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

[Chris Lattner]

Changes in directory llvm/lib/Transforms/Utils:

SimplifyCFG.cpp updated: 1.80 -> 1.81
---
Log message:

Finally, add the required constraint checks to fix  Transforms/SimplifyCFG/2005-08-01-PHIUpdateFail.ll
the right way


---
Diffs of the changes:  (+29 -2)

 SimplifyCFG.cpp |   31 +++++++++++++++++++++++++++++--
 1 files changed, 29 insertions(+), 2 deletions(-)


Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
diff -u llvm/lib/Transforms/Utils/SimplifyCFG.cpp:1.80 llvm/lib/Transforms/Utils/SimplifyCFG.cpp:1.81
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp:1.80	Tue Aug  2 19:38:27 2005
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp	Tue Aug  2 19:59:12 2005
@@ -98,8 +98,35 @@
         }
       }
   }
-
-  return true;
+    
+  // Finally, if BB has PHI nodes that are used by things other than the PHIs in
+  // Succ and Succ has predecessors that are not Succ and not Pred, we cannot
+  // fold these blocks, as we don't know whether BB dominates Succ or not to
+  // update the PHI nodes correctly.
+  if (!isa<PHINode>(BB->begin()) || Succ->getSinglePredecessor()) return true;
+
+  // If the predecessors of Succ are only BB and Succ itself, we can handle this.
+  bool IsSafe = true;
+  for (pred_iterator PI = pred_begin(Succ), E = pred_end(Succ); PI != E; ++PI)
+    if (*PI != Succ && *PI != BB) {
+      IsSafe = false;
+      break;
+    }
+  if (IsSafe) return true;
+  
+  // If the PHI nodes in BB are only used by instructions in Succ, we are ok.
+  IsSafe = true;
+  for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I) && IsSafe; ++I) {
+    PHINode *PN = cast<PHINode>(I);
+    for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E;
+         ++UI)
+      if (cast<Instruction>(*UI)->getParent() != Succ) {
+        IsSafe = false;
+        break;
+      }
+  }
+  
+  return IsSafe;
 }
 
 /// TryToSimplifyUncondBranchFromEmptyBlock - BB contains an unconditional