[Bug 295431] CURRENT compiler miscompiles lang/mit-scheme

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=295431

--- Comment #8 from Dimitry Andric <dim@FreeBSD.org> ---
(In reply to John F. Carr from comment #6)
Yes, I ended up at the same commit (llvmorg-20-init-8443-gced15cd418d9). With
the latest version as of today (llvmorg-23-init-16335-ge57ade6b0922), the "mov
%rcx, 0" is still emitted:

        movabsq $7493989779944505344, %rcx      # imm = 0x6800000000000000
        orq     %rax, %rcx
        movq    $0, stack_pointer(%rip)
        movq    %rcx, 0
        movq    stack_pointer(%rip), %rax

(In reply to John F. Carr from comment #7)
> Commenting out the addition of no-unsigned-wrap fixes the problem.

Do you mean that the "mov %rcx, 0" goes away, or also that the whole port then
builds?

There has been another related change in upstream, where -fwrapv no longer
implied wrapping for pointers, so that you have to explicitly add
-fwrapv-pointer to get that behavior now.

On the other hand, building the whole port with -fwrapv -fwrapv-pointer didn't
prevent the crash... :)

In any case, it might be appropriate to submit an upstream bug report for this.
Submitting the .ll file might be enough, or otherwise it might be nice to
isolate the piece of .c code that shows the problem.

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