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

[Arthur Eubanks via llvm-commits]

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@@ -0,0 +1,105 @@
+//===- 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. Special lists (take 8-bit as an example):
+//
+// {[0, 0)}     = Empty set
+// {[255, 255)} = Full Set
+//
+// For EmptySet or FullSet, the list size is 1 but it's not allowed to access
+// the range.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_CONSTANTRANGELIST_H
+#define LLVM_IR_CONSTANTRANGELIST_H
+
+#include "llvm/ADT/APInt.h"
+#include "llvm/IR/ConstantRange.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:
+  /// Initialize a full or empty set for the specified bit width.
+  explicit ConstantRangeList(uint32_t BitWidth, bool isFullSet);
+
+  ConstantRangeList(int64_t Lower, int64_t Upper);
+
+  /// It's not allowed to access EmptySet's or FullSet's range.
+  SmallVectorImpl<ConstantRange>::iterator begin() {
+    assert(!isEmptySet() && !isFullSet());
+    return Ranges.begin();
+  }
+  SmallVectorImpl<ConstantRange>::iterator end() { return Ranges.end(); }
+  SmallVectorImpl<ConstantRange>::const_iterator begin() const {
+    assert(!isEmptySet() && !isFullSet());
+    return Ranges.begin();
+  }
+  SmallVectorImpl<ConstantRange>::const_iterator end() const {
+    return Ranges.end();
+  }
+  ConstantRange getRange(unsigned i) const {
+    assert(!isEmptySet() && !isFullSet() && i < Ranges.size());
+    return Ranges[i];
+  }
+
+  /// Return true if this set contains no members.
+  bool isEmptySet() const {
+    return Ranges.size() == 1 && Ranges[0].isEmptySet();
+  }
+
+  /// Return true if this set contains all of the elements possible
+  /// for this data-type.
+  bool isFullSet() const { return Ranges.size() == 1 && Ranges[0].isFullSet(); }
+
+  /// Get the bit width of this ConstantRangeList.
+  uint32_t getBitWidth() const { return Ranges[0].getBitWidth(); }
+
+  /// For EmptySet or FullSet, the CRL size is 1 not 0.
+  size_t size() const { return Ranges.size(); }
+
+  /// Insert a range to Ranges. Keep the list ordered
+  /// and no overlapping (merge ranges if needed).
+  void insert(const ConstantRange &Range);
+  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 is equal to another range.
----------------
aeubanks wrote:

nit: this is a list of ranges, not a range

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