[llvm-branch-commits] [llvm] [HLSL][RootSignature] Implement `ResourceRange` as an `IntervalMap` (PR #140957)

[Deric C. via llvm-branch-commits]

================
@@ -222,6 +222,67 @@ MDNode *MetadataBuilder::BuildDescriptorTableClause(
            });
 }
 
+std::optional<const RangeInfo *>
+ResourceRange::getOverlapping(const RangeInfo &Info) const {
+  IMap::const_iterator Interval = Intervals.find(Info.LowerBound);
+  if (!Interval.valid() || Info.UpperBound < Interval.start())
+    return std::nullopt;
+  return Interval.value();
+}
+
+const RangeInfo *ResourceRange::lookup(uint32_t X) const {
+  return Intervals.lookup(X, nullptr);
+}
+
+std::optional<const RangeInfo *> ResourceRange::insert(const RangeInfo &Info) {
+  uint32_t LowerBound = Info.LowerBound;
+  uint32_t UpperBound = Info.UpperBound;
+
+  std::optional<const RangeInfo *> Res = std::nullopt;
+  IMap::iterator Interval = Intervals.begin();
+
+  while (true) {
+    if (UpperBound < LowerBound)
+      break;
+
+    Interval.advanceTo(LowerBound);
+    if (!Interval.valid()) // No interval found
+      break;
+
+    // Let Interval = [x;y] and [LowerBound;UpperBound] = [a;b] and note that
+    // a <= y implicitly from Intervals.find(LowerBound)
+    if (UpperBound < Interval.start())
+      break; // found interval does not overlap with inserted one
+
+    if (!Res.has_value()) // Update to be the first found intersection
+      Res = Interval.value();
+
+    if (Interval.start() <= LowerBound && UpperBound <= Interval.stop()) {
+      // x <= a <= b <= y implies that [a;b] is covered by [x;y]
+      //  -> so we don't need to insert this, report an overlap
+      return Res;
+    } else if (LowerBound <= Interval.start() &&
+               Interval.stop() <= UpperBound) {
+      // a <= x <= y <= b implies that [x;y] is covered by [a;b]
+      //  -> so remove the existing interval that we will cover with the
+      //  overwrite
+      Interval.erase();
+    } else if (LowerBound < Interval.start() && UpperBound <= Interval.stop()) {
+      // a < x <= b <= y implies that [a; x] is not covered but [x;b] is
+      //  -> so set b = x - 1 such that [a;x-1] is now the interval to insert
+      UpperBound = Interval.start() - 1;
+    } else if (Interval.start() <= LowerBound && Interval.stop() < UpperBound) {
+      // a < x <= b <= y implies that [y; b] is not covered but [a;y] is
----------------
Icohedron wrote:

```suggestion
      // x <= a <= y < b implies that [y; b] is not covered but [a;y] is
```

https://github.com/llvm/llvm-project/pull/140957