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Move PHIElimination's SplitCriticalEdge for MachineBasicBlocks out

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into a utility routine, teach it how to update MachineLoopInfo, and
make use of it in MachineLICM to split critical edges on demand.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106555 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2010-06-22 17:25:57 +00:00
parent 6ff1c3f36c
commit 853d3fb8d2
5 changed files with 141 additions and 77 deletions
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53
lib/CodeGen/PHIElimination.cpp
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@@ -34,7 +34,6 @@
using namespace llvm;
STATISTIC(NumAtomic, "Number of atomic phis lowered");
STATISTIC(NumSplits, "Number of critical edges split on demand");
STATISTIC(NumReused, "Number of reused lowered phis");
char PHIElimination::ID = 0;
@@ -391,58 +390,8 @@ bool llvm::PHIElimination::SplitPHIEdges(MachineFunction &MF,
// (not considering PHI nodes). If the register is live in to this block
// anyway, we would gain nothing from splitting.
if (!LV.isLiveIn(Reg, MBB) && LV.isLiveOut(Reg, *PreMBB))
SplitCriticalEdge(PreMBB, &MBB);
PreMBB->SplitCriticalEdge(&MBB, this);
}
}
return true;
}
MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
MachineBasicBlock *B) {
assert(A && B && "Missing MBB end point");
MachineFunction *MF = A->getParent();
DebugLoc dl; // FIXME: this is nowhere
// We may need to update A's terminator, but we can't do that if AnalyzeBranch
// fails. If A uses a jump table, we won't touch it.
const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
MachineBasicBlock *TBB = 0, *FBB = 0;
SmallVector<MachineOperand, 4> Cond;
if (TII->AnalyzeBranch(*A, TBB, FBB, Cond))
return NULL;
++NumSplits;
MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
MF->insert(llvm::next(MachineFunction::iterator(A)), NMBB);
DEBUG(dbgs() << "PHIElimination splitting critical edge:"
" BB#" << A->getNumber()
<< " -- BB#" << NMBB->getNumber()
<< " -- BB#" << B->getNumber() << '\n');
A->ReplaceUsesOfBlockWith(B, NMBB);
A->updateTerminator();
// Insert unconditional "jump B" instruction in NMBB if necessary.
NMBB->addSuccessor(B);
if (!NMBB->isLayoutSuccessor(B)) {
Cond.clear();
MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, B, NULL, Cond, dl);
}
// Fix PHI nodes in B so they refer to NMBB instead of A
for (MachineBasicBlock::iterator i = B->begin(), e = B->end();
i != e && i->isPHI(); ++i)
for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
if (i->getOperand(ni+1).getMBB() == A)
i->getOperand(ni+1).setMBB(NMBB);
if (LiveVariables *LV=getAnalysisIfAvailable<LiveVariables>())
LV->addNewBlock(NMBB, A, B);
if (MachineDominatorTree *MDT=getAnalysisIfAvailable<MachineDominatorTree>())
MDT->addNewBlock(NMBB, A);
return NMBB;
}