[patch][rfa] Representation of ISA Attribute in CGEN

[Dave Brolley <brolley@redhat.com>]

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Hi,

These changes have been in our local tree for a few years now and were 
developed for an internal port which requires *much* more than 32 ISAs 
or even 64 ISAs. These changes could be of benifit to others, so I would 
like to submit them for approval.

Currently, ISA is represented as an integer, like all the other 
non-boolean attributes. It is a bit mask with each bit representing 
whether a particular ISA is supported. Our port requires that there be 
no fixed limit on the number of ISAs, and so, we developed an open-ended 
representation for a bitset using a bitstring and a length. It is called 
CGEN_BITSET and is declared in include/opcode/cgen-bitset.h and 
supported by several new functions in opcodes/cgen-opc.c. All 
manipulation of these bitsets is done using these functions which hide 
the internal representation. See cgen-bitset.h (attached) for a 
description of the implementation

The patch has 3 parts:
1) Extension of CGEN_ATTR_VALUE_TYPE to be a union allowing the use of 
CGEN_BITSET as well as its supporting macros.

2) Changes to CGEN so that it generates code to correctly access and 
initialize the new definition of CGEN_ATTR_VALUE_TYPE and to use the 
proper cover functions when manipulating ISAs.

3) Changes to hand written portions of existing opcodes, sim and sid 
ports as in 2). Fortunately, the use of existing CGEN macros made these 
changes minimal.

I have also included in the patch the regenerated source for the frv 
port so that you can see the effect on the generated code. None of the 
generated code for existing sid ports is affected.

One natural extension of this work would be use the same representation 
for all bitset attributes in CGEN. I believe that MACH is the only other 
one at this time.

Seeking comments and approval to commit.

Thanks,
Dave

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