#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/CFG.h"
namespace {
struct PNE : public MachineFunctionPass {
// into the phi node destination.
//
MachineBasicBlock::iterator AfterPHIsIt = MBB.begin();
- if (AfterPHIsIt != MBB.end())
- while ((*AfterPHIsIt)->getOpcode() == TargetInstrInfo::PHI) ++AfterPHIsIt;
+ while (AfterPHIsIt != MBB.end() &&
+ (*AfterPHIsIt)->getOpcode() == TargetInstrInfo::PHI)
+ ++AfterPHIsIt; // Skip over all of the PHI nodes...
RegInfo->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC);
// Update live variable information if there is any...
MachineInstr *PHICopy = *(AfterPHIsIt-1);
// Add information to LiveVariables to know that the incoming value is
- // dead. This says that the register is dead, not killed, because we
- // cannot use the live variable information to indicate that the variable
- // is defined in multiple entry blocks. Instead, we pretend that this
- // instruction defined it and killed it at the same time.
+ // killed. Note that because the value is defined in several places (once
+ // each for each incoming block), the "def" block and instruction fields
+ // for the VarInfo is not filled in.
//
- LV->addVirtualRegisterDead(IncomingReg, PHICopy);
+ LV->addVirtualRegisterKilled(IncomingReg, &MBB, PHICopy);
// Since we are going to be deleting the PHI node, if it is the last use
// of any registers, or if the value itself is dead, we need to move this
//
std::pair<LiveVariables::killed_iterator, LiveVariables::killed_iterator>
RKs = LV->killed_range(MI);
+ std::vector<std::pair<MachineInstr*, unsigned> > Range;
if (RKs.first != RKs.second) {
- for (LiveVariables::killed_iterator I = RKs.first; I != RKs.second; ++I)
- LV->addVirtualRegisterKilled(I->second, PHICopy);
+ // Copy the range into a vector...
+ Range.assign(RKs.first, RKs.second);
+
+ // Delete the range...
LV->removeVirtualRegistersKilled(RKs.first, RKs.second);
+
+ // Add all of the kills back, which will update the appropriate info...
+ for (unsigned i = 0, e = Range.size(); i != e; ++i)
+ LV->addVirtualRegisterKilled(Range[i].second, &MBB, PHICopy);
}
RKs = LV->dead_range(MI);
if (RKs.first != RKs.second) {
- for (LiveVariables::killed_iterator I = RKs.first; I != RKs.second; ++I)
- LV->addVirtualRegisterDead(I->second, PHICopy);
+ // Works as above...
+ Range.assign(RKs.first, RKs.second);
LV->removeVirtualRegistersDead(RKs.first, RKs.second);
+ for (unsigned i = 0, e = Range.size(); i != e; ++i)
+ LV->addVirtualRegisterDead(Range[i].second, &MBB, PHICopy);
}
}
for (unsigned i = 0, e = PrevInst->getNumOperands(); i != e; ++i) {
MachineOperand &MO = PrevInst->getOperand(i);
if (MO.isVirtualRegister() && MO.getReg() == IncomingReg)
- if (MO.opIsDef() || MO.opIsDefAndUse()) {
+ if (MO.opIsDefOnly() || MO.opIsDefAndUse()) {
HaveNotEmitted = false;
break;
}
}
}
- if (HaveNotEmitted) {
+ if (HaveNotEmitted) { // If the copy has not already been emitted, do it.
assert(opVal.isVirtualRegister() &&
"Machine PHI Operands must all be virtual registers!");
- RegInfo->copyRegToReg(opBlock, I, IncomingReg, opVal.getReg(), RC);
+ unsigned SrcReg = opVal.getReg();
+ RegInfo->copyRegToReg(opBlock, I, IncomingReg, SrcReg, RC);
+
+ // Now update live variable information if we have it.
+ if (LV) {
+ // We want to be able to insert a kill of the register if this PHI
+ // (aka, the copy we just inserted) is the last use of the source
+ // value. Live variable analysis conservatively handles this by
+ // saying that the value is live until the end of the block the PHI
+ // entry lives in. If the value really is dead at the PHI copy, there
+ // will be no successor blocks which have the value live-in.
+ //
+ // Check to see if the copy is the last use, and if so, update the
+ // live variables information so that it knows the copy source
+ // instruction kills the incoming value.
+ //
+ LiveVariables::VarInfo &InRegVI = LV->getVarInfo(SrcReg);
+
+ // Loop over all of the successors of the basic block, checking to see
+ // if the value is either live in the block, or if it is killed in the
+ // block. Also check to see if this register is in use by another PHI
+ // node which has not yet been eliminated. If so, it will be killed
+ // at an appropriate point later.
+ //
+ bool ValueIsLive = false;
+ BasicBlock *BB = opBlock.getBasicBlock();
+ for (succ_iterator SI = succ_begin(BB), E = succ_end(BB);
+ SI != E && !ValueIsLive; ++SI) {
+ const std::pair<MachineBasicBlock*, unsigned> &
+ SuccInfo = LV->getBasicBlockInfo(*SI);
+
+ // Is it alive in this successor?
+ unsigned SuccIdx = SuccInfo.second;
+ if (SuccIdx < InRegVI.AliveBlocks.size() &&
+ InRegVI.AliveBlocks[SuccIdx]) {
+ ValueIsLive = true;
+ break;
+ }
+
+ // Is it killed in this successor?
+ MachineBasicBlock *MBB = SuccInfo.first;
+ for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i)
+ if (InRegVI.Kills[i].first == MBB) {
+ ValueIsLive = true;
+ break;
+ }
+
+ // Is it used by any PHI instructions in this block?
+ if (ValueIsLive) break;
+
+ // Loop over all of the PHIs in this successor, checking to see if
+ // the register is being used...
+ for (MachineBasicBlock::iterator BBI = MBB->begin(), E=MBB->end();
+ BBI != E && (*BBI)->getOpcode() == TargetInstrInfo::PHI;
+ ++BBI)
+ for (unsigned i = 1, e = (*BBI)->getNumOperands(); i < e; i += 2)
+ if ((*BBI)->getOperand(i).getReg() == SrcReg) {
+ ValueIsLive = true;
+ break;
+ }
+ }
+
+ // Okay, if we now know that the value is not live out of the block,
+ // we can add a kill marker to the copy we inserted saying that it
+ // kills the incoming value!
+ //
+ if (!ValueIsLive)
+ LV->addVirtualRegisterKilled(SrcReg, &opBlock, *(I-1));
+ }
}
}
projects / oota-llvm.git / blobdiff