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JIT: Incorrectly optimized double-negation in face of inlining #61908

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#61912
Closed
JIT: Incorrectly optimized double-negation in face of inlining#61908
#61912
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jakobbotsch
Labels
area-CodeGen-coreclrCLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI
Milestone
7.0.0

Description

@jakobbotsch
jakobbotsch
opened on Nov 22, 2021

Description

The following program has different behavior in debug and release mode.

Reproduction Steps

// Generated by Fuzzlyn v1.5 on 2021-11-21 16:25:19
// Run on Arm64 Linux
// Seed: 3319480715990956994
// Reduced from 26.2 KiB to 0.4 KiB in 00:00:42
// Debug: No output
// Release: Prints 0
public class Program
{
    public static bool s_3;
    public static void Main()
    {
        var vr6 = M3(s_3);
        if (M3(vr6))
        {
            System.Console.WriteLine(0);
        }
    }

    public static bool M3(bool arg0)
    {
        arg0 = !arg0;
        return arg0;
    }
}

Expected behavior

Same behavior.

Actual behavior

Different behavior.

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

Does not repro with .NET 6.

Activity

  1. ghost added
    area-CodeGen-coreclrCLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI
    on Nov 22, 2021
  2. ghost added
    untriagedNew issue has not been triaged by the area owner
    on Nov 22, 2021

  4. jakobbotsch commented on Nov 22, 2021

    @jakobbotsch
    jakobbotsch
    on Nov 22, 2021
    MemberAuthor

    cc @dotnet/jit-contrib

  5. jakobbotsch
    changed the title [-]ARM64 JIT: Incorrectly optimized double-negation in face of inlining[/-] [+]JIT: Incorrectly optimized double-negation in face of inlining[/+] on Nov 22, 2021

  6. jakobbotsch commented on Nov 22, 2021

    @jakobbotsch
    jakobbotsch
    on Nov 22, 2021
    MemberAuthor

    Looks like this is not ARM64 related after all, I can repro in x64 as well, but not in .NET 6. So this seems to be a recent regression.

  7. jakobbotsch commented on Nov 22, 2021

    @jakobbotsch
    jakobbotsch
    on Nov 22, 2021
    MemberAuthor

    This seems to be related to the new forward subst in redundant branch opts, we go from

    ***** BB01
STMT00006 ( 0x000[E-] ... ??? )
N003 (  4,  5) [000021] -A--G---R---              ▌  ASG       bool  
N002 (  1,  1) [000020] D------N----              ├──▌  LCL_VAR   int    V01 tmp1         d:1
N001 (  4,  5) [000000] ----G-------              └──▌  CLS_VAR   bool   Hnd=0xa5be4bc0 Fseq[s_3]

***** BB01
STMT00005 ( INL01 @ 0x000[E-] ... ??? ) <- INLRT @ 0x000[E-]
N005 (  6,  3) [000017] -A------R---              ▌  ASG       int   
N004 (  1,  1) [000016] D------N----              ├──▌  LCL_VAR   int    V01 tmp1         d:2
N003 (  6,  3) [000014] ------------              └──▌  EQ        int   
N001 (  1,  1) [000012] ------------                 ├──▌  LCL_VAR   int    V01 tmp1         u:1 (last use)
N002 (  1,  1) [000013] ------------                 └──▌  CNS_INT   int    0

***** BB01
STMT00007 ( INL02 @ 0x000[E-] ... ??? ) <- INLRT @ 0x000[E-]
N005 (  6,  3) [000029] -A------R---              ▌  ASG       int   
N004 (  1,  1) [000028] D------N----              ├──▌  LCL_VAR   int    V02 tmp2         d:1
N003 (  6,  3) [000026] ------------              └──▌  EQ        int   
N001 (  1,  1) [000024] ------------                 ├──▌  LCL_VAR   int    V01 tmp1         u:2 (last use)
N002 (  1,  1) [000025] ------------                 └──▌  CNS_INT   int    0

***** BB01
STMT00002 ( 0x000[E-] ... ??? )
N004 (  5,  5) [000008] ------------              ▌  JTRUE     void  
N003 (  3,  3) [000007] J------N----              └──▌  EQ        int   
N001 (  1,  1) [000030] ------------                 ├──▌  LCL_VAR   int    V02 tmp2         u:1 (last use)
N002 (  1,  1) [000006] ------------                 └──▌  CNS_INT   int    0

    to

    ***** BB01
STMT00006 ( 0x000[E-] ... ??? )
N003 (  4,  5) [000021] -A--G---R---              ▌  ASG       bool   <l:$182, c:$183>
N002 (  1,  1) [000020] D------N----              ├──▌  LCL_VAR   int    V01 tmp1         d:1 <l:$182, c:$183>
N001 (  4,  5) [000000] ----G-------              └──▌  CLS_VAR   bool   Hnd=0xa5be4bc0 Fseq[s_3] <l:$180, c:$181>

***** BB01
STMT00005 ( INL01 @ 0x000[E-] ... ??? ) <- INLRT @ 0x000[E-]
N005 (  6,  3) [000017] -A------R---              ▌  ASG       int    <l:$185, c:$184>
N004 (  1,  1) [000016] D------N----              ├──▌  LCL_VAR   int    V01 tmp1         d:2 <l:$185, c:$184>
N003 (  6,  3) [000014] ------------              └──▌  EQ        int    <l:$185, c:$184>
N001 (  1,  1) [000012] ------------                 ├──▌  LCL_VAR   int    V01 tmp1         u:1 (last use) <l:$182, c:$183>
N002 (  1,  1) [000013] ------------                 └──▌  CNS_INT   int    0 $43

***** BB01
STMT00002 ( 0x000[E-] ... ??? )
N004 (  5,  5) [000008] ------------              ▌  JTRUE     void  
N003 (  6,  3) [000026] J------N----              └──▌  EQ        int    <l:$187, c:$186>
N001 (  1,  1) [000024] ------------                 ├──▌  LCL_VAR   int    V01 tmp1         u:2 (last use) <l:$185, c:$184>
N002 (  1,  1) [000025] ------------                 └──▌  CNS_INT   int    0 $43

    the dump from redundant branch opts being

    optRedundantRelop in BB01; jump tree is
N004 (  5,  5) [000008] ------------              ▌  JTRUE     void  
N003 (  3,  3) [000007] J------N----              └──▌  EQ        int    <l:$185, c:$184>
N001 (  1,  1) [000030] ------------                 ├──▌  LCL_VAR   int    V02 tmp2         u:1 (last use) <l:$187, c:$186>
N002 (  1,  1) [000006] ------------                 └──▌  CNS_INT   int    0 $43
 ... checking previous tree
N005 (  6,  3) [000029] -A------R---              ▌  ASG       int    <l:$187, c:$186>
N004 (  1,  1) [000028] D------N----              ├──▌  LCL_VAR   int    V02 tmp2         d:1 <l:$187, c:$186>
N003 (  6,  3) [000026] ------------              └──▌  EQ        int    <l:$187, c:$186>
N001 (  1,  1) [000024] ------------                 ├──▌  LCL_VAR   int    V01 tmp1         u:2 (last use) <l:$185, c:$184>
N002 (  1,  1) [000025] ------------                 └──▌  CNS_INT   int    0 $43
  -- prev tree has relop with reversed liberal VN
 -- prev tree is viable candidate for relop fwd sub!
 ... checking previous tree
N005 (  6,  3) [000017] -A------R---              ▌  ASG       int    <l:$185, c:$184>
N004 (  1,  1) [000016] D------N----              ├──▌  LCL_VAR   int    V01 tmp1         d:2 <l:$185, c:$184>
N003 (  6,  3) [000014] ------------              └──▌  EQ        int    <l:$185, c:$184>
N001 (  1,  1) [000012] ------------                 ├──▌  LCL_VAR   int    V01 tmp1         u:1 (last use) <l:$182, c:$183>
N002 (  1,  1) [000013] ------------                 └──▌  CNS_INT   int    0 $43
  -- prev tree has relop with same liberal VN
 -- prev tree ref to V01 interferes

removing useless STMT00007 ( INL02 @ 0x000[E-] ... ??? ) <- INLRT @ 0x000[E-]
N005 (  6,  3) [000029] -A------R---              ▌  ASG       int    <l:$187, c:$186>
N004 (  1,  1) [000028] D------N----              ├──▌  LCL_VAR   int    V02 tmp2         d:1 <l:$187, c:$186>
N003 (  6,  3) [000026] J------N----              └──▌  EQ        int    <l:$187, c:$186>
N001 (  1,  1) [000024] ------------                 ├──▌  LCL_VAR   int    V01 tmp1         u:2 (last use) <l:$185, c:$184>
N002 (  1,  1) [000025] ------------                 └──▌  CNS_INT   int    0 $43
 from BB01
 -- done! new jump tree is
N004 (  5,  5) [000008] ------------              ▌  JTRUE     void  
N003 (  6,  3) [000026] J------N----              └──▌  EQ        int    <l:$187, c:$186>
N001 (  1,  1) [000024] ------------                 ├──▌  LCL_VAR   int    V01 tmp1         u:2 (last use) <l:$185, c:$184>
N002 (  1,  1) [000025] ------------                 └──▌  CNS_INT   int    0 $43

    cc @AndyAyersMS

  8. ghost added
    in-prThere is an active PR which will close this issue when it is merged
    on Nov 22, 2021
  9. JulieLeeMSFT
    assigned
    jakobbotsch
    on Nov 22, 2021
  10. JulieLeeMSFT
    added this to the 7.0.0 milestone on Nov 22, 2021
  11. JulieLeeMSFT
    removed
    untriagedNew issue has not been triaged by the area owner
    on Nov 22, 2021
  12. jakobbotsch
    closed this as completedin #61912on Nov 22, 2021
  13. jakobbotsch
    added a commit that references this issue on Nov 22, 2021

    Use correct VN relation kind for redundant relop opts (#61912)

    106afdc
  14. ghost removed
    in-prThere is an active PR which will close this issue when it is merged
    on Nov 22, 2021
  15. ghost locked as resolved and limited conversation to collaborators on Dec 22, 2021
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