I found that when I enable ThinLTO, a miscompilation triggers that had
been hidden all the time previously. The bug appears to happen as
follows:
1. TinyGo generates a function with a runtime.trackPointer call, but
without an alloca (or the alloca gets optimized away).
2. LLVM sees that no alloca needs to be kept alive across the
runtime.trackPointer call, and therefore it adds the 'tail' flag.
One of the effects of this flag is that it makes it undefined
behavior to keep allocas alive across the call (which is still safe
at that point).
3. The GC lowering pass adds a stack slot alloca and converts
runtime.trackPointer calls into alloca stores.
The last step triggers the bug: the compiler inserts an alloca where
there was none before but that's not valid as long as the 'tail' flag is
present.
This patch fixes the bug in a somewhat dirty way, by always creating a
dummy alloca so that LLVM won't do the optimization in step 2 (and
possibly other optimizations that rely on there being no alloca
instruction).
This is purely a refactor, to make the next change simpler.
The wordpack functionality used to be necessary in transform passes, but
now it isn't anymore so let's not complicate this more than necessary.
This implements the block-based GC as a partially precise GC. This means
that for most heap allocations it is known which words contain a pointer
and which don't. This should in theory make the GC faster (because it
can skip non-pointer object) and have fewer false positives in a GC
cycle. It does however use a bit more RAM to store the layout of each
object.
Right now this GC seems to be slower than the conservative GC, but
should be less likely to run out of memory as a result of false
positives.
This makes it much easier to read the value at runtime, as pointer
indices are naturally little endian. It should not affect anything else
in the program.
There were two types that could result in a compiler stack overflow.
This is difficult to fix in LLVM 14, so I won't even bother. However,
this is trivial to fix with opaque pointers in LLVM 15. Therefore, this
fix is for LLVM 15 only.
Fixes: https://github.com/tinygo-org/tinygo/issues/3341
ThinLTO results in a small code size reduction, which is nice
(especially on these very small chips). It also brings us one step
closer to using ThinLTO everywhere.
This flag is necessary in LLVM 15 because it appears that LLVM 15 has
changed the default target ABI from lp64 to lp64d. This results in a
linker failure. Setting the "target-abi" forces the RISC-V backend to
use the intended target ABI.
A number of llvm.Const* functions (in particular extractvalue and
insertvalue) were removed in LLVM 15, so we have to use a builder
instead. This builder will create the same constant values, it simply
uses a different API.
--allow-undefined can be a problem: it allows compiling code that will
fail when loaded. This change makes sure that if some symbols are
undefined, they are reported as an error by the linker.
Previously, people could get away with importing a function that was not
defined, like this:
func add(int a, int b) int
func test() {
println(add(3, 5))
}
This was always unintended but mostly worked. With this change, it isn't
possible anymore. Now every function needs to be marked with //export
explicitly:
//export add
func add(int a, int b) int
func test() {
println(add(3, 5))
}
As before, functions will be placed in the `env` module with the name
set from the `//export` tag. This can be overridden with
`//go:import-module`:
//go:import-module math
//export add
func add(int a, int b) int
func test() {
println(add(3, 5))
}
For the syscall/js package, I needed to give a list of symbols that are
undefined. This list is based on the JavaScript functions defined in
targets/wasm_exec.js.
This is really a few more-or-less separate changes:
* Remove all math aliases that were used in Go 1.16 and below (the
math.[A-Z] aliases).
* Replace math aliases with an assembly implementation (the math.arch*
aliases) with a LLVM intrinsic, where one is available.
* Include missing math functions in picolibc build.
This leaves just four math aliases:
* math.archHypot and math.archModf do not have a LLVM builtin
equivalent. They could be replaced with calls to libm, and I think
that would be a good idea in the long term.
* math.archMax and math.archMin do have a LLVM builtin equivalent
(llvm.maximum.f64, llvm.minimum.f64), but unfortunately they crash
when used. Apparently these exact operations are not yet widely
supported in hardware and they don't have a libm equivalent either.
There are more LLVM builtins that we could use for the math package
(such as FMA), but I will leave that to a future change. It could
potentially speed up some math operations.
Instead of changing the calls, replace the function bodies themselves.
This is useful for a number of reasons, see
https://github.com/tinygo-org/tinygo/pull/2920 for more information.
I have removed the math intrinsics tests because they are no longer
useful. Instead, I think `tinygo test math` should suffice.
This gives some more optimization opportunities to LLVM, because it
understands these intrinsics. For example, it might convert
llvm.sqrt.f64 to llvm.sqrt.f32 if possible.
For some reason, the type of a function parameter can sometimes be of
interface type, while it should be the underlying type. This might be a
bug in the x/tools/go/ssa package but this is a simple workaround.
ed25519vectors_test.go still fails because:
* It relies on "go mod download" which doesn't work, as well as fork/exec.
* It relies on JSON parsing which has problems with reflection.
But, with the vectors hard coded in the test file the tests *do* succeed, so the encryption is working.
Go 1.19 started reformatting code in a way that makes it more obvious
how it will be rendered on pkg.go.dev. It gets it almost right, but not
entirely. Therefore, I had to modify some of the comments so that they
are formatted correctly.
For some reason, these aren't lowered when a generic function is
instantiated by the SSA package.
I've left unsafe.Offsetof to be implemented later, it's a bit difficult
to do correctly the way the code is currently structured.
Without this change, the compiler would probably have worked just fine
but the generated types would look odd.
You can see in the test case that it now doesn't use `main.Point` but
rather the correct `main.Poin[float32]` etc.
These are reserved registers on MacOS so don't need to be clobbered, and
result in a compiler waring:
ld.lld-14: warning: inline asm clobber list contains reserved registers: X18, FP
Reserved registers on the clobber list may not be preserved across the asm statement, and clobbering them may lead to undefined behaviour.
This has always been unsupported on MacOS and has in fact been removed
from upstream Go a few releases ago. So do the same for TinyGo.
Linux seems to be the only supported OS with a stable syscall interface.
This changes the compiler from treating calls to sync/atomic.* functions
as special calls (emitted directly at the call site) to actually
defining their declarations when there is no Go SSA implementation. And
rely on the inliner to inline these very small functions.
This works a bit better in practice. For example, this makes it possible
to use these functions in deferred function calls.
This commit is a bit large because it also needs to refactor a few
things to make it possible to define such intrinsic functions.
I don't understand why this wasn't caught in CI. It should have. In any
case, because the llvm-features string was updated, these IR outputs
were updated.
You can see that it works with the following command:
tinygo run -target=simavr ./testdata/recover.go
This also gets the following tests to pass again:
go test -run=Build -target=simavr -v
Adding support for AVR was a bit more compliated because it's also
necessary to save and restore the Y register.
For example, this commit moves the 'throw' branch of an assertion (nil
check, slice index check, etc) to the end of the function while
inserting the "continue" branch right after the insert location. This
makes the resulting IR easier to follow.
For some reason, this also reduces code size a bit on average. The
TinyGo smoke tests saw a reduction of 0.22%, mainly from WebAssembly.
The drivers repo saw little average change in code size (-0.01%).
This commit also adds a few compiler tests for the defer keyword.
llvm.AddBasicBlock should never be used. Instead, we should use the
AddBasicBlock method of the current LLVM context.
This didn't lead to any bugs... yet. But probably would, eventually.
Ayke van Laethem
Avi
Damian Gryski
Phil Kedy
Dan Kegel
Federico G. Schwindt
José Carlos Chávez