There were a few problems with the go/packages package. While it is more
or less designed for our purpose, it didn't work quite well as it didn't
provide access to indirectly imported packages (most importantly the
runtime package). This led to a workaround that sometimes broke
`tinygo test`.
This PR contains a number of related changes:
* It uses `go list` directly to retrieve the list of packages/files to
compile, instead of relying on the go/packages package.
* It replaces our custom TestMain replace code with the standard code
for running tests (generated by `go list`).
* It adds a dummy runtime/pprof package and modifies the testing
package, to get tests to run again with the code generated by
`go list`.
This commit replaces the existing ad-hoc package loader with a package
loader that uses the x/tools/go/packages package to find all
to-be-loaded packages.
This commit lets the compiler know about interrupts and allows
optimizations to be performed based on that: interrupts are eliminated
when they appear to be unused in a program. This is done with a new
pseudo-call (runtime/interrupt.New) that is treated specially by the
compiler.
This is directly useful to avoid some unsafety around runtime.alloc and
should be useful in general.
This pragma has the same form as in the main Go compiler:
https://github.com/golang/go/issues/12312
This is part of a larger rafactor that tries to shrink the ir package
and in general tries to shrink the amount of state that is kept around
in the compiler. The end goal is being able to compile packages
independent of each other, linking them together in a later stage. Along
the way, it cleans up lots of old cruft that has accumulated over the
months.
This refactor also results in globals being loaded lazily. This may be a
problem for some specific programs but will probably change back in a
commit in the near future.
The interp package does a much better job at interpretation, and is
implemented as a pass on the IR which makes it much easier to compose.
Also, the implementation works much better as it is based on LLVM IR
instead of Go SSA.
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.
This reduces complexity in the compiler without affecting binary sizes
too much.
Cortex-M0: no changes
Linux x64: no changes
WebAssembly: some testcases (calls, coroutines, map) are slightly bigger
This commit changes many things:
* Most interface-related operations are moved into an optimization
pass for more modularity. IR construction creates pseudo-calls which
are lowered in this pass.
* Type codes are assigned in this interface lowering pass, after DCE.
* Type codes are sorted by usage: types more often used in type
asserts are assigned lower numbers to ease jump table construction
during machine code generation.
* Interface assertions are optimized: they are replaced by constant
false, comparison against a constant, or a typeswitch with only
concrete types in the general case.
* Interface calls are replaced with unreachable, direct calls, or a
concrete type switch with direct calls depending on the number of
implementing types. This hopefully makes some interface patterns
zero-cost.
These changes lead to a ~0.5K reduction in code size on Cortex-M for
testdata/interface.go. It appears that a major cause for this is the
replacement of function pointers with direct calls, which are far more
susceptible to optimization. Also, not having a fixed global array of
function pointers greatly helps dead code elimination.
This change also makes future optimizations easier, like optimizations
on interface value comparisons.
This is one step towards removing unnecessary special casts in most
cases. It is also part of removing as much magic as possible from the
compiler (the pragma is explicit, the special name is not).
