Atomic operations on `intptr_t` (`__intcap_t`) generate invalid code

[davidchisnall]

_Atomic(uintptr_t) uintptr;
...
uintptr++

Generates the following code sequence on CHERIoT:

8000740c: 0601955b      ct.cincoffset   ca0, cgp, 0x60
80007410: 0085255b      ct.csetbounds   ca0, ca0, 0x8
80007414: 01854283      ct.clbu t0, 0x18(ca0)

I'm not sure why it's trying to load a byte from out of the bounds of the object, or why it's trying to load a byte at all.

[resistor]

Fixed in 5254e71

[davidchisnall]

It looks as if the code that this is generating is suboptimal, in that it isn't using the fixed-sized builtins, even though the size is known at compile time and is a word-sized value.

[resistor]

Code quality fixed in #230