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Speed up jump table switch detection. 

PR tree-optimization/100393

gcc/ChangeLog:

	* tree-switch-conversion.c (group_cluster::dump): Use
	  get_comparison_count.
	(jump_table_cluster::find_jump_tables): Pre-compute number of
	comparisons and then decrement it. Cache also max_ratio.
	(jump_table_cluster::can_be_handled): Change signature.
	* tree-switch-conversion.h (get_comparison_count): New.
This commit is contained in:
Martin Liska 2021-08-13 17:22:35 +02:00
parent 29020d0527
commit c517cf2e68
2 changed files with 35 additions and 21 deletions
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42
gcc/tree-switch-conversion.c
View File

@ -1091,7 +1091,7 @@ group_cluster::dump (FILE *f, bool details)
for (unsigned i = 0; i < m_cases.length (); i++)
{
simple_cluster *sc = static_cast<simple_cluster *> (m_cases[i]);
comparison_count += sc->m_range_p ? 2 : 1;
comparison_count += sc->get_comparison_count ();
}
unsigned HOST_WIDE_INT range = get_range (get_low (), get_high ());
@ -1186,11 +1186,24 @@ jump_table_cluster::find_jump_tables (vec<cluster *> &clusters)
min.quick_push (min_cluster_item (0, 0, 0));
unsigned HOST_WIDE_INT max_ratio
= (optimize_insn_for_size_p ()
? param_jump_table_max_growth_ratio_for_size
: param_jump_table_max_growth_ratio_for_speed);
for (unsigned i = 1; i <= l; i++)
{
/* Set minimal # of clusters with i-th item to infinite. */
min.quick_push (min_cluster_item (INT_MAX, INT_MAX, INT_MAX));
/* Pre-calculate number of comparisons for the clusters. */
HOST_WIDE_INT comparison_count = 0;
for (unsigned k = 0; k <= i - 1; k++)
{
simple_cluster *sc = static_cast<simple_cluster *> (clusters[k]);
comparison_count += sc->get_comparison_count ();
}
for (unsigned j = 0; j < i; j++)
{
unsigned HOST_WIDE_INT s = min[j].m_non_jt_cases;
@ -1201,10 +1214,15 @@ jump_table_cluster::find_jump_tables (vec<cluster *> &clusters)
if ((min[j].m_count + 1 < min[i].m_count
|| (min[j].m_count + 1 == min[i].m_count
&& s < min[i].m_non_jt_cases))
&& can_be_handled (clusters, j, i - 1))
&& can_be_handled (clusters, j, i - 1, max_ratio,
comparison_count))
min[i] = min_cluster_item (min[j].m_count + 1, j, s);
simple_cluster *sc = static_cast<simple_cluster *> (clusters[j]);
comparison_count -= sc->get_comparison_count ();
}
gcc_checking_assert (comparison_count == 0);
gcc_checking_assert (min[i].m_count != INT_MAX);
}
@ -1242,7 +1260,9 @@ jump_table_cluster::find_jump_tables (vec<cluster *> &clusters)
bool
jump_table_cluster::can_be_handled (const vec<cluster *> &clusters,
unsigned start, unsigned end)
unsigned start, unsigned end,
unsigned HOST_WIDE_INT max_ratio,
unsigned HOST_WIDE_INT comparison_count)
{
/* If the switch is relatively small such that the cost of one
indirect jump on the target are higher than the cost of a
@ -1261,10 +1281,6 @@ jump_table_cluster::can_be_handled (const vec<cluster *> &clusters,
if (start == end)
return true;
unsigned HOST_WIDE_INT max_ratio
= (optimize_insn_for_size_p ()
? param_jump_table_max_growth_ratio_for_size
: param_jump_table_max_growth_ratio_for_speed);
unsigned HOST_WIDE_INT range = get_range (clusters[start]->get_low (),
clusters[end]->get_high ());
/* Check overflow. */
@ -1278,18 +1294,6 @@ jump_table_cluster::can_be_handled (const vec<cluster *> &clusters,
if (lhs < range)
return false;
/* First make quick guess as each cluster
can add at maximum 2 to the comparison_count. */
if (lhs > 2 * max_ratio * (end - start + 1))
return false;
unsigned HOST_WIDE_INT comparison_count = 0;
for (unsigned i = start; i <= end; i++)
{
simple_cluster *sc = static_cast<simple_cluster *> (clusters[i]);
comparison_count += sc->m_range_p ? 2 : 1;
}
return lhs <= max_ratio * comparison_count;
}

14
gcc/tree-switch-conversion.h
View File

@ -180,6 +180,13 @@ public:
return tree_int_cst_equal (get_low (), get_high ());
}
/* Return number of comparisons needed for the case. */
unsigned
get_comparison_count ()
{
return m_range_p ? 2 : 1;
}
/* Low value of the case. */
tree m_low;
@ -267,9 +274,12 @@ public:
static vec<cluster *> find_jump_tables (vec<cluster *> &clusters);
/* Return true when cluster starting at START and ending at END (inclusive)
can build a jump-table. */
can build a jump-table. COMPARISON_COUNT is number of comparison
operations needed if the clusters are expanded as decision tree.
MAX_RATIO tells about the maximum code growth (in percent). */
static bool can_be_handled (const vec<cluster *> &clusters, unsigned start,
unsigned end);
unsigned end, unsigned HOST_WIDE_INT max_ratio,
unsigned HOST_WIDE_INT comparison_count);
/* Return true if cluster starting at START and ending at END (inclusive)
is profitable transformation. */