This PR fixes two bugs at once:
1. Indices were incorrectly extended to a bigger type. Specifically,
unsigned integers were sign extended and signed integers were zero
extended. This commit swaps them around.
2. The getelementptr instruction was given the raw index, even if it
was a uint8 for example. However, getelementptr assumes the indices
are signed, and therefore an index of uint8(200) was interpreted as
an index of int8(-56).
This matches Clang, and with that, it adds support for inlining between
Go and C because LLVM only allows inlining if the "target-cpu" and
"target-features" string attributes match.
For example, take a look at the following code:
// int add(int a, int b) {
// return a + b;
// }
import "C"
func main() {
println(C.add(3, 5))
}
The 'add' function is not inlined into the main function before this
commit, but after it, it can be inlined and trivially be optimized to
`println(8)`.
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.
Instead of doing everything in the interrupt lowering pass, generate
some more code in gen-device to declare interrupt handler functions and
do some work in the compiler so that interrupt lowering becomes a lot
simpler.
This has several benefits:
- Overall code is smaller, in particular the interrupt lowering pass.
- The code should be a bit less "magical" and instead a bit easier to
read. In particular, instead of having a magic
runtime.callInterruptHandler (that is fully written by the interrupt
lowering pass), the runtime calls a generated function like
device/sifive.InterruptHandler where this switch already exists in
code.
- Debug information is improved. This can be helpful during actual
debugging but is also useful for other uses of DWARF debug
information.
For an example on debug information improvement, this is what a
backtrace might look like before this commit:
Breakpoint 1, 0x00000b46 in UART0_IRQHandler ()
(gdb) bt
#0 0x00000b46 in UART0_IRQHandler ()
#1 <signal handler called>
[..etc]
Notice that the debugger doesn't see the source code location where it
has stopped.
After this commit, breaking at the same line might look like this:
Breakpoint 1, (*machine.UART).handleInterrupt (arg1=..., uart=<optimized out>) at /home/ayke/src/github.com/tinygo-org/tinygo/src/machine/machine_nrf.go:200
200 uart.Receive(byte(nrf.UART0.RXD.Get()))
(gdb) bt
#0 (*machine.UART).handleInterrupt (arg1=..., uart=<optimized out>) at /home/ayke/src/github.com/tinygo-org/tinygo/src/machine/machine_nrf.go:200
#1 UART0_IRQHandler () at /home/ayke/src/github.com/tinygo-org/tinygo/src/device/nrf/nrf51.go:176
#2 <signal handler called>
[..etc]
By now, the debugger sees an actual source location for UART0_IRQHandler
(in the generated file) and an inlined function.
This commit has a few related changes:
* It sets the optsize attribute immediately in the compiler instead of
adding it to each function afterwards in a loop. This seems to me
like the more appropriate way to do it.
* It centralizes setting the optsize attribute in the transform
package, to make later changes easier.
* It sets the optsize in a few more places: to runtime.initAll and to
WebAssembly i64 wrappers.
This commit does not affect the binary size of any of the smoke tests,
so should be risk-free.
This commit adds object layout information to new heap allocations. It
is not yet used anywhere: the next commit will make use of it.
Object layout information will eventually be used for a (mostly) precise
garbage collector. This is what the data is made for. However, it is
also useful in the interp package which can work better if it knows the
memory layout and thus the approximate LLVM type of heap-allocated
objects.
This layout parameter is currently always nil and ignored, but will
eventually contain a pointer to a memory layout.
This commit also adds module verification to the transform tests, as I
found out that it didn't (and therefore didn't initially catch all
bugs).
This commit simplifies the IR a little bit: instead of calling
pseudo-functions runtime.interfaceImplements and
runtime.interfaceMethod, real declared functions are being called that
are then defined in the interface lowering pass. This should simplify
the interaction between various transformation passes. It also reduces
the number of lines of code, which is generally a good thing.
This adds support for a construct like this:
type foo func(fn foo)
Unfortunately, LLVM cannot create function pointers that look like this.
LLVM only supports named types for structs (not for pointers) and thus
can't add a pointer to a function type of the same type to a parameter
of that function type.
The fix is simple: cast all function pointers to a void function, in
LLVM IR:
void ()*
Raw function pointers are cast to this type before storing, and cast
back to the regular function type before calling. This means that
function parameters will never refer to its own type because raw
function types are fixed at that one type.
Somehow, this does have an effect on binary size in some cases. The
effect is small and goes both ways. On top of that, there is work
underway in LLVM which would make all pointer types opaque (without a
pointee type). This would make this whole commit useless and therefore
should fix any size increases that might happen.
https://llvm.org/docs/OpaquePointers.html
The division and remainder operations were lowered directly to LLVM IR.
This is wrong however because the Go specification defines exactly what
happens on a divide by zero or signed integer overflow and LLVM IR
itself treats those cases as undefined behavior. Therefore, this commit
implements divide by zero and signed integer overflow according to the
Go specification.
This does have an impact on the generated code, but it is surprisingly
small. I've used the drivers repo to test the code before and after, and
to my surprise most driver smoke tests are not changed at all. Those
that are, have only a small increase in code size. At the same time,
this change makes TinyGo more compliant to the Go specification.
This attribute is also set by Clang when it compiles C source files
(unless -fexceptions is set). The advantage is that no unwind tables are
emitted on Linux (and perhaps other systems). It also avoids
__aeabi_unwind_cpp_pr0 on ARM when using the musl libc.
For example, the following did not work before but does work with this
change:
// int add(int a, int b) {
// return a + b;
// }
import "C"
func main() {
println("add:", C.add(3, 5))
}
Even better, the functions in the header are compiled together with the
rest of the Go code and so they can be optimized together! Currently,
inlining is not yet allowed but const-propagation across functions
works. This should be improved in the future.
This is a loose collection of small fixes flagged by staticcheck:
- dead code
- regexp expressions not using backticks (`foobar` / "foobar")
- redundant types of slice and map initializers
- misc other fixes
Not all of these seem very useful to me, but in particular dead code is
nice to fix. I've fixed them all just so that if there are problems,
they aren't hidden in the noise of less useful issues.
For example, in this code:
type kv struct {
v float32
}
func foo(a *kv) {
type kv struct {
v byte
}
}
Both 'kv' types would be given the same LLVM type, even though they are
different types! This is fixed by only creating a LLVM type once per Go
type (types.Type).
As an added bonus, this change gives a performance improvement of about
0.4%. Not that much, but certainly not nothing for such a small change.
This commit improves make([]T, len) to be closer to upstream Go. The
difference is unlikely to have much real-world effect, but previously
certain make([]T, len) expressions would not result in a slice out of
bounds error in TinyGo while they would have done such a thing in Go
proper. In practice, available RAM is likely to be a bigger limiting
factor.
This commit adds support for the following packages:
- crypto/md5
- crypto/sha1
- crypto/sha256
- crypto/sha512
They would normally need assembly implementations, but with these
aliases they already work everywhere.
This makes them more flexible, especially with Go 1.17 making the
situation more complicated (see
1d20a362d0).
It also makes it possible to do the same for many other functions, such
as assembly implementations of cryptographich functions which are
similarly dependent on the architecture.
This patch adds a new pragma for functions and globals to set the
section name. This can be useful to place a function or global in a
special device specific section, for example:
* Functions may be placed in RAM to make them run faster, or in flash
(if RAM is the default) to not let them take up RAM.
* DMA memory may only be placed in a special memory area.
* Some RAM may be faster than other RAM, and some globals may be
performance critical thus placing them in this special RAM area can
help.
* Some (large) global variables may need to be placed in external RAM,
which can be done by placing them in a special section.
To use it, you have to place a function or global in a special section,
for example:
//go:section .externalram
var externalRAMBuffer [1024]byte
This can then be placed in a special section of the linker script, for
example something like this:
.bss.extram (NOLOAD) : {
*(.externalram)
} > ERAM
These pragmas weren't really tested anywhere, except that some code
might break if they are not properly applied.
These tests make it easy to see they work correctly and also provide a
logical place to add new pragma tests.
I've also made a slight change to how functions and globals are created:
with the change they're also created in the IR even if they're not
referenced. This makes testing easier.
This commit includes two changes:
* It makes unexported interface methods package-private, so that it's
not possible to type-assert on an unexported method in a different
package.
* It makes the globals used to identify interface methods defined
globals, so that they can (eventually) be left in the program for an
eventual non-LTO build mode.
Do not store the context parameter (which is used for closures and
function pointers) in the goroutine start parameter bundle for direct
functions that don't need a context parameter. This avoids storing the
(undef) context parameter and thus makes the IR to start a new goroutine
simpler in most cases.
This reduces code size in the channel.go and goroutines.go tests.
Surprisingly, all test cases (when compiled with -target=microbit) have
a changed binary, I haven't investigated why but I suppose the codegen
is slightly different for the runtime.run function (which starts the
main goroutine).
Closure variables are allocated in a parent function and are thus never
nil. Don't do a nil check before reading or modifying the value.
This commit results in a slight reduction in code size in some test
cases: calls.go, channel.go, goroutines.go, json.go, sort.go -
presumably wherever closures are used.
Move the code from the compiler.go file to the goroutine.go file, which
is a more appropriate place. This keeps all the goroutine related code
in one file, to make it easier to find.
With this is possible to enable e.g., SIMD in WASM using -llvm-features
+simd128. Multiple features can be specified separated by comma,
e.g., -llvm-features +simd128,+tail-call
With help from @deadprogram and @aykevl.
In many cases, position information is not stored in Go SSA instructions
because they don't exit directly in the source code. This includes
implicit type conversions, implicit returns at the end of a function,
the creation of a (hidden) slice when calling a variadic function, and
many other cases. I'm not sure where this information is supposed to
come from, but this patch takes the value (usually) from the value the
instruction refers to. This seems to work well for these implicit
conversions.
I've also added a few extra tests to the heap-to-stack transform pass,
of which one requires this improved position information.
There is no good reason for func values to refer to interface type
codes. The only thing they need is a stable identifier for function
signatures, which is easily created as a new kind of globals. Decoupling
makes it easier to change interface related code.
Some errors were generated but never returned or never checked in the
test function. That's a problem. Therefore this commit fixes this
oversight (by me).
This commit optimizes string literals and globals by setting the
appropriate alignment and using a nil pointer in zero-length strings.
- Setting the alignment for string values has a surprisingly large
effect, up to around 2% in binary size. I suspect that LLVM will
pick some default alignment for larger byte arrays if no alignment
has been specified and forcing an alignment of 1 will pack all
strings closer together.
- Using nil for zero-length strings also has a positive effect, but
I'm not sure why. Perhaps it makes some optimizations more trivial.
- Always setting the alignment on globals improves code size slightly,
probably for the same reasons setting the alignment of string
literals improves code size. The effect is much smaller, however.
This commit might have an effect on performance, but if it does this
should be tested separately and such a large win in binary size should
definitely not be ignored for small embedded systems.
Sometimes, LLVM may rename named structs when merging modules.
Therefore, we can't rely on typecodeID structs to retain their struct
names.
This commit changes the interface lowering pass to not rely on these
names. The interp package does however still rely on this name, but I
hope to fix that in the future.
This commit adds a new transform that converts reflect Implements()
calls to runtime.interfaceImplements. At the moment, the Implements()
method is not yet implemented (how ironic) but if the value passed to
Implements is known at compile time the method call can be optimized to
runtime.interfaceImplements to make it a regular interface assert.
This commit is the last change necessary to add basic support for the
encoding/json package. The json package is certainly not yet fully
supported, but some trivial objects can be converted to JSON.
Previously there was code to avoid impossible type asserts but it wasn't
great and in fact was too aggressive when combined with reflection.
This commit improves this by checking all types that exist in the
program that may appear in an interface (even struct fields and the
like) but without creating runtime.typecodeID objects with the type
assert. This has two advantages:
* As mentioned, it optimizes impossible type asserts away.
* It allows methods on types that were only asserted on (in
runtime.typeAssert) but never used in an interface to be optimized
away using GlobalDCE. This may have a cascading effect so that other
parts of the code can be further optimized.
This sometimes massively improves code size and mostly negates the code
size regression of the previous commit.
This distinction was useful before when reflect wasn't properly
supported. Back then it made sense to only include method sets that were
actually used in an interface. But now that it is possible to get to
other values (for example, by extracting fields from structs) and it is
possible to turn them back into interfaces, it is necessary to preserve
all method sets that can possibly be used in the program in a type
assert, interface assert or interface method call.
In the future, this logic will need to be revisited again when
reflect.New or reflect.Zero gets implemented.
Code size increases a bit in some cases, but usually in a very limited
way (except for one outlier in the drivers smoke tests). The next commit
will improve the situation significantly.
Previously we used the --export-all linker flag to export most
functions. However, this is not needed and possibly increases binary
size. Instead, we should be exporting the specific functions to be
exported.
This commit switches from the previous behavior of compiling the whole
program at once, to compiling every package in parallel and linking the
LLVM bitcode files together for further whole-program optimization.
This is a small performance win, but it has several advantages in the
future:
- There are many more things that can be done per package in parallel,
avoiding the bottleneck at the end of the compiler phase. This
should speed up the compiler futher.
- This change is a necessary step towards a non-LTO build mode for
fast incremental builds that only rebuild the changed package, when
compiler speed is more important than binary size.
- This change refactors the compiler in such a way that it will be
easier to inspect the IR for one package only. Inspecting this IR
will be very helpful for compiler developers.
The SimpleDCE pass was previously used to only compile the parts of the
program that were in use. However, lately the only real purpose has been
to speed up the compiler a bit by only compiling the necessary
functions.
This pass however is a problem for compiling (and caching) packages in
parallel. Therefore, this commit removes it as a preparatory step
towards that goal.
This is a leftover from a long time ago, when everything was still in
the global context. The fact that this uses the global context is most
certainly a bug.
I have seen occasional crashes in the build-packages-indepedently branch
(and PRs based on it) which I suspect are caused by this bug. I think
this is a long-dormant bug that only surfaced when doing the compilation
steps in parallel.
Moving settings to a separate config struct has two benefits:
- It decouples the compiler a bit from other packages, most
importantly the compileopts package. Decoupling is generally a good
thing.
- Perhaps more importantly, it precisely specifies which settings are
used while compiling and affect the resulting LLVM module. This will
be necessary for caching the LLVM module.
While it would have been possible to cache without this refactor, it
would have been very easy to miss a setting and thus let the
compiler work with invalid/stale data.
This fixes a longstanding TODO comment and similar to
https://github.com/tinygo-org/tinygo/pull/1593 it removes some code out
of the compiler.CompileProgram function that doesn't need to be there.
This is a small refactor to move code away from compiler.CompilePackage,
with the goal that compiler.CompilePackage will eventually be removed
entirely in favor of compiler.CompilePackage.
Since https://github.com/tinygo-org/tinygo/pull/1571 (in particular, the first
commit that sets the main package path), the main package is always named
"main". This makes the callMain() workaround in the runtime unnecessary and
allows directly calling the main.main function with a //go:linkname pragma.
