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 <__floats...@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)
pgp public key available from keyservers
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