[LegacyPassManager] Reduce memory usage for AnalysisUsage
The LegacyPassManager was storing an instance of AnalysisUsage for each instance of each pass. In practice, most instances of a single pass class share the same dependencies. We can't rely on this because passes can (and some do) have dynamic dependencies based on instance options.
We can exploit the likely commonality by uniqueing the usage information after querying the pass, but before storing it into the pass manager. This greatly reduces memory consumption by the AnalysisUsage objects. For a long pass pipeline, I measured a decrease in memory consumption for this storage of about 50%. I have not measured on the default O3 pipeline, but I suspect it will see some benefit as well since many passes are repeated (e.g. InstCombine).
Differential Revision: http://reviews.llvm.org/D14677
llvm-svn: 254760
GitOrigin-RevId: e8aeaeb7125fd31ed368d2793fe28a34117bd7f7
diff --git a/lib/IR/LegacyPassManager.cpp b/lib/IR/LegacyPassManager.cpp
index 69f4020..08e8906 100644
--- a/lib/IR/LegacyPassManager.cpp
+++ b/lib/IR/LegacyPassManager.cpp
@@ -569,13 +569,33 @@
AnalysisUsage *PMTopLevelManager::findAnalysisUsage(Pass *P) {
AnalysisUsage *AnUsage = nullptr;
- DenseMap<Pass *, AnalysisUsage *>::iterator DMI = AnUsageMap.find(P);
+ auto DMI = AnUsageMap.find(P);
if (DMI != AnUsageMap.end())
AnUsage = DMI->second;
else {
- AnUsage = new AnalysisUsage();
- P->getAnalysisUsage(*AnUsage);
- AnUsageMap[P] = AnUsage;
+ // Look up the analysis usage from the pass instance (different instances
+ // of the same pass can produce different results), but unique the
+ // resulting object to reduce memory usage. This helps to greatly reduce
+ // memory usage when we have many instances of only a few pass types
+ // (e.g. instcombine, simplifycfg, etc...) which tend to share a fixed set
+ // of dependencies.
+ AnalysisUsage AU;
+ P->getAnalysisUsage(AU);
+
+ AUFoldingSetNode* Node = nullptr;
+ FoldingSetNodeID ID;
+ AUFoldingSetNode::Profile(ID, AU);
+ void *IP = nullptr;
+ if (auto *N = UniqueAnalysisUsages.FindNodeOrInsertPos(ID, IP))
+ Node = N;
+ else {
+ Node = new (AUFoldingSetNodeAllocator) AUFoldingSetNode(AU);
+ UniqueAnalysisUsages.InsertNode(Node, IP);
+ }
+ assert(Node && "cached analysis usage must be non null");
+
+ AnUsageMap[P] = &Node->AU;
+ AnUsage = &Node->AU;;
}
return AnUsage;
}
@@ -798,10 +818,6 @@
for (SmallVectorImpl<ImmutablePass *>::iterator
I = ImmutablePasses.begin(), E = ImmutablePasses.end(); I != E; ++I)
delete *I;
-
- for (DenseMap<Pass *, AnalysisUsage *>::iterator DMI = AnUsageMap.begin(),
- DME = AnUsageMap.end(); DMI != DME; ++DMI)
- delete DMI->second;
}
//===----------------------------------------------------------------------===//
