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Refactoring: Extract method PHIElimination::isLiveOut().

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Clean up some whitespace.
No functional changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86724 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2009-11-10 22:00:56 +00:00
parent 6f84a5feee
commit e35e3c33dc
2 changed files with 64 additions and 68 deletions
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112
lib/CodeGen/PHIElimination.cpp
View File

@@ -267,75 +267,17 @@ void llvm::PHIElimination::LowerAtomicPHINode(
// 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[BBVRegPair(&opBlock, 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 (InRegVI.AliveBlocks.test(SuccIdx)) {
ValueIsLive = true;
break;
}
OpSuccBlocks.push_back(SuccMBB);
}
// 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;
}
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;
}
}
}
bool ValueIsUsed = VRegPHIUseCount[BBVRegPair(&opBlock, SrcReg)] != 0;
// 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) {
if (!ValueIsUsed && !isLiveOut(SrcReg, opBlock, *LV)) {
// In our final twist, we have to decide which instruction kills the
// register. In most cases this is the copy, however, the first
// terminator instruction at the end of the block may also use the value.
@@ -363,7 +305,7 @@ void llvm::PHIElimination::LowerAtomicPHINode(
// This vreg no longer lives all of the way through opBlock.
unsigned opBlockNum = opBlock.getNumber();
InRegVI.AliveBlocks.reset(opBlockNum);
LV->getVarInfo(SrcReg).AliveBlocks.reset(opBlockNum);
}
}
@@ -386,3 +328,51 @@ void llvm::PHIElimination::analyzePHINodes(const MachineFunction& Fn) {
++VRegPHIUseCount[BBVRegPair(BBI->getOperand(i + 1).getMBB(),
BBI->getOperand(i).getReg())];
}
bool llvm::PHIElimination::isLiveOut(unsigned Reg, const MachineBasicBlock &MBB,
LiveVariables &LV) {
LiveVariables::VarInfo &InRegVI = LV.getVarInfo(Reg);
// 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.
std::vector<MachineBasicBlock*> OpSuccBlocks;
// Otherwise, scan successors, including the BB the PHI node lives in.
for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
E = MBB.succ_end(); SI != E; ++SI) {
MachineBasicBlock *SuccMBB = *SI;
// Is it alive in this successor?
unsigned SuccIdx = SuccMBB->getNumber();
if (InRegVI.AliveBlocks.test(SuccIdx))
return true;
OpSuccBlocks.push_back(SuccMBB);
}
// Check to see if this value is live because there is a use in a successor
// that kills it.
switch (OpSuccBlocks.size()) {
case 1: {
MachineBasicBlock *SuccMBB = OpSuccBlocks[0];
for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i)
if (InRegVI.Kills[i]->getParent() == SuccMBB)
return true;
break;
}
case 2: {
MachineBasicBlock *SuccMBB1 = OpSuccBlocks[0], *SuccMBB2 = OpSuccBlocks[1];
for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i)
if (InRegVI.Kills[i]->getParent() == SuccMBB1 ||
InRegVI.Kills[i]->getParent() == SuccMBB2)
return true;
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()))
return true;
}
return false;
}

6
lib/CodeGen/PHIElimination.h
View File

@@ -89,6 +89,12 @@ namespace llvm {
///
void analyzePHINodes(const MachineFunction& Fn);
/// isLiveOut - Determine if Reg is live out from MBB, when not
/// considering PHI nodes. This means that Reg is either killed by
/// a successor block or passed through one.
bool isLiveOut(unsigned Reg, const MachineBasicBlock &MBB,
LiveVariables &LV);
// FindCopyInsertPoint - Find a safe place in MBB to insert a copy from
// SrcReg. This needs to be after any def or uses of SrcReg, but before
// any subsequent point where control flow might jump out of the basic