On Mon, 21 Jun 2021, guojiufu wrote:
> On 2021-06-21 14:19, guojiufu via Gcc-patches wrote:
> > On 2021-06-09 19:18, guojiufu wrote:
> >> On 2021-06-09 17:42, guojiufu via Gcc-patches wrote:
> >>> On 2021-06-08 18:13, Richard Biener wrote:
> >>>> On Fri, 4 Jun 2021, Jiufu Guo wrote:
> >>>>
> >>> cut...
> > cut...
> >>
>
> Besides the method in the previous mails,
> I’m thinking of another way to split loops:
>
> foo (int *a, int *b, unsigned k, unsigned n)
> {
> while (++k != n)
> a[k] = b[k] + 1;
> }
>
> We may split it into:
> if (k<n)
> {
> while (++k < n) //loop1
> a[k] = b[k] + 1;
> }
> else
> {
> while (++k != n) //loop2
> a[k] = b[k] + 1;
> }
>
> In most cases, loop1 would be hit, the overhead of this method is only
> checking “if (k<n)”
> which would be smaller than the previous method.
That would be your original approach of versioning the loop. I think
I suggested that for this scalar evolution and dataref analysis should
be enhanced to build up conditions under which IV evolutions are
affine (non-wrapping) and the versioning code in actual transforms
should then do the appropriate versioning (like the vectorizer already
does for niter analysis ->assumptions for example).
Richard.
> And this method would be more easy to extend to nest loops like:
> unsigned int l_n = 0;
> unsigned int l_m = 0;
> unsigned int l_k = 0;
> for (l_n = 0; l_n != n; l_n++)
> for (l_k = 0; l_k != k; l_k++)
> for (l_m = 0; l_m != m; l_m++)
> xxx;
>
> Do you think this method is more valuable to implement?
> Below is a quick patch. This patch does not support nest loops yet.
>
> diff --git a/gcc/tree-ssa-loop-split.c b/gcc/tree-ssa-loop-split.c
> index 3a09bbc39e5..c9d161565e4 100644
> --- a/gcc/tree-ssa-loop-split.c
> +++ b/gcc/tree-ssa-loop-split.c
> @@ -41,6 +41,7 @@ along with GCC; see the file COPYING3. If not see
> #include "cfghooks.h"
> #include "gimple-fold.h"
> #include "gimplify-me.h"
> +#include "tree-ssa-loop-ivopts.h"
>
> /* This file implements two kinds of loop splitting.
>
> @@ -1593,6 +1594,468 @@ split_loop_on_cond (struct loop *loop)
> return do_split;
> }
>
> +/* Filter out type conversions on IDX.
> + Store the shortest type during conversion to SMALL_TYPE.
> + Store the longest type during conversion to LARGE_TYPE. */
> +
> +static gimple *
> +filter_conversions (class loop *loop, tree idx, tree *small_type = NULL,
> + tree *large_type = NULL)
> +{
> + gcc_assert (TREE_CODE (idx) == SSA_NAME);
> + gimple *stmt = SSA_NAME_DEF_STMT (idx);
> + while (is_gimple_assign (stmt)
> + && flow_bb_inside_loop_p (loop, gimple_bb (stmt)))
> + {
> + if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (stmt)))
> + {
> + idx = gimple_assign_rhs1 (stmt);
> + if (small_type)
> + {
> + tree type = TREE_TYPE (idx);
> + if (TYPE_PRECISION (*small_type) > TYPE_PRECISION (type)
> + || (TYPE_PRECISION (*small_type) == TYPE_PRECISION (type)
> + && TYPE_UNSIGNED (*small_type) && !TYPE_UNSIGNED
> (type)))
> + *small_type = type;
> + }
> + if (large_type)
> + {
> + tree type = TREE_TYPE (idx);
> + if (TYPE_PRECISION (*large_type) < TYPE_PRECISION (type)
> + || (TYPE_PRECISION (*large_type) == TYPE_PRECISION (type)
> + && !TYPE_UNSIGNED (*large_type) && TYPE_UNSIGNED
> (type)))
> + *large_type = type;
> + }
> + }
> + else
> + break;
> +
> + if (TREE_CODE (idx) != SSA_NAME)
> + break;
> + stmt = SSA_NAME_DEF_STMT (idx);
> + }
> + return stmt;
> +}
> +
> +/* Collection of loop index related elements. */
> +struct idx_elements
> +{
> + gcond *gc;
> + gphi *phi;
> + gimple *inc_stmt;
> + tree idx;
> + tree bnd;
> + tree step;
> + tree large_type;
> + tree small_type;
> + bool cmp_on_next;
> +};
> +
> +/* Analyze and get the idx related elements: bnd,
> + phi, increase stmt from exit edge E, etc.
> +
> + i = phi (b, n)
> + ...
> + n0 = ik + 1
> + n1 = (type)n0
> + ...
> + if (i != bnd) or if (n != bnd)
> + ...
> + n = ()nl
> +
> + IDX is the i' or n'. */
> +
> +bool
> +analyze_idx_elements (class loop *loop, edge e, idx_elements &data)
> +{
> + /* Avoid complicated edge. */
> + if (e->flags & EDGE_FAKE)
> + return false;
> + if (e->src != loop->header && e->src != single_pred (loop->latch))
> + return false;
> + if (!dominated_by_p (CDI_DOMINATORS, loop->latch, e->src))
> + return false;
> +
> + /* Check gcond. */
> + gimple *last = last_stmt (e->src);
> + if (!last || gimple_code (last) != GIMPLE_COND)
> + return false;
> +
> + /* Get idx and bnd from gcond. */
> + gcond *gc = as_a<gcond *> (last);
> + tree bnd = gimple_cond_rhs (gc);
> + tree idx = gimple_cond_lhs (gc);
> + if (expr_invariant_in_loop_p (loop, idx))
> + std::swap (idx, bnd);
> + else if (!expr_invariant_in_loop_p (loop, bnd))
> + return false;
> + if (TREE_CODE (idx) != SSA_NAME)
> + return false;
> +
> + gimple *inc_stmt = NULL;
> + bool cmp_next = false;
> + tree small_type = TREE_TYPE (idx);
> + tree large_type = small_type;
> + gimple *stmt = filter_conversions (loop, idx, &small_type, &large_type);
> + /* The idx on gcond is not PHI, it would be next. */
> + if (is_gimple_assign (stmt))
> + {
> + tree rhs = gimple_assign_rhs1 (stmt);
> + if (TREE_CODE (rhs) != SSA_NAME)
> + return false;
> +
> + cmp_next = true;
> + inc_stmt = stmt;
> + stmt = filter_conversions (loop, rhs, &small_type, &large_type);
> + }
> +
> + /* Get phi and next. */
> + if (gimple_code (stmt) != GIMPLE_PHI || gimple_bb (stmt) != loop->header)
> + return false;
> + gphi *phi = as_a<gphi *> (stmt);
> + tree next = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
> + if (TREE_CODE (next) != SSA_NAME)
> + return false;
> +
> + /* The define of next should be the increasement stmt. */
> + stmt = filter_conversions (loop, next, &small_type, &large_type);
> + if (inc_stmt != NULL && inc_stmt != stmt)
> + return false;
> + if (!is_gimple_assign (stmt)
> + || !flow_bb_inside_loop_p (loop, gimple_bb (stmt)))
> + return false;
> + tree_code rhs_code = gimple_assign_rhs_code (stmt);
> + if (rhs_code != PLUS_EXPR)
> + return false;
> + tree step = gimple_assign_rhs2 (stmt);
> + if (!integer_minus_onep (step) && !integer_onep (step))
> + return false;
> + inc_stmt = stmt;
> + tree prev = gimple_assign_rhs1 (stmt);
> + if (TREE_CODE (prev) != SSA_NAME)
> + return false;
> + stmt = filter_conversions (loop, prev, &small_type, &large_type);
> + if (stmt != phi)
> + return false;
> +
> + data.gc = gc;
> + data.phi = phi;
> + data.idx = idx;
> + data.bnd = bnd;
> + data.step = step;
> + data.large_type = large_type;
> + data.small_type = small_type;
> + data.inc_stmt = inc_stmt;
> + data.cmp_on_next = cmp_next;
> +
> + return true;
> +}
> +
> +/* Check if the loop is possible to wrap at index.
> + Return the assumption under which the wrap will not happen.
> + Return NULL_TREE, if wrap will not happen. */
> +
> +static tree
> +get_wrap_assumption (class loop *loop, edge *exit, idx_elements &data)
> +{
> + int i;
> + edge e;
> + if (!single_pred_p (loop->latch) || !empty_block_p (loop->latch))
> + return NULL_TREE;
> +
> + auto_vec<edge> edges = get_loop_exit_edges (loop);
> + FOR_EACH_VEC_ELT (edges, i, e)
> + {
> + if (!analyze_idx_elements (loop, e, data))
> + continue;
> +
> + /* Check if bound is MAX/MIN val of a integral type. */
> + tree bnd = data.bnd;
> + tree bnd_type = TREE_TYPE (bnd);
> + if (!INTEGRAL_TYPE_P (bnd_type) || !TYPE_UNSIGNED (bnd_type))
> + continue;
> + if (tree_int_cst_equal (bnd, TYPE_MAX_VALUE (bnd_type))
> + || tree_int_cst_equal (bnd, TYPE_MIN_VALUE (bnd_type)))
> + continue;
> +
> + /* Check if it is "idx != bnd" or "idx < bnd". */
> + gcond *gc = data.gc;
> + enum tree_code code = gimple_cond_code (gc);
> + if (bnd == gimple_cond_lhs (gc))
> + code = swap_tree_comparison (code);
> + if ((e->flags & EDGE_TRUE_VALUE) && code == EQ_EXPR)
> + code = NE_EXPR;
> + if (code != NE_EXPR && code != LT_EXPR && code != GT_EXPR)
> + continue;
> +
> + /* Check if idx is iv with base and step. */
> + affine_iv iv;
> + tree iv_niters = NULL_TREE;
> + tree idx = PHI_RESULT (data.phi);
> + if (!simple_iv_with_niters (loop, loop_containing_stmt (gc), idx, &iv,
> + &iv_niters, false))
> + continue;
> + if (!iv.base || !iv.step || !tree_int_cst_equal (iv.step, data.step))
> + continue;
> +
> + bool is_negative = tree_int_cst_sign_bit (iv.step);
> + enum tree_code expect_code = is_negative ? GT_EXPR : LT_EXPR;
> + if (code != NE_EXPR && code != expect_code)
> + continue;
> +
> + /* Update the type for base, bound and the max value of boundary. */
> + tree base = iv.base;
> + tree small_type = data.small_type;
> + tree large_type = data.large_type;
> + tree max_min_bnd = is_negative ? TYPE_MIN_VALUE (small_type)
> + : TYPE_MAX_VALUE (small_type);
> + if (large_type != TREE_TYPE (base))
> + base = fold_convert (large_type, base);
> + if (large_type != TREE_TYPE (bnd))
> + bnd = fold_convert (large_type, bnd);
> + if (large_type != small_type)
> + max_min_bnd = fold_convert (large_type, max_min_bnd);
> +
> + /* There is no wrap if bnd <= max value && base <= bnd. */
> + enum tree_code expect_code1 = is_negative ? GE_EXPR : LE_EXPR;
> + tree no_wrap
> + = fold_build2 (expect_code1, boolean_type_node, bnd, max_min_bnd);
> + no_wrap
> + = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, no_wrap,
> + fold_build2 (expect_code1, boolean_type_node, base,
> bnd));
> +
> + if (integer_zerop (no_wrap))
> + continue;
> +
> + *exit = e;
> + return no_wrap;
> + }
> +
> + return NULL_TREE;
> +}
> +
> +/* Update the idx and bnd with a suitable type for no wrap/oveflow loop.
> + Suitable type would be the largest type of the type conversion which
> + occur on index, if the largest type is unsigned, using sizetype. */
> +
> +static bool
> +update_idx_bnd_type (class loop *loop, idx_elements &data)
> +{
> + gphi *phi = data.phi;
> + tree type = TREE_TYPE (PHI_RESULT (phi));
> + tree suitable_type = data.large_type;
> + if (TYPE_UNSIGNED (suitable_type))
> + {
> + if (TYPE_PRECISION (suitable_type) == TYPE_PRECISION (sizetype))
> + return false;
> + suitable_type = sizetype;
> + }
> +
> + /* New base and new bound. */
> + tree bnd = data.bnd;
> + edge pre_e = loop_preheader_edge (loop);
> + tree base = PHI_ARG_DEF_FROM_EDGE (phi, pre_e);
> + tree new_base = fold_convert (suitable_type, base);
> + tree new_bnd = fold_convert (suitable_type, bnd);
> + gimple_seq seq = NULL;
> + new_base = force_gimple_operand (new_base, &seq, true, NULL_TREE);
> + if (seq)
> + gsi_insert_seq_on_edge_immediate (pre_e, seq);
> + seq = NULL;
> + new_bnd = force_gimple_operand (new_bnd, &seq, true, NULL_TREE);
> + if (seq)
> + gsi_insert_seq_on_edge_immediate (pre_e, seq);
> +
> + /* new_i = phi (new_b, new_n)
> + new_n = new_i + 1 */
> + edge latch_e = loop_latch_edge (loop);
> + const char *name = "idx";
> + tree new_idx = make_temp_ssa_name (suitable_type, NULL, name);
> + tree new_next = make_temp_ssa_name (suitable_type, NULL, name);
> + gphi *newphi = create_phi_node (new_idx, loop->header);
> + add_phi_arg (newphi, new_base, pre_e, UNKNOWN_LOCATION);
> + add_phi_arg (newphi, new_next, latch_e, UNKNOWN_LOCATION);
> +
> + /* New increase stmt. */
> + gimple *inc_stmt = data.inc_stmt;
> + tree step = gimple_assign_rhs2 (inc_stmt);
> + if (tree_int_cst_sign_bit(step))
> + {
> + wide_int v = wi::to_wide (step);
> + v = wide_int::from (v, TYPE_PRECISION (suitable_type),
> + SIGNED);
> +
> + step = wide_int_to_tree (suitable_type, v);
> + }
> + else
> + step = fold_convert (suitable_type, step);
> + new_idx = PHI_RESULT (newphi);
> + tree_code inc_code = gimple_assign_rhs_code (inc_stmt);
> + gimple *new_inc = gimple_build_assign (new_next, inc_code, new_idx, step);
> + gimple_stmt_iterator gsi = gsi_for_stmt (inc_stmt);
> + gsi_insert_before (&gsi, new_inc, GSI_SAME_STMT);
> +
> + /* Update gcond. */
> + gcond *gc = data.gc;
> + bool inv = bnd == gimple_cond_lhs (gc);
> + tree cmp_idx = data.cmp_on_next ? new_next : new_idx;
> + gimple_cond_set_lhs (gc, inv ? new_bnd : cmp_idx);
> + gimple_cond_set_rhs (gc, inv ? cmp_idx : new_bnd);
> + update_stmt (gc);
> +
> + /* next = (next type)new_next
> + And remove next = prev + 1. */
> + tree next = gimple_assign_lhs (inc_stmt);
> + type = TREE_TYPE (next);
> + gimple *stmt = gimple_build_assign (next, fold_convert (type, new_next));
> + gsi = gsi_for_stmt (inc_stmt);
> + gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
> +
> + gsi = gsi_for_stmt (inc_stmt);
> + gsi_remove (&gsi, true);
> +
> + /* prev = (prev type)new_prev
> + And remove prev = phi. */
> + tree idx = PHI_RESULT (phi);
> + type = TREE_TYPE (idx);
> + stmt = gimple_build_assign (idx, fold_convert (type, new_idx));
> + gsi = gsi_after_labels (loop->header);
> + gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
> +
> + gsi = gsi_for_stmt (phi);
> + gsi_remove (&gsi, true);
> +
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + fprintf (dump_file, ";; Loop index type is updated to use faster
> type.\n");
> +
> + return true;
> +}
> +
> +/* Split out a new loop which would not wrap,
> + under the guard that NO_WRAP_COND will not be true. */
> +
> +static bool
> +split_wrap_boundary (class loop *loop, edge e, tree no_wrap_cond,
> + bool is_negative_step)
> +{
> + /* Convert the condition into a suitable gcond. */
> + gimple_seq stmts = NULL;
> + no_wrap_cond = force_gimple_operand_1 (no_wrap_cond, &stmts,
> + is_gimple_condexpr, NULL_TREE);
> +
> + /* Version the loop. */
> + initialize_original_copy_tables ();
> + basic_block cond_bb;
> + loop_version (loop, no_wrap_cond, &cond_bb,
> + profile_probability::very_likely (),
> + profile_probability::very_unlikely (),
> + profile_probability::very_likely (),
> + profile_probability::very_unlikely (), true);
> + free_original_copy_tables ();
> +
> + /* Insert the statements that feed COND. */
> + if (stmts)
> + {
> + gimple_stmt_iterator gsi = gsi_last_bb (cond_bb);
> + gsi_insert_seq_before (&gsi, stmts, GSI_SAME_STMT);
> + }
> +
> + /* Update gcond code. */
> + gcond *gc = as_a<gcond *> (last_stmt (e->src));
> + enum tree_code code = gimple_cond_code (gc);
> + enum tree_code new_code;
> + bool inv = expr_invariant_in_loop_p (loop, gimple_cond_lhs (gc));
> + if (is_negative_step)
> + new_code = inv ? LT_EXPR : GT_EXPR;
> + else
> + new_code = inv ? GT_EXPR : LT_EXPR;
> + if (code == NE_EXPR || code == EQ_EXPR)
> + gimple_cond_set_code (gc, new_code);
> +
> + /* Swap edge. */
> + if (code == EQ_EXPR)
> + {
> + edge out = EDGE_SUCC (e->src, 0);
> + edge in = EDGE_SUCC (e->src, 1);
> + if (in->flags & EDGE_TRUE_VALUE)
> + std::swap (in, out);
> + in->flags |= EDGE_TRUE_VALUE;
> + in->flags &= ~EDGE_FALSE_VALUE;
> + out->flags |= EDGE_FALSE_VALUE;
> + out->flags &= ~EDGE_TRUE_VALUE;
> + }
> +
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + fprintf (dump_file, ";; Loop split on wrap index.\n");
> +
> + return true;
> +}
> +
> +/* Split loop if there is possible wrap.
> + For example:
> + transform
> +
> + void
> + foo (int *a, int *b, unsigned l, unsigned u_n)
> + {
> + while (++l != u_n)
> + a[l] = b[l] + 1;
> + }
> +
> + to:
> + if (l < u_n)
> + {
> + int li = l;
> + int n = u_n;
> + while (++li < n)
> + a[li] = b[li] + 1;
> + l = li;
> + }
> + else
> + while (++l != n)
> + a[l] = b[l] + 1;
> + */
> +static bool
> +split_loop_on_wrap (class loop *loop)
> +{
> + edge e;
> + idx_elements data;
> + tree no_wrap = get_wrap_assumption (loop, &e, data);
> +
> + if (!no_wrap)
> + return false;
> +
> + int num = 0;
> + basic_block *bbs = get_loop_body (loop);
> + for (unsigned i = 0; i < loop->num_nodes; i++)
> + num += estimate_num_insns_seq (bb_seq (bbs[i]), &eni_size_weights);
> +
> + if (num > param_max_peeled_insns)
> + {
> + free (bbs);
> + return false;
> + }
> +
> + if (!can_copy_bbs_p (bbs, loop->num_nodes))
> + {
> + free (bbs);
> + return false;
> + }
> +
> + free (bbs);
> +
> + if (integer_onep (no_wrap))
> + return update_idx_bnd_type (loop, data);
> +
> + if (split_wrap_boundary (loop, e, no_wrap, tree_int_cst_sign_bit
> (data.step)))
> + {
> + update_idx_bnd_type (loop, data);
> + return true;
> + }
> +
> + return false;
> +}
> +
> /* Main entry point. Perform loop splitting on all suitable loops. */
>
> static unsigned int
> @@ -1622,7 +2085,8 @@ tree_ssa_split_loops (void)
> if (optimize_loop_for_size_p (loop))
> continue;
>
> - if (split_loop (loop) || split_loop_on_cond (loop))
> + if (split_loop (loop) || split_loop_on_cond (loop)
> + || split_loop_on_wrap (loop))
> {
> /* Mark our containing loop as having had some split inner loops.
> */
> loop_outer (loop)->aux = loop;
>
>
> >> Here is the updated patch, thanks for your time!
> >
> > Updates:
> > . Enhance code to support negative step.
> > . Check step +-1 to make sure it hits loop condition !=
> > . Enhance runtime cases to check more boundary cases and run order cases.
> > . Refine for compiling time: check loop num of insns and can_copy_bbs_p
> > later
> >
> >>
> >> diff --git a/gcc/testsuite/gcc.dg/loop-split1.c
> >> b/gcc/testsuite/gcc.dg/loop-split1.c
> >> new file mode 100644
> >> index 00000000000..dd2d03a7b96
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/loop-split1.c
> >> @@ -0,0 +1,101 @@
> >> +/* { dg-do compile } */
> >> +/* { dg-options "-O2 -fsplit-loops -fdump-tree-lsplit-details" } */
> >> +
> >> +void
> >> +foo (int *a, int *b, unsigned l, unsigned n)
> >> +{
> >> + while (++l != n)
> >> + a[l] = b[l] + 1;
> >> +}
> >> +void
> >> +foo_1 (int *a, int *b, unsigned n)
> >> +{
> >> + unsigned l = 0;
> >> + while (++l != n)
> >> + a[l] = b[l] + 1;
> >> +}
> >> +
> >> +void
> >> +foo1 (int *a, int *b, unsigned l, unsigned n)
> >> +{
> >> + while (l++ != n)
> >> + a[l] = b[l] + 1;
> >> +}
> >> +
> >> +/* No wrap. */
> >> +void
> >> +foo1_1 (int *a, int *b, unsigned n)
> >> +{
> >> + unsigned l = 0;
> >> + while (l++ != n)
> >> + a[l] = b[l] + 1;
> >> +}
> >> +
> >> +unsigned
> >> +foo2 (char *a, char *b, unsigned l, unsigned n)
> >> +{
> >> + while (++l != n)
> >> + if (a[l] != b[l])
> >> + break;
> >> +
> >> + return l;
> >> +}
> >> +
> >> +unsigned
> >> +foo2_1 (char *a, char *b, unsigned l, unsigned n)
> >> +{
> >> + l = 0;
> >> + while (++l != n)
> >> + if (a[l] != b[l])
> >> + break;
> >> +
> >> + return l;
> >> +}
> >> +
> >> +unsigned
> >> +foo3 (char *a, char *b, unsigned l, unsigned n)
> >> +{
> >> + while (l++ != n)
> >> + if (a[l] != b[l])
> >> + break;
> >> +
> >> + return l;
> >> +}
> >> +
> >> +/* No wrap. */
> >> +unsigned
> >> +foo3_1 (char *a, char *b, unsigned l, unsigned n)
> >> +{
> >> + l = 0;
> >> + while (l++ != n)
> >> + if (a[l] != b[l])
> >> + break;
> >> +
> >> + return l;
> >> +}
> >> +
> >> +void
> >> +bar ();
> >> +void
> >> +foo4 (unsigned n, unsigned i)
> >> +{
> >> + do
> >> + {
> >> + if (i == n)
> >> + return;
> >> + bar ();
> >> + ++i;
> >> + }
> >> + while (1);
> >> +}
> >> +
> >> +unsigned
> >> +find_skip_diff (char *p, char *q, unsigned n, unsigned i)
> >> +{
> >> + while (p[i] == q[i] && ++i != n)
> >> + p++, q++;
> >> +
> >> + return i;
> >> +}
> >> +
> >> +/* { dg-final { scan-tree-dump-times "Loop split" 8 "lsplit" } } */
> >> diff --git a/gcc/testsuite/gcc.dg/loop-split2.c
> >> b/gcc/testsuite/gcc.dg/loop-split2.c
> >> new file mode 100644
> >> index 00000000000..56377e2f2f5
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/loop-split2.c
> >> @@ -0,0 +1,155 @@
> >> +/* { dg-do run } */
> >> +/* { dg-options "-O3" } */
> >> +
> >> +extern void
> >> +abort (void);
> >> +extern void
> >> +exit (int);
> >> +void
> >> +push (int);
> >> +
> >> +#define NI __attribute__ ((noinline))
> >> +
> >> +void NI
> >> +foo (int *a, int *b, unsigned char l, unsigned char n)
> >> +{
> >> + while (++l != n)
> >> + a[l] = b[l] + 1;
> >> +}
> >> +
> >> +unsigned NI
> >> +bar (int *a, int *b, unsigned char l, unsigned char n)
> >> +{
> >> + while (l++ != n)
> >> + {
> >> + push (l);
> >> + if (a[l] != b[l])
> >> + break;
> >> + push (l + 1);
> >> + }
> >> + return l;
> >> +}
> >> +
> >> +void NI
> >> +foo_1 (int *a, int *b, unsigned char l, unsigned char n)
> >> +{
> >> + while (--l != n)
> >> + a[l] = b[l] + 1;
> >> +}
> >> +
> >> +unsigned NI
> >> +bar_1 (int *a, int *b, unsigned char l, unsigned char n)
> >> +{
> >> + while (l-- != n)
> >> + {
> >> + push (l);
> >> + if (a[l] != b[l])
> >> + break;
> >> + push (l + 1);
> >> + }
> >> +
> >> + return l;
> >> +}
> >> +
> >> +int a[258];
> >> +int b[258];
> >> +int c[1024];
> >> +static int top = 0;
> >> +void
> >> +push (int e)
> >> +{
> >> + c[top++] = e;
> >> +}
> >> +
> >> +void
> >> +reset ()
> >> +{
> >> + top = 0;
> >> + __builtin_memset (c, 0, sizeof (c));
> >> +}
> >> +
> >> +#define check(a, b) (a == b)
> >> +
> >> +int
> >> +check_c (int *c, int a0, int a1, int a2, int a3, int a4, int a5)
> >> +{
> >> + return check (c[0], a0) && check (c[1], a1) && check (c[2], a2)
> >> + && check (c[3], a3) && check (c[4], a4) && check (c[5], a5);
> >> +}
> >> +
> >> +int
> >> +main ()
> >> +{
> >> + __builtin_memcpy (b, a, sizeof (a));
> >> + reset ();
> >> + if (bar (a, b, 6, 8) != 9 || !check_c (c, 7, 8, 8, 9, 0, 0))
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar (a, b, 5, 3) != 4 || !check_c (c, 6, 7, 7, 8, 8, 9)
> >> + || !check_c (c + 496, 254, 255, 255, 256, 0, 1))
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar (a, b, 6, 6) != 7 || !check_c (c, 0, 0, 0, 0, 0, 0))
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar (a, b, 253, 255) != 0 || !check_c (c, 254, 255, 255, 256, 0, 0))
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar (a, b, 253, 0) != 1 || !check_c (c, 254, 255, 255, 256, 0, 1))
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar_1 (a, b, 6, 8) != 7 || !check_c (c, 5, 6, 4, 5, 3, 4))
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar_1 (a, b, 5, 3) != 2 || !check_c (c, 4, 5, 3, 4, 0, 0))
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar_1 (a, b, 6, 6) != 5)
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar_1 (a, b, 2, 255) != 254 || !check_c (c, 1, 2, 0, 1, 255, 256))
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar_1 (a, b, 2, 0) != 255 || !check_c (c, 1, 2, 0, 1, 0, 0))
> >> + abort ();
> >> +
> >> + b[100] += 1;
> >> + reset ();
> >> + if (bar (a, b, 90, 110) != 100)
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar (a, b, 110, 105) != 100)
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar_1 (a, b, 90, 110) != 109)
> >> + abort ();
> >> +
> >> + reset ();
> >> + if (bar_1 (a, b, 2, 90) != 100)
> >> + abort ();
> >> +
> >> + foo (a, b, 99, 99);
> >> + a[99] = b[99] + 1;
> >> + for (int i = 0; i < 256; i++)
> >> + if (a[i] != b[i] + 1)
> >> + abort ();
> >> +
> >> + foo_1 (a, b, 99, 99);
> >> + a[99] = b[99] + 1;
> >> + for (int i = 0; i < 256; i++)
> >> + if (a[i] != b[i] + 1)
> >> + abort ();
> >> +
> >> + exit (0);
> >> +}
> >> diff --git a/gcc/testsuite/gcc.dg/loop-split3.c
> >> b/gcc/testsuite/gcc.dg/loop-split3.c
> >> new file mode 100644
> >> index 00000000000..ec93ee8bd12
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/loop-split3.c
> >> @@ -0,0 +1,62 @@
> >> +/* { dg-do compile } */
> >> +/* { dg-options "-O2 -fsplit-loops -fdump-tree-lsplit-details" } */
> >> +
> >> +void
> >> +foo (int *a, int *b, unsigned l, unsigned n)
> >> +{
> >> + while (--l != n)
> >> + a[l] = b[l] + 1;
> >> +}
> >> +
> >> +void
> >> +foo1 (int *a, int *b, unsigned l, unsigned n)
> >> +{
> >> + while (l-- != n)
> >> + a[l] = b[l] + 1;
> >> +}
> >> +
> >> +unsigned
> >> +foo2 (char *a, char *b, unsigned l, unsigned n)
> >> +{
> >> + while (--l != n)
> >> + if (a[l] != b[l])
> >> + break;
> >> +
> >> + return l;
> >> +}
> >> +
> >> +unsigned
> >> +foo3 (char *a, char *b, unsigned l, unsigned n)
> >> +{
> >> + while (l-- != n)
> >> + if (a[l] != b[l])
> >> + break;
> >> +
> >> + return l;
> >> +}
> >> +
> >> +void
> >> +bar ();
> >> +void
> >> +foo4 (unsigned n, unsigned i)
> >> +{
> >> + do
> >> + {
> >> + if (i == n)
> >> + return;
> >> + bar ();
> >> + --i;
> >> + }
> >> + while (1);
> >> +}
> >> +
> >> +unsigned
> >> +find_skip_diff (char *p, char *q, unsigned n, unsigned i)
> >> +{
> >> + while (p[i] == q[i] && --i != n)
> >> + p--, q--;
> >> +
> >> + return i;
> >> +}
> >> +
> >> +/* { dg-final { scan-tree-dump-times "Loop split" 6 "lsplit" } } */
> >> diff --git a/gcc/tree-ssa-loop-split.c b/gcc/tree-ssa-loop-split.c
> >> index 3a09bbc39e5..e9f23b32186 100644
> >> --- a/gcc/tree-ssa-loop-split.c
> >> +++ b/gcc/tree-ssa-loop-split.c
> >> @@ -41,6 +41,7 @@ along with GCC; see the file COPYING3. If not see
> >> #include "cfghooks.h"
> >> #include "gimple-fold.h"
> >> #include "gimplify-me.h"
> >> +#include "tree-ssa-loop-ivopts.h"
> >>
> >> /* This file implements two kinds of loop splitting.
> >>
> >> @@ -229,11 +230,14 @@ easy_exit_values (class loop *loop)
> >> conditional). I.e. the second loop can now be entered either
> >> via the original entry or via NEW_E, so the entry values of LOOP2
> >> phi nodes are either the original ones or those at the exit
> >> - of LOOP1. Insert new phi nodes in LOOP2 pre-header reflecting
> >> - this. The loops need to fulfill easy_exit_values(). */
> >> + of LOOP1. Selecting the previous value instead next value as the
> >> + exit value of LOOP1 if USE_PREV is true. Insert new phi nodes in
> >> + LOOP2 pre-header reflecting this. The loops need to fulfill
> >> + easy_exit_values(). */
> >>
> >> static void
> >> -connect_loop_phis (class loop *loop1, class loop *loop2, edge new_e)
> >> +connect_loop_phis (class loop *loop1, class loop *loop2, edge new_e,
> >> + bool use_prev = false)
> >> {
> >> basic_block rest = loop_preheader_edge (loop2)->src;
> >> gcc_assert (new_e->dest == rest);
> >> @@ -279,7 +283,8 @@ connect_loop_phis (class loop *loop1, class loop
> >> *loop2, edge new_e)
> >>
> >> gphi * newphi = create_phi_node (new_init, rest);
> >> add_phi_arg (newphi, init, skip_first, UNKNOWN_LOCATION);
> >> - add_phi_arg (newphi, next, new_e, UNKNOWN_LOCATION);
> >> + add_phi_arg (newphi, use_prev ? PHI_RESULT (phi_first) : next,
> >> new_e,
> >> + UNKNOWN_LOCATION);
> >> SET_USE (op, new_init);
> >> }
> >> }
> >> @@ -1593,6 +1598,252 @@ split_loop_on_cond (struct loop *loop)
> >> return do_split;
> >> }
> >>
> >> +/* Check if the LOOP exit branch is like "if (idx != bound)",
> >> + Return the branch edge which exit loop, if wrap may happen on "idx".
> >> */
> >> +
> >> +static edge
> >> +get_ne_cond_branch (struct loop *loop, tree *step)
> >> +{
> >> + int i;
> >> + edge e;
> >> +
> >> + auto_vec<edge> edges = get_loop_exit_edges (loop);
> >> + FOR_EACH_VEC_ELT (edges, i, e)
> >> + {
> >> + basic_block bb = e->src;
> >> +
> >> + /* Check if exit at gcond. */
> >> + gimple *last = last_stmt (bb);
> >> + if (!last || gimple_code (last) != GIMPLE_COND)
> >> + continue;
> >> + gcond *cond = as_a<gcond *> (last);
> >> + enum tree_code code = gimple_cond_code (cond);
> >> + if (!((code == NE_EXPR && (e->flags & EDGE_FALSE_VALUE))
> >> + || (code == EQ_EXPR && (e->flags & EDGE_TRUE_VALUE))))
> >> + continue;
> >> +
> >> + /* Check if bound is invarant. */
> >> + tree idx = gimple_cond_lhs (cond);
> >> + tree bnd = gimple_cond_rhs (cond);
> >> + if (expr_invariant_in_loop_p (loop, idx))
> >> + std::swap (idx, bnd);
> >> + else if (!expr_invariant_in_loop_p (loop, bnd))
> >> + continue;
> >> +
> >> + /* Only unsigned type conversion could cause wrap. */
> >> + tree type = TREE_TYPE (idx);
> >> + if (!INTEGRAL_TYPE_P (type) || TREE_CODE (idx) != SSA_NAME
> >> + || !TYPE_UNSIGNED (type))
> >> + continue;
> >> +
> >> + /* Avoid to split if bound is MAX/MIN val. */
> >> + tree bound_type = TREE_TYPE (bnd);
> >> + if (tree_int_cst_equal (bnd, TYPE_MAX_VALUE (bound_type))
> >> + || tree_int_cst_equal (bnd, TYPE_MIN_VALUE (bound_type)))
> >> + continue;
> >> +
> >> + /* Check if there is possible wrap. */
> >> + class tree_niter_desc niter;
> >> + if (!number_of_iterations_exit (loop, e, &niter, false, false))
> >> + continue;
> >> + if (niter.control.no_overflow)
> >> + return NULL;
> >> + if (niter.cmp != NE_EXPR)
> >> + continue;
> >> + if (!integer_onep (niter.control.step)
> >> + && !integer_minus_onep (niter.control.step))
> >> + continue;
> >> + *step = niter.control.step;
> >> +
> >> + /* If exit edge is just before the empty latch, it is easy to link
> >> + the split loops: just jump from the exit edge of one loop to the
> >> + header of new loop. */
> >> + if (single_pred_p (loop->latch)
> >> + && single_pred_edge (loop->latch)->src == bb
> >> + && empty_block_p (loop->latch))
> >> + return e;
> >> +
> >> + /* If exit edge is at end of header, and header contains i++ or ++i,
> >> + only, it is simple to link the split loops: jump from the end of
> >> + one loop header to the new loop header, and use unchanged PHI result
> >> + of the first loop as the entry PHI value of the second loop. */
> >> + if (bb == loop->header)
> >> + {
> >> + /* Only one phi. */
> >> + gphi_iterator psi = gsi_start_phis (bb);
> >> + if (gsi_end_p (psi))
> >> + continue;
> >> + gphi *phi = psi.phi ();
> >> + gsi_next (&psi);
> >> + if (!gsi_end_p (psi))
> >> + continue;
> >> +
> >> + /* Check it is ++i or ++i */
> >> + tree next = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
> >> + tree prev = PHI_RESULT (phi);
> >> + if (idx != prev && idx != next)
> >> + continue;
> >> +
> >> + gimple_stmt_iterator gsi = gsi_start_nondebug_after_labels_bb (bb);
> >> + if (gsi_end_p (gsi))
> >> + continue;
> >> + gimple *s1 = gsi_stmt (gsi);
> >> + if (!is_gimple_assign (s1) || gimple_assign_lhs (s1) != next
> >> + || gimple_assign_rhs1 (s1) != prev)
> >> + continue;
> >> +
> >> + gsi_next_nondebug (&gsi);
> >> + if (!gsi_end_p (gsi) && gsi_stmt (gsi) == cond)
> >> + return e;
> >> + }
> >> + }
> >> +
> >> + return NULL;
> >> +}
> >> +
> >> +/* Split the LOOP with NE_EXPR into two loops with GT_EXPR and LT_EXPR.
> >> */
> >> +
> >> +static bool
> >> +split_ne_loop (struct loop *loop, edge cond_e, tree step)
> >> +{
> >> + initialize_original_copy_tables ();
> >> +
> >> + struct loop *loop2 = loop_version (loop, boolean_true_node, NULL,
> >> + profile_probability::always (),
> >> + profile_probability::never (),
> >> + profile_probability::always (),
> >> + profile_probability::always (), true);
> >> +
> >> + gcc_assert (loop2);
> >> + update_ssa (TODO_update_ssa);
> >> +
> >> + basic_block loop2_cond_exit_bb = get_bb_copy (cond_e->src);
> >> + free_original_copy_tables ();
> >> +
> >> + gcond *gc = as_a<gcond *> (last_stmt (cond_e->src));
> >> + gcond *dup_gc = as_a<gcond *> (last_stmt (loop2_cond_exit_bb));
> >> +
> >> + /* Invert edges for gcond. */
> >> + if (gimple_cond_code (gc) == EQ_EXPR)
> >> + {
> >> + auto invert_edge = [](basic_block bb) {
> >> + edge out = EDGE_SUCC (bb, 0);
> >> + edge in = EDGE_SUCC (bb, 1);
> >> + if (in->flags & EDGE_TRUE_VALUE)
> >> + std::swap (in, out);
> >> + in->flags |= EDGE_TRUE_VALUE;
> >> + in->flags &= ~EDGE_FALSE_VALUE;
> >> + out->flags |= EDGE_FALSE_VALUE;
> >> + out->flags &= ~EDGE_TRUE_VALUE;
> >> + };
> >> +
> >> + invert_edge (gimple_bb (gc));
> >> + invert_edge (gimple_bb (dup_gc));
> >> + }
> >> +
> >> + /* Change if (i != n) to LOOP1:if (i > n) and LOOP2:if (i < n) */
> >> + bool inv = expr_invariant_in_loop_p (loop, gimple_cond_lhs (gc));
> >> + if (tree_int_cst_sign_bit (step))
> >> + inv = !inv;
> >> + enum tree_code first_loop_code = inv ? LT_EXPR : GT_EXPR;
> >> + enum tree_code second_loop_code = inv ? GT_EXPR : LT_EXPR;
> >> +
> >> + gimple_cond_set_code (gc, first_loop_code);
> >> + gimple_cond_set_code (dup_gc, second_loop_code);
> >> +
> >> + /* Link the exit cond edge to new loop. */
> >> + gcond *break_cond = as_a<gcond *> (gimple_copy (gc));
> >> + edge pred_e = single_pred_edge (loop->latch);
> >> + bool simple_loop
> >> + = pred_e && pred_e->src == cond_e->src && empty_block_p (loop->latch);
> >> + if (simple_loop)
> >> + gimple_cond_set_code (break_cond, second_loop_code);
> >> + else
> >> + gimple_cond_make_true (break_cond);
> >> +
> >> + basic_block break_bb = split_edge (cond_e);
> >> + gimple_stmt_iterator gsi = gsi_last_bb (break_bb);
> >> + gsi_insert_after (&gsi, break_cond, GSI_NEW_STMT);
> >> +
> >> + edge to_exit = single_succ_edge (break_bb);
> >> + edge to_new_loop = make_edge (break_bb, loop_preheader_edge
> >> (loop2)->src, 0);
> >> + to_new_loop->flags |= EDGE_TRUE_VALUE;
> >> + to_exit->flags |= EDGE_FALSE_VALUE;
> >> + to_exit->flags &= ~EDGE_FALLTHRU;
> >> + to_exit->probability = cond_e->probability;
> >> + to_new_loop->probability = to_exit->probability.invert ();
> >> +
> >> + update_ssa (TODO_update_ssa);
> >> +
> >> + connect_loop_phis (loop, loop2, to_new_loop, !simple_loop);
> >> +
> >> + rewrite_into_loop_closed_ssa_1 (NULL, 0, SSA_OP_USE, loop);
> >> + if (dump_file && (dump_flags & TDF_DETAILS))
> >> + fprintf (dump_file, ";; Loop split on wrap index.\n");
> >> +
> >> + return true;
> >> +}
> >> +
> >> +/* Checks if LOOP contains a suitable NE_EXPR conditional block to split.
> >> +L_H:
> >> + if (i!=N)
> >> + S;
> >> + else
> >> + goto EXIT;
> >> + i++;
> >> + goto L_H;
> >> +
> >> +The "i!=N" is like "i>N || i<N", then it could be transformed to:
> >> +
> >> +L_H:
> >> + if (i>N)
> >> + S;
> >> + else
> >> + goto EXIT;
> >> + i++;
> >> + goto L_H;
> >> +L1_H:
> >> + if (i<N)
> >> + S;
> >> + else
> >> + goto EXIT;
> >> + i++;
> >> + goto L1_H;
> >> +
> >> +The loop with "i<N" is in favor of both GIMPLE and RTL passes. */
> >> +
> >> +static bool
> >> +split_loop_on_ne_cond (class loop *loop)
> >> +{
> >> + tree step;
> >> + edge branch_edge = get_ne_cond_branch (loop, &step);
> >> + if (!branch_edge)
> >> + return false;
> >> +
> >> + int num = 0;
> >> + basic_block *bbs = get_loop_body (loop);
> >> + for (unsigned i = 0; i < loop->num_nodes; i++)
> >> + num += estimate_num_insns_seq (bb_seq (bbs[i]), &eni_size_weights);
> >> +
> >> + if (num > param_max_peeled_insns)
> >> + {
> >> + free (bbs);
> >> + return false;
> >> + }
> >> +
> >> + if (!can_copy_bbs_p (bbs, loop->num_nodes))
> >> + {
> >> + free (bbs);
> >> + return false;
> >> + }
> >> + free (bbs);
> >> +
> >> + if (split_ne_loop (loop, branch_edge, step))
> >> + return true;
> >> +
> >> + return false;
> >> +}
> >> +
> >> /* Main entry point. Perform loop splitting on all suitable loops. */
> >>
> >> static unsigned int
> >> @@ -1622,7 +1873,8 @@ tree_ssa_split_loops (void)
> >> if (optimize_loop_for_size_p (loop))
> >> continue;
> >>
> >> - if (split_loop (loop) || split_loop_on_cond (loop))
> >> + if (split_loop (loop) || split_loop_on_cond (loop)
> >> + || split_loop_on_ne_cond (loop))
> >> {
> >> /* Mark our containing loop as having had some split inner loops.
> >> */
> >> loop_outer (loop)->aux = loop;
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
