diff options
Diffstat (limited to 'lib/Transforms/Utils/SimplifyCFG.cpp')
| -rw-r--r-- | lib/Transforms/Utils/SimplifyCFG.cpp | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 3125a2c..e484b69 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -90,6 +90,11 @@ static cl::opt<bool> SpeculateOneExpensiveInst( cl::desc("Allow exactly one expensive instruction to be speculatively " "executed")); +static cl::opt<unsigned> MaxSpeculationDepth( + "max-speculation-depth", cl::Hidden, cl::init(10), + cl::desc("Limit maximum recursion depth when calculating costs of " + "speculatively executed instructions")); + STATISTIC(NumBitMaps, "Number of switch instructions turned into bitmaps"); STATISTIC(NumLinearMaps, "Number of switch instructions turned into linear mapping"); STATISTIC(NumLookupTables, "Number of switch instructions turned into lookup tables"); @@ -269,6 +274,13 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB, unsigned &CostRemaining, const TargetTransformInfo &TTI, unsigned Depth = 0) { + // It is possible to hit a zero-cost cycle (phi/gep instructions for example), + // so limit the recursion depth. + // TODO: While this recursion limit does prevent pathological behavior, it + // would be better to track visited instructions to avoid cycles. + if (Depth == MaxSpeculationDepth) + return false; + Instruction *I = dyn_cast<Instruction>(V); if (!I) { // Non-instructions all dominate instructions, but not all constantexprs |
