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LiveInterval: Implement feedback by Quentin Colombet.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225413 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -635,9 +635,8 @@ static VNInfo *searchForVNI(const SlotIndexes &Indexes, LiveRange &LR,
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// Continue at predecessors (we could even go to idom with domtree available).
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for (const MachineBasicBlock *Pred : MBB->predecessors()) {
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// Avoid going in circles.
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if (Visited.count(Pred))
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if (!Visited.insert(Pred).second)
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continue;
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Visited.insert(Pred);
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VNI = searchForVNI(Indexes, LR, Pred, Visited);
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if (VNI != nullptr) {
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@ -649,6 +648,27 @@ static VNInfo *searchForVNI(const SlotIndexes &Indexes, LiveRange &LR,
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return VNI;
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}
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static void determineMissingVNIs(const SlotIndexes &Indexes, LiveInterval &LI) {
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SmallPtrSet<const MachineBasicBlock*, 5> Visited;
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for (LiveRange::Segment &S : LI.segments) {
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if (S.valno != nullptr)
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continue;
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// This can only happen at the begin of a basic block.
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assert(S.start.isBlock() && "valno should only be missing at block begin");
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Visited.clear();
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const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(S.start);
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for (const MachineBasicBlock *Pred : MBB->predecessors()) {
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VNInfo *VNI = searchForVNI(Indexes, LI, Pred, Visited);
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if (VNI != nullptr) {
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S.valno = VNI;
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break;
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}
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}
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assert(S.valno != nullptr && "could not determine valno");
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}
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}
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void LiveInterval::constructMainRangeFromSubranges(
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const SlotIndexes &Indexes, VNInfo::Allocator &VNIAllocator) {
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// The basic observations on which this algorithm is based:
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@ -659,7 +679,7 @@ void LiveInterval::constructMainRangeFromSubranges(
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// live either.
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// We do this by scannig through all the subranges simultaneously creating new
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// segments in the main range as segments start/ends come up in the subranges.
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assert(hasSubRanges());
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assert(hasSubRanges() && "expected subranges to be present");
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assert(segments.empty() && valnos.empty() && "expected empty main range");
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// Collect subrange, iterator pairs for the walk and determine first and last
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@ -690,7 +710,9 @@ void LiveInterval::constructMainRangeFromSubranges(
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BEGIN_SEGMENT,
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END_SEGMENT,
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} Event = NOTHING;
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// Which subregister lanes are affected by the current event.
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unsigned EventMask = 0;
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// Whether a BEGIN_SEGMENT is also a valno definition point.
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bool IsDef = false;
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// Find the next begin or end of a subrange segment. Combine masks if we
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// have multiple begins/ends at the same position. Ends take precedence over
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@ -698,6 +720,8 @@ void LiveInterval::constructMainRangeFromSubranges(
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for (auto &SRP : SRs) {
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const SubRange &SR = *SRP.first;
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const_iterator &I = SRP.second;
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// Advance iterator of subrange to a segment involving Pos; the earlier
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// segments are already merged at this point.
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while (I != SR.end() &&
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(I->end < Pos ||
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(I->end == Pos && (ActiveMask & SR.LaneMask) == 0)))
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@ -706,7 +730,7 @@ void LiveInterval::constructMainRangeFromSubranges(
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continue;
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if ((ActiveMask & SR.LaneMask) == 0 &&
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Pos <= I->start && I->start <= NextPos) {
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// Merge multiple begins at the same position
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// Merge multiple begins at the same position.
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if (I->start == NextPos && Event == BEGIN_SEGMENT) {
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EventMask |= SR.LaneMask;
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IsDef |= I->valno->def == I->start;
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@ -789,27 +813,10 @@ void LiveInterval::constructMainRangeFromSubranges(
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// We might not be able to assign new valnos for all segments if the basic
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// block containing the definition comes after a segment using the valno.
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// Do a fixup pass for this uncommon case.
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if (NeedVNIFixup) {
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SmallPtrSet<const MachineBasicBlock*, 5> Visited;
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for (Segment &S : segments) {
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if (S.valno != nullptr)
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continue;
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// This can only happen at the begin of a basic block.
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assert(S.start.isBlock());
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if (NeedVNIFixup)
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determineMissingVNIs(Indexes, *this);
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Visited.clear();
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const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(S.start);
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for (const MachineBasicBlock *Pred : MBB->predecessors()) {
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VNInfo *VNI = searchForVNI(Indexes, *this, Pred, Visited);
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if (VNI != nullptr) {
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S.valno = VNI;
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break;
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}
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}
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assert(S.valno != nullptr);
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}
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}
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assert(ActiveMask == 0 && !ConstructingSegment);
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assert(ActiveMask == 0 && !ConstructingSegment && "all segments ended");
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verify();
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}
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