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LiveIntervalAnalysis: No need to deal with dead subregister defs anymore.

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The DetectDeadLaneMask already ensures that we have no dead subregister
definitions making the special handling in LiveIntervalAnalysis
unnecessary. This reverts most of r248335.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267937 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthias Braun 2016-04-28 20:35:26 +00:00
parent 9f608022e3
commit 277501abff
1 changed files with 3 additions and 20 deletions
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23
lib/CodeGen/LiveIntervalAnalysis.cpp
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@ -195,16 +195,9 @@ LiveInterval* LiveIntervals::createInterval(unsigned reg) {
void LiveIntervals::computeVirtRegInterval(LiveInterval &LI) {
assert(LRCalc && "LRCalc not initialized.");
assert(LI.empty() && "Should only compute empty intervals.");
bool ShouldTrackSubRegLiveness = MRI->shouldTrackSubRegLiveness(LI.reg);
LRCalc->reset(MF, getSlotIndexes(), DomTree, &getVNInfoAllocator());
LRCalc->calculate(LI, ShouldTrackSubRegLiveness);
bool SeparatedComponents = computeDeadValues(LI, nullptr);
if (SeparatedComponents) {
assert(ShouldTrackSubRegLiveness
&& "Separated components should only occur for unused subreg defs");
SmallVector<LiveInterval*, 8> SplitLIs;
splitSeparateComponents(LI, SplitLIs);
}
LRCalc->calculate(LI, MRI->shouldTrackSubRegLiveness(LI.reg));
computeDeadValues(LI, nullptr);
}
void LiveIntervals::computeVirtRegs() {
@ -487,13 +480,11 @@ bool LiveIntervals::computeDeadValues(LiveInterval &LI,
// Is the register live before? Otherwise we may have to add a read-undef
// flag for subregister defs.
bool DeadBeforeDef = false;
unsigned VReg = LI.reg;
if (MRI->shouldTrackSubRegLiveness(VReg)) {
if ((I == LI.begin() || std::prev(I)->end < Def) && !VNI->isPHIDef()) {
MachineInstr *MI = getInstructionFromIndex(Def);
MI->setRegisterDefReadUndef(VReg);
DeadBeforeDef = true;
}
}
@ -509,15 +500,7 @@ bool LiveIntervals::computeDeadValues(LiveInterval &LI,
// This is a dead def. Make sure the instruction knows.
MachineInstr *MI = getInstructionFromIndex(Def);
assert(MI && "No instruction defining live value");
MI->addRegisterDead(VReg, TRI);
// If we have a dead def that is completely separate from the rest of
// the liverange then we rewrite it to use a different VReg to not violate
// the rule that the liveness of a virtual register forms a connected
// component. This should only happen if subregister liveness is tracked.
if (DeadBeforeDef)
MayHaveSplitComponents = true;
MI->addRegisterDead(LI.reg, TRI);
if (dead && MI->allDefsAreDead()) {
DEBUG(dbgs() << "All defs dead: " << Def << '\t' << *MI);
dead->push_back(MI);