[llvm-commits] CVS: llvm/lib/Analysis/ScalarEvolution.cpp

[Chris Lattner]

Changes in directory llvm/lib/Analysis:

ScalarEvolution.cpp updated: 1.79 -> 1.80
---
Log message:

Fix PR1015: http://llvm.org/PR1015  and Transforms/IndVarsSimplify/2007-01-06-TripCount.ll, a
miscompilation of Qt.


---
Diffs of the changes:  (+15 -1)

 ScalarEvolution.cpp |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletion(-)


Index: llvm/lib/Analysis/ScalarEvolution.cpp
diff -u llvm/lib/Analysis/ScalarEvolution.cpp:1.79 llvm/lib/Analysis/ScalarEvolution.cpp:1.80
--- llvm/lib/Analysis/ScalarEvolution.cpp:1.79	Sat Jan  6 20:05:20 2007
+++ llvm/lib/Analysis/ScalarEvolution.cpp	Sat Jan  6 20:24:26 2007
@@ -1498,12 +1498,26 @@
   BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
   if (ExitBr == 0) return UnknownValue;
   assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
+  
+  // At this point, we know we have a conditional branch that determines whether
+  // the loop is exited.  However, we don't know if the branch is executed each
+  // time through the loop.  If not, then the execution count of the branch will
+  // not be equal to the trip count of the loop.
+  //
+  // Currently we check for this by checking to see if the Exit branch goes to
+  // the loop header.  If so, we know it will always execute the same number of
+  // times as the loop.  More extensive analysis could be done to handle more
+  // cases here.
+  if (ExitBr->getSuccessor(0) != L->getHeader() &&
+      ExitBr->getSuccessor(1) != L->getHeader())
+    return UnknownValue;
+  
   ICmpInst *ExitCond = dyn_cast<ICmpInst>(ExitBr->getCondition());
 
   // If its not an integer comparison then compute it the hard way. 
   // Note that ICmpInst deals with pointer comparisons too so we must check
   // the type of the operand.
-  if (ExitCond == 0 || !ExitCond->getOperand(0)->getType()->isIntegral()) 
+  if (ExitCond == 0 || isa<PointerType>(ExitCond->getOperand(0)->getType()))
     return ComputeIterationCountExhaustively(L, ExitBr->getCondition(),
                                           ExitBr->getSuccessor(0) == ExitBlock);