Hello Albert,
On 11-09-14 15:31, Albert ARIBAUD wrote:
Thanks, tested building rpi_b, it works now.
The, tested on versatileqemu out of curiosity and got the following
results:
1.
clang warns about Unused static functions in common/console.c, namely
console_printdevs and console_doenv (1). Why gcc does not flag this?
We have -Wall set which is supposed to imply -Wunused-functions.
It is a gcc feature, see [1]: "Warn whenever a static function is
declared but not defined or a _non-inline static function_ is unused.
This warning is enabled by -Wall."
Ok, I'll assume there is some logic in there, but then, clang does not
follow that logic -- so which one is the 'good' one? Or maybe that's
the same as the second issue, where...
well I don't know the details, but the compiler should not emit a
warning if the static inline came from a header file, perhaps that
is motivation behind it. Anyway I have a branch with 60 patches
or so fixing warnings, don't bother too much about them for the
time being.
2.
clang errors on arch/arm/lib/cache.c:28 for this:
asm("0: mrc p15, 0, r15, c7, c10, 3\n\t" "bne 0b\n" : : : "memory");
and that is a clang mistake, as for ARM926EJS r15 is a valid (albeit
quite special semantically) Rd for Test and Clean DCache, see page 2-24.
This is the integrated-as complaining (the README tells you to disable
it for the moment). The clang folks push UAL hard, up to a point we need
to think about minimum gcc version etc. To avoid that, I just left out
such changes and just use gas instead, at least for the time being.
Below are some changes to compile versatileqemu with llvm integrated-as
and gcc/gas. No idea if it actually boots though.
[..]
~ "mrc p15, 0, r15, c7, c14, 3\n"
+ "mrc p15, 0, apsr_nzcv, c7, c14, 3\n"
Is this is a hack to set the Rd field of the mrc instruction to a value
equal to what "r15" would have given, but fooling clang by using an
unrelated and, in this context, meaningless, symbol instead of "r15"?
Nope, it is UAL syntax, binutils agrees:
> arm-linux-gnueabi-objdump -S u-boot
flush_dcache:
mrc p15, 0, r15, c7, c10, 3
10320: ee17ff7a mrc 15, 0, APSR_nzcv, cr7, cr10, {3}
Clang is just pushing it a bit harder. I have a branch for that too,
but as said, I will let it bit-rot for a while, since that would require
about minimal gcc versions and other boring stuff.
Regards,
Jeroen
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