Refine SourceManager's isBeforeInTranslationUnit() cache to have more entries.
isBeforeInTranslationUnit() uses a cache to reduce the expensive work
to compute a common ancestor for two FileIDs. This work is very
expensive, so even caching the latest used FileIDs was a big win.
A closer analysis of the cache before, however, shows that the cache
access pattern would oscillate between a working set of FileIDs, and
thus caching more pairs would be profitable.
This patch adds a side table for extending caching. This side table
is bounded in size (experimentally determined in this case from
a simple Objective-C project), and when the table gets too large
we fall back to the single entry caching before as before.
On Sketch (a small example Objective-C project), this optimization
reduces -fsyntax-only time on SKTGraphicView.m by 5%. This is
for a project that is already using PCH.
Fixes <rdar://problem/13299847>
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176142 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index c5d275a..ea95650 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -1855,7 +1855,32 @@
Loc = SM.getDecomposedLoc(UpperLoc);
return false;
}
-
+
+/// Return the cache entry for comparing the given file IDs
+/// for isBeforeInTranslationUnit.
+InBeforeInTUCacheEntry &SourceManager::getInBeforeInTUCache(FileID LFID,
+ FileID RFID) const {
+ // This is a magic number for limiting the cache size. It was experimentally
+ // derived from a small Objective-C project (where the cache filled
+ // out to ~250 items). We can make it larger if necessary.
+ enum { MagicCacheSize = 300 };
+ IsBeforeInTUCacheKey Key(LFID, RFID);
+
+ // If the cache size isn't too large, do a lookup and if necessary default
+ // construct an entry. We can then return it to the caller for direct
+ // use. When they update the value, the cache will get automatically
+ // updated as well.
+ if (IBTUCache.size() < MagicCacheSize)
+ return IBTUCache[Key];
+
+ // Otherwise, do a lookup that will not construct a new value.
+ InBeforeInTUCache::iterator I = IBTUCache.find(Key);
+ if (I != IBTUCache.end())
+ return I->second;
+
+ // Fall back to the overflow value.
+ return IBTUCacheOverflow;
+}
/// \brief Determines the order of 2 source locations in the translation unit.
///
@@ -1875,6 +1900,11 @@
// If we are comparing a source location with multiple locations in the same
// file, we get a big win by caching the result.
+ InBeforeInTUCacheEntry &IsBeforeInTUCache =
+ getInBeforeInTUCache(LOffs.first, ROffs.first);
+
+ // If we are comparing a source location with multiple locations in the same
+ // file, we get a big win by caching the result.
if (IsBeforeInTUCache.isCacheValid(LOffs.first, ROffs.first))
return IsBeforeInTUCache.getCachedResult(LOffs.second, ROffs.second);