JIT: typeof() is not propagated/folded

[EgorBo]

From #71685 (comment)

bool Test()
{
    Type t = typeof(int);
    Console.WriteLine();
    return t == typeof(uint);
}

Current codegen:

; Method Program:Test():bool:this
G_M57035_IG01:
       push     rsi
       sub      rsp, 32
G_M57035_IG02:
       mov      rcx, 0xD1FFAB1E      ; System.Int32
       call     CORINFO_HELP_TYPEHANDLE_TO_RUNTIMETYPE
       mov      rsi, rax
       call     [System.Console:WriteLine()]
       mov      rcx, 0xD1FFAB1E      ; System.UInt32
       call     CORINFO_HELP_TYPEHANDLE_TO_RUNTIMETYPE
       cmp      rax, rsi
       sete     al
       movzx    rax, al
G_M57035_IG03:
       add      rsp, 32
       pop      rsi
       ret      
; Total bytes of code: 59

Expected codegen:

; Method Program:Test():bool:this
G_M57035_IG01:
       sub      rsp, 40
G_M57035_IG02:
       call     [System.Console:WriteLine()]
       xor      eax, eax
G_M57035_IG03:
       add      rsp, 40
       ret      
; Total bytes of code: 17

NOTE: it's not about Forward Substitution Phase, a similar pattern in #71685 appears later after Optimize-Layout phase.

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Issue Details

---

From #71685 (comment)

bool Test()
{
    Type t = typeof(int);
    Console.WriteLine();
    return t == typeof(uint);
}

Current codegen:

; Method Program:Test():bool:this
G_M57035_IG01:
       push     rsi
       sub      rsp, 32
G_M57035_IG02:
       mov      rcx, 0xD1FFAB1E      ; System.Int32
       call     CORINFO_HELP_TYPEHANDLE_TO_RUNTIMETYPE
       mov      rsi, rax
       call     [System.Console:WriteLine()]
       mov      rcx, 0xD1FFAB1E      ; System.UInt32
       call     CORINFO_HELP_TYPEHANDLE_TO_RUNTIMETYPE
       cmp      rax, rsi
       sete     al
       movzx    rax, al
G_M57035_IG03:
       add      rsp, 32
       pop      rsi
       ret      
; Total bytes of code: 59

Expected codegen:

; Method Program:Test():bool:this
G_M57035_IG01:
       sub      rsp, 40
G_M57035_IG02:
       call     [System.Console:WriteLine()]
       xor      eax, eax
G_M57035_IG03:
       add      rsp, 40
       ret      
; Total bytes of code: 17

Author:	EgorBo
Assignees:	-
Labels:	area-CodeGen-coreclr, untriaged
Milestone:	-

[AndyAyersMS]

Seems like this could be handled by value numbering:

N004 ( 17, 16) [000005] -AC-G---R--                         *  ASG       ref   
N003 (  1,  1) [000004] D------N---                         +--*  LCL_VAR   ref    V01 tmp1         d:1
N002 ( 17, 16) [000002] --C-G------                         \--*  CALL help ref    HELPER.CORINFO_HELP_TYPEHANDLE_TO_RUNTIMETYPE
N001 (  3, 10) [000000] H---------- arg0 in rcx                \--*  CNS_INT(h) long   0x7ff7e848b680 class

N001 [000000]   CNS_INT(h) 0x7ff7e848b680 class => $c0 {Hnd const: 0x00007FF7E848B680}
N002 [000002]   CALL help => $100 {TypeHandleToRuntimeType($c0)}
N003 [000004]   LCL_VAR   V01 tmp1         d:1 => $VN.Void
Tree [000005] assigned VN to local var V01/1: $100 {TypeHandleToRuntimeType($c0)}
N004 [000005]   ASG       => $VN.Void

N005 ( 23, 19) [000011] --C-G------                         *  RETURN    int   
N004 ( 22, 18) [000010] --C-G------                         \--*  EQ        int   
N002 ( 17, 16) [000009] --C-G------                            +--*  CALL help ref    HELPER.CORINFO_HELP_TYPEHANDLE_TO_RUNTIMETYPE
N001 (  3, 10) [000007] H---------- arg0 in rcx                |  \--*  CNS_INT(h) long   0x7ff7e84ef888 class
N003 (  1,  1) [000006] -----------                            \--*  LCL_VAR   ref    V01 tmp1         u:1 (last use)

N001 [000007]   CNS_INT(h) 0x7ff7e84ef888 class => $c1 {Hnd const: 0x00007FF7E84EF888}
N002 [000009]   CALL help => $101 {TypeHandleToRuntimeType($c1)}
N003 [000006]   LCL_VAR   V01 tmp1         u:1 (last use) => $100 {TypeHandleToRuntimeType($c0)}
N004 [000010]   EQ        => $140 {EQ($101, $100)}
N005 [000011]   RETURN    => $VN.Void

If VN sees a helper with a known type handle it could create a pseudo-constant for the type object. This would allow it to optimize the EQ and hopefully we'd then be smart enough to dead code the helper calls.

We could do likewise for GetType...

[AndyAyersMS]

Or since we already have a VN func for this helper, we could just key off that.

[AndyAyersMS]

Here's a proof of concept: main...AndyAyersMS:VNFoldTypeCompare. Could be fleshed out to handle more of the things we handle in gtFoldTypeCompare.

Codegen for case above:

IN0003: 000000 sub      rsp, 40
IN0001: 000004 call     [System.Console:WriteLine()]
IN0002: 00000A xor      eax, eax
IN0004: 00000C add      rsp, 40
IN0005: 000010 ret

Maybe 70 hits in SPMI, some of them pretty big (may be a PMI artifact)

-1128 (-93.07% of base) : 25325.dasm - Microsoft.VisualBasic.CompilerServices.Conversions:ToGenericParameter(System.Object):System.Numerics.Vector`1[Single]

[MichalPetryka]

Does it also handle the case from #71685 (comment)?

[AndyAyersMS]

Looks like it should, yes.