Refactor BigIntegerCalculator.*ShiftSelf

Author: kzrnm

src/libraries/System.Runtime.Numerics/src/System/Numerics/BigInteger.cs

@@ -2533,8 +2533,7 @@ public static implicit operator BigInteger(nuint value)
 
             bits.CopyTo(zd);
 
-            uint carry = 0;
-            BigIntegerCalculator.LeftShiftSelf(zd, smallShift, ref carry);
+            BigIntegerCalculator.LeftShiftSelf(zd, smallShift, out uint carry);
 
             Debug.Assert(carry == over);
             Debug.Assert(z[^1] != 0);
@@ -2612,8 +2611,7 @@ private static BigInteger LeftShift(int value, int digitShift, int smallShift)
             zd[^1] = 0;
             bits.Slice(digitShift).CopyTo(zd);
 
-            uint carry = 0;
-            BigIntegerCalculator.RightShiftSelf(zd, smallShift, ref carry);
+            BigIntegerCalculator.RightShiftSelf(zd, smallShift, out uint carry);
 
             bool neg = value._sign < 0;
             if (neg && (carry != 0 || bits.Slice(0, digitShift).ContainsAnyExcept(0u)))
@@ -5088,8 +5086,7 @@ static bool INumberBase<BigInteger>.TryConvertToTruncating<TOther>(BigInteger va
                 }
             }
 
-            uint carry = 0;
-            BigIntegerCalculator.RightShiftSelf(zd, smallShift, ref carry);
+            BigIntegerCalculator.RightShiftSelf(zd, smallShift, out _);
 
             BigInteger result = new BigInteger(zd, false);
 

src/libraries/System.Runtime.Numerics/src/System/Numerics/BigIntegerCalculator.ShiftRot.cs

@@ -39,8 +39,7 @@ public static void RotateLeft(Span<uint> bits, int digitShift, int smallShift)
         {
             Debug.Assert(bits.Length > 0);
 
-            uint carry = 0;
-            LeftShiftSelf(bits, smallShift, ref carry);
+            LeftShiftSelf(bits, smallShift, out uint carry);
             bits[0] |= carry;
 
             if (digitShift == 0)
@@ -53,8 +52,7 @@ public static void RotateRight(Span<uint> bits, int digitShift, int smallShift)
         {
             Debug.Assert(bits.Length > 0);
 
-            uint carry = 0;
-            RightShiftSelf(bits, smallShift, ref carry);
+            RightShiftSelf(bits, smallShift, out uint carry);
             bits[^1] |= carry;
 
             if (digitShift == 0)
@@ -98,9 +96,11 @@ stackalloc uint[StackAllocThreshold]
                 ArrayPool<uint>.Shared.Return(tmpFromPool);
         }
 
-        public static void LeftShiftSelf(Span<uint> bits, int shift, ref uint carry)
+        public static void LeftShiftSelf(Span<uint> bits, int shift, out uint carry)
         {
             Debug.Assert((uint)shift < 32);
+
+            carry = 0;
             if (shift == 0)
                 return;
 
@@ -112,9 +112,11 @@ public static void LeftShiftSelf(Span<uint> bits, int shift, ref uint carry)
                 bits[i] = value;
             }
         }
-        public static void RightShiftSelf(Span<uint> bits, int shift, ref uint carry)
+        public static void RightShiftSelf(Span<uint> bits, int shift, out uint carry)
         {
             Debug.Assert((uint)shift < 32);
+
+            carry = 0;
             if (shift == 0)
                 return;