Re: [avr-gcc-list] C<->asm docs/examples?

[Shaun Jackman]

On 2/26/07, Joerg Wunsch <address@hidden> wrote:
> David McNab <address@hidden> wrote:
>
> > The code in /doc/examples/asmdemo in the avr-libc tree is only
> > limited value, because all the assembler code seems to be just ISRs,
> > with no calling between C and assembler.
>
> Sorry, I simply couldn't fit anything into it like that that would
> serve as a useful example (i.e. something where diverting to asm was
> really justified).  The example is supposed to be a real-world one,
> nothing artificial.

Multiplying a 16-bit number by an 8-bit number to produce a 24-bit
result is a good example of something that GCC does not yet do and can
only be accomplished in assembler. GCC will multiply a 32-bit number
by a 32-bit number to produce a 32-bit result, but that takes many
more multiply instructions than necessary. This multiplication topic
was discussed on this mailing list previously.

Cheers,
Shaun