[Polly] Use separate DT/LI/SE for outlined subfn. NFC. (#102460)

DominatorTree, LoopInfo, and ScalarEvolution are function-level analyses
that expect to be called only on instructions and basic blocks of the
function they were original created for. When Polly outlined a parallel
loop body into a separate function, it reused the same analyses seemed
to work until new checks to be added in #101198.

This patch creates new analyses for the subfunctions. GenDT, GenLI, and
GenSE now refer to the analyses of the current region of code. Outside
of an outlined function, they refer to the same analysis as used for the
SCoP, but are substituted within an outlined function.

Additionally to the cross-function queries of DT/LI/SE, we must not
create SCEVs that refer to a mix of expressions for old and generated
values. Currently, SCEVs themselves do not "remember" which
ScalarEvolution analysis they were created for, but mixing them is just
as unexpected as using DT/LI across function boundaries. Hence
`SCEVLoopAddRecRewriter` was combined into `ScopExpander`.
`SCEVLoopAddRecRewriter` only replaced induction variables but left
SCEVUnknowns to reference the old function. `SCEVParameterRewriter`
would have done so but its job was effectively superseded by
`ScopExpander`, and now also `SCEVLoopAddRecRewriter`. Some issues
persist put marked with a FIXME in the code. Changing them would
possibly cause this patch to be not NFC anymore.

polly/include/polly/CodeGen/BlockGenerators.h

@@ -162,9 +162,14 @@ class BlockGenerator {
   /// The dominator tree of this function.
   DominatorTree &DT;
 
-  /// The entry block of the current function.
-  BasicBlock *EntryBB;
+  /// Relates to the region where the code is emitted into.
+  /// @{
+  DominatorTree *GenDT;
+  LoopInfo *GenLI;
+  ScalarEvolution *GenSE;
+  /// @}
 
+public:
   /// Map to resolve scalar dependences for PHI operands and scalars.
   ///
   /// When translating code that contains scalar dependences as they result from
@@ -298,6 +303,10 @@ class BlockGenerator {
   /// Split @p BB to create a new one we can use to clone @p BB in.
   BasicBlock *splitBB(BasicBlock *BB);
 
+  /// Change the function that code is emitted into.
+  void switchGeneratedFunc(Function *GenFn, DominatorTree *GenDT,
+                           LoopInfo *GenLI, ScalarEvolution *GenSE);
+
   /// Copy the given basic block.
   ///
   /// @param Stmt      The statement to code generate.

polly/include/polly/CodeGen/IslExprBuilder.h

@@ -124,6 +124,10 @@ class IslExprBuilder final {
                  llvm::ScalarEvolution &SE, llvm::DominatorTree &DT,
                  llvm::LoopInfo &LI, llvm::BasicBlock *StartBlock);
 
+  /// Change the function that code is emitted into.
+  void switchGeneratedFunc(llvm::Function *GenFn, llvm::DominatorTree *GenDT,
+                           llvm::LoopInfo *GenLI, llvm::ScalarEvolution *GenSE);
+
   /// Create LLVM-IR for an isl_ast_expr[ession].
   ///
   /// @param Expr The ast expression for which we generate LLVM-IR.
@@ -205,10 +209,15 @@ class IslExprBuilder final {
 
   const llvm::DataLayout &DL;
   llvm::ScalarEvolution &SE;
-  llvm::DominatorTree &DT;
-  llvm::LoopInfo &LI;
   llvm::BasicBlock *StartBlock;
 
+  /// Relates to the region where the code is emitted into.
+  /// @{
+  llvm::DominatorTree *GenDT;
+  llvm::LoopInfo *GenLI;
+  llvm::ScalarEvolution *GenSE;
+  /// @}
+
   llvm::Value *createOp(__isl_take isl_ast_expr *Expr);
   llvm::Value *createOpUnary(__isl_take isl_ast_expr *Expr);
   llvm::Value *createOpAccess(__isl_take isl_ast_expr *Expr);

polly/include/polly/CodeGen/IslNodeBuilder.h

@@ -72,7 +72,7 @@ class IslNodeBuilder {
         BlockGen(Builder, LI, SE, DT, ScalarMap, EscapeMap, ValueMap,
                  &ExprBuilder, StartBlock),
         RegionGen(BlockGen), DL(DL), LI(LI), SE(SE), DT(DT),
-        StartBlock(StartBlock) {}
+        StartBlock(StartBlock), GenDT(&DT), GenLI(&LI), GenSE(&SE) {}
 
   virtual ~IslNodeBuilder() = default;
 
@@ -147,6 +147,13 @@ class IslNodeBuilder {
   DominatorTree &DT;
   BasicBlock *StartBlock;
 
+  /// Relates to the region where the code is emitted into.
+  /// @{
+  DominatorTree *GenDT;
+  LoopInfo *GenLI;
+  ScalarEvolution *GenSE;
+  /// @}
+
   /// The current iteration of out-of-scop loops
   ///
   /// This map provides for a given loop a llvm::Value that contains the current
@@ -246,18 +253,6 @@ class IslNodeBuilder {
                               SetVector<Value *> &Values,
                               SetVector<const Loop *> &Loops);
 
-  /// Change the llvm::Value(s) used for code generation.
-  ///
-  /// When generating code certain values (e.g., references to induction
-  /// variables or array base pointers) in the original code may be replaced by
-  /// new values. This function allows to (partially) update the set of values
-  /// used. A typical use case for this function is the case when we continue
-  /// code generation in a subfunction/kernel function and need to explicitly
-  /// pass down certain values.
-  ///
-  /// @param NewValues A map that maps certain llvm::Values to new llvm::Values.
-  void updateValues(ValueMapT &NewValues);
-
   /// Return the most up-to-date version of the llvm::Value for code generation.
   /// @param Original The Value to check for an up to date version.
   /// @returns A remapped `Value` from ValueMap, or `Original` if no mapping

polly/include/polly/CodeGen/LoopGenerators.h

@@ -55,7 +55,7 @@ extern int PollyChunkSize;
 /// @param Builder            The builder used to create the loop.
 /// @param P                  A pointer to the pass that uses this function.
 ///                           It is used to update analysis information.
-/// @param LI                 The loop info for the current function
+/// @param LI                 The loop info we need to update
 /// @param DT                 The dominator tree we need to update
 /// @param ExitBlock          The block the loop will exit to.
 /// @param Predicate          The predicate used to generate the upper loop
@@ -128,11 +128,9 @@ llvm::DebugLoc createDebugLocForGeneratedCode(Function *F);
 class ParallelLoopGenerator {
 public:
   /// Create a parallel loop generator for the current function.
-  ParallelLoopGenerator(PollyIRBuilder &Builder, LoopInfo &LI,
-                        DominatorTree &DT, const DataLayout &DL)
-      : Builder(Builder), LI(LI), DT(DT),
-        LongType(
-            Type::getIntNTy(Builder.getContext(), DL.getPointerSizeInBits())),
+  ParallelLoopGenerator(PollyIRBuilder &Builder, const DataLayout &DL)
+      : Builder(Builder), LongType(Type::getIntNTy(Builder.getContext(),
+                                                   DL.getPointerSizeInBits())),
         M(Builder.GetInsertBlock()->getParent()->getParent()),
         DLGenerated(createDebugLocForGeneratedCode(
             Builder.GetInsertBlock()->getParent())) {}
@@ -164,11 +162,11 @@ class ParallelLoopGenerator {
   /// The IR builder we use to create instructions.
   PollyIRBuilder &Builder;
 
-  /// The loop info of the current function we need to update.
-  LoopInfo &LI;
+  /// The loop info for the generated subfunction.
+  std::unique_ptr<LoopInfo> SubFnLI;
 
-  /// The dominance tree of the current function we need to update.
-  DominatorTree &DT;
+  /// The dominance tree for the generated subfunction.
+  std::unique_ptr<DominatorTree> SubFnDT;
 
   /// The type of a "long" on this hardware used for backend calls.
   Type *LongType;
@@ -184,6 +182,12 @@ class ParallelLoopGenerator {
   llvm::DebugLoc DLGenerated;
 
 public:
+  /// Returns the DominatorTree for the generated subfunction.
+  DominatorTree *getCalleeDominatorTree() const { return SubFnDT.get(); }
+
+  /// Returns the LoopInfo for the generated subfunction.
+  LoopInfo *getCalleeLoopInfo() const { return SubFnLI.get(); }
+
   /// Create a struct for all @p Values and store them in there.
   ///
   /// @param Values The values which should be stored in the struct.

polly/include/polly/CodeGen/LoopGeneratorsGOMP.h

@@ -25,9 +25,8 @@ namespace polly {
 class ParallelLoopGeneratorGOMP final : public ParallelLoopGenerator {
 public:
   /// Create a parallel loop generator for the current function.
-  ParallelLoopGeneratorGOMP(PollyIRBuilder &Builder, LoopInfo &LI,
-                            DominatorTree &DT, const DataLayout &DL)
-      : ParallelLoopGenerator(Builder, LI, DT, DL) {}
+  ParallelLoopGeneratorGOMP(PollyIRBuilder &Builder, const DataLayout &DL)
+      : ParallelLoopGenerator(Builder, DL) {}
 
   // The functions below may be used if one does not want to generate a
   // specific OpenMP parallel loop, but generate individual parts of it

polly/include/polly/CodeGen/LoopGeneratorsKMP.h

@@ -27,9 +27,8 @@ using llvm::GlobalVariable;
 class ParallelLoopGeneratorKMP final : public ParallelLoopGenerator {
 public:
   /// Create a parallel loop generator for the current function.
-  ParallelLoopGeneratorKMP(PollyIRBuilder &Builder, LoopInfo &LI,
-                           DominatorTree &DT, const DataLayout &DL)
-      : ParallelLoopGenerator(Builder, LI, DT, DL) {
+  ParallelLoopGeneratorKMP(PollyIRBuilder &Builder, const DataLayout &DL)
+      : ParallelLoopGenerator(Builder, DL) {
     SourceLocationInfo = createSourceLocation();
   }
 

polly/include/polly/Support/ScopHelper.h

@@ -36,6 +36,9 @@ namespace polly {
 class Scop;
 class ScopStmt;
 
+/// Same as llvm/Analysis/ScalarEvolutionExpressions.h
+using LoopToScevMapT = llvm::DenseMap<const llvm::Loop *, const llvm::SCEV *>;
+
 /// Enumeration of assumptions Polly can take.
 enum AssumptionKind {
   ALIASING,
@@ -383,20 +386,24 @@ void splitEntryBlockForAlloca(llvm::BasicBlock *EntryBlock,
 /// as the call to SCEVExpander::expandCodeFor:
 ///
 /// @param S     The current Scop.
-/// @param SE    The Scalar Evolution pass.
+/// @param SE    The Scalar Evolution pass used by @p S.
+/// @param GenFn The function to generate code in. Can be the same as @p SE.
+/// @param GenSE The Scalar Evolution pass for @p GenFn.
 /// @param DL    The module data layout.
 /// @param Name  The suffix added to the new instruction names.
 /// @param E     The expression for which code is actually generated.
 /// @param Ty    The type of the resulting code.
 /// @param IP    The insertion point for the new code.
 /// @param VMap  A remapping of values used in @p E.
+/// @param LoopMap A remapping of loops used in @p E.
 /// @param RTCBB The last block of the RTC. Used to insert loop-invariant
 ///              instructions in rare cases.
 llvm::Value *expandCodeFor(Scop &S, llvm::ScalarEvolution &SE,
+                           llvm::Function *GenFn, llvm::ScalarEvolution &GenSE,
                            const llvm::DataLayout &DL, const char *Name,
                            const llvm::SCEV *E, llvm::Type *Ty,
                            llvm::Instruction *IP, ValueMapT *VMap,
-                           llvm::BasicBlock *RTCBB);
+                           LoopToScevMapT *LoopMap, llvm::BasicBlock *RTCBB);
 
 /// Return the condition for the terminator @p TI.
 ///

polly/lib/CodeGen/BlockGenerators.cpp

@@ -57,8 +57,8 @@ BlockGenerator::BlockGenerator(
     PollyIRBuilder &B, LoopInfo &LI, ScalarEvolution &SE, DominatorTree &DT,
     AllocaMapTy &ScalarMap, EscapeUsersAllocaMapTy &EscapeMap,
     ValueMapT &GlobalMap, IslExprBuilder *ExprBuilder, BasicBlock *StartBlock)
-    : Builder(B), LI(LI), SE(SE), ExprBuilder(ExprBuilder), DT(DT),
-      EntryBB(nullptr), ScalarMap(ScalarMap), EscapeMap(EscapeMap),
+    : Builder(B), LI(LI), SE(SE), ExprBuilder(ExprBuilder), DT(DT), GenDT(&DT),
+      GenLI(&LI), GenSE(&SE), ScalarMap(ScalarMap), EscapeMap(EscapeMap),
       GlobalMap(GlobalMap), StartBlock(StartBlock) {}
 
 Value *BlockGenerator::trySynthesizeNewValue(ScopStmt &Stmt, Value *Old,
@@ -75,7 +75,6 @@ Value *BlockGenerator::trySynthesizeNewValue(ScopStmt &Stmt, Value *Old,
   if (isa<SCEVCouldNotCompute>(Scev))
     return nullptr;
 
-  const SCEV *NewScev = SCEVLoopAddRecRewriter::rewrite(Scev, LTS, SE);
   ValueMapT VTV;
   VTV.insert(BBMap.begin(), BBMap.end());
   VTV.insert(GlobalMap.begin(), GlobalMap.end());
@@ -86,9 +85,9 @@ Value *BlockGenerator::trySynthesizeNewValue(ScopStmt &Stmt, Value *Old,
 
   assert(IP != Builder.GetInsertBlock()->end() &&
          "Only instructions can be insert points for SCEVExpander");
-  Value *Expanded =
-      expandCodeFor(S, SE, DL, "polly", NewScev, Old->getType(), &*IP, &VTV,
-                    StartBlock->getSinglePredecessor());
+  Value *Expanded = expandCodeFor(
+      S, SE, Builder.GetInsertBlock()->getParent(), *GenSE, DL, "polly", Scev,
+      Old->getType(), &*IP, &VTV, &LTS, StartBlock->getSinglePredecessor());
 
   BBMap[Old] = Expanded;
   return Expanded;
@@ -233,6 +232,8 @@ void BlockGenerator::copyInstScalar(ScopStmt &Stmt, Instruction *Inst,
       return;
     }
 
+    // FIXME: We will encounter "NewOperand" again if used twice. getNewValue()
+    // is meant to be called on old values only.
     NewInst->replaceUsesOfWith(OldOperand, NewOperand);
   }
 
@@ -410,7 +411,7 @@ void BlockGenerator::copyStmt(ScopStmt &Stmt, LoopToScevMapT &LTS,
 
 BasicBlock *BlockGenerator::splitBB(BasicBlock *BB) {
   BasicBlock *CopyBB = SplitBlock(Builder.GetInsertBlock(),
-                                  &*Builder.GetInsertPoint(), &DT, &LI);
+                                  &*Builder.GetInsertPoint(), GenDT, GenLI);
   CopyBB->setName("polly.stmt." + BB->getName());
   return CopyBB;
 }
@@ -431,11 +432,20 @@ BasicBlock *BlockGenerator::copyBB(ScopStmt &Stmt, BasicBlock *BB,
   return CopyBB;
 }
 
+void BlockGenerator::switchGeneratedFunc(Function *GenFn, DominatorTree *GenDT,
+                                         LoopInfo *GenLI,
+                                         ScalarEvolution *GenSE) {
+  assert(GenFn == GenDT->getRoot()->getParent());
+  assert(GenLI->getTopLevelLoops().empty() ||
+         GenFn == GenLI->getTopLevelLoops().front()->getHeader()->getParent());
+  this->GenDT = GenDT;
+  this->GenLI = GenLI;
+  this->GenSE = GenSE;
+}
+
 void BlockGenerator::copyBB(ScopStmt &Stmt, BasicBlock *BB, BasicBlock *CopyBB,
                             ValueMapT &BBMap, LoopToScevMapT &LTS,
                             isl_id_to_ast_expr *NewAccesses) {
-  EntryBB = &CopyBB->getParent()->getEntryBlock();
-
   // Block statements and the entry blocks of region statement are code
   // generated from instruction lists. This allow us to optimize the
   // instructions that belong to a certain scop statement. As the code
@@ -497,7 +507,7 @@ Value *BlockGenerator::getOrCreateAlloca(const ScopArrayInfo *Array) {
   Addr =
       new AllocaInst(Ty, DL.getAllocaAddrSpace(), nullptr,
                      DL.getPrefTypeAlign(Ty), ScalarBase->getName() + NameExt);
-  EntryBB = &Builder.GetInsertBlock()->getParent()->getEntryBlock();
+  BasicBlock *EntryBB = &Builder.GetInsertBlock()->getParent()->getEntryBlock();
   Addr->insertBefore(&*EntryBB->getFirstInsertionPt());
 
   return Addr;
@@ -554,10 +564,6 @@ void BlockGenerator::generateScalarLoads(
 
     auto *Address =
         getImplicitAddress(*MA, getLoopForStmt(Stmt), LTS, BBMap, NewAccesses);
-    assert((!isa<Instruction>(Address) ||
-            DT.dominates(cast<Instruction>(Address)->getParent(),
-                         Builder.GetInsertBlock())) &&
-           "Domination violation");
     BBMap[MA->getAccessValue()] = Builder.CreateLoad(
         MA->getElementType(), Address, Address->getName() + ".reload");
   }
@@ -615,9 +621,9 @@ void BlockGenerator::generateConditionalExecution(
   StringRef BlockName = HeadBlock->getName();
 
   // Generate the conditional block.
-  DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
+  DomTreeUpdater DTU(GenDT, DomTreeUpdater::UpdateStrategy::Eager);
   SplitBlockAndInsertIfThen(Cond, &*Builder.GetInsertPoint(), false, nullptr,
-                            &DTU, &LI);
+                            &DTU, GenLI);
   BranchInst *Branch = cast<BranchInst>(HeadBlock->getTerminator());
   BasicBlock *ThenBlock = Branch->getSuccessor(0);
   BasicBlock *TailBlock = Branch->getSuccessor(1);

polly/lib/CodeGen/IslExprBuilder.cpp

@@ -42,10 +42,23 @@ IslExprBuilder::IslExprBuilder(Scop &S, PollyIRBuilder &Builder,
                                DominatorTree &DT, LoopInfo &LI,
                                BasicBlock *StartBlock)
     : S(S), Builder(Builder), IDToValue(IDToValue), GlobalMap(GlobalMap),
-      DL(DL), SE(SE), DT(DT), LI(LI), StartBlock(StartBlock) {
+      DL(DL), SE(SE), StartBlock(StartBlock), GenDT(&DT), GenLI(&LI),
+      GenSE(&SE) {
   OverflowState = (OTMode == OT_ALWAYS) ? Builder.getFalse() : nullptr;
 }
 
+void IslExprBuilder::switchGeneratedFunc(llvm::Function *GenFn,
+                                         llvm::DominatorTree *GenDT,
+                                         llvm::LoopInfo *GenLI,
+                                         llvm::ScalarEvolution *GenSE) {
+  assert(GenFn == GenDT->getRoot()->getParent());
+  assert(GenLI->getTopLevelLoops().empty() ||
+         GenFn == GenLI->getTopLevelLoops().front()->getHeader()->getParent());
+  this->GenDT = GenDT;
+  this->GenLI = GenLI;
+  this->GenSE = GenSE;
+}
+
 void IslExprBuilder::setTrackOverflow(bool Enable) {
   // If potential overflows are tracked always or never we ignore requests
   // to change the behavior.
@@ -307,14 +320,12 @@ IslExprBuilder::createAccessAddress(__isl_take isl_ast_expr *Expr) {
 
     const SCEV *DimSCEV = SAI->getDimensionSize(u);
 
-    llvm::ValueToSCEVMapTy Map;
-    for (auto &KV : GlobalMap)
-      Map[KV.first] = SE.getSCEV(KV.second);
-    DimSCEV = SCEVParameterRewriter::rewrite(DimSCEV, SE, Map);
-    Value *DimSize =
-        expandCodeFor(S, SE, DL, "polly", DimSCEV, DimSCEV->getType(),
-                      &*Builder.GetInsertPoint(), nullptr,
-                      StartBlock->getSinglePredecessor());
+    // DimSize should be invariant to the SCoP, so no BBMap nor LoopToScev
+    // needed. But GlobalMap may contain SCoP-invariant vars.
+    Value *DimSize = expandCodeFor(
+        S, SE, Builder.GetInsertBlock()->getParent(), *GenSE, DL, "polly",
+        DimSCEV, DimSCEV->getType(), &*Builder.GetInsertPoint(), &GlobalMap,
+        /*LoopMap*/ nullptr, StartBlock->getSinglePredecessor());
 
     Type *Ty = getWidestType(DimSize->getType(), IndexOp->getType());
 
@@ -602,10 +613,10 @@ IslExprBuilder::createOpBooleanConditional(__isl_take isl_ast_expr *Expr) {
 
   auto InsertBB = Builder.GetInsertBlock();
   auto InsertPoint = Builder.GetInsertPoint();
-  auto NextBB = SplitBlock(InsertBB, &*InsertPoint, &DT, &LI);
+  auto NextBB = SplitBlock(InsertBB, &*InsertPoint, GenDT, GenLI);
   BasicBlock *CondBB = BasicBlock::Create(Context, "polly.cond", F);
-  LI.changeLoopFor(CondBB, LI.getLoopFor(InsertBB));
-  DT.addNewBlock(CondBB, InsertBB);
+  GenLI->changeLoopFor(CondBB, GenLI->getLoopFor(InsertBB));
+  GenDT->addNewBlock(CondBB, InsertBB);
 
   InsertBB->getTerminator()->eraseFromParent();
   Builder.SetInsertPoint(InsertBB);