odd 7.4 build failure on new sparc machine

I am seeing a strange failure on the new box Sun donated, when trying to
build 7.4 for the buildfarm. This is what I get:

gmake[3]: Entering directory `/export/home/oicu/bf/root/REL7_4_STABLE/pgsql.5463/src/backend/port'
ccache gcc -O2 -fno-strict-aliasing -g -Wall -Wmissing-prototypes -Wmissing-declarations -I../../../src/include -I/export/home/oicu/mysw/include -c -o dynloader.o dynloader.c
ccache gcc -O2 -fno-strict-aliasing -g -Wall -Wmissing-prototypes -Wmissing-declarations -I../../../src/include -I/export/home/oicu/mysw/include -c -o pg_sema.o pg_sema.c
ccache gcc -O2 -fno-strict-aliasing -g -Wall -Wmissing-prototypes -Wmissing-declarations -I../../../src/include -I/export/home/oicu/mysw/include -c -o pg_shmem.o pg_shmem.c
pg_shmem.c: In function `PGSharedMemoryAttach':
pg_shmem.c:394: warning: passing arg 1 of `shmdt' from incompatible pointer type
ccache gcc -O2 -fno-strict-aliasing -g -Wall -Wmissing-prototypes -Wmissing-declarations -c tas.s
/usr/ccs/bin/ld -r -o SUBSYS.o dynloader.o pg_sema.o pg_shmem.o tas.o
ld: fatal: relocation error: R_SPARC_32: file tas.o: symbol <unknown>: offset 0xec1 is non-aligned
ld: fatal: relocation error: R_SPARC_32: file tas.o: symbol <unknown>: offset 0xec5 is non-aligned
ld: fatal: relocation error: R_SPARC_32: file tas.o: symbol <unknown>: offset 0x115d is non-aligned
ld: fatal: relocation error: R_SPARC_32: file tas.o: symbol <unknown>: offset 0x46 is non-aligned
ld: fatal: relocation error: R_SPARC_32: file tas.o: symbol <unknown>: offset 0xeb7 is non-aligned
ld: fatal: relocation error: R_SPARC_32: file tas.o: symbol <unknown>: offset 0xebd is non-aligned
gmake[3]: *** [SUBSYS.o] Error 1

What is odd is that the identical file seems to succeeed on the later
8.0 and 8.1 branches.

I also don't understand the logic of what's in the file:

ldstub [%o0],%o0
!!
!! if it was already set when we set it, somebody else already
!! owned the lock -- return 1.
!!
cmp %o0,0
bne .LL2
mov 1,%o0
!!
!! otherwise, it was clear and we now own the lock -- return 0.
!!
mov 0,%o0
.LL2:
!!
!! this is a leaf procedure - no need to restore windows and
!! diddle the CWP.
!!
retl

Why do we have "mov 1,%o0" immediately followed by "mov 0,%o0"? As far
as I can understand this code it doesn't seem to do what the comments
say it does.

I'm not sure I care that much about 7.4 on this new machine, but it did
seem to me like it might indicate a deeper problem.

cheers

andrew