[Simh] VAX emulation issues on Raspberry Pi

[Paul Koning]

> On Jul 31, 2018, at 11:55 AM, Henry Bent <henry.r.bent at gmail.com> wrote:
> 
> 
> On 31 July 2018 at 11:49, Timothe Litt <litt at ieee.org> wrote:
> 
> On 31-Jul-18 10:08, Paul Koning wrote:
>>> On Jul 31, 2018, at 9:33 AM, Robert Armstrong <bob at jfcl.com>
>>>  wrote:
>>> 
>>> 
>>> FWIW, this may also say something about the quality of the code generation in gcc for ARM vs x86 processors, or it may even say something about the relative efficiency of those two architectures.
>> One thing worth doing is to use the latest gcc.  Code generation keeps improving, and it's likely that architectures such as ARM see significant benefits in newer releases.
>> 
>> ...
> 
> I did a writeup a while back about various compilers and SIMH on x86, here is the link from the archive: http://mailman.trailing-edge.com/pipermail/simh/2015-December/014102.html
> 
> Profile-guided feedback is extremely helpful for SIMH.  If you are able to recompile SIMH for your workload using feedback, the gains are extremely significant.

Interesting, and not too surprising.  Given that, it may be useful to use a recent GCC which supports LTO -- Link Time Optimization.  That's a scheme that allows whole-program optimization, rather than the normal per-sourcefile optimization.

	paul