[Polly] Avoid use of `getStmtFor(BB)` in PolyhedralInfo. NFC

[nandini12396]

Summary

Since there will be no more a 1-1 correspondence between statements and basic block, we would like to get rid of the method getStmtFor(BB) and its uses. Here we remove one of its uses in PolyhedralInfo, as suggested by Michael Sir.

[bollu]

include/polly/ScopInfo.h

2562

If we are eliminating getStmtFor, can this be removed?

lib/Analysis/PolyhedralInfo.cpp

135

Undesired change?

lib/Analysis/ScopInfo.cpp

4916

Please add an assert message along with the assert.

assert(StmtMapIt->second.size() == 1 && "We currently only have one Stmt per BB");

[nandini12396]

include/polly/ScopInfo.h

2562

yes, I am planning to remove it once I delete all its uses.

lib/Analysis/PolyhedralInfo.cpp

135

oh, this happened after polly-update-format. Thanks for pointing out.

lib/Analysis/ScopInfo.cpp

4916

oh, yes. Thanks I will add it.

[Meinersbur]

include/polly/ScopInfo.h

2565

Please do not return a copy of the entire vector. You can return:

1. A const std::vector<ScopStmt *>&
2. An ArrayRef<ScopStmt*>
3. An llvm::iterator_range<std::vector<ScopStmt *>::const_iterator>

lib/Analysis/PolyhedralInfo.cpp

129–130

These two loops only iterate once over all statements in a loop. It is simpler to do with

for (auto &SS : *S)
  if (L->contains(SS.getSurroundingLoop()))

which also protects from iterating region statements multiple times.

However, I am also fine with using getStmtListFor if we need it for other purposes as well.

[grosser]

I like Michael's idea! It does not even nee the getStmtList function.

[grosser]

Marking this as requesting changes to make sure I get notified when you update the commit.

[grosser]

This looks good to me

Let's wait for Michael's feedback!

include/polly/ScopInfo.h

public:
   /// Get an isl string representing the assumed context.
   std::string getAssumedContextStr() const;
 
   /// Get an isl string representing the invalid context.
   std::string getInvalidContextStr() const;
 
   /// Return the ScopStmt for the given @p BB or nullptr if there is
   ///        none.
   ScopStmt *getStmtFor(BasicBlock *BB) const;
 
+  /// Return the list of ScopStmts that represent the given @p BB.
+  std::vector<ScopStmt *> getStmtListFor(BasicBlock *BB) const;
+
   /// Return the last statement representing @p BB.
   ///
   /// Of the sequence of statements that represent a @p BB, this is the last one
   /// to be executed. It is typically used to determine which instruction to add
   /// a MemoryKind::PHI WRITE to. For this purpose, it is not strictly required
   /// to be executed last, only that the incoming value is available in it.
   ScopStmt *getLastStmtFor(BasicBlock *BB) const { return getStmtFor(BB); }
 

lib/Analysis/PolyhedralInfo.cpp

 //    Stmt[i0, i1] -> [i0, i1]
 __isl_give isl_union_map *PolyhedralInfo::getScheduleForLoop(const Scop *S,
                                                              Loop *L) const {
   isl_union_map *Schedule = isl_union_map_empty(S->getParamSpace());
   int CurrDim = S->getRelativeLoopDepth(L);
   DEBUG(dbgs() << "Relative loop depth:\t" << CurrDim << "\n");
   assert(CurrDim >= 0 && "Loop in region should have at least depth one");
 
   for (auto *BB : L->blocks()) {
-    auto *SS = S->getStmtFor(BB);
-    if (!SS)
-      continue;
+    for (auto *SS : S->getStmtListFor(BB)) {
 
       unsigned int MaxDim = SS->getNumIterators();
       DEBUG(dbgs() << "Maximum depth of Stmt:\t" << MaxDim << "\n");
       auto *ScheduleMap = SS->getSchedule();
-    assert(ScheduleMap &&
-           "Schedules that contain extension nodes require special handling.");
+      assert(
+          ScheduleMap &&
 
       ScheduleMap = isl_map_project_out(ScheduleMap, isl_dim_out, CurrDim + 1,
                                         MaxDim - CurrDim - 1);
       ScheduleMap =
           isl_map_set_tuple_id(ScheduleMap, isl_dim_in, SS->getDomainId());
       Schedule =
           isl_union_map_union(Schedule, isl_union_map_from_map(ScheduleMap));
     }
+  }
 
   Schedule = isl_union_map_coalesce(Schedule);
   return Schedule;
 }
 
 char PolyhedralInfo::ID = 0;
 
 Pass *polly::createPolyhedralInfoPass() { return new PolyhedralInfo(); }

lib/Analysis/ScopInfo.cpp

 ScopStmt *Scop::getStmtFor(BasicBlock *BB) const {
   auto StmtMapIt = StmtMap.find(BB);
   if (StmtMapIt == StmtMap.end())
     return nullptr;
   assert(StmtMapIt->second.size() == 1);
   return StmtMapIt->second.front();
 }
 
+std::vector<ScopStmt *> Scop::getStmtListFor(BasicBlock *BB) const {
+  auto StmtMapIt = StmtMap.find(BB);
+  if (StmtMapIt == StmtMap.end())
+    return {};
+  assert(StmtMapIt->second.size() == 1);
+  return StmtMapIt->second;
+}
+
 ScopStmt *Scop::getStmtFor(RegionNode *RN) const {
   if (RN->isSubRegion())
     return getStmtFor(RN->getNodeAs<Region>());
   return getStmtFor(RN->getNodeAs<BasicBlock>());
 }
 
 ScopStmt *Scop::getStmtFor(Region *R) const {
   ScopStmt *Stmt = getStmtFor(R->getEntry());