Hi Peter:
The relevance to the present discussion is that RTCG may require detailed
configuration discovery ABI/API that goes beyond the ABI for functional
code. I hope the work of the relevant group(s) will take this into
consideration.
Discovery ABI/API are discussed in another place, which might not be
part of psABI, it would be more like Linux specific stuffs, SiFive
folks and Rivos folks have some discussion about the design of
configuration discovery API, might included a set of new system call
to let program in user space has a mechanism get more detail
information, that will public info soon (it would be public at least
before the Linux plumber 2022 I guess).
On Wed, Jul 27, 2022 at 12:49 AM L Peter Deutsch <ghost@...> wrote:
I would like to emphasize Zalman Stern's point about trading off hardware
economy for dynamic software optimization, in the context of a larger
comment about optimizing compiled code for RISC-V. The specification of RVV
is designed very well to work well across a variety of hardware
implementations without requiring different code, but IMO one of the great
truths of system design is that "compilation beats interpretation," and in
this context, execution-time parameterization as defined for RVV is a form
of interpretation that, like many kinds of interpretation, trades space and
time overhead for convenience.
For it to be most effective, the representation *from* which run-time code
is generated must be sufficiently high-level: the higher the level, the
greater the opportunities to tailor the code to the hardware. Not having
experience with vector-amenable computation, I can't say anything more
specific, other than to note the historical tug of war between, on the one
hand, compilers that recognize vectorizable constructs in low-level
languages like C, and on the other, very high-level languages like APL or
Halide.
The relevance to the present discussion is that RTCG may require detailed
configuration discovery ABI/API that goes beyond the ABI for functional
code. I hope the work of the relevant group(s) will take this into
consideration.
--
L Peter Deutsch :: Aladdin Enterprises :: Healdsburg, CA & Burnaby, BC
