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

[Nikita Popov via llvm-commits]

================
@@ -0,0 +1,86 @@
+//===- ConstantRangeList.h - A list of constant range -----------*- C++ -*-===//
+//
+// 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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_CONSTANTRANGELIST_H
+#define LLVM_IR_CONSTANTRANGELIST_H
+
+#include "llvm/ADT/APInt.h"
+#include "llvm/IR/ConstantRange.h"
+#include "llvm/Support/Debug.h"
+#include <cstddef>
+#include <cstdint>
+
+namespace llvm {
+
+class raw_ostream;
+
+/// This class represents a list of constant ranges.
+class [[nodiscard]] ConstantRangeList {
+  SmallVector<ConstantRange, 2> Ranges;
+
+public:
+  ConstantRangeList() = default;
+  ConstantRangeList(ArrayRef<ConstantRange> RangesRef) {
+    for (const ConstantRange &R : RangesRef) {
+      assert(R.getBitWidth() == getBitWidth());
+      Ranges.push_back(R);
+    }
+  }
+  ArrayRef<ConstantRange> rangesRef() const { return Ranges; }
+  SmallVectorImpl<ConstantRange>::iterator begin() { return Ranges.begin(); }
+  SmallVectorImpl<ConstantRange>::iterator end() { return Ranges.end(); }
+  SmallVectorImpl<ConstantRange>::const_iterator begin() const {
+    return Ranges.begin();
+  }
+  SmallVectorImpl<ConstantRange>::const_iterator end() const {
+    return Ranges.end();
+  }
+  ConstantRange getRange(unsigned i) const {
+    assert(i < Ranges.size());
+    return Ranges[i];
+  }
+
+  /// Return true if this list contains no members.
+  bool empty() const { return Ranges.empty(); }
+
+  /// Get the bit width of this ConstantRangeList.
+  uint32_t getBitWidth() const { return 64; }
+
+  /// Return the number of ranges in this ConstantRangeList.
+  size_t size() const { return Ranges.size(); }
+
+  /// Insert a new range to Ranges and keep the list ordered.
+  void insert(const ConstantRange &NewRange);
+  void insert(int64_t Lower, int64_t Upper) {
+    insert(ConstantRange(APInt(64, Lower, /*isSigned=*/true),
+                         APInt(64, Upper, /*isSigned=*/true)));
+  }
+
+  /// Return true if this range list is equal to another range list.
+  bool operator==(const ConstantRangeList &CRL) const {
+    return Ranges == CRL.Ranges;
+  }
+  bool operator!=(const ConstantRangeList &CRL) const {
+    return !operator==(CRL);
+  }
+
+  /// Print out the ranges to a stream.
+  void print(raw_ostream &OS) const;
+  void dump() const;
----------------
nikic wrote:

Doesn't this also need the `#ifdef` checks?

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