In the best case, this is redundant work, because we aren't actually
going to emit a working binary this update. In the worst case, it causes
bugs because the linker may not have *seen* the thing being exported due
to the compile errors.
Resolves: #24417
This commit expands on the foundations laid by https://github.com/ziglang/zig/pull/23177
and moves even more `Sema`-only functionality from `Value`
to `Sema.arith`. Specifically all shift and bitwise operations,
`@truncate`, `@bitReverse` and `@byteSwap` have been moved and
adapted to the new rules around `undefined`.
Especially the comptime shift operations have been basically
rewritten, fixing many open issues in the process.
New rules applied to operators:
* `<<`, `@shlExact`, `@shlWithOverflow`, `>>`, `@shrExact`: compile error if any operand is undef
* `<<|`, `~`, `^`, `@truncate`, `@bitReverse`, `@byteSwap`: return undef if any operand is undef
* `&`, `|`: Return undef if both operands are undef, turn undef into actual `0xAA` bytes otherwise
Additionally this commit canonicalizes the representation of
aggregates with all-undefined members in the `InternPool` by
disallowing them and enforcing the usage of a single typed
`undef` value instead. This reduces the amount of edge cases
and fixes a bunch of bugs related to partially undefined vecs.
List of operations directly affected by this patch:
* `<<`, `<<|`, `@shlExact`, `@shlWithOverflow`
* `>>`, `@shrExact`
* `&`, `|`, `~`, `^` and their atomic rmw + reduce pendants
* `@truncate`, `@bitReverse`, `@byteSwap`
If both are used, 'else' handles named members and '_' handles
unnamed members. In this case the 'else' prong will be unrolled
to an explicit case containing all remaining named values.
Mainly affects ZIR representation of switch_block[_ref]
and special prong (detection) logic for switch.
Adds a new SpecialProng tag 'absorbing_under' that allows
specifying additional explicit tags in a '_' prong which
are respected when checking that every value is handled
during semantic analysis but are not transformed into AIR
and instead 'absorbed' by the '_' branch.
The rejection of #6025 indicates that if stackless coroutines return to
Zig, they will look quite different; see #23446 for the working draft
proposal for their return (though it will definitely be tweaked before
being accepted). Some of this test coverage was deleted in 40d11cc, but
because stackless coroutines will take on a new form if re-introduced, I
anticipate that essentially *none* of this coverage will be relevant. Of
course, if it for some reason is, we can always grab it from the Git
history.
Basically everything that has a direct replacement or no uses left.
Notable omissions:
- std.ArrayHashMap: Too much fallout, needs a separate cleanup.
- std.debug.runtime_safety: Too much fallout.
- std.heap.GeneralPurposeAllocator: Lots of references to it remain, not
a simple find and replace as "debug allocator" is not equivalent to
"general purpose allocator".
- std.io.Reader: Is being reworked at the moment.
- std.unicode.utf8Decode(): No replacement, needs a new API first.
- Manifest backwards compat options: Removal would break test data used
by TestFetchBuilder.
- panic handler needs to be a namespace: Many tests still rely on it
being a function, needs a separate cleanup.
Also remove `@frameSize`, closing #3654.
While the other machinery might remain depending on #23446, it is
settled that there will not be `async`/ `await` keywords in the
language.
This safety check was completely broken; it triggered unchecked illegal
behavior *in order to implement the safety check*. You definitely can't
do that! Instead, we must explicitly check the boundaries. This is a
tiny bit fiddly, because we need to make sure we do floating-point
rounding in the correct direction, and also handle the fact that the
operation truncates so the boundary works differently for min vs max.
Instead of implementing this safety check in Sema, there are now
dedicated AIR instructions for safety-checked intfromfloat (two
instructions; which one is used depends on the float mode). Currently,
no backend directly implements them; instead, a `Legalize.Feature` is
added which expands the safety check, and this feature is enabled for
all backends we currently test, including the LLVM backend.
The `u0` case is still handled in Sema, because Sema needs to check for
that anyway due to the comptime-known result. The old safety check here
was also completely broken and has therefore been rewritten. In that
case, we just check for 'abs(input) < 1.0'.
I've added a bunch of test coverage for the boundary cases of
`@intFromFloat`, both for successes (in `test/behavior/cast.zig`) and
failures (in `test/cases/safety/`).
Resolves: #24161
Representing this with a `GenZir` field is incredibly bug-prone.
Instead, just pass this data directly to the relevant expression in the
very few places which actually provide a name strategy.
Resolves: #22798
`castTruncatedData` was a poorly worded error (all shrinking casts
"truncate bits", it's just that we assume those bits to be zext/sext of
the other bits!), and `negativeToUnsigned` was a pointless distinction
which forced the compiler to emit worse code (since two separate safety
checks were required for casting e.g. 'i32' to 'u16') and wasn't even
implemented correctly. This commit combines those safety panics into one
function, `integerOutOfBounds`. The name maybe isn't perfect, but that's
not hugely important; what matters is the new default message, which is
clearer than the old ones: "integer does not fit in destination type".
Runtime `@shuffle` has two cases which backends generally want to handle
differently for efficiency:
* One runtime vector operand; some result elements may be comptime-known
* Two runtime vector operands; some result elements may be undefined
The latter case happens if both vectors given to `@shuffle` are
runtime-known and they are both used (i.e. the mask refers to them).
Otherwise, if the result is not entirely comptime-known, we are in the
former case. `Sema` now diffentiates these two cases in the AIR so that
backends can easily handle them however they want to. Note that this
*doesn't* really involve Sema doing any more work than it would
otherwise need to, so there's not really a negative here!
Most existing backends have their lowerings for `@shuffle` migrated in
this commit. The LLVM backend uses new lowerings suggested by Jacob as
ones which it will handle effectively. The x86_64 backend has not yet
been migrated; for now there's a panic in there. Jacob will implement
that before this is merged anywhere.
