[Simh] BLISS ( was Re: 101 Basic Games for RSTS/E (was Re: PDP11 on Simh for public access))

[Johnny Billquist]

On 2018-01-26 22:49, Hunter Goatley wrote:
> On 1/26/2018 3:28 PM, Timothe Litt wrote:
> 
>> Sounds right.  The -16 and -36 versions stayed with the native backend 
>> and didn't get much attention once GEM took off.  At least, I don't 
>> recall GEM support for them.
> 
> I believe that's correct.

So, no GEM for BLISS-16, and most likely no chance of it being ported to 
Alpha then. Thanks for confirming that.

>> All three (CMU ,BLISS, GEM) back ends used considerable creativity in 
>> interpreting the instruction sets, and as time went on gave hand-coded 
>> assembler a run for its money.  They especially liked to do 
>> computations with bizarre-looking address calculations.  (Not all of 
>> which ran fast on all processors.) In one case, a particularly 
>> "clever" encoding of a test on a link-time constant broke RMS on an 
>> unreleased VAX CPU. Interestingly, this one instruction was the ONLY 
>> time this construct was encountered in all of VMS (including the top 
>> dozen layered products), so waiting for the hardware spin wasn't as 
>> bad as it might have been.
> 
> I vaguely remember hearing about that.
> 
> BLISS-32 on VAX generated some amazing optimizations. Before I got into 
> BLISS, I programmed almost exclusively in MACRO-32, and it was fun to 
> compare code I wrote to the assembly code generated by the BLISS 
> compiler. Several times, I encountered generated code that was a lot 
> more efficient than the code I wrote, which I thought was very 
> efficient. I learned a few MACRO tricks looking at the code generated. 
> It was less fun trying to understand the GEM output for Alpha. ;-)

Heh. I've had similar experiences with BLISS-16. I've learned a trick or 
two looking at the code generated, and it can do some rather neat 
tricks. Definitely impressive code generated. Not seen that level from 
any other PDP-11 compiler.

   Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol