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//===-- Analysis/EHUtils.h - Exception handling related utils --*-//C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
#ifndef LLVM_ANALYSIS_EHUTILS_H
#define LLVM_ANALYSIS_EHUTILS_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
namespace llvm {
/// Compute a list of blocks that are only reachable via EH paths.
template <typename FunctionT, typename BlockT>
static void computeEHOnlyBlocks(FunctionT &F, DenseSet<BlockT *> &EHBlocks) {
// A block can be unknown if its not reachable from anywhere
// EH if its only reachable from start blocks via some path through EH pads
// NonEH if it's reachable from Non EH blocks as well.
enum Status { Unknown = 0, EH = 1, NonEH = 2 };
DenseSet<BlockT *> WorkList;
DenseMap<BlockT *, Status> Statuses;
auto GetStatus = [&](BlockT *BB) {
if (Statuses.contains(BB))
return Statuses[BB];
else
return Unknown;
};
auto CheckPredecessors = [&](BlockT *BB, Status Stat) {
for (auto *PredBB : predecessors(BB)) {
Status PredStatus = GetStatus(PredBB);
// If status of predecessor block has gone above current block
// we update current blocks status.
if (PredStatus > Stat)
Stat = PredStatus;
}
return Stat;
};
auto AddSuccesors = [&](BlockT *BB) {
for (auto *SuccBB : successors(BB)) {
if (!SuccBB->isEHPad())
WorkList.insert(SuccBB);
}
};
// Insert the successors of start block and landing pads successor.
BlockT *StartBlock = &F.front();
Statuses[StartBlock] = NonEH;
AddSuccesors(StartBlock);
for (auto &BB : F) {
if (BB.isEHPad()) {
AddSuccesors(&BB);
Statuses[&BB] = EH;
}
}
// Worklist iterative algorithm.
while (!WorkList.empty()) {
auto *BB = *WorkList.begin();
WorkList.erase(BB);
Status OldStatus = GetStatus(BB);
// Check on predecessors and check for
// Status update.
Status NewStatus = CheckPredecessors(BB, OldStatus);
// Did the block status change?
bool Changed = OldStatus != NewStatus;
if (Changed) {
AddSuccesors(BB);
Statuses[BB] = NewStatus;
}
}
for (auto Entry : Statuses) {
if (Entry.second == EH)
EHBlocks.insert(Entry.first);
}
}
} // namespace llvm
#endif
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