Am 05.12.2007 um 22:32 schrieb Ian Lance Taylor:
Boris Boesler <[EMAIL PROTECTED]> writes:
I assume that GCC internals assume that memory can be byte (8 bits)
addressed - for historical reasons.
No. gcc internals assume that memory can be addressed in units of
size BITS_PER_UNIT. The default for BITS_PER_UNIT is 8. I have
written backends for machines for which that is not true.
It is unusual, and there is only one official target with
BITS_PER_UNIT != 8 (c4x), so there is often some minor breakage.
Ok, so what have I to do to write a back-end where all addresses
are given in bits? Memory is addressed in bits, not bytes. So I set:
#define BITS_PER_UNIT 1
#define UNITS_PER_WORD 32
(As far as I can see, offsets are divided by BITS_PER_UNIT, so this
seems to be a precondition for bit addressing.)
All sizes and and boundary are set to 32. SImode is only four bits
wide, so I added the integer modes OI and XI:
INT_MODE(OI, 32)
INT_MODE(XI, 64)
In builtin_define_type_max I added the case "1", which will return
without doing anything.
Without these changes the compiler stops with internal error
mesages. With these changes gcc/cc1 generates a bus error.
So, what can I do to get this running for my architecture?
Thanks in advance,
Boris
