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

[Chris Lattner]

Changes in directory llvm/lib/Transforms/Utils:

SimplifyCFG.cpp updated: 1.97 -> 1.98
---
Log message:

Fix an infinite loop on Transforms/SimplifyCFG/2006-06-12-InfLoop.ll


---
Diffs of the changes:  (+10 -1)

 SimplifyCFG.cpp |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletion(-)


Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
diff -u llvm/lib/Transforms/Utils/SimplifyCFG.cpp:1.97 llvm/lib/Transforms/Utils/SimplifyCFG.cpp:1.98
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp:1.97	Sun May 14 13:45:44 2006
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp	Mon Jun 12 15:18:01 2006
@@ -1515,12 +1515,21 @@
               // keep getting unwound.
               if (PBIOp != -1 && PBI->getSuccessor(PBIOp) == BB)
                 PBIOp = BIOp = -1;
-              
+
               // Finally, if everything is ok, fold the branches to logical ops.
               if (PBIOp != -1) {
                 BasicBlock *CommonDest = PBI->getSuccessor(PBIOp);
                 BasicBlock *OtherDest  = BI->getSuccessor(BIOp ^ 1);
 
+                // If OtherDest *is* BB, then this is a basic block with just
+                // a conditional branch in it, where one edge (OtherDesg) goes
+                // back to the block.  We know that the program doesn't get
+                // stuck in the infinite loop, so the condition must be such
+                // that OtherDest isn't branched through. Forward to CommonDest,
+                // and avoid an infinite loop at optimizer time.
+                if (OtherDest == BB)
+                  OtherDest = CommonDest;
+                
                 DEBUG(std::cerr << "FOLDING BRs:" << *PBI->getParent()
                                 << "AND: " << *BI->getParent());