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

[Vitus Jensen]

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, 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:

./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.

Vitus

-- 
Vitus Jensen, Hannover, Germany, Universe (current)
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