[Bug middle-end/113395] RTL expansion of bitfield accesses drops MEM_EXPR

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113395

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Without fully lowering this on GIMPLE we could substitute the representative
for the bitfield member in the MEM_EXPR and adjust adjust_address_1 to
instead of using attrs.size to constrain the extent of the object designated
by MEM_EXPR re-discover it.  (I wonder if MEM_SIZE needs to be exact
in a must-def way - ao_ref_from_mem certainly treats it that way instead
of getting the size from the mode for non-BLKmode accesses)

That said, lowering on GIMPLE is the way to go.  Even iff only right before
RTL expansion ...