[Coco] Instruction trapping on xroar?

[Joel Rees]

Got a bit of old software that ran well enough on hardware that is across
the ocean, but does not run well on Xroar. My first random guess involves a
few places where I used instructions like

    LDB ,++X  ; Don't need high byte, want to preserve A.

and

    STD ,-U  ; Allocation changed.

in other words, deliberately misaligned auto mode indexed instructions.

In the first case, the non-tricky approach would have been a

    LEAX 1,X
    LDB ,+X

and in the second,

    LEAU -1,U
    STD ,U

So, I am wondering if anyone knows whether Xroar does anything special with
those, or simply lets the index mode be interpreted independently of the
instruction, as the real 6809 did.

(I guess I should figure this out for myself, but I'm feeling talkative.)