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https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29994 91177308-0d34-0410-b5e6-96231b3b80d8
497 lines
16 KiB
C++
497 lines
16 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 "llvm/CodeGen/LiveInterval.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Target/MRegisterInfo.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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// overlaps - Return true if the intersection of the two live intervals is
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// not empty.
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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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//
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bool LiveInterval::overlapsFrom(const LiveInterval& other,
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const_iterator StartPos) const {
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const_iterator i = begin();
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const_iterator ie = end();
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const_iterator j = StartPos;
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const_iterator je = other.end();
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assert((StartPos->start <= i->start || StartPos == other.begin()) &&
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StartPos != other.end() && "Bogus start position hint!");
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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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++StartPos;
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if (StartPos != other.end() && StartPos->start <= i->start) {
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assert(StartPos < other.end() && i < end());
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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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} else {
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return true;
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}
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if (j == je) return false;
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while (i != ie) {
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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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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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/// 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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// If the newly formed range now touches the range after it and if they have
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// the same value number, merge the two ranges into one range.
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Ranges::iterator Next = next(I);
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if (Next != ranges.end() && Next->start <= I->end && Next->ValId == ValId) {
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I->end = Next->end;
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ranges.erase(Next);
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}
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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::iterator
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LiveInterval::addRangeFrom(LiveRange LR, iterator From) {
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unsigned Start = LR.start, End = LR.end;
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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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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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" (did you def the same reg twice in a MachineInstr?)");
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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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LiveInterval::const_iterator
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LiveInterval::FindLiveRangeContaining(unsigned Idx) const {
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const_iterator It = std::upper_bound(begin(), end(), Idx);
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if (It != ranges.begin()) {
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--It;
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if (It->contains(Idx))
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return It;
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}
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return end();
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}
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LiveInterval::iterator
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LiveInterval::FindLiveRangeContaining(unsigned Idx) {
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iterator It = std::upper_bound(begin(), end(), Idx);
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if (It != begin()) {
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--It;
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if (It->contains(Idx))
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return It;
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}
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return end();
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}
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/// join - Join two live intervals (this, and other) together. This applies
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/// mappings to the value numbers in the LHS/RHS intervals as specified. If
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/// the intervals are not joinable, this aborts.
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void LiveInterval::join(LiveInterval &Other, int *LHSValNoAssignments,
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int *RHSValNoAssignments,
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SmallVector<std::pair<unsigned,
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unsigned>, 16> &NewValueNumberInfo) {
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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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//
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// Also, if one range is a physreg and one is a vreg, we always merge from the
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// vreg into the physreg, which leaves the vreg intervals pristine.
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unsigned OtherOffs = 1, ThisOffs = 0;
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if ((Other.ranges.size() > ranges.size() &&
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MRegisterInfo::isVirtualRegister(reg)) ||
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MRegisterInfo::isPhysicalRegister(Other.reg)) {
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swap(Other);
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std::swap(LHSValNoAssignments, RHSValNoAssignments);
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}
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// Determine if any of our live range values are mapped. This is uncommon, so
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// we want to avoid the interval scan if not.
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bool MustMapCurValNos = false;
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for (unsigned i = 0, e = getNumValNums(); i != e; ++i) {
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if (ValueNumberInfo[i].first == ~2U) continue; // tombstone value #
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if (i != (unsigned)LHSValNoAssignments[i]) {
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MustMapCurValNos = true;
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break;
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}
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}
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// If we have to apply a mapping to our base interval assignment, rewrite it
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// now.
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if (MustMapCurValNos) {
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// Map the first live range.
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iterator OutIt = begin();
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OutIt->ValId = LHSValNoAssignments[OutIt->ValId];
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++OutIt;
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for (iterator I = OutIt, E = end(); I != E; ++I) {
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OutIt->ValId = LHSValNoAssignments[I->ValId];
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// If this live range has the same value # as its immediate predecessor,
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// and if they are neighbors, remove one LiveRange. This happens when we
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// have [0,3:0)[4,7:1) and map 0/1 onto the same value #.
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if (OutIt->ValId == (OutIt-1)->ValId && (OutIt-1)->end == OutIt->start) {
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(OutIt-1)->end = OutIt->end;
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} else {
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if (I != OutIt) {
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OutIt->start = I->start;
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OutIt->end = I->end;
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}
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// Didn't merge, on to the next one.
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++OutIt;
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}
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}
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// If we merge some live ranges, chop off the end.
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ranges.erase(OutIt, end());
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}
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// Okay, now insert the RHS live ranges into the LHS.
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iterator InsertPos = begin();
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for (iterator I = Other.begin(), E = Other.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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I->ValId = RHSValNoAssignments[I->ValId];
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InsertPos = addRangeFrom(*I, InsertPos);
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}
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ValueNumberInfo.clear();
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ValueNumberInfo.append(NewValueNumberInfo.begin(), NewValueNumberInfo.end());
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weight += Other.weight;
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}
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/// MergeInClobberRanges - For any live ranges that are not defined in the
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/// current interval, but are defined in the Clobbers interval, mark them
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/// used with an unknown definition value.
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void LiveInterval::MergeInClobberRanges(const LiveInterval &Clobbers) {
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if (Clobbers.begin() == Clobbers.end()) return;
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// Find a value # to use for the clobber ranges. If there is already a value#
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// for unknown values, use it.
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// FIXME: Use a single sentinal number for these!
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unsigned ClobberValNo = getNextValue(~0U, 0);
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iterator IP = begin();
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for (const_iterator I = Clobbers.begin(), E = Clobbers.end(); I != E; ++I) {
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unsigned Start = I->start, End = I->end;
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IP = std::upper_bound(IP, end(), Start);
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// If the start of this range overlaps with an existing liverange, trim it.
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if (IP != begin() && IP[-1].end > Start) {
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Start = IP[-1].end;
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// Trimmed away the whole range?
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if (Start >= End) continue;
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}
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// If the end of this range overlaps with an existing liverange, trim it.
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if (IP != end() && End > IP->start) {
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End = IP->start;
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// If this trimmed away the whole range, ignore it.
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if (Start == End) continue;
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}
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// Insert the clobber interval.
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IP = addRangeFrom(LiveRange(Start, End, ClobberValNo), IP);
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}
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}
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/// MergeValueNumberInto - This method is called when two value nubmers
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/// are found to be equivalent. This eliminates V1, replacing all
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/// LiveRanges with the V1 value number with the V2 value number. This can
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/// cause merging of V1/V2 values numbers and compaction of the value space.
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void LiveInterval::MergeValueNumberInto(unsigned V1, unsigned V2) {
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assert(V1 != V2 && "Identical value#'s are always equivalent!");
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// This code actually merges the (numerically) larger value number into the
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// smaller value number, which is likely to allow us to compactify the value
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// space. The only thing we have to be careful of is to preserve the
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// instruction that defines the result value.
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// Make sure V2 is smaller than V1.
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if (V1 < V2) {
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setValueNumberInfo(V1, getValNumInfo(V2));
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std::swap(V1, V2);
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}
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// Merge V1 live ranges into V2.
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for (iterator I = begin(); I != end(); ) {
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iterator LR = I++;
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if (LR->ValId != V1) continue; // Not a V1 LiveRange.
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// Okay, we found a V1 live range. If it had a previous, touching, V2 live
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// range, extend it.
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if (LR != begin()) {
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iterator Prev = LR-1;
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if (Prev->ValId == V2 && Prev->end == LR->start) {
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Prev->end = LR->end;
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// Erase this live-range.
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ranges.erase(LR);
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I = Prev+1;
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LR = Prev;
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}
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}
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// Okay, now we have a V1 or V2 live range that is maximally merged forward.
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// Ensure that it is a V2 live-range.
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LR->ValId = V2;
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// If we can merge it into later V2 live ranges, do so now. We ignore any
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// following V1 live ranges, as they will be merged in subsequent iterations
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// of the loop.
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if (I != end()) {
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if (I->start == LR->end && I->ValId == V2) {
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LR->end = I->end;
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ranges.erase(I);
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I = LR+1;
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}
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}
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}
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// Now that V1 is dead, remove it. If it is the largest value number, just
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// nuke it (and any other deleted values neighboring it), otherwise mark it as
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// ~1U so it can be nuked later.
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if (V1 == getNumValNums()-1) {
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do {
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ValueNumberInfo.pop_back();
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} while (ValueNumberInfo.back().first == ~1U);
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} else {
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ValueNumberInfo[V1].first = ~1U;
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}
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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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void LiveInterval::print(std::ostream &OS, const MRegisterInfo *MRI) const {
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if (MRI && MRegisterInfo::isPhysicalRegister(reg))
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OS << MRI->getName(reg);
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else
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OS << "%reg" << reg;
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OS << ',' << weight;
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if (empty())
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OS << "EMPTY";
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else {
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OS << " = ";
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for (LiveInterval::Ranges::const_iterator I = ranges.begin(),
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E = ranges.end(); I != E; ++I)
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OS << *I;
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}
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// Print value number info.
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if (getNumValNums()) {
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OS << " ";
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for (unsigned i = 0; i != getNumValNums(); ++i) {
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if (i) OS << " ";
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OS << i << "@";
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if (ValueNumberInfo[i].first == ~0U) {
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OS << "?";
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} else {
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OS << ValueNumberInfo[i].first;
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}
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}
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}
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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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