On 20/02/2014 11:21 PM, Paul wrote:
At one time, a compiler would issue instructions
from about 30% of the instruction set. It would mean
a compiled program would never emit the other 70% of
them. But a person writing assembler code, would
have access to all of them, at least, as long as
the mnemonic existed in the assembler.

I think the original idea of the x86's large instruction count was to
make an assembly language as full-featured as a high-level language. x86
even had string-handling instructions!

I remember I designed an early version of the CPUID program that ran
under DOS. The whole executable including its *.exe headers was
something like 40 bytes! Got it down to under 20 bytes when I converted
it to *.com (which had no headers)! Most of the space was used to store
strings, like "This processor is a:" followed by generated strings like
386SX or 486DX, etc.

You could make some really tiny assembler programs on x86. Of course,
compiled programs ignored most of these useful high-level instructions
and stuck with simple instructions to do everything.

Yousuf Khan