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Changed MachineLICM to use a worklist list MachineCSE instead of recursion. 

Fixes <rdar://problem/10584116>

llvm-svn: 147125
This commit is contained in:
Pete Cooper 2011-12-22 02:05:40 +00:00
parent 38a400df3b
commit 1eed5b51e8
1 changed files with 126 additions and 45 deletions
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171
llvm/lib/CodeGen/MachineLICM.cpp
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@ -215,13 +215,25 @@ namespace {
/// If not then a load from this mbb may not be safe to hoist.
bool IsGuaranteedToExecute(MachineBasicBlock *BB);
/// HoistRegion - Walk the specified region of the CFG (defined by all
/// blocks dominated by the specified block, and that are in the current
/// loop) in depth first order w.r.t the DominatorTree. This allows us to
/// visit definitions before uses, allowing us to hoist a loop body in one
/// pass without iteration.
void EnterScope(MachineBasicBlock *MBB);
void ExitScope(MachineBasicBlock *MBB);
/// ExitScopeIfDone - Destroy scope for the MBB that corresponds to given
/// dominator tree node if its a leaf or all of its children are done. Walk
/// up the dominator tree to destroy ancestors which are now done.
void ExitScopeIfDone(MachineDomTreeNode *Node,
DenseMap<MachineDomTreeNode*, unsigned> &OpenChildren,
DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> &ParentMap);
/// HoistOutOfLoop - Walk the specified loop in the CFG (defined by all
/// blocks dominated by the specified header block, and that are in the
/// current loop) in depth first order w.r.t the DominatorTree. This allows
/// us to visit definitions before uses, allowing us to hoist a loop body in
/// one pass without iteration.
///
void HoistRegion(MachineDomTreeNode *N, bool IsHeader = false);
void HoistOutOfLoop(MachineDomTreeNode *LoopHeaderNode);
void HoistRegion(MachineDomTreeNode *N, bool IsHeader);
/// getRegisterClassIDAndCost - For a given MI, register, and the operand
/// index, return the ID and cost of its representative register class by
@ -356,7 +368,7 @@ bool MachineLICM::runOnMachineFunction(MachineFunction &MF) {
// being hoisted.
MachineDomTreeNode *N = DT->getNode(CurLoop->getHeader());
FirstInLoop = true;
HoistRegion(N, true);
HoistOutOfLoop(N);
CSEMap.clear();
}
}
@ -605,57 +617,126 @@ bool MachineLICM::IsGuaranteedToExecute(MachineBasicBlock *BB) {
return true;
}
/// HoistRegion - Walk the specified region of the CFG (defined by all blocks
/// dominated by the specified block, and that are in the current loop) in depth
/// first order w.r.t the DominatorTree. This allows us to visit definitions
/// before uses, allowing us to hoist a loop body in one pass without iteration.
///
void MachineLICM::HoistRegion(MachineDomTreeNode *N, bool IsHeader) {
assert(N != 0 && "Null dominator tree node?");
MachineBasicBlock *BB = N->getBlock();
void MachineLICM::EnterScope(MachineBasicBlock *MBB) {
DEBUG(dbgs() << "Entering: " << MBB->getName() << '\n');
// If the header of the loop containing this basic block is a landing pad,
// then don't try to hoist instructions out of this loop.
const MachineLoop *ML = MLI->getLoopFor(BB);
if (ML && ML->getHeader()->isLandingPad()) return;
// Remember livein register pressure.
BackTrace.push_back(RegPressure);
}
// If this subregion is not in the top level loop at all, exit.
if (!CurLoop->contains(BB)) return;
void MachineLICM::ExitScope(MachineBasicBlock *MBB) {
DEBUG(dbgs() << "Exiting: " << MBB->getName() << '\n');
BackTrace.pop_back();
}
MachineBasicBlock *Preheader = getCurPreheader();
if (!Preheader)
/// ExitScopeIfDone - Destroy scope for the MBB that corresponds to the given
/// dominator tree node if its a leaf or all of its children are done. Walk
/// up the dominator tree to destroy ancestors which are now done.
void MachineLICM::ExitScopeIfDone(MachineDomTreeNode *Node,
DenseMap<MachineDomTreeNode*, unsigned> &OpenChildren,
DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> &ParentMap) {
if (OpenChildren[Node])
return;
if (IsHeader) {
// Pop scope.
ExitScope(Node->getBlock());
// Now traverse upwards to pop ancestors whose offsprings are all done.
while (MachineDomTreeNode *Parent = ParentMap[Node]) {
unsigned Left = --OpenChildren[Parent];
if (Left != 0)
break;
ExitScope(Parent->getBlock());
Node = Parent;
}
}
/// HoistOutOfLoop - Walk the specified loop in the CFG (defined by all
/// blocks dominated by the specified header block, and that are in the
/// current loop) in depth first order w.r.t the DominatorTree. This allows
/// us to visit definitions before uses, allowing us to hoist a loop body in
/// one pass without iteration.
///
void MachineLICM::HoistOutOfLoop(MachineDomTreeNode *HeaderN) {
SmallVector<MachineDomTreeNode*, 32> Scopes;
SmallVector<MachineDomTreeNode*, 8> WorkList;
DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> ParentMap;
DenseMap<MachineDomTreeNode*, unsigned> OpenChildren;
// Perform a DFS walk to determine the order of visit.
WorkList.push_back(HeaderN);
do {
MachineDomTreeNode *Node = WorkList.pop_back_val();
assert(Node != 0 && "Null dominator tree node?");
MachineBasicBlock *BB = Node->getBlock();
// If the header of the loop containing this basic block is a landing pad,
// then don't try to hoist instructions out of this loop.
const MachineLoop *ML = MLI->getLoopFor(BB);
if (ML && ML->getHeader()->isLandingPad())
continue;
// If this subregion is not in the top level loop at all, exit.
if (!CurLoop->contains(BB))
continue;
Scopes.push_back(Node);
const std::vector<MachineDomTreeNode*> &Children = Node->getChildren();
unsigned NumChildren = Children.size();
// Don't hoist things out of a large switch statement. This often causes
// code to be hoisted that wasn't going to be executed, and increases
// register pressure in a situation where it's likely to matter.
if (BB->succ_size() >= 25)
NumChildren = 0;
OpenChildren[Node] = NumChildren;
// Add children in reverse order as then the next popped worklist node is
// the first child of this node. This means we ultimately traverse the
// DOM tree in exactly the same order as if we'd recursed.
for (int i = (int)NumChildren-1; i >= 0; --i) {
MachineDomTreeNode *Child = Children[i];
ParentMap[Child] = Node;
WorkList.push_back(Child);
}
} while (!WorkList.empty());
if (Scopes.size() != 0) {
MachineBasicBlock *Preheader = getCurPreheader();
if (!Preheader)
return;
// Compute registers which are livein into the loop headers.
RegSeen.clear();
BackTrace.clear();
InitRegPressure(Preheader);
}
// Remember livein register pressure.
BackTrace.push_back(RegPressure);
// Now perform LICM.
for (unsigned i = 0, e = Scopes.size(); i != e; ++i) {
MachineDomTreeNode *Node = Scopes[i];
MachineBasicBlock *MBB = Node->getBlock();
SpeculationState = SpeculateUnknown;
for (MachineBasicBlock::iterator
MII = BB->begin(), E = BB->end(); MII != E; ) {
MachineBasicBlock::iterator NextMII = MII; ++NextMII;
MachineInstr *MI = &*MII;
if (!Hoist(MI, Preheader))
UpdateRegPressure(MI);
MII = NextMII;
MachineBasicBlock *Preheader = getCurPreheader();
if (!Preheader)
continue;
EnterScope(MBB);
// Process the block
SpeculationState = SpeculateUnknown;
for (MachineBasicBlock::iterator
MII = MBB->begin(), E = MBB->end(); MII != E; ) {
MachineBasicBlock::iterator NextMII = MII; ++NextMII;
MachineInstr *MI = &*MII;
if (!Hoist(MI, Preheader))
UpdateRegPressure(MI);
MII = NextMII;
}
// If it's a leaf node, it's done. Traverse upwards to pop ancestors.
ExitScopeIfDone(Node, OpenChildren, ParentMap);
}
// Don't hoist things out of a large switch statement. This often causes
// code to be hoisted that wasn't going to be executed, and increases
// register pressure in a situation where it's likely to matter.
if (BB->succ_size() < 25) {
const std::vector<MachineDomTreeNode*> &Children = N->getChildren();
for (unsigned I = 0, E = Children.size(); I != E; ++I)
HoistRegion(Children[I]);
}
BackTrace.pop_back();
}
static bool isOperandKill(const MachineOperand &MO, MachineRegisterInfo *MRI) {