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it makes no sense for allocation_order iterators to visit reserved regs. The inline spiller depends on AliasAnalysis. Manage the Query state to avoid uninitialized or stale results. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118800 91177308-0d34-0410-b5e6-96231b3b80d8
281 lines
9.8 KiB
C++
281 lines
9.8 KiB
C++
//===-- LiveIntervalUnion.h - Live interval union data struct --*- C++ -*--===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// LiveIntervalUnion is a union of live segments across multiple live virtual
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// registers. This may be used during coalescing to represent a congruence
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// class, or during register allocation to model liveness of a physical
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// register.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_LIVEINTERVALUNION
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#define LLVM_CODEGEN_LIVEINTERVALUNION
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#include "llvm/CodeGen/LiveInterval.h"
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#include <vector>
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#include <set>
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namespace llvm {
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#ifndef NDEBUG
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// forward declaration
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template <unsigned Element> class SparseBitVector;
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typedef SparseBitVector<128> LvrBitSet;
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#endif
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/// A LiveSegment is a copy of a LiveRange object used within
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/// LiveIntervalUnion. LiveSegment additionally contains a pointer to its
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/// original live virtual register (LiveInterval). This allows quick lookup of
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/// the live virtual register as we iterate over live segments in a union. Note
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/// that LiveRange is misnamed and actually represents only a single contiguous
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/// interval within a virtual register's liveness. To limit confusion, in this
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/// file we refer it as a live segment.
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///
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/// Note: This currently represents a half-open interval [start,end).
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/// If LiveRange is modified to represent a closed interval, so should this.
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struct LiveSegment {
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SlotIndex start;
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SlotIndex end;
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LiveInterval *liveVirtReg;
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LiveSegment(SlotIndex s, SlotIndex e, LiveInterval *lvr)
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: start(s), end(e), liveVirtReg(lvr) {}
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bool operator==(const LiveSegment &ls) const {
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return start == ls.start && end == ls.end && liveVirtReg == ls.liveVirtReg;
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}
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bool operator!=(const LiveSegment &ls) const {
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return !operator==(ls);
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}
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// Order segments by starting point only--we expect them to be disjoint.
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bool operator<(const LiveSegment &ls) const { return start < ls.start; }
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void dump() const;
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void print(raw_ostream &os) const;
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};
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inline bool operator<(SlotIndex V, const LiveSegment &ls) {
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return V < ls.start;
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}
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inline bool operator<(const LiveSegment &ls, SlotIndex V) {
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return ls.start < V;
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}
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/// Compare a live virtual register segment to a LiveIntervalUnion segment.
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inline bool overlap(const LiveRange &lvrSeg, const LiveSegment &liuSeg) {
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return lvrSeg.start < liuSeg.end && liuSeg.start < lvrSeg.end;
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}
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template <> struct isPodLike<LiveSegment> { static const bool value = true; };
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raw_ostream& operator<<(raw_ostream& os, const LiveSegment &ls);
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/// Abstraction to provide info for the representative register.
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class AbstractRegisterDescription {
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public:
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virtual const char *getName(unsigned reg) const = 0;
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virtual ~AbstractRegisterDescription() {}
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};
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/// Union of live intervals that are strong candidates for coalescing into a
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/// single register (either physical or virtual depending on the context). We
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/// expect the constituent live intervals to be disjoint, although we may
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/// eventually make exceptions to handle value-based interference.
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class LiveIntervalUnion {
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// A set of live virtual register segments that supports fast insertion,
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// intersection, and removal.
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//
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// FIXME: std::set is a placeholder until we decide how to
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// efficiently represent it. Probably need to roll our own B-tree.
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typedef std::set<LiveSegment> LiveSegments;
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// A set of live virtual registers. Elements have type LiveInterval, where
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// each element represents the liveness of a single live virtual register.
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// This is traditionally known as a live range, but we refer is as a live
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// virtual register to avoid confusing it with the misnamed LiveRange
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// class.
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typedef std::vector<LiveInterval*> LiveVirtRegs;
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public:
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// SegmentIter can advance to the next segment ordered by starting position
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// which may belong to a different live virtual register. We also must be able
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// to reach the current segment's containing virtual register.
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typedef LiveSegments::iterator SegmentIter;
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class InterferenceResult;
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class Query;
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private:
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unsigned repReg_; // representative register number
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LiveSegments segments_; // union of virtual reg segements
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public:
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// default ctor avoids placement new
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LiveIntervalUnion() : repReg_(0) {}
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// Initialize the union by associating it with a representative register
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// number.
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void init(unsigned repReg) { repReg_ = repReg; }
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// Iterate over all segments in the union of live virtual registers ordered
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// by their starting position.
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SegmentIter begin() { return segments_.begin(); }
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SegmentIter end() { return segments_.end(); }
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// Return an iterator to the first segment after or including begin that
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// intersects with lvrSeg.
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SegmentIter upperBound(SegmentIter begin, const LiveSegment &seg);
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// Add a live virtual register to this union and merge its segments.
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// Holds a nonconst reference to the LVR for later maniplution.
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void unify(LiveInterval &lvr);
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// Remove a live virtual register's segments from this union.
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void extract(const LiveInterval &lvr);
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void dump(const AbstractRegisterDescription *regInfo) const;
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// If tri != NULL, use it to decode repReg_
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void print(raw_ostream &os, const AbstractRegisterDescription *rdesc) const;
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#ifndef NDEBUG
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// Verify the live intervals in this union and add them to the visited set.
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void verify(LvrBitSet& visitedVRegs);
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#endif
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/// Cache a single interference test result in the form of two intersecting
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/// segments. This allows efficiently iterating over the interferences. The
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/// iteration logic is handled by LiveIntervalUnion::Query which may
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/// filter interferences depending on the type of query.
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class InterferenceResult {
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friend class Query;
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LiveInterval::iterator lvrSegI_; // current position in _lvr
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SegmentIter liuSegI_; // current position in _liu
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// Internal ctor.
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InterferenceResult(LiveInterval::iterator lvrSegI, SegmentIter liuSegI)
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: lvrSegI_(lvrSegI), liuSegI_(liuSegI) {}
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public:
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// Public default ctor.
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InterferenceResult(): lvrSegI_(), liuSegI_() {}
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// Note: this interface provides raw access to the iterators because the
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// result has no way to tell if it's valid to dereference them.
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// Access the lvr segment.
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LiveInterval::iterator lvrSegPos() const { return lvrSegI_; }
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// Access the liu segment.
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SegmentIter liuSegPos() const { return liuSegI_; }
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bool operator==(const InterferenceResult &ir) const {
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return lvrSegI_ == ir.lvrSegI_ && liuSegI_ == ir.liuSegI_;
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}
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bool operator!=(const InterferenceResult &ir) const {
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return !operator==(ir);
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}
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};
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/// Query interferences between a single live virtual register and a live
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/// interval union.
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class Query {
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LiveIntervalUnion *liu_;
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LiveInterval *lvr_;
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InterferenceResult firstInterference_;
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SmallVector<LiveInterval*,4> interferingVRegs_;
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bool seenUnspillableVReg_;
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public:
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Query(): liu_(), lvr_() {}
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Query(LiveInterval *lvr, LiveIntervalUnion *liu):
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liu_(liu), lvr_(lvr), seenUnspillableVReg_(false) {}
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void clear() {
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liu_ = NULL;
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lvr_ = NULL;
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firstInterference_ = InterferenceResult();
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interferingVRegs_.clear();
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seenUnspillableVReg_ = false;
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}
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void init(LiveInterval *lvr, LiveIntervalUnion *liu) {
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if (lvr_ == lvr) {
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// We currently allow query objects to be reused acrossed live virtual
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// registers, but always for the same live interval union.
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assert(liu_ == liu && "inconsistent initialization");
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// Retain cached results, e.g. firstInterference.
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return;
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}
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liu_ = liu;
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lvr_ = lvr;
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// Clear cached results.
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firstInterference_ = InterferenceResult();
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interferingVRegs_.clear();
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seenUnspillableVReg_ = false;
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}
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LiveInterval &lvr() const { assert(lvr_ && "uninitialized"); return *lvr_; }
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bool isInterference(const InterferenceResult &ir) const {
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if (ir.lvrSegI_ != lvr_->end()) {
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assert(overlap(*ir.lvrSegI_, *ir.liuSegI_) &&
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"invalid segment iterators");
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return true;
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}
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return false;
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}
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// Does this live virtual register interfere with the union.
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bool checkInterference() { return isInterference(firstInterference()); }
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// Get the first pair of interfering segments, or a noninterfering result.
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// This initializes the firstInterference_ cache.
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InterferenceResult firstInterference();
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// Treat the result as an iterator and advance to the next interfering pair
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// of segments. Visiting each unique interfering pairs means that the same
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// lvr or liu segment may be visited multiple times.
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bool nextInterference(InterferenceResult &ir) const;
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// Count the virtual registers in this union that interfere with this
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// query's live virtual register, up to maxInterferingRegs.
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unsigned collectInterferingVRegs(unsigned maxInterferingRegs = UINT_MAX);
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// Was this virtual register visited during collectInterferingVRegs?
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bool isSeenInterference(LiveInterval *lvr) const;
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// Did collectInterferingVRegs encounter an unspillable vreg?
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bool seenUnspillableVReg() const {
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return seenUnspillableVReg_;
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}
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// Vector generated by collectInterferingVRegs.
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const SmallVectorImpl<LiveInterval*> &interferingVRegs() const {
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return interferingVRegs_;
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}
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private:
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Query(const Query&); // DO NOT IMPLEMENT
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void operator=(const Query&); // DO NOT IMPLEMENT
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// Private interface for queries
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void findIntersection(InterferenceResult &ir) const;
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};
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};
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} // end namespace llvm
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#endif // !defined(LLVM_CODEGEN_LIVEINTERVALUNION)
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