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Constify isSourceDefinedByImplicitDef function. Otherwise, just formatting

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changes that don't change functionality.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51004 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2008-05-12 22:15:05 +00:00
parent 9f8fea3531
commit ae94dda61a
1 changed files with 38 additions and 45 deletions
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83
lib/CodeGen/PHIElimination.cpp
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@ -127,11 +127,11 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
return true;
}
static bool isSourceDefinedByImplicitDef(MachineInstr *MPhi,
MachineRegisterInfo *MRI) {
static bool isSourceDefinedByImplicitDef(const MachineInstr *MPhi,
const MachineRegisterInfo *MRI) {
for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2) {
unsigned SrcReg = MPhi->getOperand(i).getReg();
MachineInstr *DefMI = MRI->getVRegDef(SrcReg);
const MachineInstr *DefMI = MRI->getVRegDef(SrcReg);
if (!DefMI || DefMI->getOpcode() != TargetInstrInfo::IMPLICIT_DEF)
return false;
}
@ -142,6 +142,7 @@ static bool isSourceDefinedByImplicitDef(MachineInstr *MPhi,
/// 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) {
// Unlink the PHI node from the basic block, but don't delete the PHI yet.
@ -155,10 +156,9 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
const TargetRegisterClass *RC = MF.getRegInfo().getRegClass(DestReg);
unsigned IncomingReg = MF.getRegInfo().createVirtualRegister(RC);
// Insert a register to register copy in the top of the current block (but
// Insert a register to register copy at the top of the current block (but
// after any remaining phi nodes) which copies the new incoming register
// into the phi node destination.
//
const TargetInstrInfo *TII = MF.getTarget().getInstrInfo();
if (isSourceDefinedByImplicitDef(MPhi, MRI))
// If all sources of a PHI node are implicit_def, just emit an implicit_def
@ -167,7 +167,7 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
else
TII->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC, RC);
// Update live variable information if there is any...
// Update live variable information if there is any.
LiveVariables *LV = getAnalysisToUpdate<LiveVariables>();
if (LV) {
MachineInstr *PHICopy = prior(AfterPHIsIt);
@ -177,15 +177,13 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
// 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.
//
// 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
// 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);
// If the result is dead, update LV.
@ -197,41 +195,39 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
LV->getVarInfo(IncomingReg).UsedBlocks[MBB.getNumber()] = true;
}
// Adjust the VRegPHIUseCount map to account for the removal of this PHI
// node.
// Adjust the VRegPHIUseCount map to account for the removal of this PHI node.
for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2)
--VRegPHIUseCount[BBVRegPair(MPhi->getOperand(i + 1).getMBB(),
MPhi->getOperand(i).getReg())];
// Now loop over all of the incoming arguments, changing them to copy into
// the IncomingReg register in the corresponding predecessor basic block.
//
// Now loop over all of the incoming arguments, changing them to copy into the
// IncomingReg register in the corresponding predecessor basic block.
SmallPtrSet<MachineBasicBlock*, 8> MBBsInsertedInto;
for (int i = NumSrcs - 1; i >= 0; --i) {
unsigned SrcReg = MPhi->getOperand(i*2+1).getReg();
assert(TargetRegisterInfo::isVirtualRegister(SrcReg) &&
"Machine PHI Operands must all be virtual registers!");
// If source is defined by an implicit def, there is no need to insert
// a copy unless it's the only source.
// If source is defined by an implicit def, there is no need to insert a
// copy unless it's the only source.
MachineInstr *DefMI = MRI->getVRegDef(SrcReg);
if (DefMI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF) {
ImpDefs.insert(DefMI);
continue;
}
// Get the MachineBasicBlock equivalent of the BasicBlock that is the
// source path the PHI.
// Get the MachineBasicBlock equivalent of the BasicBlock that is the source
// path the PHI.
MachineBasicBlock &opBlock = *MPhi->getOperand(i*2+2).getMBB();
// 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.
// This can happen because PHI nodes may have multiple entries for the same
// basic block.
if (!MBBsInsertedInto.insert(&opBlock))
continue; // If the copy has already been emitted, we're done.
// Find a safe location to insert the copy, this may be the first
// terminator in the block (or end()).
// Find a safe location to insert the copy, this may be the first terminator
// in the block (or end()).
MachineBasicBlock::iterator InsertPos = opBlock.getFirstTerminator();
// Insert the copy.
@ -240,26 +236,24 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
// 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.
// 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);
InRegVI.UsedBlocks[opBlock.getNumber()] = true;
// 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.
//
// 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[BBVRegPair(&opBlock, SrcReg)] != 0;
@ -316,12 +310,11 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
}
}
// Okay, if we now know that the value is not live out of the block,
// we can add a kill marker in this block saying that it kills the incoming
// value!
// Okay, if we now know that the value is not live out of the block, we can
// add a kill marker in this block saying that it kills the incoming value!
if (!ValueIsLive) {
// In our final twist, we have to decide which instruction kills the
// register. In most cases this is the copy, however, the first
// register. In most cases this is the copy, however, the first
// terminator instruction at the end of the block may also use the value.
// In this case, we should mark *it* as being the killing block, not the
// copy.