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Diffstat (limited to 'libbuild2/cc/compile-rule.cxx')
-rw-r--r--libbuild2/cc/compile-rule.cxx203
1 files changed, 175 insertions, 28 deletions
diff --git a/libbuild2/cc/compile-rule.cxx b/libbuild2/cc/compile-rule.cxx
index a5e5417..002c889 100644
--- a/libbuild2/cc/compile-rule.cxx
+++ b/libbuild2/cc/compile-rule.cxx
@@ -248,12 +248,34 @@ namespace build2
};
compile_rule::
- compile_rule (data&& d)
+ compile_rule (data&& d, const scope& rs)
: common (move (d)),
rule_id (string (x) += ".compile 6")
{
static_assert (sizeof (match_data) <= target::data_size,
"insufficient space");
+
+ // Locate the header cache (see enter_header() for details).
+ //
+ {
+ string mn (string (x) + ".config");
+
+ header_cache_ = rs.find_module<config_module> (mn); // Must be there.
+
+ const scope* ws (rs.weak_scope ());
+ if (ws != &rs)
+ {
+ const scope* s (&rs);
+ do
+ {
+ s = s->parent_scope ()->root_scope ();
+
+ if (const auto* m = s->find_module<config_module> (mn))
+ header_cache_ = m;
+
+ } while (s != ws);
+ }
+ }
}
template <typename T>
@@ -2044,7 +2066,7 @@ namespace build2
pair<const file*, bool> er (
enter_header (
a, bs, t, li,
- f, false /* cache */, false /* normalized */,
+ move (f), false /* cache */, false /* normalized */,
pfx_map, so_map));
ht = er.first;
@@ -2062,7 +2084,7 @@ namespace build2
// diagnostics won't really add anything to the compiler's. So
// let's only print it at -V or higher.
//
- if (ht == nullptr)
+ if (ht == nullptr) // f is still valid.
{
assert (!exists); // Sanity check.
@@ -2110,6 +2132,8 @@ namespace build2
// messy, let's keep both (it would have been nicer to print
// ours after the compiler's but that isn't easy).
//
+ // Note: if ht is NULL, f is still valid.
+ //
r = "ERROR unable to update header '";
r += (ht != nullptr ? ht->path () : f).string ();
r += '\'';
@@ -2573,7 +2597,7 @@ namespace build2
pair<const file*, bool> r (
enter_header (
a, bs, t, li,
- f, false /* cache */, false /* normalized */,
+ move (f), false /* cache */, false /* normalized */,
pfx_map, so_map));
if (!r.second) // Shouldn't be remapped.
@@ -2601,7 +2625,7 @@ namespace build2
pair<const file*, bool> er (
enter_header (
a, bs, t, li,
- f, false /* cache */, false /* normalized */,
+ move (f), false /* cache */, false /* normalized */,
pfx_map, so_map));
ht = er.first;
@@ -2620,7 +2644,7 @@ namespace build2
// diagnostics won't really add anything to the compiler's. So
// let's only print it at -V or higher.
//
- if (ht == nullptr)
+ if (ht == nullptr) // f is still valid.
{
assert (!exists); // Sanity check.
@@ -2667,6 +2691,8 @@ namespace build2
// messy, let's keep both (it would have been nicer to print
// ours after the compiler's but that isn't easy).
//
+ // Note: if ht is NULL, f is still valid.
+ //
rs = !exists
? string ("INCLUDE")
: ("ERROR unable to update header '" +
@@ -2790,17 +2816,115 @@ namespace build2
}
#endif
+ //atomic_count cache_hit {0};
+ //atomic_count cache_mis {0};
+ //atomic_count cache_cls {0};
+
+ // The fp path is only moved from on success.
+ //
// Note: this used to be a lambda inside extract_headers() so refer to the
// body of that function for the overall picture.
//
pair<const file*, bool> compile_rule::
enter_header (action a, const scope& bs, file& t, linfo li,
- path& fp, bool cache, bool norm,
+ path&& fp, bool cache, bool norm,
optional<prefix_map>& pfx_map,
const srcout_map& so_map) const
{
tracer trace (x, "compile_rule::enter_header");
+ // It's reasonable to expect the same header to be included by multiple
+ // translation units, which means we will be re-doing this work over and
+ // over again. And it's not exactly cheap, taking up to 50% of an
+ // up-to-date check time on some projects. So we are going to cache the
+ // header path to target mapping.
+ //
+ // While we pass quite a bit of specific "context" (target, base scope)
+ // to enter_file(), here is the analysis why the result will not depend
+ // on this context for the non-absent header (fp is absolute):
+ //
+ // 1. Let's start with the base scope (bs). Firstly, the base scope
+ // passed to map_extension() is the scope of the header (i.e., it is
+ // the scope of fp.directory()). Other than that, the target base
+ // scope is only passed to build_prefix_map() which is only called
+ // for the absent header (linfo is also only used here).
+ //
+ // 2. Next is the target (t). It is passed to build_prefix_map() but
+ // that doesn't matter for the same reason as in (1). Other than
+ // that, it is only passed to build2::search() which in turn passes
+ // it to target type-specific prerequisite search callback (see
+ // target_type::search) if one is not NULL. The target type in
+ // question here is one of the headers and we know all of them use
+ // the standard file_search() which ignores the passed target.
+ //
+ // 3. Finally, so_map could be used for an absolute fp. While we could
+ // simply not cache the result if it was used (second half of the
+ // result pair is true), there doesn't seem to be any harm in caching
+ // the remapped path->target mapping. In fact, if to think about it,
+ // there is no harm in caching the generated file mapping since it
+ // will be immediately generated and any subsequent inclusions we
+ // will "see" with an absolute path, which we can resolve from the
+ // cache.
+ //
+ // To put it another way, all we need to do is make sure that if we were
+ // to not return an existing cache entry, the call to enter_file() would
+ // have returned exactly the same path/target.
+ //
+ // @@ Could it be that the header is re-mapped in one config but not the
+ // other (e.g., when we do both in src and in out builds and we pick
+ // the generated header in src)? If so, that would lead to a
+ // divergence. I.e., we would cache the no-remap case first and then
+ // return it even though the re-map is necessary? Why can't we just
+ // check for re-mapping ourselves? A: the remapping logic in
+ // enter_file() is not exactly trivial.
+ //
+ // But on the other hand, I think we can assume that different
+ // configurations will end up with different caches. In other words,
+ // we can assume that for the same "cc amalgamation" we use only a
+ // single "version" of a header. Seems reasonable.
+ //
+ // Note also that while it would have been nice to have a unified cc
+ // cache, the map_extension() call is passed x_inc which is module-
+ // specific. In other words, we may end up mapping the same header to
+ // two different targets depending on whether it is included from, say,
+ // C or C++ translation unit. We could have used a unified cache for
+ // headers that were mapped using the fallback target type, which would
+ // cover the installed headers. Maybe, one day (it's also possible that
+ // separate caches reduce contention).
+ //
+ // Another related question is where we want to keep the cache: project,
+ // strong amalgamation, or weak amalgamation (like module sidebuilds).
+ // Some experimentation showed that weak has the best performance (which
+ // suggest that a unified cache will probably be a win).
+ //
+ // Note also that we don't need to clear this cache since we never clear
+ // the targets set. In other words, the only time targets are
+ // invalidated is when we destroy the build context, which also destroys
+ // the cache.
+ //
+ const config_module& hc (*header_cache_);
+
+ // First check the cache.
+ //
+ if (fp.absolute ())
+ {
+ if (!norm)
+ {
+ normalize_external (fp, "header");
+ norm = true;
+ }
+
+ slock l (hc.header_map_mutex);
+ auto i (hc.header_map.find (fp));
+ if (i != hc.header_map.end ())
+ {
+ //cache_hit.fetch_add (1, memory_order_relaxed);
+ return make_pair (i->second, false);
+ }
+
+ //cache_mis.fetch_add (1, memory_order_relaxed);
+ }
+
struct data
{
linfo li;
@@ -2810,24 +2934,44 @@ namespace build2
// If it is outside any project, or the project doesn't have such an
// extension, assume it is a plain old C header.
//
- return enter_file (
- trace, "header",
- a, bs, t,
- fp, cache, norm,
- [this] (const scope& bs, const string& n, const string& e)
+ auto r (enter_file (
+ trace, "header",
+ a, bs, t,
+ fp, cache, norm,
+ [this] (const scope& bs, const string& n, const string& e)
+ {
+ return map_extension (bs, n, e, x_inc);
+ },
+ h::static_type,
+ [this, &d] (action a, const scope& bs, const target& t)
+ -> const prefix_map&
+ {
+ if (!d.pfx_map)
+ d.pfx_map = build_prefix_map (bs, a, t, d.li);
+
+ return *d.pfx_map;
+ },
+ so_map));
+
+ // Cache.
+ //
+ if (r.first != nullptr)
+ {
+ const file* f;
{
- return map_extension (bs, n, e, x_inc);
- },
- h::static_type,
- [this, &d] (action a, const scope& bs, const target& t)
- -> const prefix_map&
+ ulock l (hc.header_map_mutex);
+ auto p (hc.header_map.emplace (move (fp), r.first));
+ f = p.second ? nullptr : p.first->second;
+ }
+
+ if (f != nullptr)
{
- if (!d.pfx_map)
- d.pfx_map = build_prefix_map (bs, a, t, d.li);
+ //cache_cls.fetch_add (1, memory_order_relaxed);
+ assert (r.first == f);
+ }
+ }
- return *d.pfx_map;
- },
- so_map);
+ return r;
}
// Note: this used to be a lambda inside extract_headers() so refer to the
@@ -3588,7 +3732,7 @@ namespace build2
if (const file* ht = enter_header (
a, bs, t, li,
- hp, cache, cache /* normalized */,
+ move (hp), cache, cache /* normalized */,
pfx_map, so_map).first)
{
// If we are reading the cache, then it is possible the file has
@@ -3603,7 +3747,7 @@ namespace build2
// Verify/add it to the dependency database.
//
if (!cache)
- dd.expect (ht->path ()); // @@ Use hp (or verify match)?
+ dd.expect (ht->path ());
skip_count++;
return *u;
@@ -3617,7 +3761,7 @@ namespace build2
return fail (*ht);
}
else
- return fail (hp);
+ return fail (hp); // hp is still valid.
};
// As above but for a header unit. Note that currently it is only used
@@ -3634,10 +3778,10 @@ namespace build2
const file* ht (
enter_header (a, bs, t, li,
- hp, true /* cache */, false /* normalized */,
+ move (hp), true /* cache */, false /* normalized */,
pfx_map, so_map).first);
- if (ht == nullptr)
+ if (ht == nullptr) // hp is still valid.
{
diag_record dr;
dr << error << "header " << hp << " not found and no rule to "
@@ -5738,6 +5882,9 @@ namespace build2
// cc.config module and that is within our amalgmantion seems like a
// good place.
//
+ // @@ TODO: maybe we should cache this in compile_rule ctor like we
+ // do for the header cache?
+ //
const scope* as (&rs);
{
const scope* ws (as->weak_scope ());
@@ -5753,7 +5900,7 @@ namespace build2
// This is also the module that registers the scope operation
// callback that cleans up the subproject.
//
- if (cast_false<bool> ((*s)["cc.core.vars.loaded"]))
+ if (cast_false<bool> (s->vars["cc.core.vars.loaded"]))
as = s;
} while (s != ws);