I think it was C+@ (pronounced CAT, as I recall).

Edit: pasting a comment of mine from here in 2019 [1]:

The language is C+@ [2]. I dug up an article about it in Dr. Dobbs Journal, the October 1993 issue. This does not seem to be the article I am remembering, since it does not go into the instruction interleaving technique anywhere near as much as I remember, but they do mention it and say it was called "beading":

The binaries produced by the C+@ compiler are independent of the underlying machine architecture. Without recompiling, applications can be moved from SPARC to 68000 to Intel x86, and so on. C+@ is not interpretive--the binaries are encoded using a sophisticated 'beading' technique developed at Bell Labs. Because of the streamlined language design, the C+@ compiler produces these portable binaries with extraordinary speed, without the need for preprocessing or front ends.

This is from the article's introduction:

The C+@ programming language, an object-oriented language derived from AT&T Bell Lab's Calico programming language, was developed to provide programmers with a true object-based language and development environment. C+@ (pronounced "cat") has the syntax of C and the power of Smalltalk. Unlike C++, C+@ includes a mature class library with more than 350 classes used throughout the system. The C+@ compiler itself is written in C+@, and all of the source for the class libraries is included with development systems. The Calico project was started at AT&T Bell Labs in the early '80s, after the introduction of Smalltalk and at the same time as C++. Calico was originally used for rapid prototyping of telecommunication services; hence, its heavy emphasis on keeping the language syntax simple and showcasing the power of the graphical development environment.*

[1] https://news.ycombinator.com/item?id=20583430

[2] https://encyclopedia2.thefreedictionary.com/C%2b%40