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Small cleanup of MachineLICM.cpp

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Specifically:
- Calculate the loop pre-header once at the stat of HoistOutOfLoop, so:
  - We don't-DFS walk the MachineDomTree if we aren't going to do anything
  - Don't call getCurPreheader for each Scope
- Don't needlessly use a do-while loop
- Use early exit for Scopes.size() == 0

No functional changes intended.

llvm-svn: 228350
This commit is contained in:
Daniel Jasper 2015-02-05 22:39:46 +00:00
parent 4a4a7fcd0d
commit 1040855bc8
1 changed files with 13 additions and 16 deletions
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29
lib/CodeGen/MachineLICM.cpp
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@ -693,6 +693,10 @@ void MachineLICM::ExitScopeIfDone(MachineDomTreeNode *Node,
/// one pass without iteration. /// one pass without iteration.
/// ///
void MachineLICM::HoistOutOfLoop(MachineDomTreeNode *HeaderN) { void MachineLICM::HoistOutOfLoop(MachineDomTreeNode *HeaderN) {
MachineBasicBlock *Preheader = getCurPreheader();
if (!Preheader)
return;
SmallVector<MachineDomTreeNode*, 32> Scopes; SmallVector<MachineDomTreeNode*, 32> Scopes;
SmallVector<MachineDomTreeNode*, 8> WorkList; SmallVector<MachineDomTreeNode*, 8> WorkList;
DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> ParentMap; DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> ParentMap;
@ -700,7 +704,7 @@ void MachineLICM::HoistOutOfLoop(MachineDomTreeNode *HeaderN) {
// Perform a DFS walk to determine the order of visit. // Perform a DFS walk to determine the order of visit.
WorkList.push_back(HeaderN); WorkList.push_back(HeaderN);
do { while (!WorkList.empty()) {
MachineDomTreeNode *Node = WorkList.pop_back_val(); MachineDomTreeNode *Node = WorkList.pop_back_val();
assert(Node && "Null dominator tree node?"); assert(Node && "Null dominator tree node?");
MachineBasicBlock *BB = Node->getBlock(); MachineBasicBlock *BB = Node->getBlock();
@ -734,28 +738,21 @@ void MachineLICM::HoistOutOfLoop(MachineDomTreeNode *HeaderN) {
ParentMap[Child] = Node; ParentMap[Child] = Node;
WorkList.push_back(Child); 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);
} }
if (Scopes.size() == 0)
return;
// Compute registers which are livein into the loop headers.
RegSeen.clear();
BackTrace.clear();
InitRegPressure(Preheader);
// Now perform LICM. // Now perform LICM.
for (unsigned i = 0, e = Scopes.size(); i != e; ++i) { for (unsigned i = 0, e = Scopes.size(); i != e; ++i) {
MachineDomTreeNode *Node = Scopes[i]; MachineDomTreeNode *Node = Scopes[i];
MachineBasicBlock *MBB = Node->getBlock(); MachineBasicBlock *MBB = Node->getBlock();
MachineBasicBlock *Preheader = getCurPreheader();
if (!Preheader)
continue;
EnterScope(MBB); EnterScope(MBB);
// Process the block // Process the block