Use BigMul in BigMul (#100918)

* Use BigMul in BigMul * Reverse usage of BigMul(uint, uint) * Add aggressive inline to Math.BigMul(ulong, ulong)
dotnet · Jun 13, 2024 · f453865 · f453865
1 parent b4f750f
commit f453865
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Showing 2 changed files with 20 additions and 9 deletions.
diff --git a/src/libraries/System.Private.CoreLib/src/System/Math.cs b/src/libraries/System.Private.CoreLib/src/System/Math.cs
@@ -238,13 +238,24 @@ public static long BigMul(long a, long b, out long low)
  return (long)high - ((a >> 63) & b) - ((b >> 63) & a);
  }
 
+ /// <summary>Produces the full product of two unsigned 64-bit numbers.</summary>
+ /// <param name="a">The first number to multiply.</param>
+ /// <param name="b">The second number to multiply.</param>
+ /// <returns>The full product of the specified numbers.</returns>
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ internal static UInt128 BigMul(ulong a, ulong b)
+ {
+ ulong high = BigMul(a, b, out ulong low);
+ return new UInt128(high, low);
+ }
+
  /// <summary>Produces the full product of two 64-bit numbers.</summary>
  /// <param name="a">The first number to multiply.</param>
  /// <param name="b">The second number to multiply.</param>
  /// <returns>The full product of the specified numbers.</returns>
  internal static Int128 BigMul(long a, long b)
  {
- long high = Math.BigMul(a, b, out long low);
+ long high = BigMul(a, b, out long low);
  return new Int128((ulong)high, (ulong)low);
  }
 

diff --git a/src/libraries/System.Private.CoreLib/src/System/UInt128.cs b/src/libraries/System.Private.CoreLib/src/System/UInt128.cs
@@ -1396,18 +1396,18 @@ internal static UInt128 BigMul(UInt128 left, UInt128 right, out UInt128 lower)
  // Basically, it's an optimized version of FOIL method applied to
  // low and high qwords of each operand
 
- UInt128 al = left._lower;
- UInt128 ah = left._upper;
+ ulong al = left._lower;
+ ulong ah = left._upper;
 
- UInt128 bl = right._lower;
- UInt128 bh = right._upper;
+ ulong bl = right._lower;
+ ulong bh = right._upper;
 
- UInt128 mull = al * bl;
- UInt128 t = ah * bl + mull._upper;
- UInt128 tl = al * bh + t._lower;
+ UInt128 mull = Math.BigMul(al, bl);
+ UInt128 t = Math.BigMul(ah, bl) + mull._upper;
+ UInt128 tl = Math.BigMul(al, bh) + t._lower;
 
  lower = new UInt128(tl._lower, mull._lower);
- return ah * bh + t._upper + tl._upper;
+ return Math.BigMul(ah, bh) + t._upper + tl._upper;
  }
 
  //