diff options
Diffstat (limited to 'lib/CodeGen/MachineSink.cpp')
| -rw-r--r-- | lib/CodeGen/MachineSink.cpp | 34 |
1 files changed, 19 insertions, 15 deletions
diff --git a/lib/CodeGen/MachineSink.cpp b/lib/CodeGen/MachineSink.cpp index ba25bca..8337793 100644 --- a/lib/CodeGen/MachineSink.cpp +++ b/lib/CodeGen/MachineSink.cpp @@ -112,7 +112,7 @@ namespace { /// for the lifetime of an iteration. /// /// \return True if the edge is marked as toSplit, false otherwise. - /// False can be retruned if, for instance, this is not profitable. + /// False can be returned if, for instance, this is not profitable. bool PostponeSplitCriticalEdge(MachineInstr *MI, MachineBasicBlock *From, MachineBasicBlock *To, @@ -504,7 +504,7 @@ bool MachineSinking::isProfitableToSinkTo(unsigned Reg, MachineInstr *MI, // If SuccToSinkTo post dominates then also it may be profitable if MI // can further profitably sinked into another block in next round. bool BreakPHIEdge = false; - // FIXME - If finding successor is compile time expensive then catch results. + // FIXME - If finding successor is compile time expensive then cache results. if (MachineBasicBlock *MBB2 = FindSuccToSinkTo(MI, SuccToSinkTo, BreakPHIEdge)) return isProfitableToSinkTo(Reg, MI, SuccToSinkTo, MBB2); @@ -553,19 +553,6 @@ MachineBasicBlock *MachineSinking::FindSuccToSinkTo(MachineInstr *MI, if (!TII->isSafeToMoveRegClassDefs(MRI->getRegClass(Reg))) return nullptr; - // FIXME: This picks a successor to sink into based on having one - // successor that dominates all the uses. However, there are cases where - // sinking can happen but where the sink point isn't a successor. For - // example: - // - // x = computation - // if () {} else {} - // use x - // - // the instruction could be sunk over the whole diamond for the - // if/then/else (or loop, etc), allowing it to be sunk into other blocks - // after that. - // Virtual register defs can only be sunk if all their uses are in blocks // dominated by one of the successors. if (SuccToSinkTo) { @@ -585,6 +572,23 @@ MachineBasicBlock *MachineSinking::FindSuccToSinkTo(MachineInstr *MI, // higher priority, otherwise prioritize smaller loop depths. SmallVector<MachineBasicBlock*, 4> Succs(MBB->succ_begin(), MBB->succ_end()); + + // Handle cases where sinking can happen but where the sink point isn't a + // successor. For example: + // + // x = computation + // if () {} else {} + // use x + // + const std::vector<MachineDomTreeNode *> &Children = + DT->getNode(MBB)->getChildren(); + for (const auto &DTChild : Children) + // DomTree children of MBB that have MBB as immediate dominator are added. + if (DTChild->getIDom()->getBlock() == MI->getParent() && + // Skip MBBs already added to the Succs vector above. + !MBB->isSuccessor(DTChild->getBlock())) + Succs.push_back(DTChild->getBlock()); + // Sort Successors according to their loop depth or block frequency info. std::stable_sort( Succs.begin(), Succs.end(), |