* improve the ZIR generated of variable decls
- utilize the same ZIR for the type and init value when possible
- init value gets a result location with the variable type.
no manual coercion is required.
* no longer use return instructions to extract values out of comptime
blocks. Instead run the analysis and then look at the corresponding
analyzed instruction, relying on the comptime mechanism to report
errors when something could not be comptime evaluated.
* move SPU code from std to self hosted compiler
* change std lib comments to be descriptive rather than prescriptive
* avoid usingnamespace
* fix case style of error codes
* remove duplication of producer_string
* generalize handling of less than 64 bit arch pointers
* clean up SPU II related test harness code
`is_pub` added to `Fn` would cost us an additional 8
bytes of memory per function, which is a real bummer
since it's only 1 bit of information.
If we wanted to really remove this, I suspect we could
make this a function isPub() which looks at the AST of
the corresponding Decl and finds if the FnProto AST node
has the pub token. However I saw an easier approach -
The data of whether something is pub or not is actually
a property of a Decl anyway, not a function, so we can
look at moving the field into Decl. Indeed, doing this,
we see that Decl already has deletion_flag: bool which
is hiding in the padding bytes between the enum (1 byte)
and the following u32 field (generation). So if we put
the is_pub bool there, it actually will take up no
additional space, with 1 byte of padding remaining.
This was an easy reworking of the code since any
func.is_pub could be changed simply to func.owner_decl.is_pub.
I also modified `Var` to make the init value non-optional
and moved the optional bit to a has_init: bool field. This is worse from
the perspective of control flow and safety, however it makes
`@sizeOf(Var)` go from 32 bytes to 24 bytes. The more code we can fit
into memory at once, the more justified we are in using the compiler as
a long-running process that does incremental updates.
