[CaptureTracker] Provide an ordered basic block to PointerMayBeCapturedBefore

This patch is a follow up from r240560 and is a step further into
mitigating the compile time performance issues in CaptureTracker.

By providing the CaptureTracker with a "cached ordered basic block"
instead of computing it every time, MemDepAnalysis can use this cache
throughout its calls to AA->callCapturesBefore, avoiding to recompute it
for every scanned instruction. In the same testcase used in r240560,
compile time is reduced from 2min to 30s.

This also fixes PR22348.

rdar://problem/19230319
Differential Revision: http://reviews.llvm.org/D11364

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243750 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/AliasAnalysis.h

@@ -55,6 +55,7 @@ class AnalysisUsage;
 class MemTransferInst;
 class MemIntrinsic;
 class DominatorTree;
+class OrderedBasicBlock;
 
 /// The possible results of an alias query.
 ///
@@ -501,16 +502,19 @@ public:
   virtual ModRefInfo getModRefInfo(ImmutableCallSite CS1,
                                    ImmutableCallSite CS2);
 
-  /// Return information about whether a particular call site modifies or reads
-  /// the specified memory location.
+  /// \brief Return information about whether a particular call site modifies
+  /// or reads the specified memory location \p MemLoc before instruction \p I
+  /// in a BasicBlock. A ordered basic block \p OBB can be used to speed up
+  /// instruction ordering queries inside the BasicBlock containing \p I.
   ModRefInfo callCapturesBefore(const Instruction *I,
-                                const MemoryLocation &MemLoc,
-                                DominatorTree *DT);
+                                const MemoryLocation &MemLoc, DominatorTree *DT,
+                                OrderedBasicBlock *OBB = nullptr);
 
-  /// A convenience wrapper to synthesize a memory location.
+  /// \brief A convenience wrapper to synthesize a memory location.
   ModRefInfo callCapturesBefore(const Instruction *I, const Value *P,
-                                uint64_t Size, DominatorTree *DT) {
-    return callCapturesBefore(I, MemoryLocation(P, Size), DT);
+                                uint64_t Size, DominatorTree *DT,
+                                OrderedBasicBlock *OBB = nullptr) {
+    return callCapturesBefore(I, MemoryLocation(P, Size), DT, OBB);
   }
 
   /// @}

include/llvm/Analysis/CaptureTracking.h

@@ -20,6 +20,7 @@ namespace llvm {
   class Use;
   class Instruction;
   class DominatorTree;
+  class OrderedBasicBlock;
 
   /// PointerMayBeCaptured - Return true if this pointer value may be captured
   /// by the enclosing function (which is required to exist).  This routine can
@@ -41,10 +42,12 @@ namespace llvm {
   /// it or not.  The boolean StoreCaptures specified whether storing the value
   /// (or part of it) into memory anywhere automatically counts as capturing it
   /// or not. Captures by the provided instruction are considered if the
-  /// final parameter is true.
+  /// final parameter is true. An ordered basic block in \p OBB could be used
+  /// to speed up capture-tracker queries.
   bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures,
                                   bool StoreCaptures, const Instruction *I,
-                                  DominatorTree *DT, bool IncludeI = false);
+                                  DominatorTree *DT, bool IncludeI = false,
+                                  OrderedBasicBlock *OBB = nullptr);
 
   /// This callback is used in conjunction with PointerMayBeCaptured. In
   /// addition to the interface here, you'll need to provide your own getters

include/llvm/Analysis/OrderedBasicBlock.h

@@ -0,0 +1,66 @@
+//===- llvm/Analysis/OrderedBasicBlock.h --------------------- -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the OrderedBasicBlock class. OrderedBasicBlock maintains
+// an interface where clients can query if one instruction comes before another
+// in a BasicBlock. Since BasicBlock currently lacks a reliable way to query
+// relative position between instructions one can use OrderedBasicBlock to do
+// such queries. OrderedBasicBlock is lazily built on a source BasicBlock and
+// maintains an internal Instruction -> Position map. A OrderedBasicBlock
+// instance should be discarded whenever the source BasicBlock changes.
+//
+// It's currently used by the CaptureTracker in order to find relative
+// positions of a pair of instructions inside a BasicBlock.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_ORDEREDBASICBLOCK_H
+#define LLVM_ANALYSIS_ORDEREDBASICBLOCK_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/IR/BasicBlock.h"
+
+namespace llvm {
+
+class Instruction;
+class BasicBlock;
+
+class OrderedBasicBlock {
+private:
+  /// \brief Map a instruction to its position in a BasicBlock.
+  SmallDenseMap<const Instruction *, unsigned, 32> NumberedInsts;
+
+  /// \brief Keep track of last instruction inserted into \p NumberedInsts.
+  /// It speeds up queries for uncached instructions by providing a start point
+  /// for new queries in OrderedBasicBlock::comesBefore.
+  BasicBlock::const_iterator LastInstFound;
+
+  /// \brief The position/number to tag the next instruction to be found.
+  unsigned NextInstPos;
+
+  /// \brief The source BasicBlock to map.
+  const BasicBlock *BB;
+
+  /// \brief Given no cached results, find if \p A comes before \p B in \p BB.
+  /// Cache and number out instruction while walking \p BB.
+  bool comesBefore(const Instruction *A, const Instruction *B);
+
+public:
+  OrderedBasicBlock(const BasicBlock *BasicB);
+
+  /// \brief Find out whether \p A dominates \p B, meaning whether \p A
+  /// comes before \p B in \p BB. This is a simplification that considers
+  /// cached instruction positions and ignores other basic blocks, being
+  /// only relevant to compare relative instructions positions inside \p BB.
+  bool dominates(const Instruction *A, const Instruction *B);
+};
+
+} // End llvm namespace
+
+#endif