runtime: Task/TaskAwaiter completion makes lots of duplicate memory reads

public async Task CompletedTask()
{
    for (int i = 0; i < 100; i++)
        await Task.CompletedTask;
}

Inlines into 06000007 <CompletedTask>d__3:MoveNext():this
  [1 IL=0019 TR=000066 06001F0C] [below ALWAYS_INLINE size] Task:get_CompletedTask():ref
  [2 IL=0024 TR=000069 06001F2E] [below ALWAYS_INLINE size] Task:GetAwaiter():struct:this
    [3 IL=0001 TR=000172 060049ED] [below ALWAYS_INLINE size] TaskAwaiter:.ctor(ref):this
  [4 IL=0032 TR=000079 060049EE] [below ALWAYS_INLINE size] TaskAwaiter:get_IsCompleted():bool:this
    [5 IL=0006 TR=000194 06001F03] [below ALWAYS_INLINE size] Task:get_IsCompleted():bool:this
      [6 IL=0010 TR=000206 06001F04] [below ALWAYS_INLINE size] Task:IsCompletedMethod(int):bool
  [7 IL=0064 TR=000109 060048CB] [below ALWAYS_INLINE size] AsyncTaskMethodBuilder:AwaitUnsafeOnCompleted(byref,byref):this
    [0 IL=0008 TR=000227 060048D5] [FAILED: has exception handling] AsyncTaskMethodBuilder`1:AwaitUnsafeOnCompleted(byref,byref):this
  [8 IL=0101 TR=000044 060049F1] [below ALWAYS_INLINE size] TaskAwaiter:GetResult():this
    [9 IL=0006 TR=000239 060049F2] [below ALWAYS_INLINE size] TaskAwaiter:ValidateEnd(ref)
      [10 IL=0001 TR=000245 06001EE7] [aggressive inline attribute] Task:get_IsWaitNotificationEnabledOrNotRanToCompletion():bool:this
      [11 IL=0009 TR=000255 060049F3] [profitable inline] TaskAwaiter:HandleNonSuccessAndDebuggerNotification(ref)
        [12 IL=0001 TR=000272 06001F03] [below ALWAYS_INLINE size] Task:get_IsCompleted():bool:this
          [13 IL=0010 TR=000327 06001F04] [below ALWAYS_INLINE size] Task:IsCompletedMethod(int):bool
        [14 IL=0019 TR=000310 06001F39] [below ALWAYS_INLINE size] Task:InternalWait(int,struct):bool:this
        [0 IL=0026 TR=000281 06001EE5] [FAILED: unprofitable inline] Task:NotifyDebuggerOfWaitCompletionIfNecessary():bool:this
        [15 IL=0033 TR=000288 06001F05] [profitable inline] Task:get_IsCompletedSuccessfully():bool:this
        [0 IL=0041 TR=000298 060049F4] [FAILED: noinline per IL/cached result] TaskAwaiter:ThrowForNonSuccess(ref)
  [0 IL=0150 TR=000151 060048CE] [FAILED: within catch region] AsyncTaskMethodBuilder:SetException(ref):this
  [16 IL=0171 TR=000126 060048CD] [profitable inline] AsyncTaskMethodBuilder:SetResult():this
    [17 IL=0011 TR=000368 060048DE] [profitable inline] AsyncTaskMethodBuilder`1:SetResult(ref):this
      [0 IL=0026 TR=000390 060048DC] [FAILED: noinline per IL/cached result] AsyncTaskMethodBuilder`1:SetExistingTaskResult(struct):this

;  V00 this         [V00,T01] ( 22, 40   )   byref  ->  [rbp+0x10]   do-not-enreg[H] this
;  V01 loc0         [V01,T12] (  2,  2   )     int  ->  rcx        
;  V02 loc1         [V02    ] (  6, 19   )  struct ( 8) [rbp-0x10]   do-not-enreg[XS] must-init addr-exposed ld-addr-op
;  V03 loc2         [V03,T04] (  2, 16   )     int  ->  rdx        
;* V04 loc3         [V04    ] (  0,  0   )     ref  ->  zero-ref    class-hnd
;  V05 OutArgs      [V05    ] (  1,  1   )  lclBlk (32) [rsp+0x00]   "OutgoingArgSpace"
;* V06 tmp1         [V06    ] (  0,  0   )     int  ->  zero-ref    "dup spill"
;  V07 tmp2         [V07,T15] (  2,  0   )     ref  ->  rdx         class-hnd "impSpillSpecialSideEff"
;  V08 tmp3         [V08,T02] (  3, 24   )     ref  ->  rdx         class-hnd "Inlining Arg"
;* V09 tmp4         [V09    ] (  0,  0   )  struct ( 8) zero-ref    "NewObj constructor temp"
;  V10 tmp5         [V10,T03] (  2, 16   )     ref  ->  rdx         class-hnd "Inlining Arg"
;  V11 tmp6         [V11,T06] (  2,  8   )     int  ->  rdx         "Inline stloc first use temp"
;  V12 tmp7         [V12,T07] (  2,  4   )   byref  ->  rcx         "Inlining Arg"
;  V13 tmp8         [V13,T00] (  7, 44   )     ref  ->  rsi         class-hnd "Inlining Arg"
;* V14 tmp9         [V14    ] (  0,  0   )  struct ( 8) zero-ref    ld-addr-op "Inline ldloca(s) first use temp"
;* V15 tmp10        [V15    ] (  0,  0   )    bool  ->  zero-ref    "Inline stloc first use temp"
;  V16 tmp11        [V16,T10] (  2,  4   )     int  ->  rcx         "Inline stloc first use temp"
;* V17 tmp12        [V17    ] (  0,  0   )  struct ( 8) zero-ref    "Inlining Arg"
;  V18 tmp13        [V18,T08] (  2,  4   )   byref  ->  rcx         "Inlining Arg"
;  V19 tmp14        [V19,T05] (  4,  8   )   byref  ->  rcx         "Inlining Arg"
;  V20 tmp15        [V20,T13] (  2,  2   )  struct ( 8) [rbp-0x18]   do-not-enreg[SF] must-init ld-addr-op "Inline ldloca(s) first use temp"
;  V21 tmp16        [V21,T09] (  2,  4   )     ref  ->  rdx         class-hnd exact "Inlining Arg"
;  V22 tmp17        [V22    ] (  6, 19   )     ref  ->  [rbp-0x10]   do-not-enreg[X] addr-exposed V02.m_task(offs=0x00) P-DEP "field V02.m_task (fldOffset=0x0)"
;* V23 tmp18        [V23    ] (  0,  0   )     ref  ->  zero-ref    V09.m_task(offs=0x00) P-INDEP "field V09.m_task (fldOffset=0x0)"
;* V24 tmp19        [V24,T11] (  0,  0   )     ref  ->  zero-ref    V14._source(offs=0x00) P-INDEP "field V14._source (fldOffset=0x0)"
;* V25 tmp20        [V25,T14] (  0,  0   )     ref  ->  zero-ref    V17._source(offs=0x00) P-INDEP "field V17._source (fldOffset=0x0)"
;  V26 PSPSym       [V26    ] (  1,  1   )    long  ->  [rbp-0x20]   do-not-enreg[X] addr-exposed "PSPSym"
;* V27 tmp22        [V27    ] (  0,  0   )   byref  ->  zero-ref    "optAddCopies"
G_M10160_IG01:
       55                   push     rbp
       56                   push     rsi
       4883EC38             sub      rsp, 56
       488D6C2440           lea      rbp, [rsp+40H]
       33C0                 xor      rax, rax
       488945F0             mov      qword ptr [rbp-10H], rax
       488945E8             mov      qword ptr [rbp-18H], rax
       488965E0             mov      qword ptr [rbp-20H], rsp
       48894D10             mov      bword ptr [rbp+10H], rcx   ; set [rbp+10H] from rcx

G_M10160_IG02:
       488B4D10             mov      rcx, bword ptr [rbp+10H]    ; read [rbp+10H] to rcx
       8B09                 mov      ecx, dword ptr [rcx]

G_M10160_IG03:
       85C9                 test     ecx, ecx
       0F8486000000         je       G_M10160_IG05
       488B4D10             mov      rcx, bword ptr [rbp+10H]    ; read [rbp+10H] to rcx  
       33D2                 xor      edx, edx
       895104               mov      dword ptr [rcx+4], edx
       488B4D10             mov      rcx, bword ptr [rbp+10H]    ; read [rbp+10H] to rcx  
       83790464             cmp      dword ptr [rcx+4], 100
       0F8DFF000000         jge      G_M10160_IG09

G_M10160_IG04:                                              ; ** for body start
       48B9783EECCFFB7F0000 mov      rcx, 0x7FFBCFEC3E78
       BA40020000           mov      edx, 576
       E81AACBA5F           call     CORINFO_HELP_GETSHARED_NONGCSTATIC_BASE
       48BAF8159DDC14020000 mov      rdx, 0x214DC9D15F8
       488B12               mov      rdx, gword ptr [rdx]
       8B0A                 mov      ecx, dword ptr [rdx]
       488955F0             mov      gword ptr [rbp-10H], rdx
       488B55F0             mov      rdx, gword ptr [rbp-10H]
       8B5234               mov      edx, dword ptr [rdx+52]
       F7C200006001         test     edx, 0x1600000
       755A                 jne      SHORT G_M10160_IG06
       488B5510             mov      rdx, bword ptr [rbp+10H]    ; read [rbp+10H] to rdx  
       33C9                 xor      ecx, ecx
       890A                 mov      dword ptr [rdx], ecx
       488B5510             mov      rdx, bword ptr [rbp+10H]    ; read [rbp+10H] to rdx    
       488D4A10             lea      rcx, bword ptr [rdx+16]
       488B55F0             mov      rdx, gword ptr [rbp-10H]
       E8EF93BA5F           call     CORINFO_HELP_CHECKED_ASSIGN_REF
       488B5510             mov      rdx, bword ptr [rbp+10H]    ; read [rbp+10H] to rdx   
       3912                 cmp      dword ptr [rdx], edx
       488B5510             mov      rdx, bword ptr [rbp+10H]    ; read [rbp+10H] to rdx  
       488D4A08             lea      rcx, bword ptr [rdx+8]
       488D55F0             lea      rdx, bword ptr [rbp-10H]
       4C8B4510             mov      r8, bword ptr [rbp+10H]
       E8D4F5FFFF           call     AsyncTaskMethodBuilder`1:AwaitUnsafeOnCompleted(byref,byref):this
       E9D0000000           jmp      G_M10160_IG11

G_M10160_IG05:
       488B4D10             mov      rcx, bword ptr [rbp+10H]    ; read [rbp+10H] to rcx  
       488B4910             mov      rcx, gword ptr [rcx+16]
       48894DF0             mov      gword ptr [rbp-10H], rcx
       488B4D10             mov      rcx, bword ptr [rbp+10H]    ; read [rbp+10H] to rcx  
       4533C0               xor      r8, r8
       4C894110             mov      qword ptr [rcx+16], r8
       488B4D10             mov      rcx, bword ptr [rbp+10H]    ; read [rbp+10H] to rcx 
       C701FFFFFFFF         mov      dword ptr [rcx], -1

G_M10160_IG06:
       488B75F0             mov      rsi, gword ptr [rbp-10H]
       8B4E34               mov      ecx, dword ptr [rsi+52]
       81E100000011         and      ecx, 0x11000000
       81F900000001         cmp      ecx, 0x1000000
       743C                 je       SHORT G_M10160_IG08
       8B4E34               mov      ecx, dword ptr [rsi+52]
       F7C100006001         test     ecx, 0x1600000
       7510                 jne      SHORT G_M10160_IG07
       488BCE               mov      rcx, rsi
       4533C0               xor      r8, r8
       BAFFFFFFFF           mov      edx, -1
       E83E27AC5A           call     Task:InternalWaitCore(int,struct):bool:this

G_M10160_IG07:
       488BCE               mov      rcx, rsi
       E8B600AC5A           call     Task:NotifyDebuggerOfWaitCompletionIfNecessary():bool:this
       8B4E34               mov      ecx, dword ptr [rsi+52]
       81E100006001         and      ecx, 0x1600000
       81F900000001         cmp      ecx, 0x1000000
       7408                 je       SHORT G_M10160_IG08
       488BCE               mov      rcx, rsi
       E8DDEBB05A           call     TaskAwaiter:ThrowForNonSuccess(ref)

G_M10160_IG08:
       488B5510             mov      rdx, bword ptr [rbp+10H]    ; read [rbp+10H] to rdx  
       8B5204               mov      edx, dword ptr [rdx+4]
       FFC2                 inc      edx
       488B4D10             mov      rcx, bword ptr [rbp+10H]    ; read [rbp+10H] to rcx  
       895104               mov      dword ptr [rcx+4], edx
       488B5510             mov      rdx, bword ptr [rbp+10H]    ; read [rbp+10H] to rdx  
       837A0464             cmp      dword ptr [rdx+4], 100
       0F8C01FFFFFF         jl       G_M10160_IG04          ; ** for body end

G_M10160_IG09:
       488B5510             mov      rdx, bword ptr [rbp+10H]    ; read [rbp+10H] to rdx  
       C702FEFFFFFF         mov      dword ptr [rdx], -2
       488B5510             mov      rdx, bword ptr [rbp+10H]    ; read [rbp+10H] to rdx  
       3912                 cmp      dword ptr [rdx], edx
       488B5510             mov      rdx, bword ptr [rbp+10H]    ; read [rbp+10H] to rdx  
       488D4A08             lea      rcx, bword ptr [rdx+8]
       48BA88259DDC14020000 mov      rdx, 0x214DC9D2588
       488B12               mov      rdx, gword ptr [rdx]
       48833900             cmp      gword ptr [rcx], 0
       7507                 jne      SHORT G_M10160_IG10
       E80F93BA5F           call     CORINFO_HELP_CHECKED_ASSIGN_REF
       EB0E                 jmp      SHORT G_M10160_IG11

G_M10160_IG10:
       C645E800             mov      byte  ptr [rbp-18H], 0
       480FBE55E8           movsx    rdx, byte  ptr [rbp-18H]
       E8FFCCB05A           call     AsyncTaskMethodBuilder`1:SetExistingTaskResult(struct):this

G_M10160_IG11:
       90                   nop      

G_M10160_IG12:
       488D65F8             lea      rsp, [rbp-08H]
       5E                   pop      rsi
       5D                   pop      rbp
       C3                   ret      

G_M10160_IG13:
       55                   push     rbp
       56                   push     rsi
       4883EC28             sub      rsp, 40
       488B6920             mov      rbp, qword ptr [rcx+32]
       48896C2420           mov      qword ptr [rsp+20H], rbp
       488D6D40             lea      rbp, [rbp+40H]

G_M10160_IG14:
       488B4D10             mov      rcx, bword ptr [rbp+10H]    ; read [rbp+10H] to rcx  
       C701FEFFFFFF         mov      dword ptr [rcx], -2
       488B4D10             mov      rcx, bword ptr [rbp+10H]    ; read [rbp+10H] to rcx  
       3909                 cmp      dword ptr [rcx], ecx
       488B4D10             mov      rcx, bword ptr [rbp+10H]    ; read [rbp+10H] to rcx  
       4883C108             add      rcx, 8
       E8A716B35A           call     AsyncTaskMethodBuilder:SetException(ref):this
       488D05C1FFFFFF       lea      rax, G_M10160_IG11

G_M10160_IG15:
       4883C428             add      rsp, 40
       5E                   pop      rsi
       5D                   pop      rbp
       C3                   ret      

; Total bytes of code 455, prolog size 29 for method <CompletedTask>d__3:MoveNext():this

Can this be elided where its not changing the register (as its just set the line or so before)

/cc @stephentoub @AndyAyersMS

category:cq theme:cse skill-level:expert cost:extra-large impact:large

About this issue

  • Original URL
  • State: open
  • Created 5 years ago
  • Comments: 31 (31 by maintainers)

Commits related to this issue

Most upvoted comments

This shows some promise – on the example above (and with dotnet/coreclr#21944):

; Assembly listing for method <CompletedTask>d__0:MoveNext():this
; Emitting BLENDED_CODE for X64 CPU with AVX - Windows
; optimized code
; rbp based frame
; fully interruptible
; Final local variable assignments
;
;  V00 this         [V00,T07] (  4,  3   )   byref  ->  [rbp+0x10]   do-not-enreg[H] this
;  V01 loc0         [V01,T13] (  2,  2   )     int  ->  rdx        
;  V02 loc1         [V02    ] (  6, 19   )  struct ( 8) [rbp-0x18]   do-not-enreg[XS] must-init addr-exposed ld-addr-op
;  V03 loc2         [V03,T04] (  2, 16   )     int  ->  rcx        
;* V04 loc3         [V04    ] (  0,  0   )     ref  ->  zero-ref    class-hnd
;  V05 OutArgs      [V05    ] (  1,  1   )  lclBlk (32) [rsp+0x00]   "OutgoingArgSpace"
;* V06 tmp1         [V06    ] (  0,  0   )     int  ->  zero-ref    "dup spill"
;  V07 tmp2         [V07,T16] (  2,  0   )     ref  ->  rdx         class-hnd "impSpillSpecialSideEff"
;  V08 tmp3         [V08,T02] (  3, 24   )     ref  ->  rdx         class-hnd exact "Inlining Arg"
;* V09 tmp4         [V09    ] (  0,  0   )  struct ( 8) zero-ref    "NewObj constructor temp"
;  V10 tmp5         [V10,T03] (  2, 16   )     ref  ->  rdx         class-hnd "Inlining Arg"
;  V11 tmp6         [V11,T06] (  2,  8   )     int  ->  rdx         "Inline stloc first use temp"
;  V12 tmp7         [V12,T08] (  2,  4   )   byref  ->  rcx         "Inlining Arg"
;  V13 tmp8         [V13,T00] (  7, 44   )     ref  ->  rdi         class-hnd "Inlining Arg"
;* V14 tmp9         [V14    ] (  0,  0   )  struct ( 8) zero-ref    ld-addr-op "Inline ldloca(s) first use temp"
;* V15 tmp10        [V15    ] (  0,  0   )    bool  ->  zero-ref    "Inline stloc first use temp"
;  V16 tmp11        [V16,T11] (  2,  4   )     int  ->  rcx         "Inline stloc first use temp"
;* V17 tmp12        [V17    ] (  0,  0   )  struct ( 8) zero-ref    "Inlining Arg"
;  V18 tmp13        [V18,T09] (  2,  4   )   byref  ->  rsi         "Inlining Arg"
;  V19 tmp14        [V19,T05] (  4,  8   )   byref  ->  rsi         "Inlining Arg"
;  V20 tmp15        [V20,T14] (  2,  2   )  struct ( 8) [rbp-0x20]   do-not-enreg[SF] must-init ld-addr-op "Inline ldloca(s) first use temp"
;  V21 tmp16        [V21,T10] (  2,  4   )     ref  ->  rdx         class-hnd "Inlining Arg"
;  V22 tmp17        [V22    ] (  6, 19   )     ref  ->  [rbp-0x18]   do-not-enreg[X] addr-exposed V02.m_task(offs=0x00) P-DEP "field V02.m_task (fldOffset=0x0)"
;* V23 tmp18        [V23    ] (  0,  0   )     ref  ->  zero-ref    V09.m_task(offs=0x00) P-INDEP "field V09.m_task (fldOffset=0x0)"
;* V24 tmp19        [V24,T12] (  0,  0   )     ref  ->  zero-ref    V14._source(offs=0x00) P-INDEP "field V14._source (fldOffset=0x0)"
;* V25 tmp20        [V25,T15] (  0,  0   )     ref  ->  zero-ref    V17._source(offs=0x00) P-INDEP "field V17._source (fldOffset=0x0)"
;  V26 PSPSym       [V26    ] (  1,  1   )    long  ->  [rbp-0x30]   do-not-enreg[X] addr-exposed "PSPSym"
;* V27 tmp22        [V27    ] (  0,  0   )   byref  ->  zero-ref    "optAddCopies"
;  V28 cse0         [V28,T01] ( 20, 37   )   byref  ->  rsi         "ValNumCSE"
;
; Lcl frame size = 64

G_M36345_IG01:
       push     rbp
       push     rdi
       push     rsi
       sub      rsp, 64
       lea      rbp, [rsp+50H]
       xor      rax, rax
       mov      qword ptr [rbp-18H], rax
       mov      qword ptr [rbp-20H], rax
       mov      qword ptr [rbp-30H], rsp
       mov      bword ptr [rbp+10H], rcx

G_M36345_IG02:
       mov      rsi, bword ptr [rbp+10H]
       mov      edx, dword ptr [rsi]

G_M36345_IG03:
       test     edx, edx
       je       SHORT G_M36345_IG05
       xor      edx, edx
       mov      dword ptr [rsi+4], edx
       cmp      dword ptr [rsi+4], 100
       jge      G_M36345_IG09

G_M36345_IG04:
       mov      rdx, 0xD1FFAB1E
       mov      rdx, gword ptr [rdx]
       mov      ecx, dword ptr [rdx]
       mov      gword ptr [rbp-18H], rdx
       mov      rdx, gword ptr [rbp-18H]
       mov      edx, dword ptr [rdx+52]
       test     edx, 0xD1FFAB1E
       jne      SHORT G_M36345_IG06
       xor      edx, edx
       mov      dword ptr [rsi], edx
       lea      rcx, bword ptr [rsi+16]
       mov      rdx, gword ptr [rbp-18H]
       call     CORINFO_HELP_CHECKED_ASSIGN_REF
       lea      rcx, bword ptr [rsi+8]
       lea      rdx, bword ptr [rbp-18H]
       mov      r8, rsi
       call     AsyncTaskMethodBuilder`1:AwaitUnsafeOnCompleted(byref,byref):this
       jmp      G_M36345_IG11

G_M36345_IG05:
       mov      rcx, gword ptr [rsi+16]
       mov      gword ptr [rbp-18H], rcx
       xor      rcx, rcx
       mov      qword ptr [rsi+16], rcx
       mov      dword ptr [rsi], -1

G_M36345_IG06:
       mov      rdi, gword ptr [rbp-18H]
       mov      ecx, dword ptr [rdi+52]
       and      ecx, 0xD1FFAB1E
       cmp      ecx, 0xD1FFAB1E
       je       SHORT G_M36345_IG08
       mov      ecx, dword ptr [rdi+52]
       test     ecx, 0xD1FFAB1E
       jne      SHORT G_M36345_IG07
       mov      rcx, rdi
       xor      r8, r8
       mov      edx, -1
       call     Task:InternalWaitCore(int,struct):bool:this

G_M36345_IG07:
       mov      rcx, rdi
       call     Task:NotifyDebuggerOfWaitCompletionIfNecessary():bool:this
       mov      ecx, dword ptr [rdi+52]
       and      ecx, 0xD1FFAB1E
       cmp      ecx, 0xD1FFAB1E
       je       SHORT G_M36345_IG08
       mov      rcx, rdi
       call     TaskAwaiter:ThrowForNonSuccess(ref)

G_M36345_IG08:
       mov      ecx, dword ptr [rsi+4]
       inc      ecx
       mov      dword ptr [rsi+4], ecx
       cmp      dword ptr [rsi+4], 100
       jl       G_M36345_IG04

G_M36345_IG09:
       mov      dword ptr [rsi], -2
       add      rsi, 8
       mov      rcx, 0xD1FFAB1E
       mov      edx, 0x5F8
       call     CORINFO_HELP_GETSHARED_NONGCSTATIC_BASE
       mov      rdx, 0xD1FFAB1E
       mov      rdx, gword ptr [rdx]
       cmp      gword ptr [rsi], 0
       jne      SHORT G_M36345_IG10
       mov      rcx, rsi
       call     CORINFO_HELP_CHECKED_ASSIGN_REF
       jmp      SHORT G_M36345_IG11

G_M36345_IG10:
       mov      byte  ptr [rbp-20H], 0
       mov      rcx, rsi
       movsx    rdx, byte  ptr [rbp-20H]
       call     AsyncTaskMethodBuilder`1:SetExistingTaskResult(struct):this

G_M36345_IG11:
       nop      

G_M36345_IG12:
       lea      rsp, [rbp-10H]
       pop      rsi
       pop      rdi
       pop      rbp
       ret      

G_M36345_IG13:
       push     rbp
       push     rdi
       push     rsi
       sub      rsp, 48
       mov      rbp, qword ptr [rcx+32]
       mov      qword ptr [rsp+20H], rbp
       lea      rbp, [rbp+50H]

G_M36345_IG14:
       mov      rsi, bword ptr [rbp+10H]
       mov      dword ptr [rsi], -2
       cmp      dword ptr [rsi], esi
       lea      rcx, bword ptr [rsi+8]
       call     AsyncTaskMethodBuilder:SetException(ref):this
       lea      rax, G_M36345_IG11

G_M36345_IG15:
       add      rsp, 48
       pop      rsi
       pop      rdi
       pop      rbp
       ret      

; Total bytes of code 387, prolog size 30 for method <CompletedTask>d__0:MoveNext():this

and more widely there are some nice wins and a net win, but also some regressions to investigate:

PMI Diffs for System.Private.CoreLib.dll, framework assemblies for x64 default jit
Summary:
(Lower is better)
Total bytes of diff: -70631 (-0.19% of base)
    diff is an improvement.
Top file regressions by size (bytes):
        3629 : System.Threading.Tasks.Dataflow.dasm (0.57% of base)
        1982 : System.Linq.Expressions.dasm (0.27% of base)
        1058 : System.Diagnostics.TraceSource.dasm (2.54% of base)
         835 : System.Collections.dasm (0.20% of base)
         820 : Newtonsoft.Json.dasm (0.13% of base)
Top file improvements by size (bytes):
      -29815 : System.Private.Xml.dasm (-0.83% of base)
      -10207 : System.Net.Http.dasm (-1.84% of base)
       -9746 : NuGet.Protocol.Core.v3.dasm (-3.84% of base)
       -3426 : System.Private.CoreLib.dasm (-0.09% of base)
       -3378 : CommandLine.dasm (-0.94% of base)
116 total files with size differences (52 improved, 64 regressed), 13 unchanged.
Top method regressions by size (bytes):
         676 ( 8.48% of base) : System.Private.Xml.dasm - SchemaCollectionPreprocessor:Preprocess(ref,ref,int):this
         614 (11.97% of base) : System.Net.HttpListener.dasm - <CloseAsyncCore>d__55:MoveNext():this
         429 ( 8.55% of base) : System.Net.WebClient.dasm - <UploadBitsAsync>d__152:MoveNext():this
         390 ( 6.24% of base) : System.Threading.Tasks.Dataflow.dasm - TransformManyBlock`2:StoreOutputItemsNonReorderedWithIteration(ref):this (5 methods)
         385 (12.48% of base) : Microsoft.CodeAnalysis.dasm - <ComputeAnalyzerDiagnosticsAsync>d__51:MoveNext():this
Top method improvements by size (bytes):
       -2009 (-11.51% of base) : NuGet.Protocol.Core.v3.dasm - <TryCreate>d__1:MoveNext():this (20 methods)
       -1207 (-8.30% of base) : System.Net.Http.dasm - <SendAsyncCore>d__56:MoveNext():this
       -1035 (-11.69% of base) : System.Linq.Parallel.dasm - TakeOrSkipWhileQueryOperatorEnumerator`1:MoveNext(byref,byref):bool:this (5 methods)
        -993 (-21.91% of base) : System.Security.Cryptography.Primitives.dasm - <ReadAsyncCore>d__43:MoveNext():this
        -885 (-13.08% of base) : System.Private.Xml.dasm - <WriteEndAttributeAsync_SepcialAtt>d__134:MoveNext():this
Top method regressions by size (percentage):
          53 (17.21% of base) : System.Private.CoreLib.dasm - SecureString:MarshalToBSTRCore():long:this
         286 (16.96% of base) : System.Net.HttpListener.dasm - <OnKeepAlive>d__80:MoveNext():this
         133 (16.84% of base) : System.Private.Xml.dasm - XmlILOptimizerVisitor:FoldXsltConvert(ref,ref):ref:this
          16 (16.00% of base) : System.Security.Cryptography.Algorithms.dasm - RSA:ExportRSAPrivateKey():ref:this
         154 (15.56% of base) : System.Data.Common.dasm - DbDataAdapter:UpdateBatchExecute(ref,int,ref):this
Top method improvements by size (percentage):
         -68 (-27.09% of base) : System.Private.CoreLib.dasm - StreamReader:Dispose(bool):this
         -44 (-23.40% of base) : System.Private.CoreLib.dasm - StreamWriter:CloseStreamFromDispose(bool):this
         -72 (-23.08% of base) : System.Security.Cryptography.Primitives.dasm - CryptoStream:Dispose(bool):this
        -218 (-22.78% of base) : System.Reflection.Metadata.dasm - <GetContentToSign>d__29:MoveNext():bool:this
         -84 (-22.70% of base) : System.Private.DataContractSerialization.dasm - XmlBaseWriter:Close():this
5556 total methods with size differences (2136 improved, 3420 regressed), 187883 unchanged.
+2
AndyAyersMS on Jan 15, 2019
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