[llvm-commits] CVS: llvm/lib/CodeGen/PHIElimination.cpp
Chris Lattner
lattner at cs.uiuc.edu
Sun Oct 2 21:47:19 PDT 2005
Changes in directory llvm/lib/CodeGen:
PHIElimination.cpp updated: 1.37 -> 1.38
---
Log message:
Break the body of the loop out into a new method
---
Diffs of the changes: (+154 -143)
PHIElimination.cpp | 297 +++++++++++++++++++++++++++--------------------------
1 files changed, 154 insertions(+), 143 deletions(-)
Index: llvm/lib/CodeGen/PHIElimination.cpp
diff -u llvm/lib/CodeGen/PHIElimination.cpp:1.37 llvm/lib/CodeGen/PHIElimination.cpp:1.38
--- llvm/lib/CodeGen/PHIElimination.cpp:1.37 Tue Aug 23 18:42:17 2005
+++ llvm/lib/CodeGen/PHIElimination.cpp Sun Oct 2 23:47:08 2005
@@ -22,6 +22,7 @@
#include "llvm/Target/TargetMachine.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
+#include <set>
using namespace llvm;
namespace {
@@ -46,6 +47,10 @@
/// in predecessor basic blocks.
///
bool EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB);
+ void LowerAtomicPHINode(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator AfterPHIsIt,
+ DenseMap<unsigned, VirtReg2IndexFunctor> &VUC,
+ unsigned BBIsSuccOfPreds);
};
RegisterPass<PNE> X("phi-node-elimination",
@@ -60,11 +65,7 @@
///
bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
if (MBB.empty() || MBB.front().getOpcode() != TargetInstrInfo::PHI)
- return false; // Quick exit for normal case...
-
- LiveVariables *LV = getAnalysisToUpdate<LiveVariables>();
- const TargetInstrInfo &MII = *MF.getTarget().getInstrInfo();
- const MRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
+ return false; // Quick exit for basic blocks without PHIs.
// VRegPHIUseCount - Keep track of the number of times each virtual register
// is used by PHI nodes in successors of this block.
@@ -84,169 +85,179 @@
}
// Get an iterator to the first instruction after the last PHI node (this may
- // also be the end of the basic block). While we are scanning the PHIs,
- // populate the VRegPHIUseCount map.
+ // also be the end of the basic block).
MachineBasicBlock::iterator AfterPHIsIt = MBB.begin();
while (AfterPHIsIt != MBB.end() &&
AfterPHIsIt->getOpcode() == TargetInstrInfo::PHI)
++AfterPHIsIt; // Skip over all of the PHI nodes...
while (MBB.front().getOpcode() == TargetInstrInfo::PHI) {
- // Unlink the PHI node from the basic block, but don't delete the PHI yet.
- MachineInstr *MPhi = MBB.remove(MBB.begin());
+ LowerAtomicPHINode(MBB, AfterPHIsIt, VRegPHIUseCount, BBIsSuccOfPreds);
+ }
+ return true;
+}
- assert(MRegisterInfo::isVirtualRegister(MPhi->getOperand(0).getReg()) &&
- "PHI node doesn't write virt reg?");
+/// LowerAtomicPHINode - Lower the PHI node at the top of the specified block,
+/// under the assuption that it needs to be lowered in a way that supports
+/// atomic execution of PHIs. This lowering method is always correct all of the
+/// time.
+void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator AfterPHIsIt,
+ DenseMap<unsigned, VirtReg2IndexFunctor> &VRegPHIUseCount,
+ unsigned BBIsSuccOfPreds) {
+ // Unlink the PHI node from the basic block, but don't delete the PHI yet.
+ MachineInstr *MPhi = MBB.remove(MBB.begin());
+
+ unsigned DestReg = MPhi->getOperand(0).getReg();
+
+ // Create a new register for the incoming PHI arguments/
+ MachineFunction &MF = *MBB.getParent();
+ const TargetRegisterClass *RC = MF.getSSARegMap()->getRegClass(DestReg);
+ unsigned IncomingReg = MF.getSSARegMap()->createVirtualRegister(RC);
+
+ // Insert a register to register copy in the top of the current block (but
+ // after any remaining phi nodes) which copies the new incoming register
+ // into the phi node destination.
+ //
+ const MRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
+ RegInfo->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC);
- unsigned DestReg = MPhi->getOperand(0).getReg();
+ // Update live variable information if there is any...
+ LiveVariables *LV = getAnalysisToUpdate<LiveVariables>();
+ if (LV) {
+ MachineInstr *PHICopy = prior(AfterPHIsIt);
- // Create a new register for the incoming PHI arguments
- const TargetRegisterClass *RC = MF.getSSARegMap()->getRegClass(DestReg);
- unsigned IncomingReg = MF.getSSARegMap()->createVirtualRegister(RC);
+ // Add information to LiveVariables to know that the incoming value is
+ // 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->addVirtualRegisterKilled(IncomingReg, PHICopy);
- // Insert a register to register copy in the top of the current block (but
- // after any remaining phi nodes) which copies the new incoming register
- // into the phi node destination.
+ // 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
+ // information over to the new copy we just inserted.
//
- RegInfo->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC);
+ LV->removeVirtualRegistersKilled(MPhi);
- // Update live variable information if there is any...
- if (LV) {
- MachineInstr *PHICopy = prior(AfterPHIsIt);
-
- // Add information to LiveVariables to know that the incoming value is
- // 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->addVirtualRegisterKilled(IncomingReg, 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
- // information over to the new copy we just inserted.
- //
- 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);
- LV->removeVirtualRegistersDead(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);
+ LV->removeVirtualRegistersDead(MPhi);
}
+ }
- // Adjust the VRegPHIUseCount map to account for the removal of this PHI
- // node.
- for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2)
- VRegPHIUseCount[MPhi->getOperand(i).getReg()] -= BBIsSuccOfPreds;
-
- // Now loop over all of the incoming arguments, changing them to copy into
- // the IncomingReg register in the corresponding predecessor basic block.
+ // Adjust the VRegPHIUseCount map to account for the removal of this PHI
+ // node.
+ for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2)
+ VRegPHIUseCount[MPhi->getOperand(i).getReg()] -= BBIsSuccOfPreds;
+
+ // Now loop over all of the incoming arguments, changing them to copy into
+ // the IncomingReg register in the corresponding predecessor basic block.
+ //
+ for (int i = MPhi->getNumOperands() - 1; i >= 2; i-=2) {
+ MachineOperand &opVal = MPhi->getOperand(i-1);
+
+ // 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!
//
- for (int i = MPhi->getNumOperands() - 1; i >= 2; i-=2) {
- MachineOperand &opVal = MPhi->getOperand(i-1);
+ bool HaveNotEmitted = true;
- // 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;
-
- 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;
- }
- }
+ 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;
+ }
}
+ }
+
+ 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]) {
+ ValueIsLive = true;
+ break;
+ }
- 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]) {
+ // 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 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;
- }
+ // 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;
- }
+ // 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;
}
- return true;
+
+ // Really delete the PHI instruction now!
+ delete MPhi;
}
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