[PassManager] Tuning Memory Usage of AnalysisUsage
authorPhilip Reames <listmail@philipreames.com>
Tue, 8 Dec 2015 00:10:56 +0000 (00:10 +0000)
committerPhilip Reames <listmail@philipreames.com>
Tue, 8 Dec 2015 00:10:56 +0000 (00:10 +0000)
We were using unneccessarily large initial sizes for these SmallVectors.  This was wasting around 50kb of memory for the O3 pipeline, even after the uniquing changes.  We're still using around 20kb which is a bit much, but it's definitely better.  This is about a 6% improvement in total O3 memory usage.

Note: The raw data on structure size which were used to pick these thresholds can be found in the review thread.

Differential Revision: http://reviews.llvm.org/D15244

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254974 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/PassAnalysisSupport.h

index f6265b6..492a4ef 100644 (file)
@@ -36,11 +36,17 @@ namespace llvm {
 ///
 class AnalysisUsage {
 public:
-  typedef SmallVector<AnalysisID, 32> VectorType;
+  typedef SmallVectorImpl<AnalysisID> VectorType;
 
 private:
   /// Sets of analyses required and preserved by a pass
-  VectorType Required, RequiredTransitive, Preserved, Used;
+  // TODO: It's not clear that SmallVector is an appropriate data structure for
+  // this usecase.  The sizes were picked to minimize wasted space, but are
+  // otherwise fairly meaningless.
+  SmallVector<AnalysisID, 8> Required;
+  SmallVector<AnalysisID, 2> RequiredTransitive;
+  SmallVector<AnalysisID, 2> Preserved;
+  SmallVector<AnalysisID, 0> Used;
   bool PreservesAll;
 
 public: