Instead of storing the value to send/receive in the coroutine promise,
store only a pointer in the promise. This simplifies the code a lot and
allows larger value sizes to be sent across a channel.
Unfortunately, this new system has a code size impact. For example,
compiling testdata/channel.go for the BBC micro:bit, there is an
increase in code size from 4776 bytes to 4856 bytes. However, the
improved flexibility and simplicity of the code should be worth it. If
this becomes an issue, we can always refactor the code at a later time.
This commit adds getValue which gets a const, global, or result of a
local SSA expression and replaces (almost) all uses of parseExpr with
getValue. The only remaining use is in parseInstr, which makes sure an
instruction is only evaluated once.
This commit replaces "unknown type" errors in getLLVMType with panics.
The main reason this is done is that it simplifies the code *a lot*.
Many `if err != nil` lines were there just because of type information.
Additionally, simply panicking is probably a better approach as the only
way this error can be produced is either with big new language features
or a serious compiler bug. Panicking is probably a better way to handle
this error anyway.
Support for channels is not complete. The following pieces are missing:
* Channels with values bigger than int. An int in TinyGo can always
contain at least a pointer, so pointers are okay to send.
* Buffered channels.
* The select statement.
