This makes sure that the LLVM target features match the one generated by
Clang:
- This fixes a bug introduced when setting the target CPU for all
targets: Cortex-M4 would now start using floating point operations
while they were disabled in C.
- This will make it possible in the future to inline C functions in Go
and vice versa. This will need some more work though.
There is a code size impact. Cortex-M4 targets are increased slightly in
binary size while Cortex-M0 targets tend to be reduced a little bit.
Other than that, there is little impact.
This brings some consistency to the CFlags and fixes the issue that on
some platforms (Linux, MacOS), no optimization level was set and
therefore C files in packages were not optimized at all.
At the moment, all targets use the Clang compiler to compile C and
assembly files. There is no good reason to make this configurable
anymore and in fact it will make future changes more complicated (and
thus more likely to have bugs). Therefore, I've removed support for
setting the compiler.
Note that the same is not true for the linker. While it makes sense to
standardize on the Clang compiler (because if Clang doesn't support a
target, TinyGo is unlikely to support it either), linkers will remain
configurable for the foreseeable future. One example is Xtensa, which is
supported by the Xtensa LLVM fork but doesn't have support in ld.lld
yet.
I've also fixed a bug in compileAndCacheCFile: it wasn't using the right
CFlags for caching purposes. This could lead to using stale caches. This
commit fixes that too.
Instead of putting tinygo_scanCurrentStack in scheduler_*.S files, put
them in dedicated files. The function tinygo_scanCurrentStack has
nothing to do with scheduling and so doesn't belong there. Additionally,
while scheduling code is made specific for the Cortex-M, the
tinygo_scanCurrentStack is generic to all ARM targets so this move
removes some duplication there.
Specifically:
* tinygo_scanCurrentStack is moved out of scheduler_cortexm.S as it
isn't really part of the scheduler. It is now gc_arm.S.
* Same for the AVR target.
* Same for the RISCV target.
* scheduler_gba.S is removed, using gc_arm.S instead as it only
contains tinygo_scanCurrentStack.
The frame pointer was already omitted in the object files that TinyGo
emits, but wasn't yet omitted in the C files it compiles. Omitting the
frame pointer is good for code size (and perhaps performance).
The frame pointer was originally used for printing stack traces in a
debugger. However, advances in DWARF debug info have made it largely
unnecessary (debug info contains enough information now to recover the
frame pointer even without an explicit frame pointer register). In fact,
GDB has been able to produce backtraces in TinyGo compiled code for a
while now while it didn't include a frame pointer.
This is necessary for better CGo support on bare metal. Existing
libraries expect to be able to include parts of libc and expect to be
able to link to those symbols.
Because with this all targets have a working libc, it is now possible to
add tests to check that a libc in fact works basically.
Not all parts of picolibc are included, such as the math or stdio parts.
These should be added later, when needed.
This commit also avoids the need for the custom memcpy/memset/memcmp
symbols that are sometimes emitted by LLVM. The C library will take care
of that.
This scheduler is intended to live along the (stackless) coroutine based
scheduler which is needed for WebAssembly and unsupported platforms. The
stack based scheduler is somewhat simpler in implementation as it does
not require full program transform passes and supports things like
function pointers and interface methods out of the box with no changes.
Code size is reduced in most cases, even in the case where no scheduler
scheduler is used at all. I'm not exactly sure why but these changes
likely allowed some further optimizations somewhere. Even RAM is
slightly reduced, perhaps some global was elminated in the process as
well.
dumb -> leaking:
make it more clear what this "GC" does: leak everything.
marksweep -> conservative:
"marksweep" is too generic, use "conservative" to differentiate
between future garbage collectors: precise marksweep / mark-compact /
refcounting.
This is very useful for debugging. It differentiates between a stack
overflow and other errors (because it's easy to see when a stack
overflow occurs) and prints the old stack pointer and program counter if
available.
LLD version 8 has added support for armv6m:
https://reviews.llvm.org/D55555
This means we can use LLD instead of arm-none-eabi-ld, eliminating our
dependency on GNU binutils.
There are small differences in code size, but never more than a few
bytes.
So far, we've pretended to be js/wasm in baremetal targets to make the
stdlib happy. Unfortunately, this has various problems because
syscall/js (a dependency of many stdlib packages) thinks it can do JS
calls, and emulating them gets quite hard with all changes to the
syscall/js packages in Go 1.12.
This commit does a few things:
* It lets baremetal targets pretend to be linux/arm instead of
js/wasm.
* It lets the loader only select particular packages from the src
overlay, instead of inserting them just before GOROOT. This makes it
possible to pick which packages to overlay for a given target.
* It adds a baremetal-only syscall package that stubs out almost all
syscalls.
This commit does two things:
* It adds support for the GOOS and GOARCH environment variables. They
fall back to runtime.GO* only when not available.
* It adds support for 3 new architectures: 386, arm, and arm64. For
now, this is Linux-only.
This avoids a ton of duplication and makes it easier to change a generic
target (for example, the "cortex-m" target) for all boards that use it.
Also, by making it possible to inherit properties from a parent target
specification, it is easier to support out-of-tree boards that don't
have to be updated so often. A target specification for a
special-purpose board can simply inherit the specification of a
supported chip and override the properites it needs to override (like
the programming interface).
Ayke van Laethem
Elliott Sales de Andrade
sago35
Yannis Huber