STATISTIC(NumRemoved, "Number of unreachable basic blocks removed");
+// Max recursion depth for collectBitParts used when detecting bswap and
+// bitreverse idioms
+static const unsigned BitPartRecursionMaxDepth = 64;
+
//===----------------------------------------------------------------------===//
// Local constant propagation.
//
/// does not invalidate internal references (std::map instead of DenseMap).
static const Optional<BitPart> &
collectBitParts(Value *V, bool MatchBSwaps, bool MatchBitReversals,
- std::map<Value *, Optional<BitPart>> &BPS) {
+ std::map<Value *, Optional<BitPart>> &BPS, int Depth) {
auto I = BPS.find(V);
if (I != BPS.end())
return I->second;
auto &Result = BPS[V] = None;
auto BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
+ // Prevent stack overflow by limiting the recursion depth
+ if (Depth == BitPartRecursionMaxDepth) {
+ LLVM_DEBUG(dbgs() << "collectBitParts max recursion depth reached.\n");
+ return Result;
+ }
+
if (Instruction *I = dyn_cast<Instruction>(V)) {
// If this is an or instruction, it may be an inner node of the bswap.
if (I->getOpcode() == Instruction::Or) {
auto &A = collectBitParts(I->getOperand(0), MatchBSwaps,
- MatchBitReversals, BPS);
+ MatchBitReversals, BPS, Depth + 1);
auto &B = collectBitParts(I->getOperand(1), MatchBSwaps,
- MatchBitReversals, BPS);
+ MatchBitReversals, BPS, Depth + 1);
if (!A || !B)
return Result;
return Result;
auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
- MatchBitReversals, BPS);
+ MatchBitReversals, BPS, Depth + 1);
if (!Res)
return Result;
Result = Res;
return Result;
auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
- MatchBitReversals, BPS);
+ MatchBitReversals, BPS, Depth + 1);
if (!Res)
return Result;
Result = Res;
// If this is a zext instruction zero extend the result.
if (I->getOpcode() == Instruction::ZExt) {
auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
- MatchBitReversals, BPS);
+ MatchBitReversals, BPS, Depth + 1);
if (!Res)
return Result;
// Try to find all the pieces corresponding to the bswap.
std::map<Value *, Optional<BitPart>> BPS;
- auto Res = collectBitParts(I, MatchBSwaps, MatchBitReversals, BPS);
+ auto Res = collectBitParts(I, MatchBSwaps, MatchBitReversals, BPS, 0);
if (!Res)
return false;
auto &BitProvenance = Res->Provenance;