Re: Package Logical performance optimizations

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Al asks

<<Has anyone written the body for package logical (from the PAL) using
package machine code for the 680x0 and/or the intel x86 family of
processors?
 
If so could you please post or send them to me.>>

You need to say what compiler you are using, since package Machine_Code
will vary from one compiler to another. Also note that in Ada 95, the
implementation of package Machine_Code is not required, even if you
support annex C, since it is possible to provide (the much more useful
approach) of machine intrinsics instead (GNAT provides both).

The one exception is the Motorola 88000. For this machine, the official
ABI includes a specification of what package Machine_Code should look
like in Ada compilers for this machine, so presumably there would be
no portability issue with this machine (unfortunately, as far as I know
there are virtually no computers using this chip any more, the manufacturer
has abandoned the chip, and there are no Ada compilers available -- although
a GNAT compiler could easily be constructed, so this is all a bit academic).

It would be nice to standardize machine code, but it is tough. For example,
in GNAT, we directly interface to the gcc capability, which is extremely
flexible, since it allows linking directly into the RTL structure, using
symbolic registers if you want), but it is highly gcc dependent.

The old Alsys 386 compiler had what I thought was a very nice set of
instrinsics (I designed them :-) which were reasonably compiler independent,
but I don't think anyone followed them (I don't even know if Object Ada
duplicates this facility ...)