A call to .IsConstant() also returns true for constant globals, not just
constant expressions. Do an extra check that we're really operating on a
constant expression.
This function returns the current timestamp, or 0 at compile time.
runtime.nanotime is used at package initialization by the time package
starting with Go 1.12.
Whenever interp hits an unreachable instruction, it bails out at that
point. However, it used to insert new instructions at the bottom with
the old init calls still at the top. So when a panic() happened in a
non-main package, the last packages to init would actually be called
first.
This commit fixes this by setting the insert point at the top of
runtime.initAll before starting interpretation, so the initialization
order is still correct when a panic() happens during init.
There were a few issues that made interp not perform as it should:
* The scan was non-recursive due to a bug.
* Recursive scanning would always return the severity level, which is
not always the best strategy.
The interp package interprets calls in runtime.initAll and replaces
these calls with non-interpretable instructions if needed.
When hitting an unreachable instruction, this call should be removed,
but it wasn't. This commit makes sure the call is removed even before
trying to interpret the package init function.
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.
* Loading from a dirty global must be done at runtime (!). For some
reason this wasn't already the case.
* Global variables somehow had IsConstant() the wrong way round,
returning the inverse from what they should.
* Do binary and logical operations at runtime if necessary, relying on
const propagation in the IR builder.
* Don't try to interpret functions that take a dirty parameter. Call
them at runtime.
Cast operations will still be evaluated at compile time in all cases
they did before because of the built-in constant propagation of the
IRBuilder, but when one of the parameters is not a constant it will
transparently be evaluated at runtime.
This avoids some errors in the partial evaluator. It is not yet complete
as all binops will need a similar treatment.
This interpreter currently complements the Go SSA level interpreter. It
may stay complementary or may be the only interpreter in the future.
This interpreter is experimental and not yet finished (there are known
bugs!) so it is disabled by default. It can be enabled by passing the
-initinterp flag.
The goal is to be able to run all initializations at compile time except
for the ones having side effects. This mostly works except perhaps for a
few edge cases.
In the future, this interpeter may be used to actually run regular Go
code, perhaps in a shell.
