359 lines
12 KiB
C++
359 lines
12 KiB
C++
//===-- LiveInterval.cpp - Live Interval Representation -------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the LiveRange and LiveInterval classes. Given some
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// numbering of each the machine instructions an interval [i, j) is said to be a
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// live interval for register v if there is no instruction with number j' > j
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// such that v is live at j' abd there is no instruction with number i' < i such
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// that v is live at i'. In this implementation intervals can have holes,
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// i.e. an interval might look like [1,20), [50,65), [1000,1001). Each
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// individual range is represented as an instance of LiveRange, and the whole
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// interval is represented as an instance of LiveInterval.
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//
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//===----------------------------------------------------------------------===//
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#include "LiveInterval.h"
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#include "llvm/ADT/STLExtras.h"
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#include <algorithm>
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#include <iostream>
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#include <map>
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using namespace llvm;
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// An example for liveAt():
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//
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// this = [1,4), liveAt(0) will return false. The instruction defining this
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// spans slots [0,3]. The interval belongs to an spilled definition of the
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// variable it represents. This is because slot 1 is used (def slot) and spans
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// up to slot 3 (store slot).
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//
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bool LiveInterval::liveAt(unsigned I) const {
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Ranges::const_iterator r = std::upper_bound(ranges.begin(), ranges.end(), I);
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if (r == ranges.begin())
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return false;
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--r;
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return r->contains(I);
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}
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// An example for overlaps():
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//
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// 0: A = ...
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// 4: B = ...
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// 8: C = A + B ;; last use of A
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//
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// The live intervals should look like:
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//
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// A = [3, 11)
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// B = [7, x)
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// C = [11, y)
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//
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// A->overlaps(C) should return false since we want to be able to join
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// A and C.
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bool LiveInterval::overlaps(const LiveInterval& other) const {
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Ranges::const_iterator i = ranges.begin();
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Ranges::const_iterator ie = ranges.end();
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Ranges::const_iterator j = other.ranges.begin();
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Ranges::const_iterator je = other.ranges.end();
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if (i->start < j->start) {
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i = std::upper_bound(i, ie, j->start);
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if (i != ranges.begin()) --i;
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} else if (j->start < i->start) {
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j = std::upper_bound(j, je, i->start);
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if (j != other.ranges.begin()) --j;
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} else {
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return true;
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}
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while (i != ie && j != je) {
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if (i->start == j->start)
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return true;
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if (i->start > j->start) {
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std::swap(i, j);
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std::swap(ie, je);
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}
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assert(i->start < j->start);
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if (i->end > j->start)
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return true;
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++i;
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}
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return false;
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}
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/// joinable - Two intervals are joinable if the either don't overlap at all
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/// or if the destination of the copy is a single assignment value, and it
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/// only overlaps with one value in the source interval.
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bool LiveInterval::joinable(const LiveInterval &other, unsigned CopyIdx) const {
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const LiveRange *SourceLR = other.getLiveRangeContaining(CopyIdx-1);
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const LiveRange *DestLR = getLiveRangeContaining(CopyIdx);
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assert(SourceLR && DestLR && "Not joining due to a copy?");
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unsigned OtherValIdx = SourceLR->ValId;
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unsigned ThisValIdx = DestLR->ValId;
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Ranges::const_iterator i = ranges.begin();
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Ranges::const_iterator ie = ranges.end();
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Ranges::const_iterator j = other.ranges.begin();
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Ranges::const_iterator je = other.ranges.end();
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if (i->start < j->start) {
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i = std::upper_bound(i, ie, j->start);
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if (i != ranges.begin()) --i;
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} else if (j->start < i->start) {
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j = std::upper_bound(j, je, i->start);
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if (j != other.ranges.begin()) --j;
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}
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while (i != ie && j != je) {
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if (i->start == j->start) {
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// If this is not the allowed value merge, we cannot join.
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if (i->ValId != ThisValIdx || j->ValId != OtherValIdx)
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return false;
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} else if (i->start < j->start) {
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if (i->end > j->start) {
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if (i->ValId != ThisValIdx || j->ValId != OtherValIdx)
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return false;
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}
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} else {
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if (j->end > i->start) {
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if (i->ValId != ThisValIdx || j->ValId != OtherValIdx)
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return false;
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}
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}
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if (i->end < j->end)
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++i;
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else
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++j;
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}
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return true;
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}
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/// extendIntervalEndTo - This method is used when we want to extend the range
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/// specified by I to end at the specified endpoint. To do this, we should
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/// merge and eliminate all ranges that this will overlap with. The iterator is
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/// not invalidated.
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void LiveInterval::extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd) {
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assert(I != ranges.end() && "Not a valid interval!");
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unsigned ValId = I->ValId;
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// Search for the first interval that we can't merge with.
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Ranges::iterator MergeTo = next(I);
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for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) {
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assert(MergeTo->ValId == ValId && "Cannot merge with differing values!");
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}
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// If NewEnd was in the middle of an interval, make sure to get its endpoint.
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I->end = std::max(NewEnd, prior(MergeTo)->end);
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// Erase any dead ranges
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ranges.erase(next(I), MergeTo);
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}
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/// extendIntervalStartTo - This method is used when we want to extend the range
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/// specified by I to start at the specified endpoint. To do this, we should
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/// merge and eliminate all ranges that this will overlap with.
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LiveInterval::Ranges::iterator
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LiveInterval::extendIntervalStartTo(Ranges::iterator I, unsigned NewStart) {
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assert(I != ranges.end() && "Not a valid interval!");
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unsigned ValId = I->ValId;
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// Search for the first interval that we can't merge with.
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Ranges::iterator MergeTo = I;
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do {
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if (MergeTo == ranges.begin()) {
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I->start = NewStart;
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ranges.erase(MergeTo, I);
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return I;
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}
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assert(MergeTo->ValId == ValId && "Cannot merge with differing values!");
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--MergeTo;
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} while (NewStart <= MergeTo->start);
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// If we start in the middle of another interval, just delete a range and
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// extend that interval.
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if (MergeTo->end >= NewStart && MergeTo->ValId == ValId) {
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MergeTo->end = I->end;
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} else {
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// Otherwise, extend the interval right after.
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++MergeTo;
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MergeTo->start = NewStart;
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MergeTo->end = I->end;
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}
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ranges.erase(next(MergeTo), next(I));
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return MergeTo;
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}
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LiveInterval::Ranges::iterator
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LiveInterval::addRangeFrom(LiveRange LR, Ranges::iterator From) {
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unsigned Start = LR.start, End = LR.end;
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Ranges::iterator it = std::upper_bound(From, ranges.end(), Start);
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// If the inserted interval starts in the middle or right at the end of
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// another interval, just extend that interval to contain the range of LR.
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if (it != ranges.begin()) {
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Ranges::iterator B = prior(it);
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if (LR.ValId == B->ValId) {
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if (B->start <= Start && B->end >= Start) {
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extendIntervalEndTo(B, End);
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return B;
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}
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} else {
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// Check to make sure that we are not overlapping two live ranges with
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// different ValId's.
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assert(B->end <= Start &&
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"Cannot overlap two LiveRanges with differing ValID's");
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}
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}
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// Otherwise, if this range ends in the middle of, or right next to, another
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// interval, merge it into that interval.
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if (it != ranges.end())
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if (LR.ValId == it->ValId) {
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if (it->start <= End) {
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it = extendIntervalStartTo(it, Start);
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// If LR is a complete superset of an interval, we may need to grow its
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// endpoint as well.
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if (End > it->end)
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extendIntervalEndTo(it, End);
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return it;
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}
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} else {
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// Check to make sure that we are not overlapping two live ranges with
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// different ValId's.
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assert(it->start >= End &&
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"Cannot overlap two LiveRanges with differing ValID's");
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}
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// Otherwise, this is just a new range that doesn't interact with anything.
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// Insert it.
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return ranges.insert(it, LR);
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}
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/// removeRange - Remove the specified range from this interval. Note that
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/// the range must already be in this interval in its entirety.
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void LiveInterval::removeRange(unsigned Start, unsigned End) {
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// Find the LiveRange containing this span.
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Ranges::iterator I = std::upper_bound(ranges.begin(), ranges.end(), Start);
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assert(I != ranges.begin() && "Range is not in interval!");
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--I;
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assert(I->contains(Start) && I->contains(End-1) &&
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"Range is not entirely in interval!");
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// If the span we are removing is at the start of the LiveRange, adjust it.
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if (I->start == Start) {
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if (I->end == End)
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ranges.erase(I); // Removed the whole LiveRange.
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else
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I->start = End;
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return;
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}
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// Otherwise if the span we are removing is at the end of the LiveRange,
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// adjust the other way.
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if (I->end == End) {
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I->end = Start;
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return;
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}
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// Otherwise, we are splitting the LiveRange into two pieces.
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unsigned OldEnd = I->end;
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I->end = Start; // Trim the old interval.
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// Insert the new one.
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ranges.insert(next(I), LiveRange(End, OldEnd, I->ValId));
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}
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/// getLiveRangeContaining - Return the live range that contains the
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/// specified index, or null if there is none.
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const LiveRange *LiveInterval::getLiveRangeContaining(unsigned Idx) const {
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Ranges::const_iterator It = std::upper_bound(ranges.begin(),ranges.end(),Idx);
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if (It != ranges.begin()) {
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const LiveRange &LR = *prior(It);
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if (LR.contains(Idx))
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return &LR;
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}
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return 0;
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}
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/// join - Join two live intervals (this, and other) together. This operation
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/// is the result of a copy instruction in the source program, that occurs at
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/// index 'CopyIdx' that copies from 'Other' to 'this'.
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void LiveInterval::join(LiveInterval &Other, unsigned CopyIdx) {
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const LiveRange *SourceLR = Other.getLiveRangeContaining(CopyIdx-1);
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const LiveRange *DestLR = getLiveRangeContaining(CopyIdx);
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assert(SourceLR && DestLR && "Not joining due to a copy?");
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unsigned MergedSrcValIdx = SourceLR->ValId;
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unsigned MergedDstValIdx = DestLR->ValId;
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// Try to do the least amount of work possible. In particular, if there are
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// more liverange chunks in the other set than there are in the 'this' set,
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// swap sets to merge the fewest chunks in possible.
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if (Other.ranges.size() > ranges.size()) {
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std::swap(MergedSrcValIdx, MergedDstValIdx);
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std::swap(ranges, Other.ranges);
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std::swap(NumValues, Other.NumValues);
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}
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// Join the ranges of other into the ranges of this interval.
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Ranges::iterator InsertPos = ranges.begin();
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std::map<unsigned, unsigned> Dst2SrcIdxMap;
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for (Ranges::iterator I = Other.ranges.begin(),
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E = Other.ranges.end(); I != E; ++I) {
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// Map the ValId in the other live range to the current live range.
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if (I->ValId == MergedSrcValIdx)
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I->ValId = MergedDstValIdx;
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else {
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unsigned &NV = Dst2SrcIdxMap[I->ValId];
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if (NV == 0) NV = getNextValue();
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I->ValId = NV;
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}
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InsertPos = addRangeFrom(*I, InsertPos);
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}
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weight += Other.weight;
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}
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std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) {
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return os << '[' << LR.start << ',' << LR.end << ':' << LR.ValId << ")";
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}
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void LiveRange::dump() const {
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std::cerr << *this << "\n";
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}
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std::ostream& llvm::operator<<(std::ostream& os, const LiveInterval& li) {
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os << "%reg" << li.reg << ',' << li.weight;
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if (li.empty())
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return os << "EMPTY";
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os << " = ";
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for (LiveInterval::Ranges::const_iterator i = li.ranges.begin(),
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e = li.ranges.end(); i != e; ++i)
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os << *i;
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return os;
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}
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void LiveInterval::dump() const {
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std::cerr << *this << "\n";
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}
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