[llvm-commits] CVS: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

[Chris Lattner]

Changes in directory llvm/lib/CodeGen/SelectionDAG:

DAGCombiner.cpp updated: 1.308 -> 1.309
---
Log message:

prevent exponential recursion in isNegatibleForFree


---
Diffs of the changes:  (+9 -6)

 DAGCombiner.cpp |   15 +++++++++------
 1 files changed, 9 insertions(+), 6 deletions(-)


Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.308 
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.309
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.308 Fri May 18 13:41:29 2007
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp       Wed May 23 02:35:22 2007
@@ -352,7 +352,10 @@
 /// isNegatibleForFree - Return 1 if we can compute the negated form of the
 /// specified expression for the same cost as the expression itself, or 2 if we
 /// can compute the negated form more cheaply than the expression itself.
-static char isNegatibleForFree(SDOperand Op) {
+static char isNegatibleForFree(SDOperand Op, unsigned Depth = 0) {
+  // Don't recurse exponentially.
+  if (Depth > 6) return false;
+  
   // fneg is removable even if it has multiple uses.
   if (Op.getOpcode() == ISD::FNEG) return 2;
   
@@ -368,10 +371,10 @@
     if (!UnsafeFPMath) return 0;
     
     // -(A+B) -> -A - B
-    if (char V = isNegatibleForFree(Op.getOperand(0)))
+    if (char V = isNegatibleForFree(Op.getOperand(0), Depth+1))
       return V;
     // -(A+B) -> -B - A
-    return isNegatibleForFree(Op.getOperand(1));
+    return isNegatibleForFree(Op.getOperand(1), Depth+1);
   case ISD::FSUB:
     // We can't turn -(A-B) into B-A when we honor signed zeros. 
     if (!UnsafeFPMath) return 0;
@@ -384,15 +387,15 @@
     if (HonorSignDependentRoundingFPMath()) return 0;
     
     // -(X*Y) -> (-X * Y) or (X*-Y)
-    if (char V = isNegatibleForFree(Op.getOperand(0)))
+    if (char V = isNegatibleForFree(Op.getOperand(0), Depth+1))
       return V;
       
-    return isNegatibleForFree(Op.getOperand(1));
+    return isNegatibleForFree(Op.getOperand(1), Depth+1);
     
   case ISD::FP_EXTEND:
   case ISD::FP_ROUND:
   case ISD::FSIN:
-    return isNegatibleForFree(Op.getOperand(0));
+    return isNegatibleForFree(Op.getOperand(0), Depth+1);
   }
 }
 



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