[oe] powerpc-g++ 4.2.4 problem casting long long to double

[Khem Raj]

On Tue, May 25, 2010 at 8:15 AM, Vitus Jensen <vjensen at gmx.de> wrote:
> On Mon, 24 May 2010, Khem Raj wrote:
>>
>> On (24/05/10 18:36), Vitus Jensen wrote:
>
>
>>> Hmm, I'm using angstrom with glibc.  And I'm testing on the real
>>> device and saw that -mhard-float is implied by mcpu=603e.  Using the
>>> FPU would certainly explain differences between qemu and the real
>>> thing.  But __floatdidf is hard to understand, all macro.  Is it
>>> really using the FPU?
>>
>> Yeah that could be something to look at. In general if gcc is using
>> fp instruction to schedule then it might be using them.
>>
>> You should try to find which libgcc is it linking to when using g++
>> and gcc. It could be that its linking in two different libgcc versions
>>
>> secondly try to compile program statically and then run it.
>
>
> Using -static-libgcc and -shared-libgcc was interesting, it just affects the
> gcc support code.  static is default for C, shared for C++ and forcing
> static for C++ produced correct output.  When comparing implementations:
>
> * static uses inline fpu code, source
> work/i686-ppc603e-sdk-angstrom-linux/gcc-cross-sdk-4.4.4-r2.1/gcc-4.4.4/gcc/libgcc2.c
>
> * shared calls into libgcc_s.so.1 which uses software, excerpt:
> Dump of assembler code for function __floatdidf:
> => 0x0fe12878 <+0>:     stwu    r1,-32(r1)
>   0x0fe1287c <+4>:     mflr    r0
>   0x0fe12880 <+8>:     stmw    r26,8(r1)
>   0x0fe12884 <+12>:    mr      r27,r4
>   0x0fe12888 <+16>:    mr      r26,r3
>   0x0fe1288c <+20>:    srawi   r9,r26,31
>   0x0fe12890 <+24>:    srawi   r10,r26,0
>   0x0fe12894 <+28>:    stw     r0,36(r1)
>   0x0fe12898 <+32>:    mr      r3,r10
>   0x0fe1289c <+36>:    bl      0xfe31244 <__floatsidf at plt>
>   0x0fe128a0 <+40>:    lis     r5,16880
>
>
> [STABLE/2009] There are 2 libgcc_s.so.1 versions in TMPDIR/cross, the bigger
> ./ppc603e/powerpc-angstrom-linux/lib/nof/libgcc_s.so.1 matches the installed
> version,

thats the problem

if one copies the smaller version (uses fpu code) to target:/lib/
> the results of -shared-libgcc applications are OK.
>
> So, hard-fpu and soft-fpu are incompatible?  The incorrect version matches
> (strip; cmp -l) several paths in TMPDIR/work:

its more the calling convention.

>
> ./ppc603e-angstrom-linux/gcc-4.2.4-r3/image/lib/libgcc_s.so.1
> ./ppc603e-angstrom-linux/gcc-4.2.4-r3/gcc-4.2.4/build.powerpc-angstrom-linux.powerpc-angstrom-linux/gcc/nof/libgcc_s.so.1
> ./ppc603e-angstrom-linux/gcc-cross-4.2.4-r5/install/libgcc/lib/libgcc_s.so.1
> ./ppc603e-angstrom-linux/gcc-cross-4.2.4-r5/image/lib/libgcc_s.so.1
> ./ppc603e-angstrom-linux/gcc-cross-4.2.4-r5/staging-pkg/cross/powerpc-angstrom-linux/lib/nof/libgcc_s.so.1
> ./ppc603e-angstrom-linux/gcc-cross-4.2.4-r5/gcc-4.2.4/build.i686-linux.powerpc-angstrom-linux/gcc/nof/libgcc_s.so.1
>
> But there are 4 other smaller versions of that library, the good one coming
> from gcc-4.2.4. or gcc-cross-4.2.4.  Which recipes decides which version to
> copy into the image?  For now it seems enough to copy a fpu-version by hand
> into the image but this is hardly an universal solution.

actually it should have packaged the fpu version into /lib on target
but its a bug that it instead copied
nof version.

I think I touched this area and saw this problem in past. Can you try
gcc 4.4.4 and see if the problem still
happens there.

>
> Vitus
>
> --
> Vitus Jensen, Hannover, Germany, Universe (current)
> pgp public key available from keyservers
>
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