Re: mutex in frame code

[David Edelsohn <dje at watson dot ibm dot com>]

>>>>> Joe Buck writes:

Joe> Certainly, if it is true that every member of the PowerPC family has
Joe> exactly the same instructions, then specifying that the processor to
Joe> tune to is, say the 604, gives you the information that the architecture
Joe> is powerpc.  This information can be defaulted.

	Uh, no.  Each processor implementation of the same architecture
has different timing parameters and number of function units.  -mtune
embodies that information.  One can specify "common" architecture yet tune
for 604.  Or specify 32-bit architecture yet tune for 64-bit processor.

	The rs6000 port already has the equivalent of -march flags in
-mpower, -mpower2, -mpowerpc, -mpowerpc64, -mpowerpc-gfxopt, etc. flags.
The rs6000 architectures are not mutually-exclusive or nested: "common"
is none of those flags, ppc601 is -mpower and -mpowerpc flags combined,
etc.  I do not see any benefit in converting those flags to -march as they
cannot be used the same way as -march on other ports where a single option
combines a number of flags.  The "rs6000" architectures already are
described in a more well-defined set of basis options.

David