Revert "[polly] Fix ScopDetectionDiagnostic test failure caused by r310940"

This reverts commit 950849ece9bb8fdd2b41e3ec348b9653b4e37df6.

This commit broke various buildbots.

llvm-svn: 311692

polly/include/polly/ScopDetectionDiagnostic.h

@@ -86,6 +86,7 @@ enum class RejectReasonKind {
   LastAffFunc,
 
   LoopBound,
+  LoopHasNoExit,
   LoopOnlySomeLatches,
 
   FuncCall,
@@ -576,6 +577,36 @@ public:
   //@}
 };
 
+//===----------------------------------------------------------------------===//
+/// Captures errors when loop has no exit.
+class ReportLoopHasNoExit : public RejectReason {
+  //===--------------------------------------------------------------------===//
+
+  /// The loop that has no exit.
+  Loop *L;
+
+  const DebugLoc Loc;
+
+public:
+  ReportLoopHasNoExit(Loop *L)
+      : RejectReason(RejectReasonKind::LoopHasNoExit), L(L),
+        Loc(L->getStartLoc()) {}
+
+  /// @name LLVM-RTTI interface
+  //@{
+  static bool classof(const RejectReason *RR);
+  //@}
+
+  /// @name RejectReason interface
+  //@{
+  virtual std::string getRemarkName() const override;
+  virtual const Value *getRemarkBB() const override;
+  virtual std::string getMessage() const override;
+  virtual const DebugLoc &getDebugLoc() const override;
+  virtual std::string getEndUserMessage() const override;
+  //@}
+};
+
 //===----------------------------------------------------------------------===//
 /// Captures errors when not all loop latches are part of the scop.
 class ReportLoopOnlySomeLatches : public RejectReason {

polly/lib/Analysis/ScopDetection.cpp

@@ -1166,6 +1166,17 @@ bool ScopDetection::isValidInstruction(Instruction &Inst,
   return invalid<ReportUnknownInst>(Context, /*Assert=*/true, &Inst);
 }
 
+/// Check whether @p L has exiting blocks.
+///
+/// @param L The loop of interest
+///
+/// @return True if the loop has exiting blocks, false otherwise.
+static bool hasExitingBlocks(Loop *L) {
+  SmallVector<BasicBlock *, 4> ExitingBlocks;
+  L->getExitingBlocks(ExitingBlocks);
+  return !ExitingBlocks.empty();
+}
+
 bool ScopDetection::canUseISLTripCount(Loop *L,
                                        DetectionContext &Context) const {
   // Ensure the loop has valid exiting blocks as well as latches, otherwise we
@@ -1186,18 +1197,34 @@ bool ScopDetection::isValidLoop(Loop *L, DetectionContext &Context) const {
   // Loops that contain part but not all of the blocks of a region cannot be
   // handled by the schedule generation. Such loop constructs can happen
   // because a region can contain BBs that have no path to the exit block
-  // (infinite loops, UnreachableInst).
-  // We do not have to verify against infinite loops here -- they are
-  // postdominated only by the virtual exit and do not appear in regions.
-  // Instead of an infinite loop, a dead end can also be formed by an
-  // UnreachableInst. This case is already caught by isErrorBlock().
-
-#ifndef NDEBUG
-  // Make sure that the loop has exits (i.e. is not infinite).
-  SmallVector<BasicBlock *, 4> ExitingBlocks;
-  L->getExitingBlocks(ExitingBlocks);
-  assert(!ExitingBlocks.empty() && "Region with an infinite loop found!");
-#endif
+  // (Infinite loops, UnreachableInst), but such blocks are never part of a
+  // loop.
+  //
+  // _______________
+  // | Loop Header | <-----------.
+  // ---------------             |
+  //        |                    |
+  // _______________       ______________
+  // | RegionEntry |-----> | RegionExit |----->
+  // ---------------       --------------
+  //        |
+  // _______________
+  // | EndlessLoop | <--.
+  // ---------------    |
+  //       |            |
+  //       \------------/
+  //
+  // In the example above, the loop (LoopHeader,RegionEntry,RegionExit) is
+  // neither entirely contained in the region RegionEntry->RegionExit
+  // (containing RegionEntry,EndlessLoop) nor is the region entirely contained
+  // in the loop.
+  // The block EndlessLoop is contained in the region because Region::contains
+  // tests whether it is not dominated by RegionExit. This is probably to not
+  // having to query the PostdominatorTree. Instead of an endless loop, a dead
+  // end can also be formed by an UnreachableInst. This case is already caught
+  // by isErrorBlock(). We hence only have to reject endless loops here.
+  if (!hasExitingBlocks(L))
+    return invalid<ReportLoopHasNoExit>(Context, /*Assert=*/true, L);
 
   if (canUseISLTripCount(L, Context))
     return true;

polly/lib/Analysis/ScopDetectionDiagnostic.cpp

@@ -60,6 +60,7 @@ llvm::Statistic RejectStatistics[] = {
     SCOP_STAT(DifferentElementSize, "Accesses with differing sizes"),
     SCOP_STAT(LastAffFunc, ""),
     SCOP_STAT(LoopBound, "Uncomputable loop bounds"),
+    SCOP_STAT(LoopHasNoExit, "Loop without exit"),
     SCOP_STAT(LoopOnlySomeLatches, "Not all loop latches in scop"),
     SCOP_STAT(FuncCall, "Function call with side effects"),
     SCOP_STAT(NonSimpleMemoryAccess,
@@ -458,6 +459,29 @@ std::string ReportLoopBound::getEndUserMessage() const {
   return "Failed to derive an affine function from the loop bounds.";
 }
 
+//===----------------------------------------------------------------------===//
+// ReportLoopHasNoExit.
+
+std::string ReportLoopHasNoExit::getRemarkName() const {
+  return "LoopHasNoExit";
+}
+
+const Value *ReportLoopHasNoExit::getRemarkBB() const { return L->getHeader(); }
+
+std::string ReportLoopHasNoExit::getMessage() const {
+  return "Loop " + L->getHeader()->getName() + " has no exit.";
+}
+
+bool ReportLoopHasNoExit::classof(const RejectReason *RR) {
+  return RR->getKind() == RejectReasonKind::LoopHasNoExit;
+}
+
+const DebugLoc &ReportLoopHasNoExit::getDebugLoc() const { return Loc; }
+
+std::string ReportLoopHasNoExit::getEndUserMessage() const {
+  return "Loop cannot be handled because it has no exit.";
+}
+
 //===----------------------------------------------------------------------===//
 // ReportLoopOnlySomeLatches
 
@@ -475,7 +499,7 @@ std::string ReportLoopOnlySomeLatches::getMessage() const {
 }
 
 bool ReportLoopOnlySomeLatches::classof(const RejectReason *RR) {
-  return RR->getKind() == RejectReasonKind::LoopOnlySomeLatches;
+  return RR->getKind() == RejectReasonKind::LoopHasNoExit;
 }
 
 const DebugLoc &ReportLoopOnlySomeLatches::getDebugLoc() const { return Loc; }

polly/test/ScopDetectionDiagnostics/ReportLoopHasNoExit.ll

@@ -1,7 +1,7 @@
 ; XFAIL: *
 
 ; The test case stopped making sense after r310940 that added infinite loops to
-; the PostDominatorTree. Infinite loops are postdominated only by the virtual
+; the PostDominatorTree. Infinite loops are postdominated ony by the virtual
 ; root, which causes them not to appear in regions in ScopDetection anymore.
 
 ; RUN: opt %loadPolly -pass-remarks-missed="polly-detect" -polly-allow-nonaffine-loops -analyze  -polly-detect < %s 2>&1 | FileCheck %s