Re-apply 85799. It turns out my code isn't buggy.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85947 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp
index 7b64047..1306aa6 100644
--- a/lib/CodeGen/MachineLICM.cpp
+++ b/lib/CodeGen/MachineLICM.cpp
@@ -56,12 +56,12 @@
// State that is updated as we process loops
bool Changed; // True if a loop is changed.
+ bool FirstInLoop; // True if it's the first LICM in the loop.
MachineLoop *CurLoop; // The current loop we are working on.
MachineBasicBlock *CurPreheader; // The preheader for CurLoop.
- // For each BB and opcode pair, keep a list of hoisted instructions.
- DenseMap<std::pair<unsigned, unsigned>,
- std::vector<const MachineInstr*> > CSEMap;
+ // For each opcode, keep a list of potentail CSE instructions.
+ DenseMap<unsigned, std::vector<const MachineInstr*> > CSEMap;
public:
static char ID; // Pass identification, replacement for typeid
MachineLICM() : MachineFunctionPass(&ID) {}
@@ -115,6 +115,11 @@
/// that is safe to hoist, this instruction is called to do the dirty work.
///
void Hoist(MachineInstr *MI);
+
+ /// InitCSEMap - Initialize the CSE map with instructions that are in the
+ /// current loop preheader that may become duplicates of instructions that
+ /// are hoisted out of the loop.
+ void InitCSEMap(MachineBasicBlock *BB);
};
} // end anonymous namespace
@@ -140,7 +145,7 @@
bool MachineLICM::runOnMachineFunction(MachineFunction &MF) {
DEBUG(errs() << "******** Machine LICM ********\n");
- Changed = false;
+ Changed = FirstInLoop = false;
TM = &MF.getTarget();
TII = TM->getInstrInfo();
TRI = TM->getRegisterInfo();
@@ -152,8 +157,7 @@
DT = &getAnalysis<MachineDominatorTree>();
AA = &getAnalysis<AliasAnalysis>();
- for (MachineLoopInfo::iterator
- I = LI->begin(), E = LI->end(); I != E; ++I) {
+ for (MachineLoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) {
CurLoop = *I;
// Only visit outer-most preheader-sporting loops.
@@ -170,7 +174,11 @@
if (!CurPreheader)
continue;
+ // CSEMap is initialized for loop header when the first instruction is
+ // being hoisted.
+ FirstInLoop = true;
HoistRegion(DT->getNode(CurLoop->getHeader()));
+ CSEMap.clear();
}
return Changed;
@@ -191,10 +199,7 @@
for (MachineBasicBlock::iterator
MII = BB->begin(), E = BB->end(); MII != E; ) {
MachineBasicBlock::iterator NextMII = MII; ++NextMII;
- MachineInstr &MI = *MII;
-
- Hoist(&MI);
-
+ Hoist(&*MII);
MII = NextMII;
}
@@ -430,6 +435,27 @@
return NewMIs[0];
}
+void MachineLICM::InitCSEMap(MachineBasicBlock *BB) {
+ for (MachineBasicBlock::iterator I = BB->begin(),E = BB->end(); I != E; ++I) {
+ const MachineInstr *MI = &*I;
+ // FIXME: For now, only hoist re-materilizable instructions. LICM will
+ // increase register pressure. We want to make sure it doesn't increase
+ // spilling.
+ if (TII->isTriviallyReMaterializable(MI, AA)) {
+ unsigned Opcode = MI->getOpcode();
+ DenseMap<unsigned, std::vector<const MachineInstr*> >::iterator
+ CI = CSEMap.find(Opcode);
+ if (CI != CSEMap.end())
+ CI->second.push_back(MI);
+ else {
+ std::vector<const MachineInstr*> CSEMIs;
+ CSEMIs.push_back(MI);
+ CSEMap.insert(std::make_pair(Opcode, CSEMIs));
+ }
+ }
+ }
+}
+
/// Hoist - When an instruction is found to use only loop invariant operands
/// that are safe to hoist, this instruction is called to do the dirty work.
///
@@ -454,11 +480,14 @@
errs() << "\n";
});
+ // If this is the first instruction being hoisted to the preheader,
+ // initialize the CSE map with potential common expressions.
+ InitCSEMap(CurPreheader);
+
// Look for opportunity to CSE the hoisted instruction.
- std::pair<unsigned, unsigned> BBOpcPair =
- std::make_pair(CurPreheader->getNumber(), MI->getOpcode());
- DenseMap<std::pair<unsigned, unsigned>,
- std::vector<const MachineInstr*> >::iterator CI = CSEMap.find(BBOpcPair);
+ unsigned Opcode = MI->getOpcode();
+ DenseMap<unsigned, std::vector<const MachineInstr*> >::iterator
+ CI = CSEMap.find(Opcode);
bool DoneCSE = false;
if (CI != CSEMap.end()) {
const MachineInstr *Dup = LookForDuplicate(MI, CI->second, RegInfo);
@@ -477,15 +506,15 @@
// Otherwise, splice the instruction to the preheader.
if (!DoneCSE) {
- CurPreheader->splice(CurPreheader->getFirstTerminator(),
- MI->getParent(), MI);
+ CurPreheader->splice(CurPreheader->getFirstTerminator(),MI->getParent(),MI);
+
// Add to the CSE map.
if (CI != CSEMap.end())
CI->second.push_back(MI);
else {
std::vector<const MachineInstr*> CSEMIs;
CSEMIs.push_back(MI);
- CSEMap.insert(std::make_pair(BBOpcPair, CSEMIs));
+ CSEMap.insert(std::make_pair(Opcode, CSEMIs));
}
}