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Cache the fairly expensive last split point computation and provide a fast

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inlined path for the common case.

Most basic blocks don't contain a call that may throw, so the last split point
os simply the first terminator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128874 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2011-04-05 04:20:27 +00:00
parent f05b1dcf87
commit 1a7744501a
3 changed files with 58 additions and 14 deletions
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46
lib/CodeGen/SplitKit.cpp
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@ -48,7 +48,8 @@ SplitAnalysis::SplitAnalysis(const VirtRegMap &vrm,
LIS(lis),
Loops(mli),
TII(*MF.getTarget().getInstrInfo()),
CurLI(0) {}
CurLI(0),
LastSplitPoint(MF.getNumBlockIDs()) {}
void SplitAnalysis::clear() {
UseSlots.clear();
@ -58,10 +59,39 @@ void SplitAnalysis::clear() {
CurLI = 0;
}
bool SplitAnalysis::canAnalyzeBranch(const MachineBasicBlock *MBB) {
MachineBasicBlock *T, *F;
SmallVector<MachineOperand, 4> Cond;
return !TII.AnalyzeBranch(const_cast<MachineBasicBlock&>(*MBB), T, F, Cond);
SlotIndex SplitAnalysis::computeLastSplitPoint(unsigned Num) {
const MachineBasicBlock *MBB = MF.getBlockNumbered(Num);
const MachineBasicBlock *LPad = MBB->getLandingPadSuccessor();
std::pair<SlotIndex, SlotIndex> &LSP = LastSplitPoint[Num];
// Compute split points on the first call. The pair is independent of the
// current live interval.
if (!LSP.first.isValid()) {
MachineBasicBlock::const_iterator FirstTerm = MBB->getFirstTerminator();
if (FirstTerm == MBB->end())
LSP.first = LIS.getMBBEndIdx(MBB);
else
LSP.first = LIS.getInstructionIndex(FirstTerm);
// If there is a landing pad successor, also find the call instruction.
if (!LPad)
return LSP.first;
// There may not be a call instruction (?) in which case we ignore LPad.
LSP.second = LSP.first;
for (MachineBasicBlock::const_iterator I = FirstTerm, E = MBB->begin();
I != E; --I)
if (I->getDesc().isCall()) {
LSP.second = LIS.getInstructionIndex(I);
break;
}
}
// If CurLI is live into a landing pad successor, move the last split point
// back to the call that may throw.
if (LPad && LSP.second.isValid() && !LIS.isLiveInToMBB(*CurLI, LPad))
return LSP.second;
else
return LSP.first;
}
/// analyzeUses - Count instructions, basic blocks, and loops using CurLI.
@ -125,11 +155,7 @@ bool SplitAnalysis::calcLiveBlockInfo() {
// all successor blocks. If interference reaches LastSplitPoint, it is not
// possible to insert a split or reload that makes CurLI live in the
// outgoing bundle.
MachineBasicBlock::iterator LSP = LIS.getLastSplitPoint(*CurLI, BI.MBB);
if (LSP == BI.MBB->end())
BI.LastSplitPoint = Stop;
else
BI.LastSplitPoint = LIS.getInstructionIndex(LSP);
BI.LastSplitPoint = getLastSplitPoint(BI.MBB->getNumber());
// LVI is the first live segment overlapping MBB.
BI.LiveIn = LVI->start <= Start;