The compiler actually doesn't need any functional changes for this: Sema
does reification based on the tag indices of `std.builtin.Type` already!
So, no zig1.wasm update is necessary.
This change is necessary to disallow name clashes between fields and
decls on a type, which is a prerequisite of #9938.
Pointer subtraction on `void *` or function pointers is UB by the C
spec, but is permitted by GCC and Clang as an extension. So, avoid
crashing translate-c in such cases, and follow the extension behavior --
there's nothing else that could really be intended.
Implements the accepted proposal to introduce `@branchHint`. This
builtin is permitted as the first statement of a block if that block is
the direct body of any of the following:
* a function (*not* a `test`)
* either branch of an `if`
* the RHS of a `catch` or `orelse`
* a `switch` prong
* an `or` or `and` expression
It lowers to the ZIR instruction `extended(branch_hint(...))`. When Sema
encounters this instruction, it sets `sema.branch_hint` appropriately,
and `zirCondBr` etc are expected to reset this value as necessary. The
state is on `Sema` rather than `Block` to make it automatically
propagate up non-conditional blocks without special handling. If
`@panic` is reached, the branch hint is set to `.cold` if none was
already set; similarly, error branches get a hint of `.unlikely` if no
hint is explicitly provided. If a condition is comptime-known, `cold`
hints from the taken branch are allowed to propagate up, but other hints
are discarded. This is because a `likely`/`unlikely` hint just indicates
the direction this branch is likely to go, which is redundant
information when the branch is known at comptime; but `cold` hints
indicate that control flow is unlikely to ever reach this branch,
meaning if the branch is always taken from its parent, then the parent
is also unlikely to ever be reached.
This branch information is stored in AIR `cond_br` and `switch_br`. In
addition, `try` and `try_ptr` instructions have variants `try_cold` and
`try_ptr_cold` which indicate that the error case is cold (rather than
just unlikely); this is reachable through e.g. `errdefer unreachable` or
`errdefer @panic("")`.
A new API `unwrapSwitch` is introduced to `Air` to make it more
convenient to access `switch_br` instructions. In time, I plan to update
all AIR instructions to be accessed via an `unwrap` method which returns
a convenient tagged union a la `InternPool.indexToKey`.
The LLVM backend lowers branch hints for conditional branches and
switches as follows:
* If any branch is marked `unpredictable`, the instruction is marked
`!unpredictable`.
* Any branch which is marked as `cold` gets a
`llvm.assume(i1 true) [ "cold"() ]` call to mark the code path cold.
* If any branch is marked `likely` or `unlikely`, branch weight metadata
is attached with `!prof`. Likely branches get a weight of 2000, and
unlikely branches a weight of 1. In `switch` statements, un-annotated
branches get a weight of 1000 as a "middle ground" hint, since there
could be likely *and* unlikely *and* un-annotated branches.
For functions, a `cold` hint corresponds to the `cold` function
attribute, and other hints are currently ignored -- as far as I can tell
LLVM doesn't really have a way to lower them. (Ideally, we would want
the branch hint given in the function to propagate to call sites.)
The compiler and standard library do not yet use this new builtin.
Resolves: #21148
I don't recall why I put these checks here -- they aren't correct. We
can freely recreate a type even if its fields have changed, because we
are going to re-do all type resolution.
The only conditions for recreations are (a) the ZIR index must not be
lost and (b) the number of captures must be the same. These conditions
are permissible because if either is violated, we can guarantee that
analysis of a valid `zirStructDecl` (etc) will never reference this
type (since the ZIR index has just been tracked, and the captures have
just been created based on the ZIR).
Adds a corresponding test case.
Resolves: #21185
* Indices of referenced captures
* Line and column of `@src()`
The second point aligns with a reversal of the "incremental compilation"
section of https://github.com/ziglang/zig/issues/2029#issuecomment-645793168.
This reversal was already done as #17688 (46a6d50), with the idea to
push incremental compilation down the line. My proposal is to keep it as
comptime-known, and simply re-analyze uses of `@src()` whenever their
line/column change.
I think this decision is reasonable for a few reasons:
* The Zig compiler is quite fast. Occasionally re-analyzing a few
functions containing `@src()` calls is perfectly acceptable and won't
noticably impact update times.
* The system described by Andrew in #2029 is currently vaporware.
* The system described by Andrew in #2029 is non-trivial to implement.
In particular, it requires some way to have backends update a single
global in certain cases, without re-doing semantic analysis. There is
no other part of incremental compilation which requires this.
* Having `@src().line` be comptime-known is useful. For instance, #17688
was justified by broken Tracy integration because the source line
couldn't be comptime-known.
In a `memoized_call`, store how many backwards braches the call
performs. Add this to `sema.branch_count` when using a memoized call. If
this exceeds the quota, perform a non-memoized call to get a correct
"exceeded X backwards branches" error.
Also, do not memoize calls which do `@setEvalBranchQuota` or similar, as
this affects global state which must apply to the caller.
Change some eval branch quotas so that the compiler itself still builds correctly.
This commit manually changes a file in Aro which is automatically
generated. The sources which generate the file are not in this repo.
Upstream Aro should make the suitable changes on their end before the
next sync of Aro sources into the Zig repo.
This replaces the constant `Zir.Inst.Ref` tags (and the analagous tags
in `Air.Inst.Ref`, `InternPool.Index`) referring to types in
`std.builtin` with a ZIR instruction `extended(builtin_type(...))` which
instructs Sema to fetch such a type, effectively as if it were a
shorthand for the ZIR for `@import("std").builtin.xyz`.
Previously, this was achieved through constant tags in `Ref`. The
analagous `InternPool` indices began as `simple_type` values, and were
later rewritten to the correct type information. This system was kind of
brittle, and more importantly, isn't compatible with incremental
compilation of std, since incremental compilation relies on the ability
to recreate types at different indices when they change. Replacing the
old system with this instruction slightly increases the size of ZIR, but
it simplifies logic and allows incremental compilation to work correctly
on the standard library.
This shouldn't have a significant impact on ZIR size or compiler
performance, but I will take measurements in the PR to confirm this.
Without this, incremental updates which would change inferred error sets
fail, since they assume the IES is resolved and equals the old set,
resulting in false positive compile errors when e.g. coercing to an IES.
This function now has to allocate anyway to resolve references, so we
may as well just build the error bundle and check its length.
Also remove some unnecessary calls of this function for efficiency.
The old logic here had bitrotted, largely because there were some
incorrect `else` cases. This is now implemented correctly for all
current ZIR instructions. This prevents instructions being lost in
incremental updates, which is important for updates to be minimal.
Another big commit, sorry! This commit makes all fixes necessary for
incremental updates of the compiler itself (specifically, adding a
breakpoint to `zirCompileLog`) to succeed, at least on the frontend.
The biggest change here is a reform to how types are handled. It works
like this:
* When a type is first created in `zirStructDecl` etc, its namespace is
scanned. If the type requires resolution, an `interned` dependency is
declared for the containing `AnalUnit`.
* `zirThis` also declared an `interned` dependency for its `AnalUnit` on
the namespace's owner type.
* If the type's namespace changes, the surrounding source declaration
changes hash, so `zirStructDecl` etc will be hit again. We check
whether the namespace has been scanned this generation, and re-scan it
if not.
* Namespace lookups also check whether the namespace in question
requires a re-scan based on the generation. This is because there's no
guarantee that the `zirStructDecl` is re-analyzed before the namespace
lookup is re-analyzed.
* If a type's structure (essentially its fields) change, then the type's
`Cau` is considered outdated. When the type is re-analyzed due to
being outdated, or the `zirStructDecl` is re-analyzed by being
transitively outdated, or a corresponding `zirThis` is re-analyzed by
being transitively outdated, the struct type is recreated at a new
`InternPool` index. The namespace's owner is updated (but not
re-scanned, since that is handled by the mechanisms above), and the
old type, while remaining a valid `Index`, is removed from the map
metadata so it will never be found by lookups. `zirStructDecl` and
`zirThis` store an `interned` dependency on the *new* type.
When a type becomes outdated, there will still be lingering references
to the old index -- for instance, any declaration whose value was that
type holds a reference to that index. These references may live for an
arbitrarily long time in some cases. So, we can't just remove the type
from the pool -- the old `Index` must remain valid!
Instead, we want to preserve the old `Index`, but avoid it from ever
appearing in lookups. (It's okay if analysis of something referencing
the old `Index` does weird stuff -- such analysis are guaranteed by the
incremental compilation model to always be unreferenced.) So, we use the
new `InternPool.putKeyReplace` to replace the shard entry for this index
with the newly-created index.
An enum type is kind of like a struct or union type, in that field
errors are happening during type resolution. The only difference is that
type resolution happens at the time the type is created. So, errors in
fields should not cause the type to be deleted: we've already added a
reference entry, and incremenetal dependencies which must be invalidated
if the compile error is fixed. Once we call `WipEnumType.prepare`, we
should never call `WipEnumType.cancel`. This is analagous to logic for
enum declarations in `Sema.zirEnumDecl`.
Two fixes here.
* Prevent a crash when sorting the list of analysis errors when some
errors refer to lost source locations. These errors can be sorted
anywhere in the list, because they are (in theory) guaranteed to never
be emitted by the `resolveReferences` logic. This case occurs, for
instance, when a declaration has compile errors in the initial update
and is deleted in the second update.
* Prevent a crash when resolving the source location for `entire_file`
errors for a non-existent file. This is the bug underlying #20954.
Resolves: #20954.
This commit updates `Zcu.resolveReferences` to traverse the graph of
`AnalUnit` references (starting from the 1-3 roots of analysis) in order
to determine which `AnalUnit`s are referenced in an update. Errors for
unreferenced entities are omitted from the error bundle. However, note
that unreferenced `Nav`s are not removed from the binary.
This commit makes more progress towards incremental compilation, fixing
some crashes in the frontend. Notably, it fixes the regressions introduced
by #20964. It also cleans up the "outdated file root" mechanism, by
virtue of deleting it: we now detect outdated file roots just after
updating ZIR refs, and re-scan their namespaces.
Eliding the namespace when a container type has no decls was an
experiment in saving memory, but it ended up causing more trouble than
it was worth in various places. So, take the small memory hit for
reified types, and just give every container type a namespace.
The type `Zcu.Decl` in the compiler is problematic: over time it has
gained many responsibilities. Every source declaration, container type,
generic instantiation, and `@extern` has a `Decl`. The functions of
these `Decl`s are in some cases entirely disjoint.
After careful analysis, I determined that the two main responsibilities
of `Decl` are as follows:
* A `Decl` acts as the "subject" of semantic analysis at comptime. A
single unit of analysis is either a runtime function body, or a
`Decl`. It registers incremental dependencies, tracks analysis errors,
etc.
* A `Decl` acts as a "global variable": a pointer to it is consistent,
and it may be lowered to a specific symbol by the codegen backend.
This commit eliminates `Decl` and introduces new types to model these
responsibilities: `Cau` (Comptime Analysis Unit) and `Nav` (Named
Addressable Value).
Every source declaration, and every container type requiring resolution
(so *not* including `opaque`), has a `Cau`. For a source declaration,
this `Cau` performs the resolution of its value. (When #131 is
implemented, it is unsolved whether type and value resolution will share
a `Cau` or have two distinct `Cau`s.) For a type, this `Cau` is the
context in which type resolution occurs.
Every non-`comptime` source declaration, every generic instantiation,
and every distinct `extern` has a `Nav`. These are sent to codegen/link:
the backends by definition do not care about `Cau`s.
This commit has some minor technically-breaking changes surrounding
`usingnamespace`. I don't think they'll impact anyone, since the changes
are fixes around semantics which were previously inconsistent (the
behavior changed depending on hashmap iteration order!).
Aside from that, this changeset has no significant user-facing changes.
Instead, it is an internal refactor which makes it easier to correctly
model the responsibilities of different objects, particularly regarding
incremental compilation. The performance impact should be negligible,
but I will take measurements before merging this work into `master`.
Co-authored-by: Jacob Young <jacobly0@users.noreply.github.com>
Co-authored-by: Jakub Konka <kubkon@jakubkonka.com>
This eliminates the statically-reachable recursion loop between code
generation backends and Sema. This is beneficial for optimizers
(although I do not measure any performance improvement for this change),
and for profilers.
Note that the `_ = Address` statements in tests previously were a nop,
and now actually check that the type is valid. However, on WASI, the
type is *not* valid.
I'm so sorry.
This commit was just meant to be making all types fully resolve by
queueing resolution at the moment of their creation. Unfortunately, a
lot of dominoes ended up falling. Here's what happened:
* I added a work queue job to fully resolve a type.
* I realised that from here we could eliminate `Sema.types_to_resolve`
if we made function codegen a separate job. This is desirable for
simplicity of both spec and implementation.
* This led to a new AIR traversal to detect whether any required type is
unresolved. If a type in the AIR failed to resolve, then we can't run
codegen.
* Because full type resolution now occurs by the work queue job, a bug
was exposed whereby error messages for type resolution were associated
with the wrong `Decl`, resulting in duplicate error messages when the
type was also resolved "by" its owner `Decl` (which really *all*
resolution should be done on).
* A correct fix for this requires using a different `Sema` when
performing type resolution: we need a `Sema` owned by the type. Also
note that this fix is necessary for incremental compilation.
* This means a whole bunch of functions no longer need to take `Sema`s.
* First-order effects: `resolveTypeFields`, `resolveTypeLayout`, etc
* Second-order effects: `Type.abiAlignmentAdvanced`, `Value.orderAgainstZeroAdvanced`, etc
The end result of this is, in short, a more correct compiler and a
simpler language specification. This regressed a few error notes in the
test cases, but nothing that seems worth blocking this change.
Oh, also, I ripped out the old code in `test/src/Cases.zig` which
introduced a dependency on `Compilation`. This dependency was
problematic at best, and this code has been unused for a while. When we
re-enable incremental test cases, we must rewrite their executor to use
the compiler server protocol.
This change modifies `Zcu.ErrorMsg` to store a `Zcu.LazySrcLoc` rather
than a `Zcu.SrcLoc`. Everything else is dominoes.
The reason for this change is incremental compilation. If a failed
`AnalUnit` is up-to-date on an update, we want to re-use the old error
messages. However, the file containing the error location may have been
modified, and `SrcLoc` cannot survive such a modification. `LazySrcLoc`
is designed to be correct across incremental updates. Therefore, we
defer source location resolution until `Compilation` gathers the compile
errors into the `ErrorBundle`.
Previously, `reference_table` mapped from a `Decl` being referenced to
the `Decl` that performed the reference. This is convenient for
constructing error messages, but problematic for incremental
compilation. This is because on an incremental update, we want to
efficiently remove all references triggered by an `AnalUnit` which is
being re-analyzed.
For this reason, `reference_table` now maps the other way: from the
`AnalUnit` *performing* the reference, to the `AnalUnit` whose analysis
was triggered. As a general rule, any call to any of the following
functions should be preceded by a call to `Sema.addReferenceEntry`:
* `Zcu.ensureDeclAnalyzed`
* `Sema.ensureDeclAnalyzed`
* `Zcu.ensureFuncBodyAnalyzed`
* `Zcu.ensureFuncBodyAnalysisQueued`
This is not just important for error messages, but also more
fundamentally for incremental compilation. When an incremental update
occurs, we must determine whether any `AnalUnit` has become
unreferenced: in this case, we should ignore its associated error
messages, and perhaps even remove it from the binary. For this reason,
we no longer store only one reference to every `AnalUnit`, but every
reference. At the end of an update, `Zcu.resolveReferences` will
construct the reverse mapping, and as such identify which `AnalUnit`s
are still referenced. The current implementation doesn't quite do what
we need for incremental compilation here, but the framework is in place.
Note that `Zcu.resolveReferences` does constitute a non-trivial amount
of work on every incremental update. However, for incremental
compilation, this work -- which will effectively be a graph traversal
over all `AnalUnit` references -- seems strictly necessary. At the
moment, this work is only done if the `Zcu` has any errors, when
collecting them into the final `ErrorBundle`.
An unsolved problem here is how to represent inline function calls in
the reference trace. If `foo` performs an inline call to `bar` which
references `qux`, then ideally, `bar` would be shown on the reference
trace between `foo` and `qux`, but this is not currently the case. The
solution here is probably for `Zcu.Reference` to store information about
the source locations of active inline calls betweeen the referencer and
its reference.
This change seeks to more appropriately model the way semantic analysis
works by drawing a more clear line between errors emitted by analyzing a
`Decl` (in future a `Cau`) and errors emitted by analyzing a runtime
function.
This does change a few compile errors surrounding compile logs by adding
more "also here" notes. The new notes are more technically correct, but
perhaps not so helpful. They're not doing enough harm for me to put
extensive thought into this for now.
This commit reworks our representation of exported Decls and values in
Zcu to be memory-optimized and trivially serialized.
All exports are now stored in the `all_exports` array on `Zcu`. An
`AnalUnit` which performs an export (either through an `export`
annotation or by containing an analyzed `@export`) gains an entry into
`single_exports` if it performs only one export, or `multi_exports` if
it performs multiple.
We no longer store a persistent mapping from a `Decl`/value to all
exports of that entity; this state is not necessary for the majority of
the pipeline. Instead, we construct it in `Zcu.processExports`, just
before flush. This does not affect the algorithmic complexity of
`processExports`, since this function already iterates all exports in
the `Zcu`.
The elimination of `decl_exports` and `value_exports` led to a few
non-trivial backend changes. The LLVM backend has been wrangled into a
more reasonable state in general regarding exports and externs. The C
backend is currently disabled in this commit, because its support for
`export` was quite broken, and that was exposed by this work -- I'm
hoping @jacobly0 will be able to pick this up!
This is essentially just a rename. I also changed the representation of
`AnalSubject` to use a `packed struct` rather than a non-exhaustive
enum, but that change is relatively trivial.
LLVM fails to notice that in release builds, `logFn` ignores its
arguments, so their computation can be elided. So, LLVM fails to elide
this hashmap lookup. Its cost isn't too significant, but doing it in the
hottest loop in Sema adds up!
Technically, we could do the lookup a single time, before the loop, but
it was cleanest (and a little faster) to just disable this log call at
comptime when debug logging is disabled.
Since we track `reify` instructions across incremental updates, it is
acceptable to treat it as the baseline for a relative source location.
This turns out to be a good idea, since it makes it easy to define the
source location for a reified type.
When analyzing `zirFunc` to instantiate a generic function,
`sema.owner_decl` is not the owner Decl of the generic instance, but
instead of the call site, so that dependencies are propagated correctly.
(This aligns with the fact that in future, generic instantiations will
not have a corresponding `Cau`.) So, when deciding the callconv in this
case, we must check `sema.generic_owner` to determine whether the
function is exported.
🦀 src_decl is gone 🦀
This commit eliminates the `src_decl` field from `Sema.Block`. This
change goes further to eliminating unnecessary responsibilities of
`Decl` in preparation for its major upcoming refactor.
The two main remaining reponsibilities had to do with namespace types:
`src_decl` was used to determine their line number and their name. The
former use case is solved by storing the line number alongside type
declarations (and reifications) in ZIR; this is actually more correct,
since previously the line number assigned to the type was really the
line number of the source declaration it was syntactically contained
within, which does not necessarily line up. Consequently, this change
makes debug info for namespace types more correct, although I am not
sure how debuggers actually utilize this line number, if at all. Naming
types was solved by a new field on `Block`, called `type_name_ctx`. In a
sense, it represents the "namespace" we are currently within, including
comptime function calls etc. We might want to revisit this in future,
since the type naming rules seem to be a bit hand-wavey right now.
As far as I can tell, there isn't any more preliminary work needed for
me to start work on the behemoth task of splitting `Zcu.Decl` into the
new `Nav` (Named Addressable Value) and `Cau` (Comptime Analysis Unit)
types. This will be a sweeping change, impacting essentially every part
of the pipeline after `AstGen`.
`LazySrcLoc` now stores a reference to the "base AST node" to which it
is relative. The previous tagged union is `LazySrcLoc.Offset`. To make
working with this structure convenient, `Sema.Block` contains a
convenience `src` method which takes an `Offset` and returns a
`LazySrcLoc`.
The "base node" of a source location is no longer given by a `Decl`, but
rather a `TrackedInst` representing either a `declaration`,
`struct_decl`, `union_decl`, `enum_decl`, or `opaque_decl`. This is a
more appropriate model, and removes an unnecessary responsibility from
`Decl` in preparation for the upcoming refactor which will split it into
`Nav` and `Cau`.
As a part of these `Decl` reworks, the `src_node` field is eliminated.
This change aids incremental compilation, and simplifies `Decl`. In some
cases -- particularly in backends -- the source location of a
declaration is desired. This was previously `Decl.srcLoc` and worked for
any `Decl`. Now, it is `Decl.navSrcLoc` in reference to the upcoming
refactor, since the set of `Decl`s this works for precisely corresponds
to what will in future become a `Nav` -- that is, source-level
declarations and generic function instantiations, but *not* type owner
Decls.
This commit introduces more tags to `LazySrcLoc.Offset` so as to
eliminate the concept of `error.NeededSourceLocation`. Now, `.unneeded`
should only be used to assert that an error path is unreachable. In the
future, uses of `.unneeded` can probably be replaced with `undefined`.
The `src_decl` field of `Sema.Block` no longer has a role in type
resolution. Its main remaining purpose is to handle namespacing of type
names. It will be eliminated entirely in a future commit to remove
another undue responsibility from `Decl`.
It is worth noting that in future, the `Zcu.SrcLoc` type should probably
be eliminated entirely in favour of storing `Zcu.LazySrcLoc` values.
This is because `Zcu.SrcLoc` is not valid across incremental updates,
and we want to be able to reuse error messages from previous updates
even if the source file in question changed. The error reporting logic
should instead simply resolve the location from the `LazySrcLoc` on the
fly.
This is in preparation for some upcoming changes to how we represent
source locations in the compiler. The bulk of the change here is dealing
with the removal of `src()` methods from `Zir` types.
The justification for using relative source nodes in ZIR is that it
allows source locations -- which may be serialized across incremental
updates -- to be relative to the source location of their containing
declaration. However, having those "baseline" instructions themselves be
relative to their own parent is counterproductive, since the source
location updating problem is only being moved to `Decl`. Storing the
absolute node here instead makes more sense, since it allows for this
source location update logic to be elided entirely in the future by
storing a `TrackedInst.Index` to resolve a source location relative to
rather than a `Decl.Index`.
These instructions are not emitted by AstGen. They also would have no
effect even if they did appear in ZIR: the Sema handling for these
instructions creates a Decl which the name strategy is applied to, and
proceeds to never use it. This pointless CPU heater is now gone, saving
2 ZIR tags in the process.
* correctly report time spent analyzing function bodies
* print fully qualified decl names
* also have a progress node for codegen
The downside of these changes is that it's a bit flickerey, but the
upside is that it's accurate; you can see what the compiler's doing!
This fix is already in master branch for stdin, stdout, and stderr; this
commit solves the same problem but for the progress pipe.
Both fixes were originally included in one commit on this branch,
however it was split it into two so that master branch could receive the
fix before the progress branch is merged.
The added comment explains the issue here relatively well. The new
progress API made this bug obvious because it became visibly clear that
certain Compile steps were seemingly "hanging" until other steps
completed. As it turned out, these child processes had raced to spawn,
and hence one had inherited the other's stdio pipes, meaning the `poll`
call in `std.Build.Step.evalZigProcess` was not identifying the child
stdout as closed until an unrelated process terminated.
mlugg