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Switch BasicAliasAnalysis' cache to SmallDenseMap.

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It relies on clear() being fast and the cache rarely has more than 1 or 2
elements, so give it an inline capacity and always shrink it back down in case
it grows. DenseMap will grow to 64 buckets which makes clear() a lot slower.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163215 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2012-09-05 16:49:37 +00:00
parent 4c3d3ecdf8
commit 998d3cca29
1 changed files with 7 additions and 9 deletions
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16
lib/Analysis/BasicAliasAnalysis.cpp
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@ -419,13 +419,7 @@ namespace {
/// BasicAliasAnalysis - This is the primary alias analysis implementation.
struct BasicAliasAnalysis : public ImmutablePass, public AliasAnalysis {
static char ID; // Class identification, replacement for typeinfo
BasicAliasAnalysis() : ImmutablePass(ID),
// AliasCache rarely has more than 1 or 2 elements,
// so start it off fairly small so that clear()
// doesn't have to tromp through 64 (the default)
// elements on each alias query. This really wants
// something like a SmallDenseMap.
AliasCache(8) {
BasicAliasAnalysis() : ImmutablePass(ID) {
initializeBasicAliasAnalysisPass(*PassRegistry::getPassRegistry());
}
@ -445,7 +439,11 @@ namespace {
"BasicAliasAnalysis doesn't support interprocedural queries.");
AliasResult Alias = aliasCheck(LocA.Ptr, LocA.Size, LocA.TBAATag,
LocB.Ptr, LocB.Size, LocB.TBAATag);
AliasCache.clear();
// AliasCache rarely has more than 1 or 2 elements, always use
// shrink_and_clear so it quickly returns to the inline capacity of the
// SmallDenseMap if it ever grows larger.
// FIXME: This should really be shrink_to_inline_capacity_and_clear().
AliasCache.shrink_and_clear();
return Alias;
}
@ -483,7 +481,7 @@ namespace {
private:
// AliasCache - Track alias queries to guard against recursion.
typedef std::pair<Location, Location> LocPair;
typedef DenseMap<LocPair, AliasResult> AliasCacheTy;
typedef SmallDenseMap<LocPair, AliasResult, 8> AliasCacheTy;
AliasCacheTy AliasCache;
// Visited - Track instructions visited by pointsToConstantMemory.