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

[Dave Brolley]

This patch has now been committed.....

Dave Brolley wrote:

> 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
>