[LAA-memchecks 3/3] Introduce pointer partitions for memchecks

This is the final patch that actually introduces the new parameter of
partition mapping to RuntimePointerCheck::needsChecking.

Another API (LAI::getInstructionsForAccess) is also exposed that helps
to map pointers to instructions because ultimately we partition
instructions.

The WIP version of the Loop Distribution pass in D6930 has been adapted
to use all this.  See for example, how
InstrPartitionContainer::computePartitionSetForPointers sets up the
partitions using the above API and then calls to LAI::addRuntimeCheck
with the pointer partitions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231818 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/LoopAccessAnalysis.h

@@ -231,6 +231,10 @@ public:
     return InstMap;
   }
 
+  /// \brief Find the set of instructions that read or write via \p Ptr.
+  SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr,
+                                                         bool isWrite) const;
+
 private:
   ScalarEvolution *SE;
   const Loop *InnermostLoop;
@@ -328,10 +332,20 @@ public:
 
     /// \brief Decide whether we need to issue a run-time check for pointer at
     /// index \p I and \p J to prove their independence.
-    bool needsChecking(unsigned I, unsigned J) const;
+    ///
+    /// If \p PtrPartition is set, it contains the partition number for
+    /// pointers (-1 if the pointer belongs to multiple partitions).  In this
+    /// case omit checks between pointers belonging to the same partition.
+    bool needsChecking(unsigned I, unsigned J,
+                       const SmallVectorImpl<int> *PtrPartition) const;
 
     /// \brief Print the list run-time memory checks necessary.
-    void print(raw_ostream &OS, unsigned Depth = 0) const;
+    ///
+    /// If \p PtrPartition is set, it contains the partition number for
+    /// pointers (-1 if the pointer belongs to multiple partitions).  In this
+    /// case omit checks between pointers belonging to the same partition.
+    void print(raw_ostream &OS, unsigned Depth = 0,
+               const SmallVectorImpl<int> *PtrPartition = nullptr) const;
 
     /// This flag indicates if we need to add the runtime check.
     bool Need;
@@ -383,8 +397,13 @@ public:
   /// Returns a pair of instructions where the first element is the first
   /// instruction generated in possibly a sequence of instructions and the
   /// second value is the final comparator value or NULL if no check is needed.
+  ///
+  /// If \p PtrPartition is set, it contains the partition number for pointers
+  /// (-1 if the pointer belongs to multiple partitions).  In this case omit
+  /// checks between pointers belonging to the same partition.
   std::pair<Instruction *, Instruction *>
-    addRuntimeCheck(Instruction *Loc) const;
+  addRuntimeCheck(Instruction *Loc,
+                  const SmallVectorImpl<int> *PtrPartition = nullptr) const;
 
   /// \brief The diagnostics report generated for the analysis.  E.g. why we
   /// couldn't analyze the loop.
@@ -394,6 +413,13 @@ public:
   /// loop-independent and loop-carried dependences between memory accesses.
   const MemoryDepChecker &getDepChecker() const { return DepChecker; }
 
+  /// \brief Return the list of instructions that use \p Ptr to read or write
+  /// memory.
+  SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr,
+                                                         bool isWrite) const {
+    return DepChecker.getInstructionsForAccess(Ptr, isWrite);
+  }
+
   /// \brief Print the information about the memory accesses in the loop.
   void print(raw_ostream &OS, unsigned Depth = 0) const;
 

lib/Analysis/LoopAccessAnalysis.cpp

@@ -127,8 +127,8 @@ void LoopAccessInfo::RuntimePointerCheck::insert(
   AliasSetId.push_back(ASId);
 }
 
-bool LoopAccessInfo::RuntimePointerCheck::needsChecking(unsigned I,
+bool LoopAccessInfo::RuntimePointerCheck::needsChecking(
-                                                        unsigned J) const {
+    unsigned I, unsigned J, const SmallVectorImpl<int> *PtrPartition) const {
   // No need to check if two readonly pointers intersect.
   if (!IsWritePtr[I] && !IsWritePtr[J])
     return false;
@@ -141,11 +141,19 @@ bool LoopAccessInfo::RuntimePointerCheck::needsChecking(unsigned I,
   if (AliasSetId[I] != AliasSetId[J])
     return false;
 
+  // If PtrPartition is set omit checks between pointers of the same partition.
+  // Partition number -1 means that the pointer is used in multiple partitions.
+  // In this case we can't omit the check.
+  if (PtrPartition && (*PtrPartition)[I] != -1 &&
+      (*PtrPartition)[I] == (*PtrPartition)[J])
+    return false;
+
   return true;
 }
 
-void LoopAccessInfo::RuntimePointerCheck::print(raw_ostream &OS,
+void LoopAccessInfo::RuntimePointerCheck::print(
-                                                unsigned Depth) const {
+    raw_ostream &OS, unsigned Depth,
+    const SmallVectorImpl<int> *PtrPartition) const {
   unsigned NumPointers = Pointers.size();
   if (NumPointers == 0)
     return;
@@ -154,10 +162,16 @@ void LoopAccessInfo::RuntimePointerCheck::print(raw_ostream &OS,
   unsigned N = 0;
   for (unsigned I = 0; I < NumPointers; ++I)
     for (unsigned J = I + 1; J < NumPointers; ++J)
-      if (needsChecking(I, J)) {
+      if (needsChecking(I, J, PtrPartition)) {
         OS.indent(Depth) << N++ << ":\n";
-        OS.indent(Depth + 2) << *Pointers[I] << "\n";
+        OS.indent(Depth + 2) << *Pointers[I];
-        OS.indent(Depth + 2) << *Pointers[J] << "\n";
+        if (PtrPartition)
+          OS << " (Partition: " << (*PtrPartition)[I] << ")";
+        OS << "\n";
+        OS.indent(Depth + 2) << *Pointers[J];
+        if (PtrPartition)
+          OS << " (Partition: " << (*PtrPartition)[J] << ")";
+        OS << "\n";
       }
 }
 
@@ -835,6 +849,18 @@ bool MemoryDepChecker::areDepsSafe(DepCandidates &AccessSets,
   return SafeForVectorization;
 }
 
+SmallVector<Instruction *, 4>
+MemoryDepChecker::getInstructionsForAccess(Value *Ptr, bool isWrite) const {
+  MemAccessInfo Access(Ptr, isWrite);
+  auto &IndexVector = Accesses.find(Access)->second;
+
+  SmallVector<Instruction *, 4> Insts;
+  std::transform(IndexVector.begin(), IndexVector.end(),
+                 std::back_inserter(Insts),
+                 [&](unsigned Idx) { return this->InstMap[Idx]; });
+  return Insts;
+}
+
 const char *MemoryDepChecker::Dependence::DepName[] = {
     "NoDep", "Unknown", "Forward", "ForwardButPreventsForwarding", "Backward",
     "BackwardVectorizable", "BackwardVectorizableButPreventsForwarding"};
@@ -1169,8 +1195,8 @@ static Instruction *getFirstInst(Instruction *FirstInst, Value *V,
   return nullptr;
 }
 
-std::pair<Instruction *, Instruction *>
+std::pair<Instruction *, Instruction *> LoopAccessInfo::addRuntimeCheck(
-LoopAccessInfo::addRuntimeCheck(Instruction *Loc) const {
+    Instruction *Loc, const SmallVectorImpl<int> *PtrPartition) const {
   Instruction *tnullptr = nullptr;
   if (!PtrRtCheck.Need)
     return std::pair<Instruction *, Instruction *>(tnullptr, tnullptr);
@@ -1211,7 +1237,7 @@ LoopAccessInfo::addRuntimeCheck(Instruction *Loc) const {
   Value *MemoryRuntimeCheck = nullptr;
   for (unsigned i = 0; i < NumPointers; ++i) {
     for (unsigned j = i+1; j < NumPointers; ++j) {
-      if (!PtrRtCheck.needsChecking(i, j))
+      if (!PtrRtCheck.needsChecking(i, j, PtrPartition))
         continue;
 
       unsigned AS0 = Starts[i]->getType()->getPointerAddressSpace();