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Optimize Enumerable.Min/Max<T> for value types with Comparer<T>.Default intrinsic #48273

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Merged
merged 1 commit into from
Feb 14, 2021
Merged

Optimize Enumerable.Min/Max<T> for value types with Comparer<T>.Default intrinsic #48273

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13 changes: 5 additions & 8 deletions src/libraries/System.Linq/src/System/Linq/Max.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -448,11 +448,10 @@ public static decimal Max(this IEnumerable<decimal> source)
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
}

Comparer<TSource> comparer = Comparer<TSource>.Default;
TSource? value = default;
if (value == null)
using (IEnumerator<TSource> e = source.GetEnumerator())
{
using (IEnumerator<TSource> e = source.GetEnumerator())
if (value == null)
{
do
{
Expand All @@ -465,6 +464,7 @@ public static decimal Max(this IEnumerable<decimal> source)
}
while (value == null);

Comparer<TSource> comparer = Comparer<TSource>.Default;
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Out of curiosity, what is the motivation for not optimizing reference types?

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See issue #10050 for more details

while (e.MoveNext())
{
TSource x = e.Current;
Expand All @@ -474,10 +474,7 @@ public static decimal Max(this IEnumerable<decimal> source)
}
}
}
}
else
{
using (IEnumerator<TSource> e = source.GetEnumerator())
else
{
if (!e.MoveNext())
{
Expand All @@ -488,7 +485,7 @@ public static decimal Max(this IEnumerable<decimal> source)
while (e.MoveNext())
{
TSource x = e.Current;
if (comparer.Compare(x, value) > 0)
if (Comparer<TSource>.Default.Compare(x, value) > 0)
{
value = x;
}
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13 changes: 5 additions & 8 deletions src/libraries/System.Linq/src/System/Linq/Min.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -406,11 +406,10 @@ public static decimal Min(this IEnumerable<decimal> source)
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
}

Comparer<TSource> comparer = Comparer<TSource>.Default;
TSource? value = default;
if (value == null)
using (IEnumerator<TSource> e = source.GetEnumerator())
{
using (IEnumerator<TSource> e = source.GetEnumerator())
if (value == null)
{
do
{
Expand All @@ -423,6 +422,7 @@ public static decimal Min(this IEnumerable<decimal> source)
}
while (value == null);

Comparer<TSource> comparer = Comparer<TSource>.Default;
while (e.MoveNext())
{
TSource x = e.Current;
Expand All @@ -432,10 +432,7 @@ public static decimal Min(this IEnumerable<decimal> source)
}
}
}
}
else
{
using (IEnumerator<TSource> e = source.GetEnumerator())
else
{
if (!e.MoveNext())
{
Expand All @@ -446,7 +443,7 @@ public static decimal Min(this IEnumerable<decimal> source)
while (e.MoveNext())
{
TSource x = e.Current;
if (comparer.Compare(x, value) < 0)
if (Comparer<TSource>.Default.Compare(x, value) < 0)
{
value = x;
}
Expand Down