[ADT] IntervalMap: fix setStart and setStop

[mlemay-intel]

Summary

These functions currently require that the new closed interval has a length of
at least 2. They also currently permit empty half-open intervals. This patch
defines nonEmpty in each traits structure and uses it to correct the
implementations of setStart and setStop.

[vsk]

Could you add unit tests to unittest/ADT/IntervalMapTest? I want to make sure that:

• We're allowed to create 1-element intervals using setStart/setStop.
• If we create a 0-element interval using setStart/setStop, it just gets deleted.

[mlemay-intel]

In D26064#581794, @vsk wrote:

...

• If we create a 0-element interval using setStart/setStop, it just gets deleted.

The revised assertion will fail in that case. Is deleting the interval actually the desired behavior?

[vsk]

In D26064#582164, @mlemay-intel wrote:

In D26064#581794, @vsk wrote:

...

• If we create a 0-element interval using setStart/setStop, it just gets deleted.

The revised assertion will fail in that case. Is deleting the interval actually the desired behavior?

Looking at it more, it shouldn't be possible to do what I described (creating a 0-element interval using setStart/setStop). I'm walking the request for that test back :).

[mlemay-intel]

In D26064#582202, @vsk wrote:

In D26064#582164, @mlemay-intel wrote:

In D26064#581794, @vsk wrote:

...

• If we create a 0-element interval using setStart/setStop, it just gets deleted.

The revised assertion will fail in that case. Is deleting the interval actually the desired behavior?

Looking at it more, it shouldn't be possible to do what I described (creating a 0-element interval using setStart/setStop). I'm walking the request for that test back :).

Sounds good, thanks. :)

[mlemay-intel]

Added unit tests.

[vsk]

LGTM. Could you wait a day or two before committing? I haven't worked on IntervalMap before, so it'd be nice to others a chance to chime in.

unittests/ADT/IntervalMapTest.cpp

19 ↗

(On Diff #76273)

nit: You don't need the extra space, 'IntervalMapHalfOpenInfo<unsigned>>' would be fine.

[mlemay-intel]

In D26064#582725, @vsk wrote:

LGTM. Could you wait a day or two before committing? I haven't worked on IntervalMap before, so it'd be nice to others a chance to chime in.

Sure, I'll wait a couple of days. Thanks!

[mlemay-intel]

Eliminated unnecessary space in template instantiation.
Revised test for half-open intervals to cover using setStop to create an interval with a length of 1.

include/llvm/ADT/IntervalMap.h

struct IntervalMapInfo {
   }
 
   /// adjacent - Return true when the intervals [x;a] and [b;y] can coalesce.
   /// This is a+1 == b for closed intervals, a == b for half-open intervals.
   static inline bool adjacent(const T &a, const T &b) {
     return a+1 == b;
   }
 
+  /// nonEmpty - Return true if [a;b] is non-empty.
+  /// This is a <= b for a closed interval, a < b for [a;b) half-open intervals.
+  static inline bool nonEmpty(const T &a, const T &b) {
+    return a <= b;
+  }
+
 };
 
 template <typename T>
 struct IntervalMapHalfOpenInfo {
 
   /// startLess - Return true if x is not in [a;b).
   static inline bool startLess(const T &x, const T &a) {
     return x < a;
   }
 
   /// stopLess - Return true if x is not in [a;b).
   static inline bool stopLess(const T &b, const T &x) {
     return b <= x;
   }
 
   /// adjacent - Return true when the intervals [x;a) and [b;y) can coalesce.
   static inline bool adjacent(const T &a, const T &b) {
     return a == b;
   }
 
+  /// nonEmpty - Return true if [a;b) is non-empty.
+  static inline bool nonEmpty(const T &a, const T &b) {
+    return a < b;
+  }
+
 };
 
 /// IntervalMapImpl - Namespace used for IntervalMap implementation details.
 /// It should be considered private to the implementation.
 namespace IntervalMapImpl {
 
 // Forward declarations.
 template <typename, typename, unsigned, typename> class LeafNode;
iterator::setNodeStop(unsigned Level, KeyT Stop) {
   }
   // Update root separately since it has a different layout.
   P.node<RootBranch>(Level).stop(P.offset(Level)) = Stop;
 }
 
 template <typename KeyT, typename ValT, unsigned N, typename Traits>
 void IntervalMap<KeyT, ValT, N, Traits>::
 iterator::setStart(KeyT a) {
-  assert(Traits::stopLess(a, this->stop()) && "Cannot move start beyond stop");
+  assert(Traits::nonEmpty(a, this->stop()) && "Cannot move start beyond stop");
   KeyT &CurStart = this->unsafeStart();
   if (!Traits::startLess(a, CurStart) || !canCoalesceLeft(a, this->value())) {
     CurStart = a;
     return;
   }
   // Coalesce with the interval to the left.
   --*this;
   a = this->start();
   erase();
   setStartUnchecked(a);
 }
 
 template <typename KeyT, typename ValT, unsigned N, typename Traits>
 void IntervalMap<KeyT, ValT, N, Traits>::
 iterator::setStop(KeyT b) {
-  assert(Traits::stopLess(this->start(), b) && "Cannot move stop beyond start");
+  assert(Traits::nonEmpty(this->start(), b) && "Cannot move stop beyond start");
   if (Traits::startLess(b, this->stop()) ||
       !canCoalesceRight(b, this->value())) {
     setStopUnchecked(b);
     return;
   }
   // Coalesce with interval to the right.
   KeyT a = this->start();
   erase();