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When joining two intervals where the RHS is really simple, use a light-weight

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method for joining the live ranges instead of the fully-general one.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30049 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-09-02 05:26:59 +00:00
parent 6bda49fd9f
commit f21f0205b5
2 changed files with 172 additions and 11 deletions
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17
lib/CodeGen/LiveInterval.cpp
View File

@ -351,6 +351,23 @@ void LiveInterval::join(LiveInterval &Other, int *LHSValNoAssignments,
weight += Other.weight;
}
/// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
/// interval as the specified value number. The LiveRanges in RHS are
/// allowed to overlap with LiveRanges in the current interval, but only if
/// the overlapping LiveRanges have the specified value number.
void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
unsigned LHSValNo) {
// TODO: Make this more efficient.
iterator InsertPos = begin();
for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
// Map the ValId in the other live range to the current live range.
LiveRange Tmp = *I;
Tmp.ValId = LHSValNo;
InsertPos = addRangeFrom(Tmp, InsertPos);
}
}
/// MergeInClobberRanges - For any live ranges that are not defined in the
/// current interval, but are defined in the Clobbers interval, mark them
/// used with an unknown definition value.

166
lib/CodeGen/LiveIntervalAnalysis.cpp
View File

@ -883,6 +883,140 @@ static unsigned ComputeUltimateVN(unsigned VN,
return ThisValNoAssignments[VN] = UltimateVN;
}
Statistic<> A("x", "a");
Statistic<> B("x", "b");
Statistic<> C("x", "c");
Statistic<> D("x", "d");
static bool InVector(unsigned Val, const SmallVector<unsigned, 8> &V) {
return std::find(V.begin(), V.end(), Val) != V.end();
}
/// SimpleJoin - Attempt to joint the specified interval into this one. The
/// caller of this method must guarantee that the RHS only contains a single
/// value number and that the RHS is not defined by a copy from this
/// interval. This returns false if the intervals are not joinable, or it
/// joins them and returns true.
bool LiveIntervals::SimpleJoin(LiveInterval &LHS, LiveInterval &RHS) {
assert(RHS.containsOneValue());
// Some number (potentially more than one) value numbers in the current
// interval may be defined as copies from the RHS. Scan the overlapping
// portions of the LHS and RHS, keeping track of this and looking for
// overlapping live ranges that are NOT defined as copies. If these exist, we
// cannot coallesce.
LiveInterval::iterator LHSIt = LHS.begin(), LHSEnd = LHS.end();
LiveInterval::iterator RHSIt = RHS.begin(), RHSEnd = RHS.end();
if (LHSIt->start < RHSIt->start) {
LHSIt = std::upper_bound(LHSIt, LHSEnd, RHSIt->start);
if (LHSIt != LHS.begin()) --LHSIt;
} else if (RHSIt->start < LHSIt->start) {
RHSIt = std::upper_bound(RHSIt, RHSEnd, LHSIt->start);
if (RHSIt != RHS.begin()) --RHSIt;
}
SmallVector<unsigned, 8> EliminatedLHSVals;
while (1) {
// Determine if these live intervals overlap.
bool Overlaps = false;
if (LHSIt->start <= RHSIt->start)
Overlaps = LHSIt->end > RHSIt->start;
else
Overlaps = RHSIt->end > LHSIt->start;
// If the live intervals overlap, there are two interesting cases: if the
// LHS interval is defined by a copy from the RHS, it's ok and we record
// that the LHS value # is the same as the RHS. If it's not, then we cannot
// coallesce these live ranges and we bail out.
if (Overlaps) {
// If we haven't already recorded that this value # is safe, check it.
if (!InVector(LHSIt->ValId, EliminatedLHSVals)) {
// Copy from the RHS?
unsigned SrcReg = LHS.getSrcRegForValNum(LHSIt->ValId);
if (rep(SrcReg) != RHS.reg)
return false; // Nope, bail out.
EliminatedLHSVals.push_back(LHSIt->ValId);
}
// We know this entire LHS live range is okay, so skip it now.
if (++LHSIt == LHSEnd) break;
continue;
}
if (LHSIt->end < RHSIt->end) {
if (++LHSIt == LHSEnd) break;
} else {
// One interesting case to check here. It's possible that we have
// something like "X3 = Y" which defines a new value number in the LHS,
// and is the last use of this liverange of the RHS. In this case, we
// want to notice this copy (so that it gets coallesced away) even though
// the live ranges don't actually overlap.
if (LHSIt->start == RHSIt->end) {
if (InVector(LHSIt->ValId, EliminatedLHSVals)) {
// We already know that this value number is going to be merged in
// if coallescing succeeds. Just skip the liverange.
if (++LHSIt == LHSEnd) break;
} else {
// Otherwise, if this is a copy from the RHS, mark it as being merged
// in.
if (rep(LHS.getSrcRegForValNum(LHSIt->ValId)) == RHS.reg) {
EliminatedLHSVals.push_back(LHSIt->ValId);
// We know this entire LHS live range is okay, so skip it now.
if (++LHSIt == LHSEnd) break;
}
}
}
if (++RHSIt == RHSEnd) break;
}
}
// If we got here, we know that the coallescing will be successful and that
// the value numbers in EliminatedLHSVals will all be merged together. Since
// the most common case is that EliminatedLHSVals has a single number, we
// optimize for it: if there is more than one value, we merge them all into
// the lowest numbered one, then handle the interval as if we were merging
// with one value number.
unsigned LHSValNo;
if (EliminatedLHSVals.size() > 1) {
// Loop through all the equal value numbers merging them into the smallest
// one.
unsigned Smallest = EliminatedLHSVals[0];
for (unsigned i = 1, e = EliminatedLHSVals.size(); i != e; ++i) {
if (EliminatedLHSVals[i] < Smallest) {
// Merge the current notion of the smallest into the smaller one.
LHS.MergeValueNumberInto(Smallest, EliminatedLHSVals[i]);
Smallest = EliminatedLHSVals[i];
} else {
// Merge into the smallest.
LHS.MergeValueNumberInto(EliminatedLHSVals[i], Smallest);
}
}
LHSValNo = Smallest;
} else {
assert(!EliminatedLHSVals.empty() && "No copies from the RHS?");
LHSValNo = EliminatedLHSVals[0];
}
// Okay, now that there is a single LHS value number that we're merging the
// RHS into, update the value number info for the LHS to indicate that the
// value number is defined where the RHS value number was.
LHS.setValueNumberInfo(LHSValNo, RHS.getValNumInfo(0));
// Okay, the final step is to loop over the RHS live intervals, adding them to
// the LHS.
LHS.MergeRangesInAsValue(RHS, LHSValNo);
LHS.weight += RHS.weight;
return true;
}
/// JoinIntervals - Attempt to join these two intervals. On failure, this
/// returns false. Otherwise, if one of the intervals being joined is a
/// physreg, this method always canonicalizes LHS to be it. The output
@ -894,9 +1028,6 @@ bool LiveIntervals::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS) {
SmallVector<int, 16> LHSValNoAssignments;
SmallVector<int, 16> RHSValNoAssignments;
SmallVector<std::pair<unsigned,unsigned>, 16> ValueNumberInfo;
LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
ValueNumberInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums());
// Compute ultimate value numbers for the LHS and RHS values.
if (RHS.containsOneValue()) {
@ -907,19 +1038,27 @@ bool LiveIntervals::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS) {
// Find out if the RHS is defined as a copy from some value in the LHS.
int RHSValID = -1;
std::pair<unsigned,unsigned> RHSValNoInfo;
if (unsigned RHSSrcReg = RHS.getSrcRegForValNum(0)) {
if (rep(RHSSrcReg) != LHS.reg) {
RHSValNoInfo = RHS.getValNumInfo(0);
unsigned RHSSrcReg = RHS.getSrcRegForValNum(0);
if ((RHSSrcReg == 0 || rep(RHSSrcReg) != LHS.reg)) {
// If RHS is not defined as a copy from the LHS, we can use simpler and
// faster checks to see if the live ranges are coallescable. This joiner
// can't swap the LHS/RHS intervals though.
if (!MRegisterInfo::isPhysicalRegister(RHS.reg)) {
return SimpleJoin(LHS, RHS);
} else {
// It was defined as a copy from the LHS, find out what value # it is.
unsigned ValInst = RHS.getInstForValNum(0);
RHSValID = LHS.getLiveRangeContaining(ValInst-1)->ValId;
RHSValNoInfo = LHS.getValNumInfo(RHSValID);
RHSValNoInfo = RHS.getValNumInfo(0);
}
++A;
} else {
RHSValNoInfo = RHS.getValNumInfo(0);
// It was defined as a copy from the LHS, find out what value # it is.
unsigned ValInst = RHS.getInstForValNum(0);
RHSValID = LHS.getLiveRangeContaining(ValInst-1)->ValId;
RHSValNoInfo = LHS.getValNumInfo(RHSValID);
++B;
}
LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
ValueNumberInfo.resize(LHS.getNumValNums());
// Okay, *all* of the values in LHS that are defined as a copy from RHS
@ -954,6 +1093,7 @@ bool LiveIntervals::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS) {
RHSValNoAssignments[0] = RHSValID;
} else {
++D;
// Loop over the value numbers of the LHS, seeing if any are defined from
// the RHS.
SmallVector<int, 16> LHSValsDefinedFromRHS;
@ -992,6 +1132,10 @@ bool LiveIntervals::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS) {
RHSValsDefinedFromLHS[VN] = LHS.getLiveRangeContaining(ValInst-1)->ValId;
}
LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
ValueNumberInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums());
for (unsigned VN = 0, e = LHS.getNumValNums(); VN != e; ++VN) {
if (LHSValNoAssignments[VN] >= 0 || LHS.getInstForValNum(VN) == ~2U)
continue;