RE: porting gcc can't compile libgcc2.c

["Dave Korn" <dave dot korn at artimi dot com>]

----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....