Merge pull request #26846 from gafter/master-25692

Produce much better code for CInt(Fix(number))

src/Compilers/Core/Portable/WellKnownMember.cs

@@ -433,6 +433,9 @@ internal enum WellKnownMember
 
         System_Runtime_CompilerServices_IsUnmanagedAttribute__ctor,
 
+        Microsoft_VisualBasic_Conversion__FixSingle,
+        Microsoft_VisualBasic_Conversion__FixDouble,
+
         Count
     }
 }

src/Compilers/Core/Portable/WellKnownTypes.cs

@@ -274,6 +274,8 @@ internal enum WellKnownType
         System_Runtime_InteropServices_UnmanagedType,
         System_Runtime_CompilerServices_IsUnmanagedAttribute,
 
+        Microsoft_VisualBasic_Conversion,
+
         NextAvailable,
     }
 
@@ -541,6 +543,7 @@ internal static class WellKnownTypes
             "System.ReadOnlySpan`1",
             "System.Runtime.InteropServices.UnmanagedType",
             "System.Runtime.CompilerServices.IsUnmanagedAttribute",
+            "Microsoft.VisualBasic.Conversion",
         };
 
         private readonly static Dictionary<string, WellKnownType> s_nameToTypeIdMap = new Dictionary<string, WellKnownType>((int)Count);

src/Compilers/VisualBasic/Portable/CodeGen/EmitConversion.vb

@@ -123,13 +123,6 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGen
         Private Sub EmitConvertSimpleNumeric(conversion As BoundConversion, typeFrom As PrimitiveTypeCode, typeTo As PrimitiveTypeCode, checked As Boolean)
             Debug.Assert(typeFrom.IsIntegral() OrElse typeFrom.IsFloatingPoint() OrElse typeFrom = PrimitiveTypeCode.Char)
             Debug.Assert(typeTo.IsIntegral() OrElse typeTo.IsFloatingPoint())
-
-            Debug.Assert(Not (typeFrom.IsFloatingPoint() AndAlso typeTo.IsIntegral() AndAlso
-                              Not (conversion.Operand.Kind = BoundKind.Call AndAlso
-                                   DirectCast(conversion.Operand, BoundCall).Method.Equals(
-                                       Me._module.SourceModule.ContainingSourceAssembly.DeclaringCompilation.GetWellKnownTypeMember(WellKnownMember.System_Math__RoundDouble)))),
-                         "About to ignore VB rules for rounding float numbers.")
-
             _builder.EmitNumericConversion(typeFrom, typeTo, checked)
         End Sub
 

src/Compilers/VisualBasic/Portable/Lowering/LocalRewriter/LocalRewriter_Conversion.vb

@@ -1295,19 +1295,24 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
         Private Function RewriteFloatingToIntegralConversion(node As BoundConversion, typeFrom As TypeSymbol, underlyingTypeTo As TypeSymbol) As BoundExpression
             Debug.Assert(typeFrom.IsFloatingType() AndAlso underlyingTypeTo.IsIntegralType())
             Dim result As BoundExpression = node
+            Dim operand = node.Operand
 
-            Dim mathRound As MethodSymbol
-            ' Call Math.Round method to enforce VB style rounding.
+            ' CInt(Fix(number)) and the like can be simplified to just truncate the number to the integral type
+            If operand.Kind = BoundKind.Call Then
+                Dim callOperand = DirectCast(operand, BoundCall)
+                If IsFixInvocation(callOperand) Then
+                    Return New BoundConversion(node.Syntax, callOperand.Arguments(0), node.ConversionKind, node.Checked, node.ExplicitCastInCode, node.Type)
+                End If
+            End If
 
+            ' Call Math.Round method to enforce VB style rounding.
             Const memberId As WellKnownMember = WellKnownMember.System_Math__RoundDouble
-            mathRound = DirectCast(Compilation.GetWellKnownTypeMember(memberId), MethodSymbol)
+            Dim mathRound As MethodSymbol = DirectCast(Compilation.GetWellKnownTypeMember(memberId), MethodSymbol)
 
             If Not ReportMissingOrBadRuntimeHelper(node, memberId, mathRound) Then
                 ' If we got here and passed badness check, it should be safe to assume that we have 
                 ' a "good" symbol for Double type
 
-                Dim operand = node.Operand
-
 #If DEBUG Then
                 Dim useSiteDiagnostics As HashSet(Of DiagnosticInfo) = Nothing
 #End If
@@ -1334,6 +1339,22 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             Return result
         End Function
 
+        Private Function IsFixInvocation(node As BoundCall) As Boolean
+            ' Quick test to eliminate most calls to something other that Conversion.Fix
+            If Not "Fix".Equals(node.Method.Name) Then
+                Return False
+            End If
+
+            Select Case node.Type.SpecialType
+                Case SpecialType.System_Single
+                    Return node.Method = Me.Compilation.GetWellKnownTypeMember(WellKnownMember.Microsoft_VisualBasic_Conversion__FixSingle)
+                Case SpecialType.System_Double
+                    Return node.Method = Me.Compilation.GetWellKnownTypeMember(WellKnownMember.Microsoft_VisualBasic_Conversion__FixDouble)
+                Case Else
+                    Return False
+            End Select
+        End Function
+
 #End Region
 
 #Region "DirectCast"

src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/WellKnownTypeValidationTests.vb

@@ -537,7 +537,8 @@ End Namespace
                          WellKnownType.Microsoft_VisualBasic_ApplicationServices_ApplicationBase,
                          WellKnownType.Microsoft_VisualBasic_ApplicationServices_WindowsFormsApplicationBase,
                          WellKnownType.Microsoft_VisualBasic_Information,
-                         WellKnownType.Microsoft_VisualBasic_Interaction
+                         WellKnownType.Microsoft_VisualBasic_Interaction,
+                         WellKnownType.Microsoft_VisualBasic_Conversion
                         ' Not embedded, so not available.
                         Continue For
                     Case WellKnownType.System_FormattableString,
@@ -674,7 +675,9 @@ End Namespace
                          WellKnownMember.Microsoft_VisualBasic_Information__SystemTypeName,
                          WellKnownMember.Microsoft_VisualBasic_Information__TypeName,
                          WellKnownMember.Microsoft_VisualBasic_Information__VbTypeName,
-                         WellKnownMember.Microsoft_VisualBasic_Interaction__CallByName
+                         WellKnownMember.Microsoft_VisualBasic_Interaction__CallByName,
+                         WellKnownMember.Microsoft_VisualBasic_Conversion__FixSingle,
+                         WellKnownMember.Microsoft_VisualBasic_Conversion__FixDouble
                         ' The type is not embedded, so the member is not available.
                         Continue For
                     Case WellKnownMember.System_Array__Empty,