Add early exit reduction

Author: Genbox

Src/FastData/FastDataGenerator.cs

@@ -310,6 +310,7 @@ HashData GetNumericHash(ReadOnlySpan<TKey> keySpan)
 
     private static IEarlyExit[] CombineEarlyExits(IEnumerable<IEarlyExit> mandatoryExits, IEnumerable<IEarlyExit> candidateExits)
     {
+        // Use hash set to deduplicate early exits on their direct values
         HashSet<IEarlyExit> combined = new HashSet<IEarlyExit>();
 
         foreach (IEarlyExit exit in mandatoryExits)
@@ -318,6 +319,30 @@ private static IEarlyExit[] CombineEarlyExits(IEnumerable<IEarlyExit> mandatoryE
         foreach (IEarlyExit exit in candidateExits)
             combined.Add(exit);
 
+        // Some early exits are reducible. For example, a LengthLessThan with a value of 3 is worse than one with 4.
+        // So if there are competing exits, we take the one with the best bounds.
+        if (combined.Count > 1)
+        {
+            IEarlyExit[] exits = combined.ToArray();
+
+            for (int i = 0; i < exits.Length; i++)
+            {
+                IEarlyExit exit = exits[i];
+
+                for (int j = 0; j < exits.Length; j++)
+                {
+                    if (i == j)
+                        continue;
+
+                    if (exit.IsWorseThan(exits[j]))
+                    {
+                        combined.Remove(exit);
+                        break;
+                    }
+                }
+            }
+        }
+
         return combined.ToArray();
     }
 

Src/FastData/Generators/Abstracts/IEarlyExit.cs

@@ -6,4 +6,5 @@ namespace Genbox.FastData.Generators.Abstracts;
 public interface IEarlyExit
 {
     Expression GetExpression(ParameterExpression key);
+    bool IsWorseThan(IEarlyExit other);
 }

Src/FastData/Generators/EarlyExits/Abstracts/CharBitmapEarlyExitBase.cs

@@ -24,4 +24,6 @@ public Expression GetExpression(ParameterExpression key)
         Expression selected = Or(And(lowMasked, lowMask), And(highMasked, highMask));
         return Equal(selected, Constant(0UL));
     }
+
+    public bool IsWorseThan(IEarlyExit other) => false;
 }

Src/FastData/Generators/EarlyExits/Abstracts/MethodComparisonEarlyExitBase.cs

@@ -13,4 +13,6 @@ public Expression GetExpression(ParameterExpression key)
     }
 
     protected abstract BinaryExpression Compare(Expression left, Expression right);
+
+    public abstract bool IsWorseThan(IEarlyExit other);
 }

Src/FastData/Generators/EarlyExits/Abstracts/StringAffixEarlyExitBase.cs

@@ -11,4 +11,6 @@ public Expression GetExpression(ParameterExpression key)
         MethodInfo methodInfo = typeof(StringFunctions).GetMethod(Method, [typeof(string), typeof(string)])!;
         return Not(Call(methodInfo, Constant(Affix), key));
     }
+
+    public bool IsWorseThan(IEarlyExit other) => false;
 }

Src/FastData/Generators/EarlyExits/Abstracts/ValueComparisonEarlyExitBase.cs

@@ -8,4 +8,6 @@ public abstract record ValueComparisonEarlyExitBase<T>(T Value) : IEarlyExit
     public Expression GetExpression(ParameterExpression key) => Compare(key, Constant(Value, key.Type));
 
     protected abstract BinaryExpression Compare(Expression left, Expression right);
+
+    public abstract bool IsWorseThan(IEarlyExit other);
 }

Src/FastData/Generators/EarlyExits/Exits/CharFirstGreaterThanEarlyExit.cs

@@ -1,4 +1,5 @@
 using System.Linq.Expressions;
+using Genbox.FastData.Generators.Abstracts;
 using Genbox.FastData.Generators.EarlyExits.Abstracts;
 
 namespace Genbox.FastData.Generators.EarlyExits.Exits;
@@ -7,4 +8,6 @@ namespace Genbox.FastData.Generators.EarlyExits.Exits;
 public sealed record CharFirstGreaterThanEarlyExit(char Value) : MethodComparisonEarlyExitBase<char>(Value, nameof(StringFunctions.GetFirstChar))
 {
     protected override BinaryExpression Compare(Expression left, Expression right) => GreaterThan(left, right);
+
+    public override bool IsWorseThan(IEarlyExit other) => other is CharFirstGreaterThanEarlyExit otherExit && Value > otherExit.Value;
 }

Src/FastData/Generators/EarlyExits/Exits/CharFirstLessThanEarlyExit.cs

@@ -1,4 +1,5 @@
 using System.Linq.Expressions;
+using Genbox.FastData.Generators.Abstracts;
 using Genbox.FastData.Generators.EarlyExits.Abstracts;
 
 namespace Genbox.FastData.Generators.EarlyExits.Exits;
@@ -7,4 +8,6 @@ namespace Genbox.FastData.Generators.EarlyExits.Exits;
 public sealed record CharFirstLessThanEarlyExit(char Value) : MethodComparisonEarlyExitBase<char>(Value, nameof(StringFunctions.GetFirstChar))
 {
     protected override BinaryExpression Compare(Expression left, Expression right) => LessThan(left, right);
+
+    public override bool IsWorseThan(IEarlyExit other) => other is CharFirstLessThanEarlyExit otherExit && Value < otherExit.Value;
 }

Src/FastData/Generators/EarlyExits/Exits/CharFirstNotEqualEarlyExit.cs

@@ -1,4 +1,5 @@
 using System.Linq.Expressions;
+using Genbox.FastData.Generators.Abstracts;
 using Genbox.FastData.Generators.EarlyExits.Abstracts;
 
 namespace Genbox.FastData.Generators.EarlyExits.Exits;
@@ -7,4 +8,6 @@ namespace Genbox.FastData.Generators.EarlyExits.Exits;
 public sealed record CharFirstNotEqualEarlyExit(char Value, bool IgnoreCase) : MethodComparisonEarlyExitBase<char>(Value, IgnoreCase ? nameof(StringFunctions.GetFirstCharLower) : nameof(StringFunctions.GetFirstChar))
 {
     protected override BinaryExpression Compare(Expression left, Expression right) => NotEqual(left, right);
+
+    public override bool IsWorseThan(IEarlyExit other) => false;
 }

Src/FastData/Generators/EarlyExits/Exits/CharLastGreaterThanEarlyExit.cs

@@ -1,4 +1,5 @@
 using System.Linq.Expressions;
+using Genbox.FastData.Generators.Abstracts;
 using Genbox.FastData.Generators.EarlyExits.Abstracts;
 
 namespace Genbox.FastData.Generators.EarlyExits.Exits;
@@ -7,4 +8,6 @@ namespace Genbox.FastData.Generators.EarlyExits.Exits;
 public sealed record CharLastGreaterThanEarlyExit(char Value) : MethodComparisonEarlyExitBase<char>(Value, nameof(StringFunctions.GetLastChar))
 {
     protected override BinaryExpression Compare(Expression left, Expression right) => GreaterThan(left, right);
+
+    public override bool IsWorseThan(IEarlyExit other) => other is CharLastGreaterThanEarlyExit otherExit && Value > otherExit.Value;
 }