----Original Message----
>From: Eric Fisher
>Sent: 01 September 2005 09:43
> Hello,
>
> Here is a question about porting gcc. After I modified machine.md and
> other backend files, I can make cc1 and xgcc now. But libgcc2.o still
> failed. I'd like to know does we must make libgcc2.o since the target
> machine don't have float registers and 64bit registers.
>
> Thanks a lot.
>
> Eric
If it doesn't have float registers, get libgcc2 to use fp emulation:
-----------------------------<snip>-----------------------------
File: gccint.info, Node: Target Fragment, Next: Host Fragment, Up:
Fragments
Target Makefile Fragments
=========================
Target makefile fragments can set these Makefile variables.
-----------------------------<snip>-----------------------------
`Floating Point Emulation'
To have GCC include software floating point libraries in `libgcc.a'
define `FPBIT' and `DPBIT' along with a few rules as follows:
# We want fine grained libraries, so use the new code
# to build the floating point emulation libraries.
FPBIT = fp-bit.c
DPBIT = dp-bit.c
fp-bit.c: $(srcdir)/config/fp-bit.c
echo '#define FLOAT' > fp-bit.c
cat $(srcdir)/config/fp-bit.c >> fp-bit.c
dp-bit.c: $(srcdir)/config/fp-bit.c
cat $(srcdir)/config/fp-bit.c > dp-bit.c
You may need to provide additional #defines at the beginning of
`fp-bit.c' and `dp-bit.c' to control target endianness and other
options.
-----------------------------<snip>-----------------------------
As for the 64-bit registers, just don't tell it you have any:
-----------------------------<snip>-----------------------------
File: gccint.info, Node: Values in Registers, Next: Leaf Functions, Prev:
Al\
location Order, Up: Registers
How Values Fit in Registers
---------------------------
This section discusses the macros that describe which kinds of values
(specifically, which machine modes) each register can hold, and how many
consecutive registers are needed for a given mode.
`HARD_REGNO_NREGS (REGNO, MODE)'
A C expression for the number of consecutive hard registers,
starting at register number REGNO, required to hold a value of mode
MODE.
On a machine where all registers are exactly one word, a suitable
definition of this macro is
#define HARD_REGNO_NREGS(REGNO, MODE) \
((GET_MODE_SIZE (MODE) + UNITS_PER_WORD - 1) \
/ UNITS_PER_WORD)
`HARD_REGNO_MODE_OK (REGNO, MODE)'
A C expression that is nonzero if it is permissible to store a
value of mode MODE in hard register number REGNO (or in several
registers starting with that one). For a machine where all
registers are equivalent, a suitable definition is
#define HARD_REGNO_MODE_OK(REGNO, MODE) 1
-----------------------------<snip>-----------------------------
With those macros you can tell it to store floats and 64-bit ints in two
(or more) consecutive hard registers.
cheers,
DaveK
--
Can't think of a witty .sigline today....
