[PATCH] D132199: [LoopPassManager] Ensure to construct loop nests with the outermost loop

[Congzhe Cao via Phabricator via llvm-commits]

congzhe updated this revision to Diff 457680.
congzhe added a comment.

Rebased on D132581 <https://reviews.llvm.org/D132581>.

This update is not a final version but is posted for review and discussion. Subtleties can be discussed upon, e.g., whether it is necessary to interact with the LPM::Updater, etc. Comments are appreciated :)


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132199/new/

https://reviews.llvm.org/D132199

Files:
  llvm/include/llvm/Transforms/Scalar/LoopPassManager.h
  llvm/lib/Transforms/Scalar/LoopInterchange.cpp
  llvm/lib/Transforms/Scalar/LoopPassManager.cpp


Index: llvm/lib/Transforms/Scalar/LoopPassManager.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopPassManager.cpp
+++ llvm/lib/Transforms/Scalar/LoopPassManager.cpp
@@ -78,6 +78,8 @@
 
   unsigned LoopPassIndex = 0, LoopNestPassIndex = 0;
 
+  Loop *OuterMostLoop = &L;
+
   for (size_t I = 0, E = IsLoopNestPass.size(); I != E; ++I) {
     Optional<PreservedAnalyses> PassPA;
     if (!IsLoopNestPass[I]) {
@@ -87,9 +89,17 @@
     } else {
       // The `I`-th pass is a loop-nest pass.
       auto &Pass = LoopNestPasses[LoopNestPassIndex++];
-
-      LoopNest &LN = AM.getResult<LoopNestAnalysis>(L, AR);
+      assert(OuterMostLoop->isOutermost() &&
+             "LoopNest should be constructed only with the outermost loop!");
+      LoopNest &LN = AM.getResult<LoopNestAnalysis>(*OuterMostLoop, AR);
       PassPA = runSinglePass(LN, Pass, AM, AR, U, PI);
+
+      // Restore the correct loopnest status.
+      if (U.isLoopNestChanged()) {
+        while (auto *PL = OuterMostLoop->getParentLoop())
+          OuterMostLoop = PL;
+        U.markLoopNestChanged(false);
+      }
     }
 
     // `PassPA` is `None` means that the before-pass callbacks in
Index: llvm/lib/Transforms/Scalar/LoopInterchange.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -44,6 +44,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Scalar/LoopPassManager.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/LoopUtils.h"
 #include <cassert>
@@ -1766,5 +1767,6 @@
   OptimizationRemarkEmitter ORE(&F);
   if (!LoopInterchange(&AR.SE, &AR.LI, &DI, &AR.DT, CC, &ORE).run(LN))
     return PreservedAnalyses::all();
+  U.markLoopNestChanged(true);
   return getLoopPassPreservedAnalyses();
 }
Index: llvm/include/llvm/Transforms/Scalar/LoopPassManager.h
===================================================================
--- llvm/include/llvm/Transforms/Scalar/LoopPassManager.h
+++ llvm/include/llvm/Transforms/Scalar/LoopPassManager.h
@@ -356,6 +356,14 @@
     Worklist.insert(CurrentL);
   }
 
+  bool isLoopNestChanged() const {
+    return LoopNestChanged;
+  }
+
+  void markLoopNestChanged(bool Changed) {
+    LoopNestChanged = Changed;
+  }
+
 private:
   friend class llvm::FunctionToLoopPassAdaptor;
 
@@ -368,6 +376,7 @@
   Loop *CurrentL;
   bool SkipCurrentLoop;
   const bool LoopNestMode;
+  bool LoopNestChanged;
 
 #ifdef LLVM_ENABLE_ABI_BREAKING_CHECKS
   // In debug builds we also track the parent loop to implement asserts even in
@@ -376,8 +385,10 @@
 #endif
 
   LPMUpdater(SmallPriorityWorklist<Loop *, 4> &Worklist,
-             LoopAnalysisManager &LAM, bool LoopNestMode = false)
-      : Worklist(Worklist), LAM(LAM), LoopNestMode(LoopNestMode) {}
+             LoopAnalysisManager &LAM, bool LoopNestMode = false,
+             bool LoopNestChanged = false)
+      : Worklist(Worklist), LAM(LAM), LoopNestMode(LoopNestMode),
+        LoopNestChanged(LoopNestChanged) {}
 };
 
 template <typename IRUnitT, typename PassT>


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