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Teach EmitLiveInCopies to omit copies for unused virtual registers,

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and to clean up unused incoming physregs from the live-in list.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106805 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2010-06-24 22:23:02 +00:00
parent f241b26792
commit fe5e4dabbf
3 changed files with 32 additions and 21 deletions
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39
lib/CodeGen/MachineRegisterInfo.cpp
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@ -182,21 +182,32 @@ MachineRegisterInfo::EmitLiveInCopies(MachineBasicBlock *EntryMBB,
const TargetRegisterInfo &TRI,
const TargetInstrInfo &TII) {
// Emit the copies into the top of the block.
for (MachineRegisterInfo::livein_iterator LI = livein_begin(),
E = livein_end(); LI != E; ++LI)
if (LI->second) {
const TargetRegisterClass *RC = getRegClass(LI->second);
bool Emitted = TII.copyRegToReg(*EntryMBB, EntryMBB->begin(),
LI->second, LI->first, RC, RC,
DebugLoc());
assert(Emitted && "Unable to issue a live-in copy instruction!\n");
(void) Emitted;
}
for (unsigned i = 0, e = LiveIns.size(); i != e; ++i)
if (LiveIns[i].second) {
if (use_empty(LiveIns[i].second)) {
// The livein has no uses. Drop it.
//
// It would be preferable to have isel avoid creating live-in
// records for unused arguments in the first place, but it's
// complicated by the debug info code for arguments.
LiveIns.erase(LiveIns.begin() + i);
--i; --e;
} else {
// Emit a copy.
const TargetRegisterClass *RC = getRegClass(LiveIns[i].second);
bool Emitted = TII.copyRegToReg(*EntryMBB, EntryMBB->begin(),
LiveIns[i].second, LiveIns[i].first,
RC, RC, DebugLoc());
assert(Emitted && "Unable to issue a live-in copy instruction!\n");
(void) Emitted;
// Add function live-ins to entry block live-in set.
for (MachineRegisterInfo::livein_iterator I = livein_begin(),
E = livein_end(); I != E; ++I)
EntryMBB->addLiveIn(I->first);
// Add the register to the entry block live-in set.
EntryMBB->addLiveIn(LiveIns[i].first);
}
} else {
// Add the register to the entry block live-in set.
EntryMBB->addLiveIn(LiveIns[i].first);
}
}
void MachineRegisterInfo::closePhysRegsUsed(const TargetRegisterInfo &TRI) {