From c52dbda804a2863c1280bd4c6f9ad3382db2c72b Mon Sep 17 00:00:00 2001
From: Andrea Shepard <andrea@persephoneslair.org>
Date: Sun, 20 Nov 2016 10:15:23 +0000
Subject: [PATCH] Add depth cutoff for splits in charset exec plan to avoid
spinning on complex charsets
---
src/backends/llvm.c | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)
diff --git a/src/backends/llvm.c b/src/backends/llvm.c
index 2013a4a2..8f53a932 100644
--- a/src/backends/llvm.c
+++ b/src/backends/llvm.c
@@ -191,6 +191,8 @@ struct llvm_charset_exec_plan_s {
llvm_charset_exec_plan_action_t action;
/* Estimated cost metric */
int cost;
+ /* Depth in exec plan */
+ int depth;
/* Children, if any (zero, one or two depending on action) */
llvm_charset_exec_plan_t *children[2];
};
@@ -410,7 +412,7 @@ static llvm_charset_exec_plan_t * h_llvm_build_charset_exec_plan_impl_alloc(
static int h_llvm_build_charset_exec_plan_impl(HAllocator* mm__, HCharset cs,
llvm_charset_exec_plan_t *parent, llvm_charset_exec_plan_t *cep,
int allow_complement, uint8_t *split_point) {
- int eligible_for_accept, best_cost;
+ int eligible_for_accept, best_cost, depth;
int estimated_complement_cost, estimated_scan_cost, estimated_split_cost;
int estimated_bitmap_cost;
uint8_t idx_start, idx_end;
@@ -440,6 +442,10 @@ static int h_llvm_build_charset_exec_plan_impl(HAllocator* mm__, HCharset cs,
idx_end = UINT8_MAX;
}
+ /* Get the depth in the exec plan */
+ if (parent) depth = parent->depth + 1;
+ else depth = 0;
+
eligible_for_accept = h_llvm_charset_eligible_for_accept(cs, idx_start, idx_end);
if (eligible_for_accept) {
/* if we can use CHARSET_ACTION_ACCEPT, always do so */
@@ -450,6 +456,7 @@ static int h_llvm_build_charset_exec_plan_impl(HAllocator* mm__, HCharset cs,
cep->split_point = 0;
/* Acceptance (or rejection, under a complement) is free */
cep->cost = 0;
+ cep->depth = depth;
cep->action = CHARSET_ACTION_ACCEPT;
cep->children[0] = NULL;
cep->children[1] = NULL;
@@ -481,6 +488,7 @@ static int h_llvm_build_charset_exec_plan_impl(HAllocator* mm__, HCharset cs,
complement_cep.idx_start = idx_start;
complement_cep.idx_end = idx_end;
complement_cep.split_point = 0;
+ complement_cep.depth = depth;
complement_cep.action = CHARSET_ACTION_COMPLEMENT;
complement_cep.children[0] = h_new(llvm_charset_exec_plan_t, 1);
memset(complement_cep.children[0], 0, sizeof(llvm_charset_exec_plan_t));
@@ -497,8 +505,11 @@ static int h_llvm_build_charset_exec_plan_impl(HAllocator* mm__, HCharset cs,
h_free(child_cs);
}
- /* Set up split node if it makes sense */
- if (idx_start < idx_end) {
+ /*
+ * Set up split node if it makes sense; the depth cutoff here limits the
+ * cost of the search for complex charsets.
+ */
+ if (idx_start < idx_end && depth < 5) {
split_cep.cs = copy_charset(mm__, cs);
charset_restrict_to_range(split_cep.cs, idx_start, idx_end);
split_cep.idx_start = idx_start;
@@ -506,6 +517,7 @@ static int h_llvm_build_charset_exec_plan_impl(HAllocator* mm__, HCharset cs,
split_cep.split_point = 0;
split_cep.action = CHARSET_ACTION_SPLIT;
split_cep.cost = -1;
+ split_cep.depth = depth;
split_cep.children[0] = NULL;
split_cep.children[1] = NULL;
/* h_llvm_find_best_split() sets split_cep.cost */
@@ -555,6 +567,7 @@ static int h_llvm_build_charset_exec_plan_impl(HAllocator* mm__, HCharset cs,
cep->split_point = 0;
cep->action = CHARSET_ACTION_SCAN;
cep->cost = estimated_scan_cost;
+ cep->depth = depth;
cep->children[0] = NULL;
cep->children[1] = NULL;
break;
@@ -567,6 +580,7 @@ static int h_llvm_build_charset_exec_plan_impl(HAllocator* mm__, HCharset cs,
cep->split_point = 0;
cep->action = CHARSET_ACTION_BITMAP;
cep->cost = estimated_bitmap_cost;
+ cep->depth = depth;
cep->children[0] = NULL;
cep->children[1] = NULL;
break;
@@ -872,7 +886,7 @@ static void h_llvm_pretty_print_charset_exec_plan_impl(HAllocator *mm__, llvm_ch
pfx, pfx_incr, cep->idx_start, cep->idx_end);
}
- printf("%s%s cost = %d\n", pfx, pfx_incr, cep->cost);
+ printf("%s%s cost = %d, depth = %d\n", pfx, pfx_incr, cep->cost, cep->depth);
if (n_children > 0) {
if (n_children > 1) {
--
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