[Bug libffi/40242] New: unsupported asm instructions in libffi/src/arm/sysv.S

["mkl at pengutronix dot de" <gcc-bugzilla@gcc.gnu.org>]

Hello,

during cross compilation of gcc, the libffi build for the target breaks with
this error message:

libtool: compile:  /home/frogger/pengutronix/toolchain/libffi/build/./gcc/xgcc
-B/home/frogger/pengutronix/toolchain/libffi/build/./gcc/
-B/usr/local/arm-1136jfs-linux-gnueabi/bin/
-B/usr/local/arm-1136jfs-linux-gnueabi/lib/ -isystem
/usr/local/arm-1136jfs-linux-gnueabi/include -isystem
/usr/local/arm-1136jfs-linux-gnueabi/sys-include -I.
-I../../../gcc-4.4.0/libffi/include -Iinclude -I../../../gcc-4.4.0/libffi/src
-g -O2 -c ../../../gcc-4.4.0/libffi/src/arm/sysv.S  -fPIC -DPIC -o
src/arm/.libs/sysv.o
../../../gcc-4.4.0/libffi/src/arm/sysv.S: Assembler messages:
../../../gcc-4.4.0/libffi/src/arm/sysv.S:202: Error: selected processor does
not support `stfeqs f0,[r2]'
../../../gcc-4.4.0/libffi/src/arm/sysv.S:207: Error: selected processor does
not support `stfeqd f0,[r2]'
../../../gcc-4.4.0/libffi/src/arm/sysv.S:282: Error: selected processor does
not support `ldfs f0,[sp]'
../../../gcc-4.4.0/libffi/src/arm/sysv.S:285: Error: selected processor does
not support `ldfd f0,[sp]'
../../../gcc-4.4.0/libffi/src/arm/sysv.S:288: Error: selected processor does
not support `ldfd f0,[sp]'

the offending code is:

#ifndef __SOFTFP__
        beq     LSYM(Lepilogue)

@ return FLOAT
        cmp     r3, #FFI_TYPE_FLOAT
        stfeqs  f0, [r2]
        beq     LSYM(Lepilogue)

@ return DOUBLE or LONGDOUBLE
        cmp     r3, #FFI_TYPE_DOUBLE
        stfeqd  f0, [r2]
#endif


gcc is configured this way:

../gcc-4.4.0/configure --enable-languages=c,c++,java
--target=arm-1136jfs-linux-gnueabi
--with-mpfr=/home/frogger/pengutronix/toolchain/OSELAS.Toolchain-trunk/platform-arm-v4t-linux-gnueabi-gcc-4.4.0-glibc-2.9-binutils-2.19.1-kernel-2.6.29-sanitized/sysroot-host
--with-gmp=/home/frogger/pengutronix/toolchain/OSELAS.Toolchain-trunk/platform-arm-v4t-linux-gnueabi-gcc-4.4.0-glibc-2.9-binutils-2.19.1-kernel-2.6.29-sanitized/sysroot-host
--with-float=softfp --with-fpu=vfp  --with-cpu=arm1136jf-s
--with-sysroot=/opt/OSELAS.Toolchain-1.99.3/arm-1136jfs-linux-gnueabi/gcc-4.3.2-glibc-2.8-binutils-2.19-kernel-2.6.27-sanitized/sysroot-arm-1136jfs-linux-gnueabi

I.e. as an arm-eabi target, --with-fpu=vfp and --with-float=softfp. Which means
floats are passed in integer registers, but in function the compiler generates
floating point instructions, the preprocessor doesn't define a "__SOFTFP__"
symbol.

If configuring the compiler with "--with-float=soft" it will pass floats in
integer registers and it will generate softfloat emulation code. In this case
the preprocessor defines "__SOFTFP__".

In both variants the function calling convention is the same, but in one case
we have the __SOFTFP__ symbol in the other not.

libffi changes it's behaviour depending on this symbol, which is IMHO not
correct.

I've tested some combinations, this is the summary of
(echo | arm-v4t-linux-gnueabi-cpp -dM -mfloat-abi=XXX -mfpu=YYY| egrep -i
'vfp|fp|soft|hard|float'):

-mfloat-abi=soft   -mfpu=vfp    __SOFTFP__ __VFP_FP__
-mfloat-abi=softfp -mfpu=vfp               __VFP_FP__
-mfloat-abi=hard   -mfpu=vfp               __VFP_FP__ (sorry, unimplemented)

-mfloat-abi=soft   -mfpu=fpa    __SOFTFP__
-mfloat-abi=softfp -mfpu=fpa
-mfloat-abi=hard   -mfpu=fpa

I'm not sure which of these combinations makes sense, or are actually used, the
3rd one seems not to be implemented, though. We at pengutronix use usually 1.
and 2. In some weird projects 4. and 6. but not with the current gcc.

This table shows that it's not possible to distinguish between the "hard" and
"softfp" case, a diff off the preprocessor's output shows no difference in the
symbols tough. On the upside the vfp-hard case seems not to be implemented.

So the question is which is the correct symbol for libffi?

cheers, Marc


-- 
           Summary: unsupported asm instructions in libffi/src/arm/sysv.S
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libffi
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mkl at pengutronix dot de
 GCC build triplet: x86_64-unknown-linux-gnu
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: arm-1136jfs-linux-gnueabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40242