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I do so want to go for six shooters at sunset, but mostly you are right,
however this presupposes the C writer is able to write efficient code,
because without that the compiler, no matter how efficient, is of
limited help. The number of times I see people do something that needs a
division, lets say an average, and they pick some arbitrary value such
as 11, when 8 or 16 makes more sense and codes cleanly. No compiler can
make up for dumb thought processes, whereas assembler tends to make you
think more in line with how the CPU hardware works, at least when I
write software that's how I think, basically track the operands through
the hardware in my thoughts. Similarly C programmers tend to be in love
with floating point, when integer is more accurate, and faster. In 40+
years I've very rarely had the need to revert to floating point, yet
most of the C programs I see for micros use it whenever the program has
to handles numbers.
So while I agree that in the hands of a good programmer C should be
quite fast and compact, I suspect that the number of C programmers out
there who are capable of making use of these features are as few and far
between as assembler programmers of any ilk. However a good compiler can
make an average C programmer look a lot better than they really are. I
truly believe that the higher level language you program in the lazier,
sloppier and less efficient most people get because they can, without
much fear of being found out, and if it doesn't work just throw a bigger
faster processor at it.
I get it, but don't want to be a part of it, and don't have to be so I
shall plod along with the rest of the dinosaurs waiting for the next
major extinction event to come along.
Cheers
Al
On 13/01/2016 9:48 AM, David Brown [email protected] [msp430] wrote:
> On 12/01/16 22:28, Jon Kirwan [email protected] [msp430] wrote:
>> On Tue, 12 Jan 2016 10:04:54 +0100, David wrote:
>>
>> ><snip>
>> >gcc will generate better
>> >code than most assembler programmers in many circumstances - assuming
>> >the code has to be written in a clear, understandable, safe,
>> >maintainable manner.
>> ><snip>
>>
>> Although we've discussed the subject in the long past here,
>> this really has very little to do with the current thread
>> started by Craig. Craig was interested in "sample code in
>> Asm."
>>
>> While I do think there are a number of related topics to the
>> question of sample assembly code (for example, which
>> assembler tool is in use so that the appropriate sample
>> source can be suggested -- gas assembler is quite different
>> from IAR, as we both know), I don't for a second imagine that
>> his question should instill a response saying that gcc
>> generates better code than "most assembler programers," which
>> seems more about uncovering some old sore point than anything
>> else. (Besides, there are a few folks here who are definitely
>> better than "most assembler programmers.")
>>
> When I see someone looking for help with assembly, I think it is
> perfectly reasonable to point out the options with compilers. You have
> to ask yourself /why/ that person is asking about assembly, and think
> can you be more helpful by pointing them in a different direction.
>
> Let's consider the reasons why a person might want to start working on
> an msp430 in assembly. (Note that I don't know to what extent the OP is
> /starting/ with assembly, but the discussion on choice of assembler
> tools suggest he might be.)
>
> 1. They want to learn about the cpu, and see exactly how it works.
> That's great!
>
> 2. It's for fun - also great.
>
> 3. They want to do something that cannot be done using C. There are
> /very/ few cases where this is realistic - in most cases, the person is
> mistaken.
>
> 4. They want to write the most efficient possible code, and think that
> means assembly. In most cases, they are mistaken.
>
> 5. Assembly is all they know, and they don't want to learn C. If this
> is for a hobby project, then that's fair enough - but if it is in a
> professional context, then they are not doing a good job. Writing
> maintainable code in a language that many people understand, and using
> tools that give much greater developer efficiency, means C trumps
> assembly in almost all cases for professional development. There are
> always exceptions, of course, but exceptions are rare.
>
> 6. They think C compilers for small microcontrollers are inefficient or
> limited. That may be true on some cores, but not on the msp430.
>
> 7. They think that C compilers are expensive. Again, that is true for
> some cores, and it used to be true for the msp430, but it is not true now.
>
>
> My experience is that most people who choose to work in assembler these
> days, do so for invalid or inappropriate reasons. This certainly does
> not apply to /all/ people who pick assembler - but it applies to many.
> So in the interest of helping the original poster, it makes sense to
> bring up C as an alternative. It would be unreasonable to try to push
> it on him if he has good reason to use assembler, but it is a good think
> to suggest it.
>
> So when the OP was asking about different sized multiply and divide
> routines in msp430 assembly, my first thought is /why/ bother? Write "x
> = y * z;" and "x = y / z;" and let the compiler generate the code. It
> will make code that is at least as small and efficient as you can do by
> hand - and if it can figure out some of the values at compile time, it
> will do far better than the assembly programmer. And it will do so as
> fast as you can type a couple of lines of code, and will do so correctly
> - no need to search for sample code, figure out how to integrate it,
> worry about possible mismatches of register uses, and so on.
>
> David
>
>
>
> ------------------------------------
> Posted by: David Brown <[email protected]>
> ------------------------------------
>
> To unsubscribe from the msp430 group, send an email to:
> [email protected]
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>
>
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<font size="-1">I do so want to go for six shooters at sunset, but
mostly you are right, however this presupposes the C writer is
able to write efficient code, because without that the compiler,
no matter how efficient, is of limited help. The number of times I
see people do something that needs a division, lets say an
average, and they pick some arbitrary value such as 11, when 8 or
16 makes more sense and codes cleanly. No compiler can make up for
dumb thought processes, whereas assembler tends to make you think
more in line with how the CPU hardware works, at least when I
write software that's how I think, basically track the operands
through the hardware in my thoughts. Similarly C programmers tend
to be in love with floating point, when integer is more accurate,
and faster. In 40+ years I've very rarely had the need to revert
to floating point, yet most of the C programs I see for micros use
it whenever the program has to handles numbers. <br>
<br>
So while I agree that in the hands of a good programmer C should
be quite fast and compact, I suspect that the number of C
programmers out there who are capable of making use of these
features are as few and far between as assembler programmers of
any ilk. However a good compiler can make an average C programmer
look a lot better than they really are. I truly believe that the
higher level language you program in the lazier, sloppier and less
efficient most people get because they can, without much fear of
being found out, and if it doesn't work just throw a bigger faster
processor at it.<br>
<br>
I get it, but don't want to be a part of it, and don't have to be
so I shall plod along with the rest of the dinosaurs waiting for
the next major extinction event to come along.<br>
<br>
Cheers<br>
<br>
Al<br>
</font><br>
<div class="moz-cite-prefix">On 13/01/2016 9:48 AM, David Brown
<a class="moz-txt-link-abbreviated" href="mailto:[email protected]">[email protected]</a> [msp430] wrote:<br>
</div>
<blockquote cite="mid:[email protected]" type="cite">
<pre wrap="">On 12/01/16 22:28, Jon Kirwan <a class="moz-txt-link-abbreviated" href="mailto:[email protected]">[email protected]</a> [msp430] wrote:
</pre>
<blockquote type="cite">
<pre wrap="">On Tue, 12 Jan 2016 10:04:54 +0100, David wrote:
><snip>
>gcc will generate better
>code than most assembler programmers in many circumstances - assuming
>the code has to be written in a clear, understandable, safe,
>maintainable manner.
><snip>
Although we've discussed the subject in the long past here,
this really has very little to do with the current thread
started by Craig. Craig was interested in "sample code in
Asm."
While I do think there are a number of related topics to the
question of sample assembly code (for example, which
assembler tool is in use so that the appropriate sample
source can be suggested -- gas assembler is quite different
from IAR, as we both know), I don't for a second imagine that
his question should instill a response saying that gcc
generates better code than "most assembler programers," which
seems more about uncovering some old sore point than anything
else. (Besides, there are a few folks here who are definitely
better than "most assembler programmers.")
</pre>
</blockquote>
<pre wrap="">
When I see someone looking for help with assembly, I think it is
perfectly reasonable to point out the options with compilers. You have
to ask yourself /why/ that person is asking about assembly, and think
can you be more helpful by pointing them in a different direction.
Let's consider the reasons why a person might want to start working on
an msp430 in assembly. (Note that I don't know to what extent the OP is
/starting/ with assembly, but the discussion on choice of assembler
tools suggest he might be.)
1. They want to learn about the cpu, and see exactly how it works.
That's great!
2. It's for fun - also great.
3. They want to do something that cannot be done using C. There are
/very/ few cases where this is realistic - in most cases, the person is
mistaken.
4. They want to write the most efficient possible code, and think that
means assembly. In most cases, they are mistaken.
5. Assembly is all they know, and they don't want to learn C. If this
is for a hobby project, then that's fair enough - but if it is in a
professional context, then they are not doing a good job. Writing
maintainable code in a language that many people understand, and using
tools that give much greater developer efficiency, means C trumps
assembly in almost all cases for professional development. There are
always exceptions, of course, but exceptions are rare.
6. They think C compilers for small microcontrollers are inefficient or
limited. That may be true on some cores, but not on the msp430.
7. They think that C compilers are expensive. Again, that is true for
some cores, and it used to be true for the msp430, but it is not true now.
My experience is that most people who choose to work in assembler these
days, do so for invalid or inappropriate reasons. This certainly does
not apply to /all/ people who pick assembler - but it applies to many.
So in the interest of helping the original poster, it makes sense to
bring up C as an alternative. It would be unreasonable to try to push
it on him if he has good reason to use assembler, but it is a good think
to suggest it.
So when the OP was asking about different sized multiply and divide
routines in msp430 assembly, my first thought is /why/ bother? Write "x
= y * z;" and "x = y / z;" and let the compiler generate the code. It
will make code that is at least as small and efficient as you can do by
hand - and if it can figure out some of the values at compile time, it
will do far better than the assembly programmer. And it will do so as
fast as you can type a couple of lines of code, and will do so correctly
- no need to search for sample code, figure out how to integrate it,
worry about possible mismatches of register uses, and so on.
David
------------------------------------
Posted by: David Brown <a class="moz-txt-link-rfc2396E" href="mailto:[email protected]"><[email protected]></a>
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