SWI argument with (code pointer | flags)

[Dave Lambley]

Hello,
 
I have been working on riscose[1] and have come across an odd usage of OS_Control in some very old code. R0 is being passed with bit 31 set. I have two questions.
 
1) Is OSLib able to represent an argument being a code pointer being OR'd with flags? I remember there being some calls which did in 26 bit times, but cannot find today.
 
2) Might anyone remember what the flag would indicate? It's not documented in the online PRMs. The RISC OS 2 source has a BIC with 0xfc000003 before jumping to the error handler, which suggests to me that at some point those bits were used for something.
 
http://www.riscos.com/support/developers/prm/progenv.html#88693
 
Cheers,
Dave
 
[1] https://repo.or.cz/riscose.git
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