[MemDep] allow to select block-scan-limit when constructing MemoryDependenceAnalysis

[fedor.sergeev]

Summary

Introducing non-global control for default block-scan-limit in MemDep analysis.
Useful when there are many compilations per initialized LLVM instance (e.g. JIT).

[fedor.sergeev]

add parameter to MemoryDependenceAnalysis constructor, clang-format

[asbirlea]

lgtm.

llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h

private:
   /// Current AA implementation, just a cache.
   AliasAnalysis &AA;
   AssumptionCache ∾
   const TargetLibraryInfo &TLI;
   DominatorTree &DT;
   PhiValues &PV;
   PredIteratorCache PredCache;
 
+  unsigned DefaultBlockScanLimit;
+
 public:
   MemoryDependenceResults(AliasAnalysis &AA, AssumptionCache &AC,
-                          const TargetLibraryInfo &TLI,
-                          DominatorTree &DT, PhiValues &PV)
-      : AA(AA), AC(AC), TLI(TLI), DT(DT), PV(PV) {}
+                          const TargetLibraryInfo &TLI, DominatorTree &DT,
+                          PhiValues &PV, unsigned DefaultBlockScanLimit)
+      : AA(AA), AC(AC), TLI(TLI), DT(DT), PV(PV),
+        DefaultBlockScanLimit(DefaultBlockScanLimit) {}
 
   /// Handle invalidation in the new PM.
   bool invalidate(Function &F, const PreservedAnalyses &PA,
                   FunctionAnalysisManager::Invalidator &Inv);
 
   /// Some methods limit the number of instructions they will examine.
   /// The return value of this method is the default limit that will be
   /// used if no limit is explicitly passed in.

 /// This is essentially a no-op because the results are computed entirely
 /// lazily.
 class MemoryDependenceAnalysis
     : public AnalysisInfoMixin<MemoryDependenceAnalysis> {
   friend AnalysisInfoMixin<MemoryDependenceAnalysis>;
 
   static AnalysisKey Key;
 
+  unsigned DefaultBlockScanLimit;
+
 public:
   using Result = MemoryDependenceResults;
 
+  MemoryDependenceAnalysis();
+  MemoryDependenceAnalysis(unsigned DefaultBlockScanLimit) : DefaultBlockScanLimit(DefaultBlockScanLimit) { }
+
   MemoryDependenceResults run(Function &F, FunctionAnalysisManager &AM);
 };
 
 /// A wrapper analysis pass for the legacy pass manager that exposes a \c
 /// MemoryDepnedenceResults instance.
 class MemoryDependenceWrapperPass : public FunctionPass {
   Optional<MemoryDependenceResults> MemDep;
 

llvm/lib/Analysis/MemoryDependenceAnalysis.cpp

if (Inst->mayReadFromMemory())
     return ModRefInfo::Ref;
   return ModRefInfo::NoModRef;
 }
 
 /// Private helper for finding the local dependencies of a call site.
 MemDepResult MemoryDependenceResults::getCallDependencyFrom(
     CallBase *Call, bool isReadOnlyCall, BasicBlock::iterator ScanIt,
     BasicBlock *BB) {
-  unsigned Limit = BlockScanLimit;
+  unsigned Limit = getDefaultBlockScanLimit();
 
   // Walk backwards through the block, looking for dependencies.
   while (ScanIt != BB->begin()) {
     Instruction *Inst = &*--ScanIt;
     // Debug intrinsics don't cause dependences and should not affect Limit
     if (isa<DbgInfoIntrinsic>(Inst))
       continue;
 

 }
 
 MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
     const MemoryLocation &MemLoc, bool isLoad, BasicBlock::iterator ScanIt,
     BasicBlock *BB, Instruction *QueryInst, unsigned *Limit,
     OrderedBasicBlock *OBB) {
   bool isInvariantLoad = false;
 
-  unsigned DefaultLimit = BlockScanLimit;
+  unsigned DefaultLimit = getDefaultBlockScanLimit();
   if (!Limit)
     Limit = &DefaultLimit;
 
   // We must be careful with atomic accesses, as they may allow another thread
   //   to touch this location, clobbering it. We are conservative: if the
   //   QueryInst is not a simple (non-atomic) memory access, we automatically
   //   return getClobber.
   // If it is simple, we know based on the results of
for (ValueIsLoadPair P : DepKV.second)
       assert(P != ValueIsLoadPair(D, false) && P != ValueIsLoadPair(D, true) &&
              "Inst occurs in ReverseNonLocalPtrDeps map");
   }
 #endif
 }
 
 AnalysisKey MemoryDependenceAnalysis::Key;
 
+MemoryDependenceAnalysis::MemoryDependenceAnalysis()
+    : DefaultBlockScanLimit(BlockScanLimit) {}
+
+void MemoryDependenceAnalysis::setDefaultBlockScanLimit(
+    unsigned DefaultBlockScanLimit) {
+  this->DefaultBlockScanLimit = DefaultBlockScanLimit;
+}
+
 MemoryDependenceResults
 MemoryDependenceAnalysis::run(Function &F, FunctionAnalysisManager &AM) {
   auto &AA = AM.getResult<AAManager>(F);
   auto &AC = AM.getResult<AssumptionAnalysis>(F);
   auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
   auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
   auto &PV = AM.getResult<PhiValuesAnalysis>(F);
-  return MemoryDependenceResults(AA, AC, TLI, DT, PV);
+  return MemoryDependenceResults(AA, AC, TLI, DT, PV, DefaultBlockScanLimit);
 }
 
 char MemoryDependenceWrapperPass::ID = 0;
 
 INITIALIZE_PASS_BEGIN(MemoryDependenceWrapperPass, "memdep",
                       "Memory Dependence Analysis", false, true)
 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
if (Inv.invalidate<AAManager>(F, PA) ||
       Inv.invalidate<PhiValuesAnalysis>(F, PA))
     return true;
 
   // Otherwise this analysis result remains valid.
   return false;
 }
 
 unsigned MemoryDependenceResults::getDefaultBlockScanLimit() const {
-  return BlockScanLimit;
+  return DefaultBlockScanLimit;
 }
 
 bool MemoryDependenceWrapperPass::runOnFunction(Function &F) {
   auto &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
   auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
   auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
   auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
   auto &PV = getAnalysis<PhiValuesWrapperPass>().getResult();
-  MemDep.emplace(AA, AC, TLI, DT, PV);
+  MemDep.emplace(AA, AC, TLI, DT, PV, BlockScanLimit);
   return false;
 }