This commit changes how we represent comptime-mutable memory
(`comptime var`) in the compiler in order to implement the intended
behavior that references to such memory can only exist at comptime.
It does *not* clean up the representation of mutable values, improve the
representation of comptime-known pointers, or fix the many bugs in the
comptime pointer access code. These will be future enhancements.
Comptime memory lives for the duration of a single Sema, and is not
permitted to escape that one analysis, either by becoming runtime-known
or by becoming comptime-known to other analyses. These restrictions mean
that we can represent comptime allocations not via Decl, but with state
local to Sema - specifically, the new `Sema.comptime_allocs` field. All
comptime-mutable allocations, as well as any comptime-known const allocs
containing references to such memory, live in here. This allows for
relatively fast checking of whether a value references any
comptime-mtuable memory, since we need only traverse values up to
pointers: pointers to Decls can never reference comptime-mutable memory,
and pointers into `Sema.comptime_allocs` always do.
This change exposed some faulty pointer access logic in `Value.zig`.
I've fixed the important cases, but there are some TODOs I've put in
which are definitely possible to hit with sufficiently esoteric code. I
plan to resolve these by auditing all direct accesses to pointers (most
of them ought to use Sema to perform the pointer access!), but for now
this is sufficient for all realistic code and to get tests passing.
This change eliminates `Zcu.tmp_hack_arena`, instead using the Sema
arena for comptime memory mutations, which is possible since comptime
memory is now local to the current Sema.
This change should allow `Decl` to store only an `InternPool.Index`
rather than a full-blown `ty: Type, val: Value`. This commit does not
perform this refactor.
This commit eliminates the `dbg_block_{begin,end}` instructions from
both ZIR and AIR. Instead, lexical scoping of `dbg_var_{ptr,val}`
instructions is decided based on the AIR block they exist within. This
is a much more robust system, and also results in a huge drop in ZIR
bytes - around 7% for Sema.zig.
This required some enhancements to Sema to prevent elision of blocks
when they are required for debug variable scoping. This can be observed
by looking at the AIR for the following simple test program with and
without `-fstrip`:
```zig
export fn f() void {
{
var a: u32 = 0;
_ = &a;
}
{
var a: u32 = 0;
_ = &a;
}
}
```
When `-fstrip` is passed, no AIR blocks are generated. When `-fno-strip`
is passed, the ZIR blocks are lowered to true AIR blocks to give correct
lexical scoping to the debug vars.
The changes here incidentally reolve #19060. A corresponding behavior
test has been added.
Resolves: #19060
Introduce the concept of "target query" and "resolved target". A target
query is what the user specifies, with some things left to default. A
resolved target has the default things discovered and populated.
In the future, std.zig.CrossTarget will be rename to std.Target.Query.
Introduces `std.Build.resolveTargetQuery` to get from one to the other.
The concept of `main_mod_path` is gone, no longer supported. You have to
put the root source file at the module root now.
* remove deprecated API
* update build.zig for the breaking API changes in this branch
* move std.Build.Step.Compile.BuildId to std.zig.BuildId
* add more options to std.Build.ExecutableOptions, std.Build.ObjectOptions,
std.Build.SharedLibraryOptions, std.Build.StaticLibraryOptions, and
std.Build.TestOptions.
* remove `std.Build.constructCMacro`. There is no use for this API.
* deprecate `std.Build.Step.Compile.defineCMacro`. Instead,
`std.Build.Module.addCMacro` is provided.
- remove `std.Build.Step.Compile.defineCMacroRaw`.
* deprecate `std.Build.Step.Compile.linkFrameworkNeeded`
- use `std.Build.Module.linkFramework`
* deprecate `std.Build.Step.Compile.linkFrameworkWeak`
- use `std.Build.Module.linkFramework`
* move more logic into `std.Build.Module`
* allow `target` and `optimize` to be `null` when creating a Module.
Along with other fields, those unspecified options will be inherited
from parent `Module` when inserted into an import table.
* the `target` field of `addExecutable` is now required. pass `b.host`
to get the host target.
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
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`.
fixes#10731
Thanks @nektro for previous work in #14878
This change creates a small breaking change:
It removes the `is_pub` field of a decl in `@typeInfo`
Most of this migration was performed automatically with `zig fmt`. There
were a few exceptions which I had to manually fix:
* `@alignCast` and `@addrSpaceCast` cannot be automatically rewritten
* `@truncate`'s fixup is incorrect for vectors
* Test cases are not formatted, and their error locations change
