Re: programming language that does not inhibit further optimization by gcc

[Albert Abramson <abramson dot albert at gmail dot com>]

Now I'm on a totally unrelated project, writing code in C, but still using
the GCC compiler under the hood.  The previous developers used raw pointers
quite a bit.  However, as I expand the code, I'd like to use some of the
features in C++, but Atmel Studio doesn't REALLY support C++.
 Code::Blocks is letting me turn warning flags on and off, but I don't see
the same for individual C++ features.  (Lots of subsets of C++, but I
really need a true superset of C.)

Is there some way to manually turn on individual C++17 features, one at a
time?  I read somewhere that you can, but I don't see the post online
anywhere.  And if I create a list of individual C++ features, can this made
into a kind of standard, shared with other programmers?  In other words,
I'd like to make use of lambdas, namespaces, smart pointers, range-based
for loops, and a few others that would save me a lot of time and maybe even
reduce the size of the binary (since we're very RAM limited in the embedded
world).

I'm writing about this on the Facebook page "C+ Project," which is open to
all programmers.

On Tue, Oct 15, 2013 at 8:00 AM Rob <robpilling@gmail.com> wrote:

> GCC does value analysis similar to what you mentioned. You'll find it
> under the -fdump-tree-vrp options. To provide extra information you
> can add range checks which GCC will pick up on. If you know a value is
> small, use a small integer type and gcc will pick up the range of
> values which can be assigned to it.
>
> What are the problems you're trying to solve? Is it a low memory
> system you're running on?
>
> If you're after performance, add restrict to your parameters and
> either use unions to get around aliasing or do what the Linux dev team
> do with -fno-strict-aliasing.
>
> Regarding threading - I think trying to use multiple threads without
> having to learn thread libraries is a bit of a gamble. Threading is
> difficult even in high level languages and you should have a good
> background before approaching.
>
> For struct packing, I suppose you could just order your entries
> largest-first which is one approach, but it's kinda like the 0-1
> knapsack problem.
>
>
> On 15 October 2013 01:31, Albert Abramson <abramson.albert@gmail.com>
> wrote:
> > I have been looking everywhere online and talking to other coders at
> > every opportunity about this, but cannot find a complete answer.
> > Different languages have different obstacles to complete optimization.
> >  Software developers often have to drop down into non-portable
> > Assembly because they can't get the performance or small size of
> > hand-optimized Assembly for their particular platform.
> >
> > The C language has the alias issue that limits the hoisting of loads.
> > Unless the programmer specifies that two arrays will never overlap
> > using the 'restrict' keyword, the compiler may not be able to handle
> > operations on arrays efficiently because of the unlikely event that
> > the arrays could overlap.  Most/all languages also demand the
> > appearance of serialization of instructions and memory operations, as
> > well as extreme correctness in even the most unlikely circumstances,
> > even where the programmer may not need them.
> >
> > Is there a language out there (similar to Fortran or a dialect of C)
> > that doesn't inhibit the compiler from taking advantage of every
> > optimization possible?  Is there some way to provide a C/C++ compiler
> > with extra information about variables and programs so that it can
> > maximize performance or minimize size?  For example:
> >
> > int age = 21;    //[0, 150)  setting maximum limits, compiler could use
> byte int
> > int outsideTemp = 20;    //[-273, 80]
> > float ERA = 297;           //[0, 1000, 3]   [min, max, digits of
> > accuracy needed]
> >
> > Better yet, allow some easier way of spawning multiple threads without
> > have to learn all of the Boost libraries, OpenCL, or OpenGL.  In other
> > words, is there yet a language that is designed only for performance
> > that places no limits on compiler optimizations?  Is there a language
> > that allows the compiler to pack struct variables in tighter by
> > reorganizing those values, etc?
> >
> > If not, is it possible to put together some dialect of C/C++ that
> > replaces Assembly outright?
> >
> > --
> > Max Abramson
> > “In the end, more than freedom, they wanted security. They wanted a
> > comfortable life, and they lost it all – security, comfort, and
> > freedom. When the Athenians finally wanted not to give to society but
> > for society to give to them, when the freedom they wished for most was
> > freedom from responsibility, then Athens ceased to be free and was
> > never free again.” --Sir Edward Gibbon
>


-- 
“In the end, more than freedom, they wanted security. They wanted a
comfortable life, and they lost it all – security, comfort, and freedom.
When the Athenians finally wanted not to give to society but for society to
give to them, when the freedom they wished for most was freedom from
responsibility, then Athens ceased to be free and was never free again.”
--Sir Edward Gibbon