[Libre-soc-bugs] [Bug 238] POWER Compressed Formal Standard writeup

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=238

--- Comment #159 from Alexandre Oliva <oliva at gnu.org> ---
2.1.4 states branches always branch to a 4-byte aligned address

I thought it was also the case that branch targets also had to be in
uncompressed mode, but that unconditional branches have M and even N suggest
otherwise:

| N | offs2   | | 000.LK | offs!=0        | M | b, bl

as for conditional branches, do M and N apply whether or not the branch is
taken?

| N | BO3 BI3 | | 001.0  | LK BI | BO     | M | bclr, bclrl

what about when they're not there?  M=N=1 suggest immediate mode, that's always
followed by another uncompressed insn:

| 1 | offs2   | | 000.LK | BI    | BO1 oo | 1 | bc, bcl

but the LK variants would suggest function calls, targeting entry points in
uncompressed mode.  should they imply a switch to uncompressed mode at least
when the branch is taken?

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