🚀 go-pugleaf

In article <lgbhcmINNmbc@exodus.Eng.Sun.COM>, grover@brahmand.Eng.Sun.COM (Vinod Grover) writes...
> [text deleted]
>The third is to have clever compilers, that make the machine "appear"
>fast.  How do you tell the difference?. If you measured VAX-780 with
>modern compilers today, I bet it would do more than 1 SPEC{fp,int}92
>mark.
> [text deleted]

This experiment has been done, at least in part, by applying the KAP
preprocessor and an up to date FORTRAN compiler to classic VAX's.  For
SPECmark89, the 11/780 is indeed a "1.3 SPECmark89" machine -- mostly
because of the inflation of MATRIX300 seen in other systems.  For SPEC92,
there is less impact.

The reason better compilers can do little with the 11/780 is that it is
not, at base, a pipelined machine.  The principal optimizations to make
for the 780 would be:

	- Inlining, to minimize use of the high overhead procedure
	  call and return instructions
	- Cache blocking, to maximize use of the 8KB cache
	- Global register allocation, to minimize register spills
	- Careful instruction selection, to use the fastest sequences
	  among alternatives

Recent VAX processors, which are heavily pipelined, benefit for more
aggressive compiler techniques just like RISC processors.

Bob Supnik	>Supnik@human.enet.dec.com
		>All opinions expressed are those of a hardline microcoder
		>and do not reflect those of Digital Equipment Corporation