summaryrefslogtreecommitdiffstats
path: root/llvm
diff options
context:
space:
mode:
Diffstat (limited to 'llvm')
-rw-r--r--llvm/lib/CodeGen/PHIElimination.cpp217
1 files changed, 116 insertions, 101 deletions
diff --git a/llvm/lib/CodeGen/PHIElimination.cpp b/llvm/lib/CodeGen/PHIElimination.cpp
index 80c884dc9ae..91805a93edf 100644
--- a/llvm/lib/CodeGen/PHIElimination.cpp
+++ b/llvm/lib/CodeGen/PHIElimination.cpp
@@ -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.
+ // 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);
+
+ // 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.
//
- // 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!
+ // 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.
//
- bool HaveNotEmitted = true;
-
- 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;
- }
+ 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;
}
OpenPOWER on IntegriCloud