This commit makes a number of changes:
* It avoids a dependency on Compiler.emitStartGoroutine.
* It moves the func-lowering pass to the transform package.
* It adds testing to func lowering.
No functionality should have changed with this commit.
This code is required by transformation passes which are being moved
into a separate package, but is too complicated to simply copy.
Therefore, I decided to move them into a new package.
Linked lists are usually implemented as follows:
type linkedList struct {
next *linkedList
data int // whatever
}
This caused a stack overflow while writing out the reflect run-time type
information. This has now been fixed by splitting the allocation of a
named type number from setting the underlying type in the sidetable.
Make sure all allocas are created in the entry block and are given the
right lifetimes. This is good for code quality:
* Moving allocas to the entry block makes sure they are always
allocated statically (avoiding the need for a frame pointer) and do
not grow the stack on each new alloca instruction. This is
especially useful in loops where it could otherwise lead to a stack
overflow even though there is no recursion.
* Adding lifetime markers allows LLVM to reuse stack areas for
different allocas as long as their lifetimes do not overlap.
All in all, this reduces code size in all tested cases for the BBC
micro:bit, and reduces code size for most cases for WebAssembly.
By moving all allocas used in hashmap operations to the entry block, the
stack frame remains at a fixed size known at compile time. This avoids
stack overflows when doing map operations in loops and in general
improves code quality: the compiled size of testdata/map.go went from
3776 to 3632 in .text size.
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.
Before this commit, goroutine support was spread through the compiler.
This commit changes this support, so that the compiler itself only
generates simple intrinsics and leaves the real support to a compiler
pass that runs as one of the TinyGo-specific optimization passes.
The biggest change, that was done together with the rewrite, was support
for goroutines in WebAssembly for JavaScript. The challenge in
JavaScript is that in general no blocking operations are allowed, which
means that programs that call time.Sleep() but do not start goroutines
also have to be scheduled by the scheduler.
Ayke van Laethem
Jaden Weiss