[Vm-dev] ARM Cog progress
Tobias Pape
Das.Linux at gmx.de
Sun Jun 7 16:35:42 UTC 2015
On 07.06.2015, at 17:58, tim Rowledge <tim at rowledge.org> wrote:
>
>
> On 07-06-2015, at 12:32 AM, Holger Freyther <holger at freyther.de> wrote:
>>> On 07 Jun 2015, at 01:25, tim Rowledge <tim at rowledge.org> wrote:
>>>
>>>
>>> GCC is such fun.
>>
>> given the amount of warnings emitted during compilation, have you considered
>> that it might be the input given to gcc that is the issue here? ;)
>
> I dunno; I get a total of 59 warnings when compiling the ARM Cog VM, none in the core vm code. I’d love to see it be 0. I rather suspect the world would come to an end if that happened.
>
> On the other hand, I can’t see how it is acceptable for a compiler to produce code that blows up at one level of optimisation but not at another. Come to that I’m not sure why there are different levels; I can sort of see asking to optimise in different ways - the NorCroft compiler for ARM can be asked to optimise for runtime speed or executable size, for example.
>
not so uncommon:
gcc:
-O0 no opt
-O1 'Optimize' (= -O)
-O2 'Optimize even more'
-O3 'Optimize yet more'
-Os 'Optimize for size' (like -O2 minus size-increasing opts)
-Ofast 'Disregard strict standards compliance'
clang: as gcc, plus
-Oz 'Like -Os (and thus -O2), but reduces code size further'
(-O4 'currently like -O3')
-flto 'Generate output files in LLVM formats, suitable for link time optimization'
Also: a lot of -f… flags
Best regards
-Tobias
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