SPIR-V doesn't support true element indexing, so we probably
need to switch over to isByRef like in llvm for this to work
properly. Currently a temporary is used, which at least
seems to work.
This was previously implemented by analyzing the AIR prior to the ZIR
`make_ptr_const` instruction. This solution was highly delicate, and in
particular broke down whenever there was a second `alloc` between the
`store` and `alloc` instructions, which is especially common in
destructure statements.
Sema now uses a different strategy to detect whether a `const` is
comptime-known. When the `alloc` is created, Sema begins tracking all
pointers and stores which refer to that allocation in temporary local
state. If any store is not comptime-known or has a higher runtime index
than the allocation, the allocation is marked as being runtime-known.
When we reach the `make_ptr_const` instruction, if the allocation is not
marked as runtime-known, it must be comptime-known. Sema will use the
set of `store` instructions to re-initialize the value in comptime
memory. We optimize for the common case of a single `store` instruction
by not creating a comptime alloc in this case, instead directly plucking
the result value from the instruction.
Resolves: #16083
This changeset fixes the handling of alignment in several places. The
new rules are:
* `@alignOf(T)` where `T` is a runtime zero-bit type is at least 1,
maybe greater.
* Zero-bit fields in `extern` structs *do* force alignment, potentially
offsetting following fields.
* Zero-bit fields *do* have addresses within structs which can be
observed and are consistent with `@offsetOf`.
These are not necessarily all implemented correctly yet (see disabled
test), but this commit fixes all regressions compared to master, and
makes one new test pass.
Currently, the compiler (like @typeName) writes it `fn(...) Type` but
zig fmt writes it `fn (...) Type` (notice the space after `fn`).
This inconsistency is now resolved and function types are consistently
written the zig fmt way. Before this there were more `fn (...) Type`
occurrences than `fn(...) Type` already.
Safety is not a global flag that should be enabled or disabled for all
stores - it's lowered by the frontend directly into AIR instruction
semantics. The flag for this is communicated via the `store` vs
`store_safe` AIR instructions, and whether to write 0xaa bytes or not
should be decided in `airStore` and passed down via function parameters.
This commit is a step backwards since it removes functionality but it
aims our feet towards a better mountain to climb.
C99 introduced designated initializers for structs. Omitted fields are
implicitly initialized to zero. Some C APIs are designed with this in
mind. Defaulting to zero values for translated struct fields permits Zig
code to comfortably use such an API.
Closes#8165
This introduces the concept of a "weak global name" into translate-c.
translate-c consists of two passes. The first is important, because it
discovers all global names, which are used to prevent naming conflicts:
whenever we see an identifier in the second pass, we can mangle it if it
conflicts with any global or any other in-scope identifier.
Unfortunately, this is a bit tricky for structs, unions, and enums. In
C, these types are not represented by normal identifers, but by separate
tags - `struct foo` does not prevent an unrelated identifier `foo`
existing. In general, we want to translate type names to user-friendly
ones such as `struct_foo` and `foo` where possible, but we can't
guarantee such names will not conflict with real variable names.
This is where weak global names come in. In the initial pass, when a
global type declaration is seen, `struct_foo` and `foo` are both added
as weak global names. This essentially means that we will use these
names for the type *if possible*, but if there is another global with
the same name, we will mangle the type name instead. Then, when actually
translating the declaration, we check whether there's a "true" global
with a conflicting name, in which case we mangle our name. If the
user-friendly alias `foo` conflicts, we do not attempt to mangle it: we
just don't emit it, because a mangled alias isn't particularly helpful.
Consider this C macro:
```c
#define FOO(x) struct x
```
Previously, translate-c did not detect that the `x` in the body referred
to the argument, so wrongly translated this code as using the
nonexistent `struct_x`. Since undefined identifiers are noticed in
AstGen, this prevents the translated file from being usable at all.
translate-c now instead detects this case and emits an appropriate
compile error in the macro's place.
AstGen emits an error when a closure over a known-runtime value crosses
a namespace boundary. This usually makes sense: however, this usage is
actually valid if the capture is within a `@TypeOf` operand. Sema
already has a special case to allow such closure within `@TypeOf` when
AstGen could not determine a value to be runtime-known. This commit
simply introduces analagous logic to AstGen to allow `var`s to cross
namespace boundaries within `@TypeOf`.
This is supposed to be the case, similar to how pointers to generic
functions are comptime-only (several pieces of logic already assumed
this). These types being considered runtime was causing `dbg_var_val`
AIR instructions to be wrongly emitted for such values, causing codegen
backends to create a runtime reference to the inline function, which (at
least on the LLVM backend) triggers an error.
Resolves: #38
This change implements the following syntax into the compiler:
```zig
const x: u32, var y, foo.bar = .{ 1, 2, 3 };
```
A destructure expression may only appear within a block (i.e. not at
comtainer scope). The LHS consists of a sequence of comma-separated var
decls and/or lvalue expressions. The RHS is a normal expression.
A new result location type, `destructure`, is used, which contains
result pointers for each component of the destructure. This means that
when the RHS is a more complicated expression, peer type resolution is
not used: each result value is individually destructured and written to
the result pointers. RLS is always used for destructure expressions,
meaning every `const` on the LHS of such an expression creates a true
stack allocation.
Aside from anonymous array literals, Sema is capable of destructuring
the following types:
* Tuples
* Arrays
* Vectors
A destructure may be prefixed with the `comptime` keyword, in which case
the entire destructure is evaluated at comptime: this means all `var`s
in the LHS are `comptime var`s, every lvalue expression is evaluated at
comptime, and the RHS is evaluated at comptime. If every LHS is a
`const`, this is not allowed: as with single declarations, the user
should instead mark the RHS as `comptime`.
There are a few subtleties in the grammar changes here. For one thing,
if every LHS is an lvalue expression (rather than a var decl), a
destructure is considered an expression. This makes, for instance,
`if (cond) x, y = .{ 1, 2 };` valid Zig code. A destructure is allowed
in almost every context where a standard assignment expression is
permitted. The exception is `switch` prongs, which cannot be
destructures as the comma is ambiguous with the end of the prong.
A follow-up commit will begin utilizing this syntax in the Zig compiler.
Resolves: #498
The `coerce_result_ptr` instruction is highly problematic and leads to
unintentional memory reinterpretation in some cases. It is more correct
to simply not forward result pointers through this builtin.
`coerce_result_ptr` is still used for struct and array initializations,
where it can still cause issues. Eliminating this usage will be a future
change.
Resolves: #16991
