P.S. Follow up to my last post

[jacob navia]

OF COURSE « march » is mentioned. But -march=rv64gc_zbb is NOT.

Where please give me a link) that option is mentioned?

It is NOT mentioned in

https://gcc.gnu.org/onlinedocs/gcc/RISC-V-Options.html

The idea that the compiler could figure out the processor it is running on it is completely far fetched isn’t it?

Jacob



> Le 25 août 2023 à 15:07, jacob navia <jacob@jacob.remcomp.fr> a écrit :
> 
> OK, there is no bug, I didn’t expect anything else.
> 
> SO:
> 
> To use all the instruction of the processor he/she is running on, the user should:
> 
> 1)Be aware that gcc doesn’t see crucial instructions of the processor by verifying its assembler output.
> 
> 2) Be aware that there is an (undocumented) option -march… that will enable the assembler and the compiler to generate all the instructions of the current processor.
> 
> Well, there is NO BUG!
> 
> This is by design then.
> 
> Thank you very much.
> 
> Jacob
> 
> 
> 
>> Le 25 août 2023 à 14:00, Jan Beulich <jbeulich@suse.com> a écrit :
>> 
>> On 25.08.2023 13:52, jacob navia wrote:
>>> The lack of the Ebb instructions is CRUCIAL for performance when accessing tables / arrays!
>>> This instructions allow to combine an addition and a shift by 1, 2 or 3, to access tables of shorts, ints or doubles.
>>> This speeds up the access to tables enormously and would allow gcc to generate much better code.
>> 
>> Since you're writing to binutils@, you may want to also mention what gas
>> bug you think you see. So far (also in the other mail) you've talked of
>> only gcc. If you meant to say that like in gcc you need to enable use of
>> the instructions in gas, then yes, that's the way the RISC-V assembler
>> works (like e.g. also the PPC one, but unlike e.g. the x86 one).
>> 
>> Jan
>