Hi Jeroen,
On Thu, 11 Sep 2014 13:17:20 +0200, Jeroen Hofstee jeroen@myspectrum.nl wrote:
Hello Albert,
On do, 2014-09-11 at 10:32 +0200, Albert ARIBAUD wrote:
On Wed, 10 Sep 2014 20:08:50 +0200, Jeroen Hofstee jeroen@myspectrum.nl wrote:
Changes since v2:
As Albert pointed out the clang instructions don't work with Debian based binary packages. While I was aware of that it is for a different reason then I thought, it is not that ARM is not enabled as a backend but older versions are a bit more picky on the target argument and don't tolerate a trailing dash to it as used for CROSS_COMPILE etc. The README is updated accordingly.
As a side note clang3.5-svn as shipped in Ubuntu is not the 3.5 release but an snapshot of some svn commit and hence explain why the recompiled 3.5 can behave different then the ubuntu clang-3.5. Since it misses some patches, the clang3.5-svn can build less boards then 3.4 or an actual 3.5 release.
While add it, include Masahiro suggestion to also use c++ instead of g++.
Drop dependencies from the cover-letter as they are merged.
only patch 7/8 and 8/8 are reposted. 1..6 are the same as v2.
Thanks, tested building rpi_b, it works now.
The, tested on versatileqemu out of curiosity and got the following results:
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...
There is also an unused variable warning in disk/part.c28 (block_drvr). I haven't looked at why clang warns about it and not gcc, but it could raise the same question as the functions above.
Also a gcc feature, see [2]. The constant is indeed not used.
... apparently, it's a case of trying to balance false positives and missed true issue, and each team has its own view of where to set the limit. :/
(anyway -- here clearly, clang is right in warning us and gcc is wrong in not doing it)
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.
Jeroen, do you feel like raising point 2 to the clang/LLVM folks?
It is removed on purpose as far as I understood. I don't think they regards it as a bug, see obfuscated patch below.
Other than that, the patch series seems to be good. I'll apply it soonish.
Thanks, Jeroen
~ "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"?
Amicalement,