1. Changed Zig pointers to functions to be typedef'd so then we can
treat them the same as other types.
2. Distinguished between const slices (zig_L prefix) and mut slices
(zig_M prefix).
3. Changed lowering of Zig "const pointers" (e.g. *const u8) to to C
"pointers to const" (e.g. const char *) rather than C "const
pointers" (e.g. char * const)
4. Ensured that all typedefs are "linked" even if the decl doesn't
require any forward declarations
5. Added test that exercises function pointer type rendering
6. Changed .slice_ptr instruction to allocate pointer local rather than
a uintptr_t local
New AIR instruction: `optional_payload_ptr_set`
It's like `optional_payload_ptr` except it sets the non-null bit.
When storing to the payload via a result location that is an optional,
`optional_payload_ptr_set` is now emitted. There is a new algorithm in
`zirCoerceResultPtr` which stores a dummy value through the result
pointer into a temporary block, and then pops off the AIR instructions
from the temporary block in order to determine how to transform the
result location pointer in case any in-between coercions need to happen.
Fixes a couple of behavior tests regarding optionals.
1. Function signatures that return a no member struct return void
2. Undefined var decls don't get a value generated for them
3. Don't generate bitcast code if the result isn't used, since
bitcast is a pure function. Right now struct handling code
generates some weird unused bitcast AIR, and this optimization
side steps that issue.
Because ArrayList.initCapacity uses 'precise' capacity allocation, this should save memory on average, and definitely will save memory in cases where ArrayList is used where a regular allocated slice could have also be used.
If these functions are called more than once, then the array list would no longer be guaranteed to have enough capacity during the appendAssumeCapacity calls. With ensureUnusedCapacity, they will always be guaranteed to have enough capacity regardless of how many times the function is called.
* test_functions: properly add dependencies of the array on test
functions and test names so that the order comes out correctly.
* fix lowering of struct literals to add parentheses around the type
name.
* omit const qualifier in slices because otherwise slices cannot be
reassigned even when they are local variables.
* special case pointer to functions and double pointer to functions in
renderTypeAndName. This code will need to be cleaned up but for now
it helps us make progress on other C backend stuff.
* fix slice element access to lower to `.ptr[` instead of `[`.
* airSliceElemVal: respect volatile slices
The main problem that motivated these changes is that global constants
which are referenced by pointer would not be emitted into the binary.
This happened because `semaDecl` did not add `codegen_decl` tasks for
global constants, instead relying on the constant values being copied as
necessary. However when the global constants are referenced by pointer,
they need to be sent to the linker to be emitted.
After making global const arrays, structs, and unions get emitted, this
uncovered a latent issue: the anonymous decls that they referenced would
get garbage collected (via `deleteUnusedDecl`) even though they would
later be referenced by the global const.
In order to solve this problem, I introduced `anon_work_queue` which is
the same as `work_queue` except a lower priority. The `codegen_decl`
task for anon decls goes into the `anon_work_queue` ensuring that the
owner decl gets a chance to mark its anon decls as alive before they are
possibly deleted.
This caused a few regressions, which I made the judgement call to add
workarounds for. Two steps forward, one step back, is still progress.
The regressions were:
* Two behavior tests having to do with unions. These tests were
intentionally exercising the LLVM constant value lowering, however,
due to the bug with garbage collection that was fixed in this commit,
the LLVM code was not getting exercised, and union types/values were
not implemented correctly, due to me forgetting that LLVM does not
allow bitcasting aggregate values.
- This is worked around by allowing those 2 test cases to regress,
moving them to the "passing for stage1 only" section.
* The test-stage2 test cases (in test/cases/*) for non-LLVM backends
previously did not have any calls to lower struct values, but now
they do. The code that was there was just `@panic("TODO")`. I
replaced that code with a stub that generates the wrong value. This
is an intentional miscompilation that will obviously need to get
fixed before any struct behavior tests pass. None of the current
tests we have exercise loading any values from these global const
structs, so there is not a problem until we try to improve these
backends.
* C pointer types always have allowzero set to true but they omit the
word allowzero when printed.
* Implement coercion from C pointers to other pointers.
* Implement in-memory coercion for slices and pointer-like optionals.
* Make slicing a C pointer drop the allowzero bit.
* Value representation for pointer-like optionals is now allowed to use
pointer tag values in addition to the `opt_payload` tag.
According to the documentation, `divTrunc` is "Truncated division.
Rounds toward zero". Lower it as a straightforward fdiv + trunc sequence
to make it behave as expected with mixed positive/negative operands.
Closes#10001
* Fix backend using wrong union field of the slice instruction.
* LLVM backend properly sets alignment on global variables.
* Sema: add coercion for *T to *[1]T
* Sema: pointers to Decls with explicit alignment now have alignment
metadata in them.
Also switch to the more efficient encoding of the bitcast instruction
when the destination type is anyerror in 2 common cases.
LLVM backend: fix using the wrong type as the optional payload type in
the `wrap_optional` AIR instruction.
AIR:
* div is renamed to div_trunc.
* Add div_float, div_floor, div_exact.
- Implemented in Sema and LLVM codegen. C backend has a stub.
Improvements to std.math.big.Int:
* Add `eqZero` function to `Mutable`.
* Fix incorrect results for `divFloor`.
Compiler-rt:
* Add muloti4 to the stage2 section.
* Restructure elemPtr a bit
* New AIR instruction: slice_elem_ptr, which returns a pointer to an element of a slice
* Value: adapt elemPtr to work on slices
* New AIR instruction: slice, which constructs a slice out of a pointer
and a length.
* AstGen: use `coerced_ty` for start and end expressions, use `none`
for the sentinel, and don't try to load the result of the slice
operation because it returns a by-value result.
* Sema: pointer arithmetic is extracted into analyzePointerArithmetic
and it is used by the implementation of slice.
- Also I implemented comptime pointer addition.
* Sema: extract logic into analyzeSlicePtr, analyzeSliceLen and use them
inside the slice semantic analysis.
- The approach in stage2 is much cleaner than stage1 because it uses
more granular analysis calls for obtaining the slice pointer, doing
arithmetic on it, and checking if the length is comptime-known.
* Sema: use the slice Value Tag for slices when doing coercion from
pointer-to-array.
* LLVM backend: detect when emitting a GEP instruction into a
pointer-to-array and add the extra index that is required.
* Type: ptrAlignment for c_void returns 0.
* Implement Value.hash and Value.eql for slices.
* Remove accidentally duplicated behavior test.
* do not add linkage scope to aliased exported symbols - this is
not respected on macOS
* special-case `MachO.openPath` in `link.File.openPath` as on macOS
we always link with zld
* redirect to `MachO.flushObject` when linking relocatable objects
in MachO linker whereas move the entire linking logic into
`MachO.flushModule`
* Sema: fix returned operands not coercing to the function return type
in some cases.
- When returning an error or an error union from a function with an
inferred error set, it will now populate the inferred error set.
- Implement error set coercion for the common case of inferred error
set to inferred error set, without forcing a full resolution.
* LLVM backend: update instruction lowering that handles error unions
to respect `isByRef`.
- Also implement `wrap_err_union_err`.
* Relax compile error for "unable to export type foo" to allow
integers, structs, arrays, and floats. This will need to be further
improved to do the same checks as we do for C ABI struct field types.
* LLVM backend: fix extern variables
* LLVM backend: implement AIR instruction `wrap_err_union_payload`
* Sema: implement peer type resolution for optionals and null.
* Rename `Module.optionalType` to `Type.optional`.
* LLVM backend: re-use anonymous values. This is especially useful when
isByRef()=true because it means re-using the same generated LLVM globals.
* LLVM backend: rework the implementation of is_null and is_non_null
AIR instructions. Generate slightly better LLVM code, and also fix
the behavior for optionals whose payload type is 0-bit.
* LLVM backend: improve `cmp` AIR instruction lowering to support
pointer-like optionals.
* `Value`: implement support for equality-checking optionals.
