This is Fred Chow's PhD thesis; it was used as the basis for the MIPSPro compilers that was later open sourced as Open64[0].

[0] https://en.wikipedia.org/wiki/Open64

And Open64 was the basis for nvcc (not sure if it still is anymore).

"NVIDIA's CUDA Compiler (NVCC) is based on the widely used LLVM open source compiler infrastructure."

https://developer.nvidia.com/cuda-llvm-compiler

Is this a seminal work? Wondering how much of LLVM is built on this work. (LLVM has a optimizer that works on machine-independent IR, right?)

LLVM was done much later in 2003 at the University of Illinois. More importantly LLVM has its own IR, LLVM IR, which is SSA-based. SSA was proposed in 1988 and Chow's work is from 1983.

We started putting SSA into gcc in the early 90s.