[Fwd: Re: [PATCH] MIPS32 DSP instructions again]

[Ian Lance Taylor]

Dominic Sweetman <dom@mips.com> writes:

> Which comes down to this: under what circumstances might it be helpful
> for the assembler to reject a piece of code which it could have
> assembled?

In general, it is better to get a compile-time error than a run-time
error.

For example, suppose some library is written to use the new
instructions.  Suppose it's a portable library, for various
processors.  I get the source code for that library, and I compile it
with the options appropriate for my processor.  Unfortunately, there
is a bug, and the library uses an asm statement with an instruction
which is not supported on my processor.  I would prefer to get a
compile-time error rather than a run-time error.

Similar examples involving assembly code in a portable OS kernel--say
one with builtin graphics support--are also fairly easy to concoct.

Ian