Re: [ECOS] Arm emulator

[fche@redhat.com (Frank Ch. Eigler)]

"james chen" <james_ch1@sina.com> writes on ecos-discuss:

: [...] I find that it was ARM instructions emulating that takes many
: PC CPU resource. In my PC( CE333) I only get 1 MIPS in emulating ARM
: instructions [using an enhanced gdb/arm simulator], are there any
: way to improve it. [...]

A target:host instruction ratio of 1:100 is about typical for an
instruction set simulator that uses ordinary fetch/decode/execute
algorithms.  Advanced interpretation techniques like cached decode
structures, native host translation, can help a lot, but are pretty
hard to create.

The sid simulator uses an ARM kernel generated by the cgen tool (both
on http://sources.redhat.com/ ), and it does have a small degree of
this sort of thing, but I don't know how it performs in comparison to
the old armulator snapshot (gdb's arm sim).  sid has a feature that
may assist simulation speed in an indirect way: state save/restore,
which lets you theoretically rerun a program from a saved snapshot.
That saves time in skipping e.g. initialization.

Apart from these, and simple mechanical improvements (like compiling
everything with maximum optimization), I can't think of a way of
significantly improving speed.

- FChE