I've been septic since I introduced it, this commit
proves that it costs more than it helps. I've also fixed
a bad bug in rega() where I alloc'ed the wrong size for
internal arrays. Enums now have names so I can use them
to cast in gdb to get the name corresponding to a constant.
It was not as simple as I thought. All constants
used in 32b context get truncated to 32 bits.
All constants in 64b contexts can either remain
as immutables are have to be evicted in a register,
this choice is taken in noimm(). The case of the
comparison needs to be documented since the context
is not clearly 32 or 64 bits.
I am still unsure if this is fully correct.
There are two things I overlooked so far.
1. Binary instructions like cmp that do not have a result
in registers need the size suffix sometimes, for example
when comparing a spill location with a constant.
2. The register allocator needs to be adapted to support the
comparison instruction: it is not possible to compare two
spill locations without using a register.
This might not be a good idea, the problem was that
many spurious registers would be added to the Bits
data-structures during compilation (and would
always remain 0). However, doing the above
modification de-uniformizes the handling of temps
and regs, this makes the code longer and not
really nicer. Also, additional Bits structures
are required to track the registers independently.
Overall this might be a bad idea to revert.
