On 22 August 2012 16:20, Johannes Bauer <dfnsonfsduifb@xxxxxx> wrote:
> Hi list,
>
> I have a problem with gcc-4.7.1 (and g++) for ARM, specifically the
> Cortex M4 (Thumb2 variant). I've compiled it with newlib and multilib
> support and am now trying to get hard float running, with no success so
> far. Showing that multilib is enabled:
>
> $ arm-none-eabi-g++ -print-multi-lib
> .;
> thumb;@mthumb
> fpu;@mfloat-abi=hard
>
> I compile with
>
> arm-none-eabi-gcc -Wall -O2 -g -mcpu=cortex-m4 -mfloat-abi=hard -mthumb
> -std=c99 -c -o foo.o foo.c
>
> Compiling the modules works fine and hard float instructions are generated:
>
> 0000013c <floattest(float)>:
> 13c: ed9f 7b08 vldr d7, [pc, #32] ; 160
> <floattest(float)+0x24>
> 140: eeb7 0ac0 vcvt.f64.f32 d0, s0
> 144: ee20 0b07 vmul.f64 d0, d0, d7
> 148: ed9f 7b07 vldr d7, [pc, #28] ; 168
> <floattest(float)+0x2c>
> 14c: eeb7 0bc0 vcvt.f32.f64 s0, d0
> 150: eeb7 0ac0 vcvt.f64.f32 d0, s0
> 154: ee30 0b07 vadd.f64 d0, d0, d7
> 158: eeb7 0bc0 vcvt.f32.f64 s0, d0
> 15c: 4770 bx lr
> 15e: bf00 nop
> 160: e631f8a1 .word 0xe631f8a1
> 164: 40c81cd6 .word 0x40c81cd6
> 168: 692b3cc5 .word 0x692b3cc5
> 16c: 3f5437c5 .word 0x3f5437c5
>
> When it comes to linking, however, this is a different story. For each
> module "m" and the final ELF target "t" I get a message:
>
> [...]/bin/arm/lib/gcc/arm-none-eabi/4.7.1/../../../../arm-none-eabi/bin/ld:
> error: m.o uses VFP register arguments, t does not
> [...]/bin/arm/lib/gcc/arm-none-eabi/4.7.1/../../../../arm-none-eabi/bin/ld:
> failed to merge target specific data of file m.o
>
> I'm guessing it's trying to link newlib stuff in from the libcrt* which
> might not be compiled with hard float, can that be correct? Then why
> would gcc's multilib show the correct strings? Could somebody please
> explain to me what I'm doing wrong?
A couple of questions which may help diagnose the issue:
1) How have you configured GCC? (What does gcc -v show?)
2) What does the following command say is the directory in use?
arm-none-eabi-gcc -Wall -O2 -g -mcpu=cortex-m4 -mfloat-abi=hard -mthumb \
-std=c99 -c -o foo.o foo.c -print-multi-directory
Thanks,
Matt
--
Matthew Gretton-Dann
Linaro Toolchain Working Group
matthew.gretton-dann@xxxxxxxxxx
