x64 only

src/System.Private.CoreLib/shared/System/Collections/Generic/Dictionary.cs

@@ -49,9 +49,11 @@ private struct Entry
  public TValue value; // Value of entry
  }
 
- private ulong _fastModMultiplier;
  private int[]? _buckets;
  private Entry[]? _entries;
+#if BIT64
+ private ulong _fastModMultiplier;
+#endif
  private int _count;
  private int _freeList;
  private int _freeCount;
@@ -340,7 +342,7 @@ private ref TValue FindValue(TKey key)
  if (comparer == null)
  {
  uint hashCode = (uint)key.GetHashCode();
- int i = buckets[HashHelpers.FastMod(hashCode, (uint)buckets.Length, _fastModMultiplier)];
+ int i = buckets[FastMod(hashCode, (uint)buckets.Length)];
  Entry[]? entries = _entries;
  uint collisionCount = 0;
  if (default(TKey)! != null) // TODO-NULLABLE: default(T) == null warning (https://github.com/dotnet/roslyn/issues/34757)
@@ -408,7 +410,7 @@ private ref TValue FindValue(TKey key)
  else
  {
  uint hashCode = (uint)comparer.GetHashCode(key);
- int i = buckets[HashHelpers.FastMod(hashCode, (uint)buckets.Length, _fastModMultiplier)];
+ int i = buckets[FastMod(hashCode, (uint)buckets.Length)];
  Entry[]? entries = _entries;
  uint collisionCount = 0;
  // Value in _buckets is 1-based; subtract 1 from i. We do it here so it fuses with the following conditional.
@@ -454,7 +456,9 @@ private ref TValue FindValue(TKey key)
  private int Initialize(int capacity)
  {
  int size = HashHelpers.GetPrime(capacity);
+#if BIT64
  _fastModMultiplier = HashHelpers.GetFastModMultiplier((uint)size);
+#endif
 
  _freeList = -1;
  _buckets = new int[size];
@@ -483,7 +487,7 @@ private bool TryInsert(TKey key, TValue value, InsertionBehavior behavior)
  uint hashCode = (uint)((comparer == null) ? key.GetHashCode() : comparer.GetHashCode(key));
 
  uint collisionCount = 0;
- ref int bucket = ref _buckets[HashHelpers.FastMod(hashCode, (uint)_buckets.Length, _fastModMultiplier)];
+ ref int bucket = ref _buckets[FastMod(hashCode, (uint)_buckets.Length)];
  // Value in _buckets is 1-based
  int i = bucket - 1;
 
@@ -627,7 +631,7 @@ private bool TryInsert(TKey key, TValue value, InsertionBehavior behavior)
  if (count == entries.Length)
  {
  Resize();
- bucket = ref _buckets[HashHelpers.FastMod(hashCode, (uint)_buckets.Length, _fastModMultiplier)];
+ bucket = ref _buckets[FastMod(hashCode, (uint)_buckets.Length)];
  }
  index = count;
  _count = count + 1;
@@ -711,7 +715,9 @@ public virtual void OnDeserialization(object? sender)
  private void Resize()
  {
  int size = HashHelpers.ExpandPrime(_count);
+#if BIT64
  _fastModMultiplier = HashHelpers.GetFastModMultiplier((uint)size);
+#endif
  Resize(size, false);
  }
 
@@ -744,7 +750,7 @@ private void Resize(int newSize, bool forceNewHashCodes)
  {
  if (entries[i].next >= -1)
  {
- uint bucket = HashHelpers.FastMod(entries[i].hashCode, (uint)newSize, _fastModMultiplier);
+ uint bucket = FastMod(entries[i].hashCode, (uint)newSize);
  // Value in _buckets is 1-based
  entries[i].next = buckets[bucket] - 1;
  // Value in _buckets is 1-based
@@ -773,7 +779,7 @@ public bool Remove(TKey key)
  Debug.Assert(entries != null, "entries should be non-null");
  uint collisionCount = 0;
  uint hashCode = (uint)(_comparer?.GetHashCode(key) ?? key.GetHashCode());
- uint bucket = HashHelpers.FastMod(hashCode, (uint)buckets.Length, _fastModMultiplier);
+ uint bucket = FastMod(hashCode, (uint)buckets.Length);
  int last = -1;
  // Value in buckets is 1-based
  int i = buckets[bucket] - 1;
@@ -842,7 +848,7 @@ public bool Remove(TKey key, [MaybeNullWhen(false)] out TValue value)
  Debug.Assert(entries != null, "entries should be non-null");
  uint collisionCount = 0;
  uint hashCode = (uint)(_comparer?.GetHashCode(key) ?? key.GetHashCode());
- uint bucket = HashHelpers.FastMod(hashCode, (uint)buckets.Length, _fastModMultiplier);
+ uint bucket = FastMod(hashCode, (uint)buckets.Length);
  int last = -1;
  // Value in buckets is 1-based
  int i = buckets[bucket] - 1;
@@ -989,7 +995,9 @@ public int EnsureCapacity(int capacity)
  if (_buckets == null)
  return Initialize(capacity);
  int newSize = HashHelpers.GetPrime(capacity);
+#if BIT64
  _fastModMultiplier = HashHelpers.GetFastModMultiplier((uint)newSize);
+#endif
  Resize(newSize, forceNewHashCodes: false);
  return newSize;
  }
@@ -1019,7 +1027,9 @@ public void TrimExcess(int capacity)
  if (capacity < Count)
  ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.capacity);
  int newSize = HashHelpers.GetPrime(capacity);
+#if BIT64
  _fastModMultiplier = HashHelpers.GetFastModMultiplier((uint)newSize);
+#endif
 
  Entry[]? oldEntries = _entries;
  int currentCapacity = oldEntries == null ? 0 : oldEntries.Length;
@@ -1039,7 +1049,7 @@ public void TrimExcess(int capacity)
  {
  ref Entry entry = ref entries![count];
  entry = oldEntries[i];
- uint bucket = HashHelpers.FastMod(hashCode, (uint)newSize, _fastModMultiplier);
+ uint bucket = FastMod(hashCode, (uint)newSize);
  // Value in _buckets is 1-based
  entry.next = buckets![bucket] - 1; // If we get here, we have entries, therefore buckets is not null.
  // Value in _buckets is 1-based
@@ -1161,6 +1171,14 @@ void IDictionary.Remove(object key)
  }
  }
 
+#if BIT64
+ private uint FastMod(uint value, uint divisor)
+ => HashHelpers.FastMod(value, divisor, _fastModMultiplier);
+#else
+ private static uint FastMod(uint value, uint divisor)
+ => value % divisor;
+#endif
+
  public struct Enumerator : IEnumerator<KeyValuePair<TKey, TValue>>,
  IDictionaryEnumerator
  {

src/System.Private.CoreLib/shared/System/Collections/HashHelpers.cs

@@ -89,6 +89,7 @@ public static int ExpandPrime(int oldSize)
  return GetPrime(newSize);
  }
 
+#if BIT64
  public static ulong GetFastModMultiplier(uint divisor)
  => ulong.MaxValue / divisor + 1;
 
@@ -111,5 +112,6 @@ public static unsafe uint FastMod(uint value, uint divisor, ulong multiplier)
  return value % divisor;
  }
  }
+#endif
  }
 }