A >32B tagged-union field (slice payload) read through a direct *struct
pointer byte-diverged: wwstage's cgloadtaggedfield always loaded R8@+24
before CX@+16, but cstage's direct-*struct-ptr arm (cgen.c ~11926) loads in
offset order CX@+16 then R8@+24. Both ran correct -- a pre-existing rule-10
asm divergence, for a local *struct ptr as well as a global one.
Thread a cxlast flag through cgloadtaggedfield: the direct-ptr site
(cgptrfieldload, the shared local+global chokepoint) passes cxlast=false to
match cstage's offset order; the other 5 callers keep cxlast=true (byte
unchanged). A global flip was rejected -- it would clobber the CX-base
callers (CX@+16 first destroys the base before the R8@+24 read), and the
chained-BX caller must stay R8-first to mirror cstage's chained twin
(cgen.c ~12021); the order is a genuine per-arm property of cstage, not
derivable from the base register.
Test: +2 rows (tagged_slice_field via global *struct ptr, _local via local
*struct ptr), runtime + byte-id; both proven to fail byte-id with only the
compiler files reverted.
Hojun-Cho
d6ea497da1