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Eliminate tuple allocation for implicitly returned formal arguments
closes #335 fixes #330 commit 05175e2a00a05dd444b9c5420946047d77167742 Author: mrange <marten_range@hotmail.com> Date: Wed Mar 25 20:15:44 2015 +0100 Added Tuple elimination IL test commit 15c32975781bbd66626b05bd1834390e02d8b17f Author: Arseny Kapoulkine <arseny.kapoulkine@gmail.com> Date: Thu Mar 26 00:20:45 2015 -0700 Eliminate tuple allocation for implicitly returned formal arguments The expression generated for implicitly returned formal arguments does not match the structure that tuple allocation elimination can understand. In particular, it generates a structure: let t = (let a0=v0 in let a1=v1 in ... in e0,e1,...) in expr However, tuple allocation elimination expects the tuple value to be a tupled expression for elimination to work. When t is an immutable local variable, we can rewrite the expression into: let a0=v0 in let a1=v1 in ... in (let t = e0,e1,... in expr) This results in a more direct binding for t, enabling allocation elimination. As a result, using match constructs on System.Collections.Generic.Dictionary TryGetValue as follows: match d.TryGetValue(key) with true, value -> ... | _ -> ... generates the same IL in optimized build as more complicated code with explicit output parameters. Other code patterns may get a similar improvement in reduced GC pressure and increased performance.
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‎src/fsharp/opt.fs

Lines changed: 38 additions & 6 deletions
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@@ -1416,15 +1416,18 @@ let rec (|KnownValApp|_|) expr =
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// This transform encourages that by allowing projections to be simplified.
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//-------------------------------------------------------------------------
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let CanExpandStructuralBinding (v: Val) =
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not v.IsCompiledAsTopLevel &&
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not v.IsMember &&
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not v.IsTypeFunction &&
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not v.IsMutable
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let ExprIsValue = function Expr.Val _ -> true | _ -> false
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let ExpandStructuralBinding cenv expr =
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let ExpandStructuralBindingRaw cenv expr =
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match expr with
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| Expr.Let (TBind(v,rhs,tgtSeqPtOpt),body,m,_)
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when (isTupleExpr rhs &&
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not v.IsCompiledAsTopLevel &&
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not v.IsMember &&
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not v.IsTypeFunction &&
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not v.IsMutable) ->
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when (isTupleExpr rhs &&
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CanExpandStructuralBinding v) ->
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let args = tryDestTuple rhs
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if List.forall ExprIsValue args then
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expr (* avoid re-expanding when recursion hits original binding *)
@@ -1440,6 +1443,35 @@ let ExpandStructuralBinding cenv expr =
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mkLetsBind m binds (mkLet tgtSeqPtOpt m v tuple body)
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(* REVIEW: other cases - records, explicit lists etc. *)
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| expr -> expr
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// Moves outer tuple binding inside near the tupled expression:
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// let t = (let a0=v0 in let a1=v1 in ... in let an=vn in e0,e1,...,em) in body
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// let a0=v0 in let a1=v1 in ... in let an=vn in (let t = e0,e1,...,em in body)
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// This way ExpandStructuralBinding can replace expressions in constants, t is directly bound
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// to a tuple expression so that other optimizations such as OptimizeTupleFieldGet work,
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// and the tuple allocation can be eliminated.
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// Most importantly, this successfully eliminates tuple allocations for implicitly returned
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// formal arguments in method calls.
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let rec RearrangeTupleBindings expr fin =
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match expr with
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| Expr.Let (bind,body,m,_) ->
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match RearrangeTupleBindings body fin with
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| Some b -> Some (mkLetBind m bind b)
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| None -> None
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| Expr.Op (TOp.Tuple,_,_,_) -> Some (fin expr)
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| _ -> None
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let ExpandStructuralBinding cenv expr =
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match expr with
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| Expr.Let (TBind(v,rhs,tgtSeqPtOpt),body,m,_)
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when (isTupleTy cenv.g v.Type &&
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not (isTupleExpr rhs) &&
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CanExpandStructuralBinding v) ->
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match RearrangeTupleBindings rhs (fun top -> mkLet tgtSeqPtOpt m v top body) with
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| Some e -> ExpandStructuralBindingRaw cenv e
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| None -> expr
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| e -> ExpandStructuralBindingRaw cenv e
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//-------------------------------------------------------------------------
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// QueryBuilder.Run elimination helpers
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//-------------------------------------------------------------------------

‎tests/fsharpqa/Source/CodeGen/EmittedIL/Tuples/TupleElimination.fs

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@@ -0,0 +1,23 @@
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// #NoMono #NoMT #CodeGen #EmittedIL #Tuples
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[<EntryPoint>]
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let main argv =
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let p v = printfn "%A" v
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let dic = System.Collections.Generic.Dictionary<int, int>()
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// Tests that the Tuple is eliminated as intended for instance methods
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let (b : bool, i : int) = dic.TryGetValue 1
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p b
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p i
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// Tests that the Tuple is eliminated as intended for static methods
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let (b : bool, l : int64) as t = System.Int64.TryParse "123"
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p b
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p l
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let tt : bool*int64 = t
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// Tests that a Tuple is created as needed when calling p
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p tt
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0

‎tests/fsharpqa/Source/CodeGen/EmittedIL/Tuples/TupleElimination.il.netfx4.bsl

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// Microsoft (R) .NET Framework IL Disassembler. Version 4.0.30319.33440
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// Metadata version: v4.0.30319
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.assembly extern mscorlib
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{
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.publickeytoken = (B7 7A 5C 56 19 34 E0 89 ) // .z\V.4..
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.ver 4:0:0:0
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}
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.assembly extern FSharp.Core
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{
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.publickeytoken = (B0 3F 5F 7F 11 D5 0A 3A ) // .?_....:
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.ver 4:4:0:9055
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}
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.assembly TupleElimination
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{
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.custom instance void [FSharp.Core]Microsoft.FSharp.Core.FSharpInterfaceDataVersionAttribute::.ctor(int32,
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int32,
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int32) = ( 01 00 02 00 00 00 00 00 00 00 00 00 00 00 00 00 )
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// --- The following custom attribute is added automatically, do not uncomment -------
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// .custom instance void [mscorlib]System.Diagnostics.DebuggableAttribute::.ctor(valuetype [mscorlib]System.Diagnostics.DebuggableAttribute/DebuggingModes) = ( 01 00 03 00 00 00 00 00 )
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.hash algorithm 0x00008004
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.ver 0:0:0:0
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}
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.mresource public FSharpSignatureData.TupleElimination
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{
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// Offset: 0x00000000 Length: 0x0000022E
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}
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.mresource public FSharpOptimizationData.TupleElimination
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{
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// Offset: 0x00000238 Length: 0x0000007B
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}
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.module TupleElimination.exe
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// MVID: {551307BF-DFDD-92DF-A745-0383BF071355}
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.imagebase 0x00400000
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.file alignment 0x00000200
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.stackreserve 0x00100000
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.subsystem 0x0003 // WINDOWS_CUI
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.corflags 0x00000001 // ILONLY
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// Image base: 0x00460000
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// =============== CLASS MEMBERS DECLARATION ===================
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.class public abstract auto ansi sealed TupleElimination
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extends [mscorlib]System.Object
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{
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.custom instance void [FSharp.Core]Microsoft.FSharp.Core.CompilationMappingAttribute::.ctor(valuetype [FSharp.Core]Microsoft.FSharp.Core.SourceConstructFlags) = ( 01 00 07 00 00 00 00 00 )
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.method assembly static void p@5<a>(!!a v) cil managed
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{
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// Code size 31 (0x1f)
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.maxstack 4
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.locals init ([0] class [FSharp.Core]Microsoft.FSharp.Core.PrintfFormat`4<class [FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<!!a,class [FSharp.Core]Microsoft.FSharp.Core.Unit>,class [mscorlib]System.IO.TextWriter,class [FSharp.Core]Microsoft.FSharp.Core.Unit,class [FSharp.Core]Microsoft.FSharp.Core.Unit> V_0)
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.language '{AB4F38C9-B6E6-43BA-BE3B-58080B2CCCE3}', '{994B45C4-E6E9-11D2-903F-00C04FA302A1}', '{5A869D0B-6611-11D3-BD2A-0000F80849BD}'
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.line 5,5 : 15,27 ''
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IL_0000: nop
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IL_0001: ldstr "%A"
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IL_0006: newobj instance void class [FSharp.Core]Microsoft.FSharp.Core.PrintfFormat`5<class [FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<!!a,class [FSharp.Core]Microsoft.FSharp.Core.Unit>,class [mscorlib]System.IO.TextWriter,class [FSharp.Core]Microsoft.FSharp.Core.Unit,class [FSharp.Core]Microsoft.FSharp.Core.Unit,!!a>::.ctor(string)
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IL_000b: stloc.0
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IL_000c: call class [mscorlib]System.IO.TextWriter [mscorlib]System.Console::get_Out()
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IL_0011: ldloc.0
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IL_0012: call !!0 [FSharp.Core]Microsoft.FSharp.Core.PrintfModule::PrintFormatLineToTextWriter<class [FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<!!0,class [FSharp.Core]Microsoft.FSharp.Core.Unit>>(class [mscorlib]System.IO.TextWriter,
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class [FSharp.Core]Microsoft.FSharp.Core.PrintfFormat`4<!!0,class [mscorlib]System.IO.TextWriter,class [FSharp.Core]Microsoft.FSharp.Core.Unit,class [FSharp.Core]Microsoft.FSharp.Core.Unit>)
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IL_0017: ldarg.0
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IL_0018: callvirt instance !1 class [FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<!!a,class [FSharp.Core]Microsoft.FSharp.Core.Unit>::Invoke(!0)
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IL_001d: pop
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IL_001e: ret
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} // end of method TupleElimination::p@5
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.method public static int32 main(string[] argv) cil managed
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{
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.entrypoint
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.custom instance void [FSharp.Core]Microsoft.FSharp.Core.EntryPointAttribute::.ctor() = ( 01 00 00 00 )
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// Code size 101 (0x65)
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.maxstack 5
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.locals init ([0] class [mscorlib]System.Collections.Generic.Dictionary`2<int32,int32> dic,
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[1] int32 V_1,
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[2] bool V_2,
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[3] int32 V_3,
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[4] int64 V_4,
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[5] bool V_5,
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[6] int64 V_6,
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[7] class [mscorlib]System.Tuple`2<bool,int64> t)
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.line 7,7 : 5,64 ''
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IL_0000: nop
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IL_0001: newobj instance void class [mscorlib]System.Collections.Generic.Dictionary`2<int32,int32>::.ctor()
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IL_0006: stloc.0
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.line 9,9 : 31,48 ''
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IL_0007: ldc.i4.0
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IL_0008: stloc.1
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IL_0009: ldloc.0
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IL_000a: ldc.i4.1
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IL_000b: ldloca.s V_1
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IL_000d: callvirt instance bool class [mscorlib]System.Collections.Generic.Dictionary`2<int32,int32>::TryGetValue(!0,
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!1&)
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IL_0012: stloc.2
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IL_0013: ldloc.1
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IL_0014: stloc.3
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.line 10,10 : 5,6 ''
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IL_0015: ldloc.2
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IL_0016: call void TupleElimination::p@5<bool>(!!0)
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IL_001b: nop
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.line 11,11 : 5,6 ''
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IL_001c: ldloc.3
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IL_001d: call void TupleElimination::p@5<int32>(!!0)
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IL_0022: nop
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.line 14,14 : 38,65 ''
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IL_0023: ldc.i8 0x0
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IL_002c: stloc.s V_4
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IL_002e: ldstr "123"
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IL_0033: ldloca.s V_4
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IL_0035: call bool [mscorlib]System.Int64::TryParse(string,
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int64&)
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IL_003a: stloc.s V_5
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IL_003c: ldloc.s V_4
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IL_003e: stloc.s V_6
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.line 14,14 : 5,65 ''
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IL_0040: ldloc.s V_5
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IL_0042: ldloc.s V_6
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IL_0044: newobj instance void class [mscorlib]System.Tuple`2<bool,int64>::.ctor(!0,
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!1)
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IL_0049: stloc.s t
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.line 15,15 : 5,6 ''
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IL_004b: ldloc.s V_5
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IL_004d: call void TupleElimination::p@5<bool>(!!0)
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IL_0052: nop
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.line 16,16 : 5,6 ''
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IL_0053: ldloc.s V_6
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IL_0055: call void TupleElimination::p@5<int64>(!!0)
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IL_005a: nop
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.line 21,21 : 5,6 ''
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IL_005b: ldloc.s t
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IL_005d: call void TupleElimination::p@5<class [mscorlib]System.Tuple`2<bool,int64>>(!!0)
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IL_0062: nop
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.line 23,23 : 5,6 ''
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IL_0063: ldc.i4.0
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IL_0064: ret
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} // end of method TupleElimination::main
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} // end of class TupleElimination
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.class private abstract auto ansi sealed '<StartupCode$TupleElimination>'.$TupleElimination
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extends [mscorlib]System.Object
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{
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} // end of class '<StartupCode$TupleElimination>'.$TupleElimination
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// =============================================================
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// *********** DISASSEMBLY COMPLETE ***********************

‎tests/fsharpqa/Source/CodeGen/EmittedIL/Tuples/env.lst

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SOURCE=Tuple08.fs ISCFLAGS="-g --test:EmitFeeFeeAs100001 --optimize-" COMPILE_ONLY=1 POSTCMD="..\\CompareIL.cmd Tuple08.exe NetFx40" # Tuple08.fs - NetFx40
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SOURCE=TupleMonster.fs ISCFLAGS="-g --test:EmitFeeFeeAs100001 --optimize-" COMPILE_ONLY=1 POSTCMD="..\\CompareIL.cmd TupleMonster.exe NetFx40" # TupleMonster.fs - NetFx40
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SOURCE=TupleElimination.fs ISCFLAGS="-g --test:EmitFeeFeeAs100001 --optimize+" COMPILE_ONLY=1 POSTCMD="..\\CompareIL.cmd TupleElimination.exe NetFx40" # TupleElimination.fs - NetFx40

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