Optimize function lookup (microsoft#1019)

Store functions in optimized TexlFunctionSet<TexlFunction> object
instead of IEnumerable<TextFunction>

Benchmark results
- -61% for Check N=1
- -77% for Check N=5
- -79% for Check N=10
- -42% for Eval N=1
- -65% for Eval N=5
- -67% for Eval N=10

Negligible improvement for Parse , Tokenize or PVA* benchmarks

.scripts/WriteBenchmark.ps1

@@ -226,7 +226,7 @@ $list = (Get-Item -Filter *.csv -Path '.\BenchmarkDotNet.Artifacts\results\*' |
 foreach ($file in [System.Linq.Enumerable]::OrderBy($list, [Func[object, string]] { param($s) if ($s -match 'Reference-report\.csv') { "" } else { $s } }))
 {
     $t = [System.IO.Path]::GetFileNameWithoutExtension($file).Split(@('.'))[-1]
-    $testCategory = $t.Substring(0, $t.Length - 7)
+    if ($t.Length -gt 7) { $testCategory = $t.Substring(0, $t.Length - 7) } else { $testCategory = $t }
 
     Write-Host "------ [TEST] $testCategory ------"
 

src/Microsoft.PowerFx.sln

@@ -57,6 +57,12 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.PowerFx.Json", "l
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.PowerFx.Json.Tests", "tests\Microsoft.PowerFx.Json.Tests\Microsoft.PowerFx.Json.Tests.csproj", "{8986E836-2F55-4D71-B23E-50F4A8427A5B}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Benchmark", "Benchmark", "{89514D49-4D5D-4423-A6EC-F0FF1D23EF43}"
+	ProjectSection(SolutionItems) = preProject
+		ReadBenchmarkData.ps1 = ReadBenchmarkData.ps1
+		..\.scripts\WriteBenchmark.ps1 = ..\.scripts\WriteBenchmark.ps1
+	EndProjectSection
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -128,6 +134,7 @@ Global
 		{142854D7-409C-4C87-A5B8-39B51477F5B2} = {5EEC2873-35B5-4364-A2A0-97AAD7BF960D}
 		{D4CC6660-8C30-41E5-A28A-C018DDDF8D96} = {4269F3C3-6B42-419B-B64A-3E6DC0F1574A}
 		{8986E836-2F55-4D71-B23E-50F4A8427A5B} = {AD743B78-D61F-4FBF-B620-FA83CE599A50}
+		{89514D49-4D5D-4423-A6EC-F0FF1D23EF43} = {4269F3C3-6B42-419B-B64A-3E6DC0F1574A}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {30372F91-B206-4351-A621-F0E2773C337B}

src/ReadBenchmarkData.ps1

@@ -21,7 +21,7 @@ function ConvertToMs([string]$str)
             ## Convert to milliseconds
             if     ($parts[1] -eq "s")  { $val *= 1000    }
             elseif ($parts[1] -eq "ms") {                 } ## Do nothing
-            elseif ($parts[1] -eq "µs") { $val /= 1000    }
+            elseif ($parts[1] -eq "μs") { $val /= 1000    }
             elseif ($parts[1] -eq "ns") { $val /= 1000000 }
             else   { throw ("Unknown unit: " + $parts[1]) }
         }
@@ -172,7 +172,7 @@ $list = (Get-Item -Filter *.csv -Path '.\BenchmarkDotNet.Artifacts\results\*' |
 foreach ($file in [System.Linq.Enumerable]::OrderBy($list, [Func[object, string]] { param($s) if ($s -match 'Reference-report\.csv') { "" } else { $s } }))
 {
     $t = [System.IO.Path]::GetFileNameWithoutExtension($file).Split(@('.'))[-1]
-    $testCategory = $t.Substring(0, $t.Length - 7)
+    if ($t.Length -gt 7) { $testCategory = $t.Substring(0, $t.Length - 7) } else { $testCategory = $t }
 
     Write-Host "------ [TEST] $testCategory ------"
 

src/libraries/Microsoft.PowerFx.Core/Binding/INameResolver.cs

@@ -34,7 +34,7 @@ internal interface INameResolver
 
         DPath CurrentEntityPath { get; }
 
-        IEnumerable<TexlFunction> Functions { get; }
+        TexlFunctionSet Functions { get; }
 
         // This advertises whether the INameResolver instance will suggest unqualified enums ("Hours")
         // or only qualified enums ("TimeUnit.Hours").

src/libraries/Microsoft.PowerFx.Core/Functions/TexlFunction.cs

@@ -7,8 +7,6 @@
 using System.Globalization;
 using System.Linq;
 using System.Numerics;
-using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.PowerFx.Core.App.ErrorContainers;
 using Microsoft.PowerFx.Core.Binding;
 using Microsoft.PowerFx.Core.Entities;
@@ -27,7 +25,6 @@
 using Microsoft.PowerFx.Core.Types;
 using Microsoft.PowerFx.Core.Utils;
 using Microsoft.PowerFx.Syntax;
-using Microsoft.PowerFx.Types;
 using static Microsoft.PowerFx.Core.IR.IRTranslator;
 using CallNode = Microsoft.PowerFx.Syntax.CallNode;
 using IRCallNode = Microsoft.PowerFx.Core.IR.Nodes.CallNode;
@@ -362,7 +359,7 @@ public TexlFunction(
         // This can be used to generate a list of enums required for a function library.
         public virtual IEnumerable<string> GetRequiredEnumNames()
         {
-            return new List<string>();
+            return Enumerable.Empty<string>();
         }
 
         // Return all signatures with at most 'arity' parameters.