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clean up this code a bit, no functionality change 

llvm-svn: 23609
This commit is contained in:
Chris Lattner 2005-10-03 07:22:07 +00:00
parent afef68baff
commit 57b21f9f10
1 changed files with 117 additions and 102 deletions
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219
llvm/lib/CodeGen/PHIElimination.cpp
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@ -22,10 +22,15 @@
#include "llvm/Target/TargetMachine.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include <set>
#include <algorithm>
using namespace llvm;
namespace {
Statistic<> NumAtomic("phielim", "Number of atomic phis lowered");
Statistic<> NumSimple("phielim", "Number of simple phis lowered");
struct PNE : public MachineFunctionPass {
bool runOnMachineFunction(MachineFunction &Fn) {
bool Changed = false;
@ -49,8 +54,7 @@ namespace {
bool EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB);
void LowerAtomicPHINode(MachineBasicBlock &MBB,
MachineBasicBlock::iterator AfterPHIsIt,
DenseMap<unsigned, VirtReg2IndexFunctor> &VUC,
unsigned BBIsSuccOfPreds);
DenseMap<unsigned, VirtReg2IndexFunctor> &VUC);
};
RegisterPass<PNE> X("phi-node-elimination",
@ -72,18 +76,15 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
DenseMap<unsigned, VirtReg2IndexFunctor> VRegPHIUseCount;
VRegPHIUseCount.grow(MF.getSSARegMap()->getLastVirtReg());
unsigned BBIsSuccOfPreds = 0; // Number of times MBB is a succ of preds
for (MachineBasicBlock::pred_iterator PI = MBB.pred_begin(),
E = MBB.pred_end(); PI != E; ++PI)
for (MachineBasicBlock::succ_iterator SI = (*PI)->succ_begin(),
E = (*PI)->succ_end(); SI != E; ++SI) {
BBIsSuccOfPreds += *SI == &MBB;
for (MachineBasicBlock::iterator BBI = (*SI)->begin(); BBI !=(*SI)->end() &&
BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI)
for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2)
VRegPHIUseCount[BBI->getOperand(i).getReg()]++;
}
E = (*PI)->succ_end(); SI != E; ++SI)
for (MachineBasicBlock::iterator BBI = (*SI)->begin(), E = (*SI)->end();
BBI != E && BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI)
for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2)
VRegPHIUseCount[BBI->getOperand(i).getReg()]++;
// Get an iterator to the first instruction after the last PHI node (this may
// also be the end of the basic block).
MachineBasicBlock::iterator AfterPHIsIt = MBB.begin();
@ -92,7 +93,7 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
++AfterPHIsIt; // Skip over all of the PHI nodes...
while (MBB.front().getOpcode() == TargetInstrInfo::PHI) {
LowerAtomicPHINode(MBB, AfterPHIsIt, VRegPHIUseCount, BBIsSuccOfPreds);
LowerAtomicPHINode(MBB, AfterPHIsIt, VRegPHIUseCount);
}
return true;
}
@ -103,8 +104,7 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
/// time.
void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
MachineBasicBlock::iterator AfterPHIsIt,
DenseMap<unsigned, VirtReg2IndexFunctor> &VRegPHIUseCount,
unsigned BBIsSuccOfPreds) {
DenseMap<unsigned, VirtReg2IndexFunctor> &VRegPHIUseCount) {
// Unlink the PHI node from the basic block, but don't delete the PHI yet.
MachineInstr *MPhi = MBB.remove(MBB.begin());
@ -140,124 +140,139 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
//
LV->removeVirtualRegistersKilled(MPhi);
std::pair<LiveVariables::killed_iterator, LiveVariables::killed_iterator>
RKs = LV->dead_range(MPhi);
if (RKs.first != RKs.second) {
for (LiveVariables::killed_iterator I = RKs.first; I != RKs.second; ++I)
LV->addVirtualRegisterDead(*I, PHICopy);
// If the result is dead, update LV.
if (LV->RegisterDefIsDead(MPhi, DestReg)) {
LV->addVirtualRegisterDead(DestReg, PHICopy);
LV->removeVirtualRegistersDead(MPhi);
}
}
// Adjust the VRegPHIUseCount map to account for the removal of this PHI
// node.
unsigned NumPreds = (MPhi->getNumOperands()-1)/2;
for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2)
VRegPHIUseCount[MPhi->getOperand(i).getReg()] -= BBIsSuccOfPreds;
VRegPHIUseCount[MPhi->getOperand(i).getReg()] -= NumPreds;
// Now loop over all of the incoming arguments, changing them to copy into
// the IncomingReg register in the corresponding predecessor basic block.
//
std::set<MachineBasicBlock*> MBBsInsertedInto;
for (int i = MPhi->getNumOperands() - 1; i >= 2; i-=2) {
MachineOperand &opVal = MPhi->getOperand(i-1);
unsigned SrcReg = MPhi->getOperand(i-1).getReg();
assert(MRegisterInfo::isVirtualRegister(SrcReg) &&
"Machine PHI Operands must all be virtual registers!");
// Get the MachineBasicBlock equivalent of the BasicBlock that is the
// source path the PHI.
MachineBasicBlock &opBlock = *MPhi->getOperand(i).getMachineBasicBlock();
MachineBasicBlock::iterator I = opBlock.getFirstTerminator();
// Check to make sure we haven't already emitted the copy for this block.
// This can happen because PHI nodes may have multiple entries for the
// same basic block. It doesn't matter which entry we use though, because
// all incoming values are guaranteed to be the same for a particular bb.
//
// If we emitted a copy for this basic block already, it will be right
// where we want to insert one now. Just check for a definition of the
// register we are interested in!
//
bool HaveNotEmitted = true;
// same basic block.
if (!MBBsInsertedInto.insert(&opBlock).second)
continue; // If the copy has already been emitted, we're done.
// Get an iterator pointing to the first terminator in the block (or end()).
// This is the point where we can insert a copy if we'd like to.
MachineBasicBlock::iterator I = opBlock.getFirstTerminator();
// Insert the copy.
RegInfo->copyRegToReg(opBlock, I, IncomingReg, SrcReg, RC);
if (I != opBlock.begin()) {
MachineBasicBlock::iterator PrevInst = prior(I);
for (unsigned i = 0, e = PrevInst->getNumOperands(); i != e; ++i) {
MachineOperand &MO = PrevInst->getOperand(i);
if (MO.isRegister() && MO.getReg() == IncomingReg)
if (MO.isDef()) {
HaveNotEmitted = false;
break;
}
// Now update live variable information if we have it. Otherwise we're done
if (!LV) continue;
// 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.
//
// Is it used by any PHI instructions in this block?
bool ValueIsLive = VRegPHIUseCount[SrcReg] != 0;
std::vector<MachineBasicBlock*> OpSuccBlocks;
// Otherwise, scan successors, including the BB the PHI node lives in.
for (MachineBasicBlock::succ_iterator SI = opBlock.succ_begin(),
E = opBlock.succ_end(); SI != E && !ValueIsLive; ++SI) {
MachineBasicBlock *SuccMBB = *SI;
// Is it alive in this successor?
unsigned SuccIdx = SuccMBB->getNumber();
if (SuccIdx < InRegVI.AliveBlocks.size() &&
InRegVI.AliveBlocks[SuccIdx]) {
ValueIsLive = true;
break;
}
OpSuccBlocks.push_back(SuccMBB);
}
if (HaveNotEmitted) { // If the copy has not already been emitted, do it.
assert(MRegisterInfo::isVirtualRegister(opVal.getReg()) &&
"Machine PHI Operands must all be virtual registers!");
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;
for (MachineBasicBlock::succ_iterator SI = opBlock.succ_begin(),
E = opBlock.succ_end(); SI != E && !ValueIsLive; ++SI) {
MachineBasicBlock *SuccMBB = *SI;
// Is it alive in this successor?
unsigned SuccIdx = SuccMBB->getNumber();
if (SuccIdx < InRegVI.AliveBlocks.size() &&
InRegVI.AliveBlocks[SuccIdx]) {
// Check to see if this value is live because there is a use in a successor
// that kills it.
if (!ValueIsLive) {
switch (OpSuccBlocks.size()) {
case 1: {
MachineBasicBlock *MBB = OpSuccBlocks[0];
for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i)
if (InRegVI.Kills[i]->getParent() == MBB) {
ValueIsLive = true;
break;
}
// Is it killed in this successor?
for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i)
if (InRegVI.Kills[i]->getParent() == SuccMBB) {
ValueIsLive = true;
break;
}
// Is it used by any PHI instructions in this block?
if (!ValueIsLive)
ValueIsLive = VRegPHIUseCount[SrcReg] != 0;
}
// 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) {
MachineBasicBlock::iterator Prev = prior(I);
LV->addVirtualRegisterKilled(SrcReg, Prev);
// This vreg no longer lives all of the way through opBlock.
unsigned opBlockNum = opBlock.getNumber();
if (opBlockNum < InRegVI.AliveBlocks.size())
InRegVI.AliveBlocks[opBlockNum] = false;
}
break;
}
case 2: {
MachineBasicBlock *MBB1 = OpSuccBlocks[0], *MBB2 = OpSuccBlocks[1];
for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i)
if (InRegVI.Kills[i]->getParent() == MBB1 ||
InRegVI.Kills[i]->getParent() == MBB2) {
ValueIsLive = true;
break;
}
break;
}
default:
std::sort(OpSuccBlocks.begin(), OpSuccBlocks.end());
for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i)
if (std::binary_search(OpSuccBlocks.begin(), OpSuccBlocks.end(),
InRegVI.Kills[i]->getParent())) {
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) {
MachineBasicBlock::iterator Prev = prior(I);
LV->addVirtualRegisterKilled(SrcReg, Prev);
// This vreg no longer lives all of the way through opBlock.
unsigned opBlockNum = opBlock.getNumber();
if (opBlockNum < InRegVI.AliveBlocks.size())
InRegVI.AliveBlocks[opBlockNum] = false;
}
}
// Really delete the PHI instruction now!
delete MPhi;
++NumAtomic;
}