prevent exponential recursion in isNegatibleForFree
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37310 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 5802310..0500011 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -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);
}
}