Improve comments a bit

Use an explicit LiveRange class to represent ranges instead of an std::pair.
This is a minor cleanup, but is really intended to make a future patch simpler
and less invasive.

Alkis, could you please take a look at LiveInterval::liveAt?  I suspect that
you can add an operator<(unsigned) to LiveRange, allowing us to speed up the
upper_bound call by quite a bit (this would also apply to other callers of
upper/lower_bound).  I would do it myself, but I still don't understand that
crazy liveAt function, despite the comment. :)

Basically I would like to see this:
    LiveRange dummy(index, index+1);
    Ranges::const_iterator r = std::upper_bound(ranges.begin(),
                                                ranges.end(),
                                                dummy);

Turn into:
    Ranges::const_iterator r = std::upper_bound(ranges.begin(),
                                                ranges.end(),
                                                index);


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15130 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/LiveIntervalAnalysis.h

@@ -29,9 +29,29 @@ namespace llvm {
     class MRegisterInfo;
     class VirtRegMap;
 
+    /// LiveRange structure - This represents a simple register range in the
+    /// program, with an inclusive start point and an exclusive end point.
+    /// These ranges are rendered as [start,end).
+    struct LiveRange {
+      unsigned start;  // Start point of the interval (inclusive)
+      unsigned end;  // End point of the interval (exclusive)
+      LiveRange(unsigned S, unsigned E) : start(S), end(E) {
+        assert(S < E && "Cannot create empty or backwards range");
+      }
+
+      bool operator<(const LiveRange &LR) const {
+        return start < LR.start || (start == LR.start && end < LR.end);
+      }
+      bool operator==(const LiveRange &LR) const {
+        return start == LR.start && end == LR.end;
+      }
+    private:
+      LiveRange(); // DO NOT IMPLEMENT
+    };
+    std::ostream& operator<<(std::ostream& os, const LiveRange &LR);
+
     struct LiveInterval {
-        typedef std::pair<unsigned, unsigned> Range;
+        typedef std::vector<LiveRange> Ranges;
-        typedef std::vector<Range> Ranges;
         unsigned reg;   // the register of this interval
         float weight;   // weight of this interval:
                         //     (number of uses *10^loopDepth)
@@ -44,14 +64,17 @@ namespace llvm {
 
         bool spilled() const;
 
+        /// start - Return the lowest numbered slot covered by interval.
         unsigned start() const {
             assert(!empty() && "empty interval for register");
-            return ranges.front().first;
+            return ranges.front().start;
         }
 
+        /// end - return the maximum point of the interval of the whole,
+        /// exclusive.
         unsigned end() const {
             assert(!empty() && "empty interval for register");
-            return ranges.back().second;
+            return ranges.back().end;
         }
 
         bool expiredAt(unsigned index) const {
@@ -62,7 +85,7 @@ namespace llvm {
 
         bool overlaps(const LiveInterval& other) const;
 
-        void addRange(unsigned start, unsigned end);
+        void addRange(LiveRange R);
 
         void join(const LiveInterval& other);
 

lib/CodeGen/LiveIntervalAnalysis.cpp

@@ -194,8 +194,8 @@ std::vector<LiveInterval*> LiveIntervals::addIntervalsForSpills(
 
     for (LiveInterval::Ranges::const_iterator
               i = li.ranges.begin(), e = li.ranges.end(); i != e; ++i) {
-        unsigned index = getBaseIndex(i->first);
+        unsigned index = getBaseIndex(i->start);
-        unsigned end = getBaseIndex(i->second-1) + InstrSlots::NUM;
+        unsigned end = getBaseIndex(i->end-1) + InstrSlots::NUM;
         for (; index != end; index += InstrSlots::NUM) {
             // skip deleted instructions
             while (index != end && !getInstructionFromIndex(index))
@@ -250,7 +250,7 @@ std::vector<LiveInterval*> LiveIntervals::addIntervalsForSpills(
                         // the spill weight is now infinity as it
                         // cannot be spilled again
                         nI.weight = HUGE_VAL;
-                        nI.addRange(start, end);
+                        nI.addRange(LiveRange(start, end));
                         added.push_back(&nI);
                         // update live variables
                         lv_->addVirtualRegisterKilled(nReg, mi);
@@ -308,7 +308,7 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
            if (killIdx > defIndex) {
               assert(vi.AliveBlocks.empty() && 
                      "Shouldn't be alive across any blocks!");
-              interval.addRange(defIndex, killIdx);
+              interval.addRange(LiveRange(defIndex, killIdx));
               DEBUG(std::cerr << "\n");
               return;
            }
@@ -318,8 +318,9 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
        // of the defining block, potentially live across some blocks, then is
        // live into some number of blocks, but gets killed.  Start by adding a
        // range that goes from this definition to the end of the defining block.
-       interval.addRange(defIndex, 
+       interval.addRange(LiveRange(defIndex, 
-                         getInstructionIndex(&mbb->back()) + InstrSlots::NUM);
+                                   getInstructionIndex(&mbb->back()) +
+                                         InstrSlots::NUM));
 
        // Iterate over all of the blocks that the variable is completely
        // live in, adding [insrtIndex(begin), instrIndex(end)+4) to the
@@ -328,9 +329,9 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
            if (vi.AliveBlocks[i]) {
                MachineBasicBlock* mbb = mf_->getBlockNumbered(i);
                if (!mbb->empty()) {
-                   interval.addRange(
+                   interval.addRange(LiveRange(
                        getInstructionIndex(&mbb->front()),
-                       getInstructionIndex(&mbb->back()) + InstrSlots::NUM);
+                       getInstructionIndex(&mbb->back()) + InstrSlots::NUM));
                }
            }
        }
@@ -339,8 +340,9 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
        // block to the 'use' slot of the killing instruction.
        for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i) {
            MachineInstr *Kill = vi.Kills[i];
-           interval.addRange(getInstructionIndex(Kill->getParent()->begin()),
+           interval.addRange(LiveRange(
-                             getUseIndex(getInstructionIndex(Kill))+1);
+                             getInstructionIndex(Kill->getParent()->begin()),
+                             getUseIndex(getInstructionIndex(Kill))+1));
        }
 
     } else {
@@ -357,8 +359,8 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
          // the defined value will be live until the end of the basic block it
          // is defined in.
          unsigned defIndex = getDefIndex(getInstructionIndex(mi));
-         interval.addRange(defIndex, 
+         interval.addRange(LiveRange(defIndex, 
-                           getInstructionIndex(&mbb->back()) + InstrSlots::NUM);
+                           getInstructionIndex(&mbb->back()) +InstrSlots::NUM));
        }
        interval.isDefinedOnce = false;
     }
@@ -410,7 +412,7 @@ void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock* mbb,
 
 exit:
     assert(start < end && "did not find end of interval?");
-    interval.addRange(start, end);
+    interval.addRange(LiveRange(start, end));
     DEBUG(std::cerr << '\n');
 }
 
@@ -682,7 +684,7 @@ bool LiveInterval::spilled() const
 //
 bool LiveInterval::liveAt(unsigned index) const
 {
-    Range dummy(index, index+1);
+    LiveRange dummy(index, index+1);
     Ranges::const_iterator r = std::upper_bound(ranges.begin(),
                                                 ranges.end(),
                                                 dummy);
@@ -690,7 +692,7 @@ bool LiveInterval::liveAt(unsigned index) const
         return false;
 
     --r;
-    return index >= r->first && index < r->second;
+    return index >= r->start && index < r->end;
 }
 
 // An example for overlaps():
@@ -713,50 +715,39 @@ bool LiveInterval::overlaps(const LiveInterval& other) const
     Ranges::const_iterator ie = ranges.end();
     Ranges::const_iterator j = other.ranges.begin();
     Ranges::const_iterator je = other.ranges.end();
-    if (i->first < j->first) {
+    if (i->start < j->start) {
         i = std::upper_bound(i, ie, *j);
         if (i != ranges.begin()) --i;
     }
-    else if (j->first < i->first) {
+    else if (j->start < i->start) {
         j = std::upper_bound(j, je, *i);
         if (j != other.ranges.begin()) --j;
     }
 
     while (i != ie && j != je) {
-        if (i->first == j->first) {
+        if (i->start == j->start)
             return true;
-        }
-        else {
-            if (i->first > j->first) {
-                swap(i, j);
-                swap(ie, je);
-            }
-            assert(i->first < j->first);
 
-            if (i->second > j->first) {
+        if (i->start > j->start) {
-                return true;
+            swap(i, j);
-            }
+            swap(ie, je);
-            else {
-                ++i;
-            }
         }
+        assert(i->start < j->start);
+
+        if (i->end > j->start)
+            return true;
+        ++i;
     }
 
     return false;
 }
 
-void LiveInterval::addRange(unsigned start, unsigned end)
+void LiveInterval::addRange(LiveRange LR) {
-{
+    DEBUG(std::cerr << " +" << LR);
-    assert(start < end && "Invalid range to add!");
-    DEBUG(std::cerr << " +[" << start << ',' << end << ")");
-    //assert(start < end && "invalid range?");
-    Range range = std::make_pair(start, end);
     Ranges::iterator it =
-        ranges.insert(std::upper_bound(ranges.begin(), ranges.end(), range),
+        ranges.insert(std::upper_bound(ranges.begin(), ranges.end(), LR), LR);
-                      range);
 
-    it = mergeRangesForward(it);
+    mergeRangesBackward(mergeRangesForward(it));
-    it = mergeRangesBackward(it);
 }
 
 void LiveInterval::join(const LiveInterval& other)
@@ -779,9 +770,9 @@ mergeRangesForward(Ranges::iterator it)
 {
     Ranges::iterator n;
     while ((n = next(it)) != ranges.end()) {
-        if (n->first > it->second)
+        if (n->start > it->end)
             break;
-        it->second = std::max(it->second, n->second);
+        it->end = std::max(it->end, n->end);
         n = ranges.erase(n);
     }
     return it;
@@ -792,17 +783,22 @@ mergeRangesBackward(Ranges::iterator it)
 {
     while (it != ranges.begin()) {
         Ranges::iterator p = prior(it);
-        if (it->first > p->second)
+        if (it->start > p->end)
             break;
 
-        it->first = std::min(it->first, p->first);
+        it->start = std::min(it->start, p->start);
-        it->second = std::max(it->second, p->second);
+        it->end = std::max(it->end, p->end);
         it = ranges.erase(p);
     }
 
     return it;
 }
 
+std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) {
+  return os << "[" << LR.start << "," << LR.end << ")";
+}
+
+
 std::ostream& llvm::operator<<(std::ostream& os, const LiveInterval& li)
 {
     os << "%reg" << li.reg << ',' << li.weight;
@@ -810,9 +806,8 @@ std::ostream& llvm::operator<<(std::ostream& os, const LiveInterval& li)
         return os << "EMPTY";
 
     os << " = ";
-    for (LiveInterval::Ranges::const_iterator
+    for (LiveInterval::Ranges::const_iterator i = li.ranges.begin(),
-             i = li.ranges.begin(), e = li.ranges.end(); i != e; ++i) {
+           e = li.ranges.end(); i != e; ++i)
-        os << "[" << i->first << "," << i->second << ")";
+        os << *i;
-    }
     return os;
 }

lib/CodeGen/LiveIntervalAnalysis.h

@@ -29,9 +29,29 @@ namespace llvm {
     class MRegisterInfo;
     class VirtRegMap;
 
+    /// LiveRange structure - This represents a simple register range in the
+    /// program, with an inclusive start point and an exclusive end point.
+    /// These ranges are rendered as [start,end).
+    struct LiveRange {
+      unsigned start;  // Start point of the interval (inclusive)
+      unsigned end;  // End point of the interval (exclusive)
+      LiveRange(unsigned S, unsigned E) : start(S), end(E) {
+        assert(S < E && "Cannot create empty or backwards range");
+      }
+
+      bool operator<(const LiveRange &LR) const {
+        return start < LR.start || (start == LR.start && end < LR.end);
+      }
+      bool operator==(const LiveRange &LR) const {
+        return start == LR.start && end == LR.end;
+      }
+    private:
+      LiveRange(); // DO NOT IMPLEMENT
+    };
+    std::ostream& operator<<(std::ostream& os, const LiveRange &LR);
+
     struct LiveInterval {
-        typedef std::pair<unsigned, unsigned> Range;
+        typedef std::vector<LiveRange> Ranges;
-        typedef std::vector<Range> Ranges;
         unsigned reg;   // the register of this interval
         float weight;   // weight of this interval:
                         //     (number of uses *10^loopDepth)
@@ -44,14 +64,17 @@ namespace llvm {
 
         bool spilled() const;
 
+        /// start - Return the lowest numbered slot covered by interval.
         unsigned start() const {
             assert(!empty() && "empty interval for register");
-            return ranges.front().first;
+            return ranges.front().start;
         }
 
+        /// end - return the maximum point of the interval of the whole,
+        /// exclusive.
         unsigned end() const {
             assert(!empty() && "empty interval for register");
-            return ranges.back().second;
+            return ranges.back().end;
         }
 
         bool expiredAt(unsigned index) const {
@@ -62,7 +85,7 @@ namespace llvm {
 
         bool overlaps(const LiveInterval& other) const;
 
-        void addRange(unsigned start, unsigned end);
+        void addRange(LiveRange R);
 
         void join(const LiveInterval& other);