gcc coldfire code generation problem

[Greg Ungerer <gerg at snapgear dot com>]

Hi All,

I have found a problem with the code generation of gcc under some
circumstances when targeted to produce Motorola ColdFire code.

I am using gcc-3.1.1, configured as target=m68k-elf. The host is a
Linux x86 PC - although I don't think this has any effect on the problem.
This problem occurs on older gcc versions too. I get the same result
with gcc-2.95.3.

gcc -v:

  Reading specs from /usr/local/lib/gcc-lib/m68k-elf/3.1.1/specs
  Configured with: ../configure --target=m68k-elf --with-gnu-ld 
--with-gnu-as : (reconfigured) ../configure --target=m68k-elf 
--with-gnu-ld --with-gnu-as --enable-languages=c
  Thread model: single
  gcc version 3.1.1

When I compile the ramdisk driver (rd.c) from the Linux kernel sources
I get the following error:

  rd.s: Assembler messages:
  rd.s:50: Error: operands mismatch -- statement `move.l 
(%a0,%d2.l*4),52(%a1)' ignored

This is not a valid ColdFire addressing mode.

The original C code line that caused this is:

  rd_bdev[unit]->bd_inode->i_size = rd_length[unit];

By reorganizing the code on this line I can get this to compile
with no errors. For example if I change it too:

  rd_bdev[unit]->bd_inode->i_size = ((volatile unsigned long *) 
rd_length)[unit];

The gcc command line I use to reproduce the problem is:

  m68k-elf-gcc --save-temps -fno-builtin -nostdinc -Wall 
-Wstrict-prototypes -Wno-trigraphs -O2 -fomit-frame-pointer 
-fno-strict-aliasing -fno-common -m5200 -Wa,-S -Wa,-m5200 -nostdinc -c 
-o rd.o rd.c

You can get a sample file that reproduces the problem at

  http://www.uclinux.org/ports/coldfire/rd.c

This file is actually the c-preprocessed output of the original ramdisk
block driver from the Linux kernel, with just the offending function
left in. I have tried to cut it down, but found it difficult to keep
reproducing the problem. This file is ~260k in size, but it is mostly
the expanded headers that cause the bloat.

Any ideas?

Regards
Greg


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