[llvm-commits] CVS: llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp

[Chris Lattner]

Changes in directory llvm/lib/Transforms/Utils:

BreakCriticalEdges.cpp updated: 1.27 -> 1.28
---
Log message:

Teach SplitCriticalEdge to update LoopInfo if it is alive.  This fixes
a problem in LoopStrengthReduction, where it would split critical edges
then confused itself with outdated loop information.


---
Diffs of the changes:  (+31 -0)

 BreakCriticalEdges.cpp |   31 +++++++++++++++++++++++++++++++
 1 files changed, 31 insertions(+)


Index: llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp
diff -u llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp:1.27 llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp:1.28
--- llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp:1.27	Fri Aug 12 16:58:07 2005
+++ llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp	Fri Aug 12 20:38:43 2005
@@ -19,6 +19,7 @@
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Function.h"
 #include "llvm/Instructions.h"
 #include "llvm/Type.h"
@@ -37,6 +38,7 @@
       AU.addPreserved<ImmediateDominators>();
       AU.addPreserved<DominatorTree>();
       AU.addPreserved<DominanceFrontier>();
+      AU.addPreserved<LoopInfo>();
 
       // No loop canonicalization guarantees are broken by this pass.
       AU.addPreservedID(LoopSimplifyID);
@@ -171,5 +173,34 @@
     NewDFSet.insert(DestBB);
     DF->addBasicBlock(NewBB, NewDFSet);
   }
+  
+  // Update LoopInfo if it is around.
+  if (LoopInfo *LI = P->getAnalysisToUpdate<LoopInfo>()) {
+    // If one or the other blocks were not in a loop, the new block is not
+    // either, and thus LI doesn't need to be updated.
+    if (Loop *TIL = LI->getLoopFor(TIBB))
+      if (Loop *DestLoop = LI->getLoopFor(DestBB)) {
+        if (TIL == DestLoop) {
+          // Both in the same loop, the NewBB joins loop.
+          DestLoop->addBasicBlockToLoop(NewBB, *LI);
+        } else if (TIL->contains(DestLoop->getHeader())) {
+          // Edge from an outer loop to an inner loop.  Add to the outer lopo.
+          TIL->addBasicBlockToLoop(NewBB, *LI);
+        } else if (DestLoop->contains(TIL->getHeader())) {
+          // Edge from an inner loop to an outer loop.  Add to the outer lopo.
+          DestLoop->addBasicBlockToLoop(NewBB, *LI);
+        } else {
+          // Edge from two loops with no containment relation.  Because these
+          // are natural loops, we know that the destination block must be the
+          // header of its loop (adding a branch into a loop elsewhere would
+          // create an irreducible loop).
+          assert(DestLoop->getHeader() == DestBB &&
+                 "Should not create irreducible loops!");
+          if (Loop *P = DestLoop->getParentLoop())
+            P->addBasicBlockToLoop(NewBB, *LI);
+        }
+      }
+    
+  }
   return true;
 }