Adapting to a specific processor

[Manfred Nowak]

downs wrote:
> I think most of this is more relevant to compiler writers than to
> programmers.

terranium wrote:
> Read AMD's "Source level optimizations" recommendation.

One might be able to notice the contradiction and please notice that 
AMD writes in Chapter 2.2:
| Source-code transformations interact with a compiler’s code
| generator, making it difficult to control the generated machine
| code from the source level.
http://www.amd.com/us-
en/assets/content_type/white_papers_and_tech_docs/40546.pdf
[cited 2008/05/05] 



Furthermore downs wrote:
> In any case, all but a few of these can't be directly influenced
> from code.

I believe that good advertising for a language that claims to support 
high level abstractions and bare bones access to hardware would be 
something like:

|   Code in this language allows for adapting to specific processors     
|   without disturbing the expressiveness for higher level
|   abstractions.


Have a look on an example from chapter 2.6: 
|  if (a <= max && a >= min && b <= max && b >= min)
seems to be some canonical code for the range checks.

But whenever a respective b are likely to be out of range AMD 
recommends:
|  if (a > max || a < min || b > max || b < min)

Reading the latter version seems to require much more capability in 
recognising the underlying abstraction. Of course this would not be 
necessary when the language would allow for an annotation like:

if (a <= max && a >= min && b <= max && b >= min; apply !)

-manfred