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Fix PR2898. Spiller delete a store for reuse before it knows for sure the reuse happened.

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Patch by Lang Hames!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57720 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2008-10-17 20:56:41 +00:00
parent cfc14c153a
commit af42fe36ac
2 changed files with 155 additions and 11 deletions
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lib/CodeGen/VirtRegMap.cpp
+26 -11
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@@ -1342,6 +1342,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
}
// Process all of the spilled uses and all non spilled reg references.
SmallVector<int, 2> PotentialDeadStoreSlots;
for (unsigned j = 0, e = VirtUseOps.size(); j != e; ++j) {
unsigned i = VirtUseOps[j];
MachineOperand &MO = MI.getOperand(i);
@@ -1446,17 +1447,14 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
if (MI.getOperand(i).isKill() &&
ReuseSlot <= VirtRegMap::MAX_STACK_SLOT) {
// This was the last use and the spilled value is still available
// for reuse. That means the spill was unnecessary!
MachineInstr* DeadStore = MaybeDeadStores[ReuseSlot];
if (DeadStore) {
DOUT << "Removed dead store:\t" << *DeadStore;
InvalidateKills(*DeadStore, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(DeadStore);
MBB.erase(DeadStore);
MaybeDeadStores[ReuseSlot] = NULL;
++NumDSE;
}
// The store of this spilled value is potentially dead, but we
// won't know for certain until we've confirmed that the re-use
// above is valid, which means waiting until the other operands
// are processed. For now we just track the spill slot, we'll
// remove it after the other operands are processed if valid.
PotentialDeadStoreSlots.push_back(ReuseSlot);
}
continue;
} // CanReuse
@@ -1560,6 +1558,23 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
DOUT << '\t' << *prior(MII);
}
// Ok - now we can remove stores that have been confirmed dead.
for (unsigned j = 0, e = PotentialDeadStoreSlots.size(); j != e; ++j) {
// This was the last use and the spilled value is still available
// for reuse. That means the spill was unnecessary!
int PDSSlot = PotentialDeadStoreSlots[j];
MachineInstr* DeadStore = MaybeDeadStores[PDSSlot];
if (DeadStore) {
DOUT << "Removed dead store:\t" << *DeadStore;
InvalidateKills(*DeadStore, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(DeadStore);
MBB.erase(DeadStore);
MaybeDeadStores[PDSSlot] = NULL;
++NumDSE;
}
}
DOUT << '\t' << MI;