Stack offset on m88k-psos

[Brian Ford <ford at vss dot fsi dot com>]

We are having some difficulties using egcs 1.1.2 as an upgrade to our old
gcc 2.6.3 compiler.  We use egcs configured as m88k-motorola-sysv4 to
target both that configuration and psos running on an auxilary processor
in that configuration.  Our problem stems from the assumption that the
stack is always 16 byte aligned in this configuration as psos does not
assure this allignment.
Here are snippets of the assembly generated by the two compilers.

gcc version 2.6.3:

text
	align	8
_max_ige_period:
	subu	r31,r31,48
	addu	r2,r31,40	# correct computation of stack offset
	st	r1,r31,36
	bsr.n	_vi_ige_max_periods

egcs 1.1.2:
text
	align	8
_max_ige_period:
	subu	r31,r31,48
	st	r29,r31,32
	addu	r29,r31,32
	st	r1,r31,36
	or	r2,r29,8	# only works on 16 byte aligned stack
	bsr.n	_vi_ige_max_periods

Does anyone know a good way around this problem and is the alignment
assumption a good and valid one.  What do we save by using the or instead
of the add?

I would appreciate any suggestions that you might have.

--
Brian Ford
Software Engineer
Vital Visual Simulation Systems
FlightSafety International
Phone: 314-551-8460
Fax:   314-551-8444