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JIT: Illegal instruction at JitTest_chain_boxunbox_il.Test.Main() under DOTNET_JitStressRegs=0x2000 #112163

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saucecontrol opened this issue Feb 4, 2025 · 8 comments · May be fixed by #112217
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JIT: Illegal instruction at JitTest_chain_boxunbox_il.Test.Main() under DOTNET_JitStressRegs=0x2000 #112163

saucecontrol opened this issue Feb 4, 2025 · 8 comments · May be fixed by #112217
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area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI in-pr There is an active PR which will close this issue when it is merged
Milestone
10.0.0

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@saucecontrol
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Description

Seen in two separate PRs on the runtime-coreclr jitstress-isas-avx512 pipeline.

https://dev.azure.com/dnceng-public/public/_build/results?buildId=939955 for #111778

and

https://dev.azure.com/dnceng-public/public/_build/results?buildId=939970 for #111853

Reproduction Steps

View logs for the above CI runs

22:36:26.039 Running test: JIT/Methodical/Boxing/boxunbox/chain_d/chain_d.dll
Fatal error. System.ExecutionEngineException: Illegal instruction: Attempted to execute an instruction code not defined by the processor.
   at JitTest_chain_boxunbox_il.Test.Main()
   at Program.<<Main>$>g__TestExecutor80|0_81(System.IO.StreamWriter, System.IO.StreamWriter, <>c__DisplayClass0_0 ByRef)
   at Program.<Main>$(System.String[])

22:45:42.226 Running test: JIT/Methodical/Boxing/boxunbox/chain_r/chain_r.dll
Fatal error. System.ExecutionEngineException: Illegal instruction: Attempted to execute an instruction code not defined by the processor.
   at JitTest_chain_boxunbox_il.Test.Main()
   at Program.<<Main>$>g__TestExecutor80|0_81(System.IO.StreamWriter, System.IO.StreamWriter, <>c__DisplayClass0_0 ByRef)
   at Program.<Main>$(System.String[])

Expected behavior

No failures

Actual behavior

Illegal Instruction crash

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response
@dotnet-issue-labeler dotnet-issue-labeler bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Feb 4, 2025
@dotnet-policy-service dotnet-policy-service bot added the untriaged New issue has not been triaged by the area owner label Feb 4, 2025
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
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@saucecontrol
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saucecontrol commented Feb 4, 2025 •
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Same instruction in both cases

00007ffc`9fb216b4 62c17e00104702  vmovss  xmm16,dword ptr [r15+8] ds:0000000a`be37d6d2=7ffc9e8f

00007ff8`7bef16b4 62c17e00104702  vmovss  xmm16,dword ptr [r15+8] ds:0000001c`6ed7d782=7ff87acc

Looks like the 00 4th byte is wrong.

@AndyAyersMS
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cc @dotnet/jit-contrib

Likely from some of the recent xarch emitter changes?

@BruceForstall
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Maybe #108796? @Ruihan-Yin

@Ruihan-Yin
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I can reproduce the bug locally, looking into it.

@Ruihan-Yin
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The wrong encoding comes from code pieces like this:

Image

JIT did the codegen in the form of vmovss xmm, xmm, m32, but this instructions does not actually have this form.

Image

It looks more like a code gen problem, instead of encoding bug, where INS_movss should not hit emitIns_R_R_A path.

From the stack, I believe the bug is from genCodeForCast, that when ins is vmovss, the code gen function should be sth other than emitIns_R_R_A.

Image

@saucecontrol
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saucecontrol commented Feb 5, 2025 •
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Ah, this may have been exposed by #111595 then.

That one showed some removed float->double->float casts in the diffs, but those may have actually ended up as float->float in some cases, and this looks suspect:

runtime/src/coreclr/jit/instr.cpp

Line 2481 in 2faef6d

return ins_Move_Extend(TYP_FLOAT, false);

@Ruihan-Yin
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I can try to fix and file a PR for it if there is no ongoing work for this bug. It will be nice to have it fixed since some of our PRs are also hitting this problem.

Ruihan-Yin added a commit to Ruihan-Yin/runtime that referenced this issue Feb 5, 2025
@Ruihan-Yin
fix dotnet#112163
d58b028
@Ruihan-Yin Ruihan-Yin mentioned this issue Feb 5, 2025
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@saucecontrol saucecontrol linked a pull request Feb 6, 2025 that will close this issue
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@dotnet-policy-service dotnet-policy-service bot added the in-pr There is an active PR which will close this issue when it is merged label Feb 6, 2025
@amanasifkhalid amanasifkhalid removed the untriaged New issue has not been triaged by the area owner label Feb 6, 2025
@amanasifkhalid amanasifkhalid added this to the 10.0.0 milestone Feb 6, 2025
@kunalspathak kunalspathak mentioned this issue Feb 6, 2025
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@anthonycanino anthonycanino mentioned this issue Feb 10, 2025
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JIT: Fix illegal instruction encoding for float->float casts saucecontrol/runtime
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@saucecontrol @AndyAyersMS @BruceForstall @amanasifkhalid @Ruihan-Yin