[TUHS] DEC Compilers (was: Re: SDB debugger

Win Treese treese at acm.org
Tue May 5 10:22:44 AEST 2020

> On May 3, 2020, at 4:26 PM, Clem Cole <clemc at ccc.com> wrote:
> Anyway back to compilers, Tru64 had a 'good enough' compiler based on the MIPS code base to get us all going, but GEM's primary target was VMS since one of the important features of GEM was the VAX->Alpha transpiler technology.   VMS was still heavily written in VAX Assembler at the time.  Plus, It actually was a little hairy because GEM had a new C/C++ front-end.   So TLE's high order bit was VMS for the Alphas.   GEM for Tru64 was about 18 months later. 

In the early days of Alpha, I was at DEC’s Cambridge Research Laboratory (directed then by Vic Vyssotsky, having retired from Bell Labs). The lab had various connections to Alpha projects, and we learned that there were (I think) 7 different C compilers running on the early port of Ultrix. That number, I think, did not include the port of gcc that DEC was funding outside the company.

Andy Payne, a recent hire at the lab, had been an intern in DEC’s semiconductor group, where he had worked on randomized testing for hardware verification. With all the compilers available, he decided to hack up a program to generate random small C programs with computable expected outputs. His program then compiled the random code with each compiler and tested the result. After finding a number of bugs this way, he got tired of submitting the bug reports, and changed his program to write and submit the bug reports automatically. 

This caused a little bit of consternation with some of the compiler teams at first.

Eventually, this led to some collaboration with the DEC languages and tools team, and Bill McKeeman published a paper that line of work in the Digital Technical Journal in 1998[1].

 - Win

[1] https://www.hpl.hp.com/hpjournal/dtj/vol10num1/vol10num1art9.pdf

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