`switch` statements on types >128bits are now lowered to conditionals.
This is necessary because Zig lowers integers with more than 128 bits to
bigints, which are not 'native' integers and thus cannot be used as case
values.
128-bit integers get special treatment because Zig will emit actual 128bit
ints if they are supported by the target. They still *may* be lowered to
bigints though, e.g. for 32-bit targets or MSVC. To solve this, this commit
adds a bunch of switch macros to `zig.h` which will either resolve to an
actual `switch` statement or to conditionals. The `if` statements this
approach can generate are not as optimal as they could be but I think this
is a good trade-off since the generated `switch` statements are still the
same as the ones generated for smaller integers. Also the macros result
in pretty readable code.
The goal of these changes is to allow the C backend to support the new
lazier type resolution system implemented by the frontend. This required
a full rewrite of the `CType` abstraction, and major changes to the C
backend "linker".
The `DebugConstPool` abstraction introduced in a previous commit turns
out to be useful for the C backend to codegen types. Because this use
case is not debug information but rather general linking (albeit when
targeting an unusual object format), I have renamed the abstraction to
`ConstPool`. With it, the C linker is told when a type's layout becomes
known, and can at that point generate the corresponding C definitions,
rather than deferring this work until `flush`.
The work done in `flush` is now more-or-less *solely* focused on
collecting all of the buffers into a big array for a vectored write.
This does unfortunately involve a non-trivial graph traversal to emit
type definitions in an appropriate order, but it's still quite fast in
practice, and it operates on fairly compact dependency data. We don't
generate the actual type *definitions* in `flush`; that happens during
compilation using `ConstPool` as discussed above. (We do generate the
typedefs for underaligned types in `flush`, but that's a trivial amount
of work in most cases.)
`CType` is now an ephemeral type: it is created only when we render a
type (the logic for which has been pushed into just 2 or 3 functions in
`codegen.c`---most of the backend now operates on unmolested Zig `Type`s
instead). C types are no longer stored in a "pool", although the type
"dependencies" of generated C code (that is, the struct, unions, and
typedefs which the generated code references) are tracked (in some
simple hash sets) and given to the linker so it can codegen the types.
It turns out we did use these in the C backend. However, it's really
just as easy, if not easier, to replicate the logic directly in C.
Synchronizes stage1/zig.h to make sure the bootstrap doesn't depend on
these functions either. The actual zig1 tarball is unmodified because
regenerating it is unnecessary in this instance.
As with Solaris (dba1bf9353), we have no way to
actually audit contributions for these OSs. IBM also makes it even harder than
Oracle to actually obtain these OSs.
closes#23695closes#23694closes#3655closes#23693
This was causing a zig2 miscomp, which emitted slightly broken debug
information, which caused extremely slow stack unwinding. We're working
on fixing or reporting this upstream, but we can use this workaround for
now, because GCC guarantees arithmetic signed shift.
This is a stupid Clang-ism:
❯ cat test.c
int main() {
int value = 42;
int const *value_ptr = &value;
int location;
__atomic_store(&location, value_ptr, __ATOMIC_SEQ_CST);
}
❯ gcc test.c -fsyntax-only
❯ clang test.c -fsyntax-only
test.c:5:31: warning: passing 'const int *' to parameter of type 'int *' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers]
5 | __atomic_store(&location, value_ptr, __ATOMIC_SEQ_CST);
| ^~~~~~~~~
1 warning generated.
I have no idea why Clang doesn't define these builtins as taking const pointers
for the parameters that are only read from. Anyway, after the next zig1.wasm
update, this change should shut up these warnings that we've been seeing in CI
during bootstrap for ages.
If present, these headers are usable even when compiling for older C language
versions.
Most notably, this enables zig.h atomics to work with slimcc and TinyCC in C99
mode (and earlier).
* Make it work for thumb and aarch64.
* Clean up std.os.windows.teb() a bit.
I also updated stage1/zig.h since the changes are backwards-compatible and are
necessary due to the std.os.windows changes that call the newly-added functions.
This was causing zig2.exe to crash during bootstrap, because there was an atomic
load of read-only memory, and the attempt to write to it as part of the (idempotent)
atomic exchange was invalid.
Aligned reads (of u32 / u64) are atomic on x86 / x64, so this is replaced with an
optimization-proof load (`__iso_volatile_load8*`) and a reordering barrier.
This reverts commit a7de02e052.
This did not implement the accepted proposal, and I did not sign off
on the changes. I would like a chance to review this, please.
Sam Connelly