[PATCH] D81236: Correctly report modified status for LoopExtractor

[serge via Phabricator via llvm-commits]

serge-sans-paille created this revision.
serge-sans-paille added reviewers: ekatz, nikic, foad, jdoerfert.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

Related to https://reviews.llvm.org/D80916

Surprisingly, retrieving the analysis triggers a normalization step that may modify the BB graph (through the addition of a dummy exit BB)


https://reviews.llvm.org/D81236

Files:
  llvm/lib/Transforms/IPO/LoopExtractor.cpp


Index: llvm/lib/Transforms/IPO/LoopExtractor.cpp
===================================================================
--- llvm/lib/Transforms/IPO/LoopExtractor.cpp
+++ llvm/lib/Transforms/IPO/LoopExtractor.cpp
@@ -131,18 +131,24 @@
   if (F.empty())
     return false;
 
+  unsigned BBCount = F.size();
   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>(F).getLoopInfo();
 
+  // This is only needed because of a violation of the analysis contract:
+  // LoopInfoWrapperPass normalizes the loop which may lead to code change
+  bool Modified = BBCount != F.size();
+
   // If there are no loops in the function.
   if (LI.empty())
-    return false;
+    return Modified;
 
   DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
 
   // If there is more than one top-level loop in this function, extract all of
   // the loops.
   if (std::next(LI.begin()) != LI.end())
-    return extractLoops(LI.begin(), LI.end(), LI, DT);
+    return Modified | extractLoops(LI.begin(), LI.end(), LI, DT);
+
 
   // Otherwise there is exactly one top-level loop.
   Loop *TLL = *LI.begin();
@@ -171,14 +177,14 @@
     }
 
     if (ShouldExtractLoop)
-      return extractLoop(TLL, LI, DT);
+      return Modified | extractLoop(TLL, LI, DT);
   }
 
   // Okay, this function is a minimal container around the specified loop.
   // If we extract the loop, we will continue to just keep extracting it
   // infinitely... so don't extract it. However, if the loop contains any
   // sub-loops, extract them.
-  return extractLoops(TLL->begin(), TLL->end(), LI, DT);
+  return Modified | extractLoops(TLL->begin(), TLL->end(), LI, DT);
 }
 
 bool LoopExtractor::extractLoops(Loop::iterator From, Loop::iterator To,


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