Dear Albert, In message <20140210182646.2de92810@lilith> you wrote: ... > - first, if "the first part of the equation" means "the compiler > setting" as opposed to the hardware setting, then the question > fails to realize that we don't (and should not) consider the > compiler and hardware settings separately; they work in > *combination*.
Right, and we have full control over both sides of this combination: we set the compiler options in the Makefiles, and adjust the hardware selections in the code. > - second, assuming the question is "how is it not a problem on our > end that some code traps due to the combined hardware and compiler > settings", the answer is: because the setting was not designed to > catch *ARMv7* issues; it was designed to catch *U-Boot* issues. In > other words, such traps show that there is code which won't work > elsewhere than on ARMv7-like hardware which does not care about > alignment. Full agreement. It is wrong to write code with only the feature set off a specific architecture in mind. > That is why I consider that the fault is in the trapped software, not > in the trap. The solution is to make the software use software, not > native, unaligned accesses. The exact solution depends on whether the > code has only a few such unaligned accesses (in which case we should > use explicit unaligned access macros) or many (in which case, for the > file considered, we can enable -mno-unaligned-access). You'll find > instances of both in the U-Boot code. I agree mostly here - except that I tend to be even more radical: if we need to enable -mno-unaligned-access, then the code is inherently non-portable and should rather be redesigned / rewritten. > - I am ok with -mno-unaligned-access applied to files which *require* > unaligned access and where individual access macros would be > impractical. I can live with this if we raise the bar sufficiently high so that only very few exceptions will be made. I would not like to see this enabled on tons of files. > - I am NOT OK with blanket -mno-unaligned-access applied on a file > where individual macros are feasible, and Full agreement. But even in this case we should first consider if the code can / should not rather be rewitten to avoid the problem alltogether. > - I am certainly NOT OK with a blanket -mno-unaligned-access on all > code and the removal of the whole ARM misalignment detection setup. I agree with Albert here. Thanks for the detailed explanation, bte. Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de The following statement is not true. The previous statement is true. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
