long) _19; + + libgomp.graphite/force-parallel-2.c: + _33 = (signed long) N_9(D); + _16 = _33 + -1; + _37 = (unsigned long) _16; + + libgomp.graphite/force-parallel-5.c: + : + # graphite_IV.5_46 = PHI <0(5), graphite_IV.5_47(11)> + : + _33 = (unsigned long) graphite_IV.5_46; + + g++.dg/tree-ssa/pr34355.C: + _2 = (unsigned int) i_9; + _3 = 4 - _2; + + gcc.dg/pr53849.c: + _5 = d.0_11 + -2; + _18 = (unsigned int) _5; + + We will be able to handle some of these cases, if we can determine when + it's safe to look past casts. */ + } + + if (alt_bound == NULL_TREE) + return false; + + transform_to_exit_first_loop_alt (loop, reduction_list, alt_bound); + return true; +} + +/* Moves the exit condition of LOOP to the beginning of its header. NIT is the + number of iterations of the loop. REDUCTION_LIST describes the reductions in + LOOP. */ static void transform_to_exit_first_loop (struct loop *loop, @@ -1522,6 +1832,18 @@ transform_to_exit_first_loop (struct loop *loop, gcond *cond_stmt, *cond_nit; tree nit_1; + /* The common case is that latch of the loop is empty (apart from the + increment) and immediately follows the loop exit test. Attempt to move the + entry of the loop directly before the exit check and increase the number of + iterations of the loop by one. */ + if (try_transform_to_exit_first_loop_alt (loop, reduction_list, nit)) + return; + + /* Fall back on the method that handles more cases, but duplicates the loop + body: move the exit condition of LOOP to the beginning of its header, and + duplicate the part of the last iteration that gets disabled to the exit of + the loop. */ + split_block_after_labels (loop->header); orig_header = single_succ (loop->header); hpred = single_succ_edge (loop->header); diff --git a/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-2.c b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-2.c new file mode 100644 index 0000000..eb5e11f --- /dev/null +++ b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-2.c @@ -0,0 +1,48 @@ +/* { dg-do run } */ +/* { dg-options "-O2 -ftree-parallelize-loops=2" } */ + +#include +#include + +#define N 1000 + +unsigned int a[N]; +unsigned int b[N]; +unsigned int c[N]; + +void __attribute__((noclone,noinline)) +f (void) +{ + int i; + + for (i = 0; i < N; ++i) + c[i] = a[i] + b[i]; +} + +int +main (void) +{ + int i, j; + + /* Complexify loop to inhibit parloops. */ + for (j = 0; j < 100; ++j) + for (i = 0; i < 10; i++) + { + int k = i + (10 * j); + a[k] = k; + b[k] = (k * 3) % 7; + c[k] = k * 2; + } + + f (); + + for (i = 0; i < N; i++) + { + unsigned int actual = c[i]; + unsigned int expected = i + ((i * 3) % 7); + if (actual != expected) + abort (); + } + + return 0; +} diff --git a/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c new file mode 100644 index 0000000..b426b3f --- /dev/null +++ b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c @@ -0,0 +1,29 @@ +/* { dg-do run } */ +/* { dg-options "-O2 -ftree-parallelize-loops=2" } */ + +unsigned int *a; + +unsigned int __attribute__((noclone,noinline)) +f (unsigned int n) +{ + int i; + unsigned int sum = 1; + + for (i = 0; i < n; ++i) + sum += a[i]; + + return sum; +} + +int +main (void) +{ + unsigned int res; + unsigned int array[4000]; + int i; + for (i = 0; i < 4000; ++i) + array[i] = i % 7; + a = &array[0]; + res = f (4000); + return !(res == 11995); +} diff --git a/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c new file mode 100644 index 0000000..d7d4003 --- /dev/null +++ b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c @@ -0,0 +1,48 @@ +/* { dg-do run } */ +/* { dg-options "-O2 -ftree-parallelize-loops=2" } */ + +#include +#include + +#define N 1000 + +unsigned int a[N]; +unsigned int b[N]; +unsigned int c[N]; + +void __attribute__((noclone,noinline)) +f (unsigned int n) +{ + int i; + + for (i = 0; i < n; ++i) + c[i] = a[i] + b[i]; +} + +int +main (void) +{ + int i, j; + + /* Complexify loop to inhibit parloops. */ + for (j = 0; j < 100; ++j) + for (i = 0; i < 10; i++) + { + int k = i + (10 * j); + a[k] = k; + b[k] = (k * 3) % 7; + c[k] = k * 2; + } + + f (N); + + for (i = 0; i < N; i++) + { + unsigned int actual = c[i]; + unsigned int expected = i + ((i * 3) % 7); + if (actual != expected) + abort (); + } + + return 0; +} -- 1.9.1