I've been investigating why the glibc build process takes so long. It takes about 1m26s on my machine for the nothing-to-do case when all files are up-to-date.
I profiled make. It's spending around 60% of the time in new_pattern_rule(), which does a linear search through the list of pattern rules to check for duplicate rules. glibc generates ~2500 rules (in sysd-rules). The patch below reduces make's time to 43s for the nothing-to-do case. It removes the check for duplicate rules. This passes make's test suite, but it changes make's behaviour (see attached makefile). I was considering refactoring this properly, but the current new_pattern_rule() doesn't look quite right. The comment says it looks for an identical rule. The actual test is the old rule has 1 target (or multiple identical targets) and there exists a target in the new rule the same as the old rule's target See attached makefile which demonstrates this. Is that the correct behaviour? It seems like it would make more sense to compare the target lists for equality. Mark diff --git a/rule.c b/rule.c index e988db5..6e12439 100644 --- a/rule.c +++ b/rule.c @@ -284,68 +284,15 @@ convert_to_pattern (void) int new_pattern_rule (struct rule *rule, int override) { - register struct rule *r, *lastrule; - register unsigned int i, j; - rule->in_use = 0; rule->terminal = 0; rule->next = 0; - - /* Search for an identical rule. */ - lastrule = 0; - for (r = pattern_rules; r != 0; lastrule = r, r = r->next) - for (i = 0; rule->targets[i] != 0; ++i) - { - for (j = 0; r->targets[j] != 0; ++j) - if (!streq (rule->targets[i], r->targets[j])) - break; - if (r->targets[j] == 0) - /* All the targets matched. */ - { - register struct dep *d, *d2; - for (d = rule->deps, d2 = r->deps; - d != 0 && d2 != 0; d = d->next, d2 = d2->next) - if (!streq (dep_name (d), dep_name (d2))) - break; - if (d == 0 && d2 == 0) - { - /* All the dependencies matched. */ - if (override) - { - /* Remove the old rule. */ - freerule (r, lastrule); - /* Install the new one. */ - if (pattern_rules == 0) - pattern_rules = rule; - else - last_pattern_rule->next = rule; - last_pattern_rule = rule; - - /* We got one. Stop looking. */ - goto matched; - } - else - { - /* The old rule stays intact. Destroy the new one. */ - freerule (rule, (struct rule *) 0); - return 0; - } - } - } - } - - matched:; - - if (r == 0) - { - /* There was no rule to replace. */ - if (pattern_rules == 0) - pattern_rules = rule; - else - last_pattern_rule->next = rule; - last_pattern_rule = rule; - } + if (pattern_rules == 0) + pattern_rules = rule; + else + last_pattern_rule->next = rule; + last_pattern_rule = rule; return 1; }
all: target_a.test \ target_b.test \ target_c1.test target_c2.test \ target_d1.test target_d2.test exists.test: exists2.test: target_a.%: exists.% @echo $@: first rule -- should not happen target_a.%: exists.% @echo $@: second rule -- should happen target_b.%: exists.% exists2.% @echo $@: first rule -- should not happen target_b.%: exists.% exists2.% @echo $@: second rule -- should happen target_c1.% target_c2.%: exists.% @echo $@: first rule -- make 3.81 behaviour target_c1.% target_c2.%: exists.% @echo $@: second rule -- does not override in make 3.81 target_d1.%: exists.% @echo $@: first rule -- does not get overridden in make 3.81 target_d1.% target_d2.%: exists.% @echo $@: second rule -- make 3.81 behaviour
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