[llvm-bugs] [Bug 37289] New: Randomly emitted all-zeros or all-ones XMM constants generate invalid code (x86-64, MCJIT, small code model)

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37289

            Bug ID: 37289
           Summary: Randomly emitted all-zeros or all-ones XMM constants
                    generate invalid code (x86-64, MCJIT, small code
                    model)
           Product: libraries
           Version: 6.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: release blocker
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: nekotekina at gmail.com
                CC: llvm-bugs at lists.llvm.org

Example of the faulty instruction (crashes with access violation):

0:  c5 c9 74 2c 25 b0 0a 00 00    vpcmpeqb xmm5,xmm6,XMMWORD PTR ds:0xab0

I'm not completely sure what's going on, but I think it's supposed to emit
RIP-relative address location. But instead, it uses ds segment register, which
is assumed to be zero.

I noticed that the constant in question is all zeros or all ones. They are
usually generated by PXOR or PCMPEQD-alike idiom.

Attachment contains ELF file produced by MCJIT, with broken function.

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