Re: How can I link the kernel with libgcc ?

[Carlos Munoz <carlos@kenati.com>]

Denis Vlasenko wrote:

>On Friday 10 March 2006 05:47, Carlos Munoz wrote:
>  
>
>>Lee Revell wrote:
>>
>>    
>>
>>>On Thu, 2006-03-09 at 19:25 -0800, Carlos Munoz wrote:
>>> 
>>>
>>>      
>>>
>>>>I figured out how to get the driver to use floating point operations.
>>>>I included source code (from an open source math library) for the
>>>>log10 function in the driver. Then I added the following lines to the
>>>>file arch/sh/kernel/sh_ksyms.c: 
>>>>   
>>>>
>>>>        
>>>>
>>>Where is the source code to your driver?
>>>
>>>Lee
>>>
>>> 
>>>
>>>      
>>>
>>Hi Lee,
>>
>>Be warned. This driver is in the early stages of development. There is 
>>still a lot of work that needs to be done (interrupt, dma, etc, etc).
>>    
>>
>
>What? You are using log10 only twice!
>
>        if (!(siu_obj_status & ST_OPEN)) {
>		...
>                /* = log2(over) */
>                ydef[22] = (u_int32_t)(log10((double)(over & 0x0000003f)) /
>                                       log10(2));
>		...
>        }
>        else {
>		...
>                if (coef) {
>                        ydef[16] = 0x03045000 | (over << 26) | (tap - 4);
>                        ydef[17] = (tap * 2 + 1);
>                        /* = log2(over) */
>                        ydef[22] = (u_int32_t)
>                                (log10((double)(over & 0x0000003f)) / log10(2));
>                }
>
>Don't you think that log10((double)(over & 0x0000003f)) / log10(2)
>can have only 64 different values depending on the result of (over & 0x3f)?
>
>Obtain them from precomputed uint32_t log10table[64].
>--
>vda
>  
>
Hi Denis,

Yes, the driver code so far only uses log10 twice, but there will be 
more uses for it as I populate the rest of the tables. However, I think 
its use will be some what limited. I wasn't aware that the floating 
point registers are not saved. I'll investigate a way to create a table 
with pre-calculated log10 values.

Thanks,


Carlos