From 501fee71e077aad705ab2ab86741aec15b779174 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Wed, 23 May 2007 07:35:22 +0000 Subject: [PATCH] prevent exponential recursion in isNegatibleForFree git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37310 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 58023105f10..05000115417 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -352,7 +352,10 @@ CombineTo(SDNode *N, SDOperand Res0, SDOperand Res1) { /// 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 @@ static char isNegatibleForFree(SDOperand Op) { 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 @@ static char isNegatibleForFree(SDOperand Op) { 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); } } -- 2.34.1