[PATCH] D126316: [clang][dataflow] Make limit on fixpoint-algorithm iterations proportional to size of CFG.

[Yitzhak Mandelbaum via Phabricator via cfe-commits]

ymandel created this revision.
ymandel added reviewers: xazax.hun, li.zhe.hua, sgatev.
Herald added subscribers: tschuett, steakhal, rnkovacs.
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Currently, the maximum number of iterations of the loop for finding the fixpoint
of the dataflow analysis is set at 2^16. When things go wrong in an analysis,
this can be far too large.  This patch changes the limit to be proportional to
the size of the CFG, which will generally be far smaller than 2^16.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D126316

Files:
  clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp


Index: clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp
===================================================================
--- clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp
+++ clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp
@@ -332,8 +332,9 @@
   // FIXME: Consider making the maximum number of iterations configurable.
   // FIXME: Set up statistics (see llvm/ADT/Statistic.h) to count average number
   // of iterations, number of functions that time out, etc.
+  static constexpr uint32_t MaxAverageVisitsPerBlock = 4;
+  const uint32_t MaxIterations = MaxAverageVisitsPerBlock * BlockStates.size();
   uint32_t Iterations = 0;
-  static constexpr uint32_t MaxIterations = 1 << 16;
   while (const CFGBlock *Block = Worklist.dequeue()) {
     if (++Iterations > MaxIterations) {
       return llvm::createStringError(std::errc::timed_out,


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