[llvm] Add the 'initializes' attribute langref and support (PR #84803)

[Haopeng Liu via llvm-commits]

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@@ -0,0 +1,73 @@
+//===- ConstantRangeList.cpp - ConstantRangeList implementation -----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Represent a list of signed ConstantRange and do NOT support wrap around the
+// end of the numeric range. Ranges in the list are ordered and no overlapping.
+// Ranges should have the same bitwidth. Each range's lower should be less than
+// its upper.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/IR/ConstantRangeList.h"
+#include <cstddef>
+
+using namespace llvm;
+
+void ConstantRangeList::insert(const ConstantRange &NewRange) {
+  if (NewRange.isEmptySet())
+    return;
+  assert(!NewRange.isFullSet() && "Do not support full set");
+  assert(NewRange.getLower().slt(NewRange.getUpper()));
+  assert(getBitWidth() == NewRange.getBitWidth());
+  // Handle common cases.
+  if (empty() || Ranges.back().getUpper().slt(NewRange.getLower())) {
+    Ranges.push_back(NewRange);
+    return;
+  }
+  if (NewRange.getUpper().slt(Ranges.front().getLower())) {
+    Ranges.insert(Ranges.begin(), NewRange);
+    return;
+  }
+  if (std::find(Ranges.begin(), Ranges.end(), NewRange) != Ranges.end()) {
+    return;
+  }
+
+  // Slow insert.
+  auto LowerBound =
+      std::lower_bound(Ranges.begin(), Ranges.end(), NewRange,
+                       [](const ConstantRange &a, const ConstantRange &b) {
+                         return a.getLower().slt(b.getLower());
+                       });
+  SmallVector<ConstantRange, 2> ExistingTail(LowerBound, Ranges.end());
+  Ranges.erase(LowerBound, Ranges.end());
+  // "sle" instead of "slt" to merge consecutive ranges.
+  if (!Ranges.empty() && NewRange.getLower().sle(Ranges.back().getUpper())) {
+    APInt NewLower = Ranges.back().getLower();
+    APInt NewUpper =
+        APIntOps::smax(NewRange.getUpper(), Ranges.back().getUpper());
+    Ranges.back() = ConstantRange(NewLower, NewUpper);
+  } else {
+    Ranges.push_back(NewRange);
+  }
+  for (auto Iter = ExistingTail.begin(); Iter != ExistingTail.end(); Iter++) {
+    if (Ranges.back().getUpper().slt(Iter->getLower())) {
+      Ranges.push_back(*Iter);
+    } else {
+      APInt NewLower = Ranges.back().getLower();
+      APInt NewUpper =
+          APIntOps::smax(Iter->getUpper(), Ranges.back().getUpper());
+      Ranges.back() = ConstantRange(NewLower, NewUpper);
+    }
+  }
+}
+
+void ConstantRangeList::print(raw_ostream &OS) const {
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haopliu wrote:

Done! Look like many dumps forward to `dbgs()`. Let me know if we prefer `errs()`.

https://github.com/llvm/llvm-project/pull/84803