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 is the kind that is used in Go (actually CGo) for exporting
functions. I think it's best to use //export instead of our custom
//go:export pragma, for consistency (they are equivalent in TinyGo).
Therefore I've updated all instances to the standard format (except for
two that are updated in https://github.com/tinygo-org/tinygo/pull/1024).
No smoke tests changed (when comparing the output hash), except for some
wasm tests that include DWARF debug info and tend to be flaky anyway.
Previously, the compiler used LLVM's shift instructions directly, which have UB whenever the shifts are large or negative.
This commit adds runtime checks for negative shifts, and handles oversized shifts.
This hack was originally introduced in
https://github.com/tinygo-org/tinygo/pull/251 to fix an escape analysis
regression after https://github.com/tinygo-org/tinygo/pull/222
introduced nil checks. Since a new optimization in LLVM (see
https://reviews.llvm.org/D60047) this hack is not necessary anymore and
can be removed.
I've compared all regular tests and smoke tests before and after to
check the size. In most cases this change was an improvement although
there are a few regressions.
This patch is a combination of two related changes:
1. The compiler now allows other types than `int` when specifying the
size of a channel in a make(chan ..., size) call.
2. The compiler now checks for maximum allowed channel sizes. Such
checks are trivially optimized out in the vast majority of cases as
channel sizes are usually constant.
I discovered this issue when trying out channels on AVR.
This commit implements nil checks for all platforms. These nil checks
can be optimized on systems with a MMU, but since a major target is
systems without MMU, keep it this way for now.
It implements three checks:
* Nil checks before dereferencing a pointer.
* Nil checks before calculating an address (*ssa.FieldAddr and
*ssa.IndexAddr)
* Nil checks before calling a function pointer.
The first check has by far the biggest impact, with around 5% increase
in code size. The other checks only trigger in only some test cases and
have a minimal impact on code size.
This first nil check is also the one that is easiest to avoid on systems
with MMU, if necessary.
Without this, the following code would not panic:
func getInt(i int) { return i }
make([][1<<18], getInt(1<<18))
Or this code would be allowed to compile for 32-bit systems:
make([][1<<18], 1<<18)
Previously, this would have resulted in a LLVM verification error
because runtime.sliceBoundsCheckMake would not accept 64-bit integers on
these platforms.
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
* Use 64-bit integers on 64-bit platforms, just like gc and gccgo:
https://golang.org/doc/go1.1#int
* Do not use a separate length type. Instead, use uintptr everywhere a
length is expected.
When doing a slice operation on a slice, use the capacity value instead
of the length. Of course, for strings and arrays, the slice operation
checks the length because there is no capacity. But according to the
spec, this check should be based on cap for slice instead of len:
> For slices, the upper index bound is the slice capacity cap(a) rather
> than the length.
https://golang.org/ref/spec#Slice_expressions
Fixes: https://github.com/aykevl/tinygo/issues/65
It is allowed to index with an int64 even on a 32-bit platform, so we
have to handle that case. But make sure the normal case isn't penalized
by using 32-bit numbers when possible.
This specifically fixes unix alloc(): previously when allocation fails
it would (recursively) call alloc() again to create an interface due to
lacking escape analysis.
Also, all other cases shouldn't try to allocate just because something
bad happens at runtime.
TODO: implement escape analysis.
Ayke van Laethem
Jaden Weiss