* Introduce `memoized_calls` to `Module` which stores all the comptime
function calls that are cached. It is keyed on the `*Fn` and the
comptime arguments, but it does not yet properly detect comptime function
pointers and avoid memoizing in this case. So it will have false
positives for when a comptime function call mutates data through a
pointer parameter.
* Sema: Add a new helper function: `resolveConstMaybeUndefVal`
* Value: add `enumToInt` method and use it in `zirEnumToInt`. It is
also used by the hashing function.
* Value: fix representation of optionals to match error unions.
Previously it would not handle nested optionals correctly. Now it
matches the memory layout of error unions and supports nested
optionals properly. This required changes in all the backends for
generating optional constants.
* TypedValue gains `eql` and `hash` methods.
* Value: Implement hashing for floats, optionals, and enums.
Additionally, the zig type tag is added to the hash, where it was not
previously, so that values of differing types will get different
hashes.
The big change in this commit is making `semaDecl` resolve the fields if
the Decl ends up being a struct or union. It needs to do this while
the `Sema` is still in scope, because it will have the resolved AIR
instructions that the field type expressions possibly reference. We do
this after the decl is populated and set to `complete` so that a `Decl`
may reference itself.
Everything else is fixes and improvements to make the test suite pass
again after making this change.
* New AIR instruction: `ptr_elem_ptr`
- Implemented for LLVM backend
* New Type tag: `type_info` which represents `std.builtin.TypeInfo`. It
is used by AstGen for the operand type of `@Type`.
* ZIR instruction `set_float_mode` uses `coerced_ty` to avoid
superfluous `as` instruction on operand.
* ZIR instruction `Type` uses `coerced_ty` to properly handle result
location type of operand.
* Fix two instances of `enum_nonexhaustive` Value Tag not handled
properly - it should generally be handled the same as `enum_full`.
* Fix struct and union field resolution not copying Type and Value
objects into its Decl arena.
* Fix enum tag value resolution discarding the ZIR=>AIR instruction map
for the child Sema, when they still needed to be accessed.
* Fix `zirResolveInferredAlloc` use-after-free in the AIR instructions
data array.
* Fix `elemPtrArray` not respecting const/mutable attribute of pointer
in the result type.
* Fix LLVM backend crashing when `updateDeclExports` is called before
`updateDecl`/`updateFunc` (which is, according to the API, perfectly
legal for the frontend to do).
* Fix LLVM backend handling element pointer of pointer-to-array. It
needed another index in the GEP otherwise LLVM saw the wrong type.
* Fix LLVM test cases not returning 0 from main, causing test failures.
Fixes a regression introduced in
6a5094872f10acc629543cc7f10533b438d0283a.
* Implement comptime shift-right.
* Implement `@Type` for integers and `@TypeInfo` for integers.
* Implement union initialization syntax.
* Implement `zirFieldType` for unions.
* Implement `elemPtrArray` for a runtime-known operand.
* Make `zirLog2IntType` support RHS of shift being `comptime_int`. In
this case it returns `comptime_int`.
The motivating test case for this commit was originally:
```zig
test "example" {
var l: List(10) = undefined;
l.array[1] = 1;
}
fn List(comptime L: usize) type {
var T = u8;
return struct {
array: [L]T,
};
}
```
However I changed it to:
```zig
test "example" {
var l: List = undefined;
l.array[1] = 1;
}
const List = blk: {
const T = [10]u8;
break :blk struct {
array: T,
};
};
```
Which ended up being a similar, smaller problem. The former test case
will require a similar solution in the implementation of comptime
function calls - checking if the result of the function call is a struct
or union, and using the child `Sema` before it is destroyed to resolve
the fields.
this made errors go from stuff like:
> type comptime_int cannot represent integer value 40
to
> type u5 cannot represent integer value 40
which makes much more sense
* AstGen: use coerced_ty ResultLoc on array types and rely on Sema
doing type coercion, to reduce the size of the ZIR for these
instructions.
* Sema: implement `@ptrCast`.
* Sema: implement coercion from `T` to `?T` with an intermediate
coercion rather than equality check.
* Value: rename `error_union` to `eu_payload` and clarify the intended
usage in the doc comments. The way error unions is represented with
Value is fixed to not have ambiguous values.
* Fix codegen for error union constants in all the backends.
* Implement the AIR instructions having to do with error unions in the
LLVM backend.
* New AIR instructions: ptr_add, ptr_sub, ptr_elem_val, ptr_ptr_elem_val
- See the doc comments for details.
* Sema: implement runtime pointer arithmetic.
* Sema: implement elem_val for many-pointers.
* Sema: support coercion from `*[N:s]T` to `[*]T`.
* Type: isIndexable handles many-pointers.
* Introduce `ret_load` ZIR instruction which does return semantics
based on a corresponding `ret_ptr` instruction. If the return type of
the function has storage for the return type, it simply returns.
However if the return type of the function is by-value, it loads the
return value from the `ret_ptr` allocation and returns that.
* AstGen: improve `finishThenElseBlock` to not emit break instructions
after a return instruction in the same block.
* Sema: `ret_ptr` instruction works correctly in comptime contexts.
Same with `alloc_mut`.
The test case with a recursive inline function having an implicitly
comptime return value now has a runtime return value because of the fact
that it calls a function in a non-comptime context.
This commit solves the problem in a much simpler way: putting
runtime-known values in place of non-comptime arguments when
instantiating a generic function.
The `comptime_args` field of Fn has a clarified purpose:
For generic function instantiations, there is a `TypedValue` here
for each parameter of the function:
* Non-comptime parameters are marked with a `generic_poison` for the value.
* Non-anytype parameters are marked with a `generic_poison` for the type.
Sema now has a `fn_ret_ty` field. Doc comments reproduced here:
> When semantic analysis needs to know the return type of the function whose body
> is being analyzed, this `Type` should be used instead of going through `func`.
> This will correctly handle the case of a comptime/inline function call of a
> generic function which uses a type expression for the return type.
> The type will be `void` in the case that `func` is `null`.
Various places in Sema are modified in accordance with this guidance.
Fixed `resolveMaybeUndefVal` not returning `error.GenericPoison` when
Value Tag of `generic_poison` is encountered.
Fixed generic function memoization incorrect equality checking. The
logic now clearly deals properly with any combination of anytype and
comptime parameters.
Fixed not removing generic function instantiation from the table in case
a compile errors in the rest of `call` semantic analysis. This required
introduction of yet another adapter which I have called
`GenericRemoveAdapter`. This one is nice and simple - it's the same hash
function (the same precomputed hash is passed in) but the equality
function checks pointers rather than doing any logic.
Inline/comptime function calls coerce each argument in accordance with
the function parameter type expressions. Likewise the return type
expression is evaluated and provided (see `fn_ret_ty` above).
There's a new compile error "unable to monomorphize function". It's
pretty unhelpful and will need to get improved in the future. It happens
when a type expression in a generic function did not end up getting
resolved at a callsite. This can happen, for example, if a runtime
parameter is attempted to be used where it needed to be comptime known:
```zig
fn foo(x: anytype) [x]u8 { _ = x; }
```
In this example, even if we pass a number such as `10` for `x`, it is
not marked `comptime`, so `x` will have a runtime known value, making
the return type unable to resolve.
In the LLVM backend I implement cmp instructions for float types to pass
some behavior tests that used floats.
When doing a function call, if the return type requires comptime, the
function is analyzed as an inline/comptime call.
There is an important TODO here. I will reproduce the comment from this
commit:
> In the case of a comptime/inline function call of a generic function,
> the function return type needs to be the resolved return type based on
> the function parameter type expressions being evaluated with comptime arguments
> passed in. Otherwise, it ends up being .generic_poison and failing the
> comptime/inline function call analysis.
* ZIR encoding for function instructions have a body for the return
type. This lets Sema for generic functions do the same thing it does
for parameters, handling `error.GenericPoison` in the evaluation of
the return type by marking the function as generic.
* Sema: fix missing block around the new Decl arena finalization. This
led to a memory corruption.
* Added some floating point support to the LLVM backend but didn't get
far enough to pass any new tests.
Module has a new field `monomorphed_funcs` which stores the set of
`*Module.Fn` objects which are generic function instantiations.
The hash is based on hashes of comptime values of parameters known to be
comptime based on an explicit comptime keyword or must-be-comptime
type expressions that can be evaluated without performing monomorphization.
This allows function calls to be semantically analyzed cheaply for
generic functions which are already instantiated.
The table is updated with a single `getOrPutAdapted` in the semantic
analysis of `call` instructions, by pre-allocating the `Fn` object and
passing it to the child `Sema`.
* The `indexable_ptr_len` ZIR instruction now uses a `none_or_ref`
ResultLoc. This prevents an unnecessary `ref` instruction from being
emitted.
* Sema: Fix `analyzeCall` using the incorrect ZIR object for the
generic function callee.
* LLVM backend: `genTypedValue` supports a `Slice` type encoded with
the `decl_ref` `Value`.
AstGen result locations now have a `coerced_ty` tag which is the same as
`ty` except it assumes that Sema will do a coercion, so it does not
redundantly add an `as` instruction into the ZIR code. This results in
cleaner ZIR and about a 14% reduction of ZIR bytes.
param and param_comptime ZIR instructions now have a block body for
their type expressions. This allows Sema to skip evaluation of the
block in the case that the parameter is comptime-provided. It also
allows a new mechanism to function: when evaluating type expressions of
generic functions, if it would depend on another parameter, it returns
`error.GenericPoison` which bubbles up and then is caught by the
param/param_comptime instruction and then handled.
This allows parameters to be evaluated independently so that the type
info for functions which have comptime or anytype parameters will still
have types populated for parameters that do not depend on values of
previous parameters (because evaluation of their param blocks will return
successfully instead of `error.GenericPoison`).
It also makes iteration over the block that contains function parameters
slightly more efficient since it now only contains the param
instructions.
Finally, it fixes the case where a generic function type expression contains
a function prototype. Formerly, this situation would cause shared state
to clobber each other; now it is in a proper tree structure so that
can't happen. This fix also required adding a field to Sema
`comptime_args_fn_inst` to make sure that the `comptime_args` field
passed into Sema is applied to the correct `func` instruction.
Source location for `node_offset_asm_ret_ty` is fixed; it was pointing at
the asm output name rather than the return type as intended.
Generic function instantiation is fixed, notably with respect to
parameter type expressions that depend on previous parameters, and with
respect to types which must be always comptime-known. This involves
passing all the comptime arguments at a callsite of a generic function,
and allowing the generic function semantic analysis to coerce the values
to the proper types (since it has access to the evaluated parameter type
expressions) and then decide based on the type whether the parameter is
runtime known or not. In the case of explicitly marked `comptime`
parameters, there is a check at the semantic analysis of the `call`
instruction.
Semantic analysis of `call` instructions does type coercion on the
arguments, which is needed both for generic functions and to make up for
using `coerced_ty` result locations (mentioned above).
Tasks left in this branch:
* Implement the memoization table.
* Add test coverage.
* Improve error reporting and source locations for compile errors.
The general strategy is that Sema will pre-map comptime arguments into
the inst_map, and then re-run the block body that contains the `param`
and `func` instructions. This re-runs all the parameter type expressions
except with comptime values populated.
In Sema, param instructions are now handled specially: they detect
whether they are comptime-elided or not. If so, they skip putting a
value in the inst_map, since it is already pre-populated. If not, then
they append to the `fields` field of `Sema` for use with the `func`
instruction.
So when the block body is re-run, a new function is generated with
all the comptime arguments elided, and the new function type has only
runtime parameters in it. TODO: give the generated Decls better names
than "foo__anon_x".
The new function is then added to the work queue to have its body
analyzed and a runtime call AIR instruction to the new function is
emitted.
When the new function gets semantically analyzed, comptime parameters are
pre-mapped to the corresponding `comptime_args` values rather than
mapped to an `arg` AIR instruction. `comptime_args` is a new field that
`Fn` has which is a `TypedValue` for each parameter. This field is non-null
for generic function instantiations only. The values are the comptime
arguments. For non-comptime parameters, a sentinel value is used. This is
because we need to know the information of which parameters are
comptime-known.
Additionally:
* AstGen: align and section expressions are evaluated in the scope that
has comptime parameters in it.
There are still some TODO items left; see the BRANCH_TODO file.
* ZIR function instructions encode the index of the block that
contains the function instruction. This allows Zig to later scan the
block and find the parameter instructions, which is needed for
semantically analyzing function bodies.
* Runtime function calls insert AIR arg instructions and then inserts
Sema inst_map entries mapping the ZIR param instructions to them.
* comptime/inline function call inserts Sema inst_map entries mapping
the ZIR param instructions to the AIR callsite arguments.
With this commit we are back to the tests passing.
ZIR encoding for functions is changed in preparation for generic
function support. As an example:
```zig
const std = @import("std");
const expect = std.testing.expect;
test "example" {
var x: usize = 0;
x += checkSize(i32, 1);
x += checkSize(bool, true);
try expect(x == 5);
}
fn checkSize(comptime T: type, x: T) usize {
_ = x;
return @sizeOf(T);
}
```
Previous ZIR for the `checkSize` function:
```zir
[165] checkSize line(10) hash(0226f62e189fd0b1c5fca02cf4617562): %55 = block_inline({
%56 = decl_val("T") token_offset:11:35
%57 = as_node(@Ref.type_type, %56) node_offset:11:35
%69 = extended(func([comptime @Ref.type_type, %57], @Ref.usize_type, {
%58 = arg("T") token_offset:11:23
%59 = as_node(@Ref.type_type, %58) node_offset:11:35
%60 = arg("x") token_offset:11:32
%61 = dbg_stmt(11, 4)
```
ZIR for the `checkSize` function after this commit:
```zir
[157] checkSize line(10) hash(0226f62e189fd0b1c5fca02cf4617562): %55 = block_inline({
%56 = param_comptime("T", @Ref.type_type) token_offset:11:23
%57 = as_node(@Ref.type_type, %56) node_offset:11:35
%58 = param("x", %57) token_offset:11:32
%67 = func(@Ref.usize_type, {
%59 = dbg_stmt(11, 4)
```
Noted differences:
* Previously the type expression was redundantly repeated.
* Previously the parameter names were redundantly stored in the ZIR
extra array.
* Instead of `arg` ZIR instructions as the first instructions within a
function body, they are now outside the function body, in the same
block as the `func` instruction. There are variants:
- param
- param_comptime
- param_anytype
- param_anytype_comptime
* The param instructions additionally encode the type.
* Because of the param instructions, the `func` instruction no longer
encodes the list of parameter types or the comptime bits.
It's implied that Sema will collect the parameters so that when a `func`
instruction is encountered, they will be implicitly used to construct
the function's type. This is so that we can satisfy all 3 ways of
performing semantic analysis on a function:
1. runtime: Sema will insert AIR arg instructions for each parameter,
and insert into the Sema inst_map ZIR param => AIR arg.
2. comptime/inline: Sema will insert into the inst_map ZIR param =>
callsite arguments.
3. generic: Sema will map *only the comptime* ZIR param instructions to
the AIR instructions for the comptime arguments at the callsite, and
then re-run Sema for the function's Decl. This will produce a new
function which is the monomorphized function.
Additionally:
* AstGen: Update usage of deprecated `ensureCapacity` to
`ensureUnusedCapacity` or `ensureTotalCapacity`.
* Introduce `Type.fnInfo` for getting a bunch of data about a function
type at once, and use it in `analyzeCall`.
This commit starts a branch to implement generic functions in stage2.
Test regressions have not been addressed yet.
`func_extended` ZIR instructions now have a one of the unused flags used
as a `has_comptime_bits` boolean. When set, it means 1 or more
parameters are `comptime`. In this case, there is a u32 per every 32
parameters (usually just 1 u32) with each bit indicating whether the
corresponding parameter is `comptime`.
Sema uses this information to correctly mark generic functions as
generic. There is now a TODO compile error in place in case a generic
function call happens. A future commit will do the generic function call
implementation.
Sema now properly handles alloc_inferred and alloc_inferred_mut ZIR
instructions inside a comptime execution context. In this case it
creates Decl objects and points to them with the new `decl_ref_mut`
Value Tag. `storePtr` is updated to mutate such Decl types and values.
In this case it destroys the old arena and makes a new one, preventing
memory growth during comptime code execution.
Additionally:
* Fix `storePtr` to emit a compile error for a pointer comptime-known
to be undefined.
* Fix `storePtr` to emit runtime instructions for all the cases that a
pointer is comptime-known but does not support comptime
dereferencing, such as `@intToPtr` on a hard-coded address, or an
extern function.
* Fix `ret_coerce` not coercing inside inline function call context.
When doing `x == true` or `x == false` it is now lowered as either a
no-op or a not, respectively, rather than a cmp instruction.
This commit also extracts a zirCmpEq function out from zirCmp, reducing
the amount of branching (on is_equality_cmp) in both functions.
* `Value.toType` accepts a buffer parameter instead of an allocator
parameter and can no longer fail.
* Module: remove the unused `mod: *Module` parameter from various
functions.
* `Value.compare` now accepts a `Type` parameter which indicates the
type of both operands. There is also a `Value.compareHetero` which
accepts only Value parameters and supports comparing mixed types.
Likewise, `Value.eql` requires a `Type` parameter.
* `Value.hash` is removed; instead the hash map context structs now
have a `ty: Type` field, and the hash function lives there, where it
has access to a Value's Type when it computes a hash.
- This allowed the hash function to be greatly simplified and sound
in the sense that the same Values, even with different
representations, always hash to the same thing.
* Sema: Fix source location of zirCmp when an operand is runtime known
but needs to be comptime known.
* Remove unused target parameter from `Value.floatCast`.
After this change, the frontend and backend cooperate to keep track of
which Decls are actually emitted into the machine code. When any backend
sees a `decl_ref` Value, it must mark the corresponding Decl `alive`
field to true.
This prevents unused comptime data from spilling into the output object
files. For example, if you do an `inline for` loop, previously, any
intermediate value calculations would have gone into the object file.
Now they are garbage collected immediately after the owner Decl has its
machine code generated.
In the frontend, when it is time to send a Decl to the linker, if it has
not been marked "alive" then it is deleted instead.
Additional improvements:
* Resolve type ABI layouts after successful semantic analysis of a
Decl. This is needed so that the backend has access to struct fields.
* Sema: fix incorrect logic in resolveMaybeUndefVal. It should return
"not comptime known" instead of a compile error for global variables.
* `Value.pointerDeref` now returns `null` in the case that the pointer
deref cannot happen at compile-time. This is true for global
variables, for example. Another example is if a comptime known
pointer has a hard coded address value.
* Binary arithmetic sets the requireRuntimeBlock source location to the
lhs_src or rhs_src as appropriate instead of on the operator node.
* Fix LLVM codegen for slice_elem_val which had the wrong logic for
when the operand was not a pointer.
As noted in the comment in the implementation of deleteUnusedDecl, a
future improvement will be to rework the frontend/linker interface to
remove the frontend's responsibility of calling allocateDeclIndexes.
I discovered some issues with the plan9 linker backend that are related
to this, and worked around them for now.
* AIR no longer has a `variables` array. Instead of the `varptr`
instruction, Sema emits a constant with a `decl_ref`.
* AIR no longer has a `ref` instruction. There is no longer any
instruction that takes a value and returns a pointer to it. If this
is desired, Sema must either create an anynomous Decl and return a
constant `decl_ref`, or in the case of a runtime value, emit an
`alloc` instruction, `store` the value to it, and then return the
`alloc`.
* The `ref_val` Value Tag is eliminated. `decl_ref` should be used
instead. Also added is `eu_payload_ptr` which points to the payload
of an error union, given an error union pointer.
In general, Sema should avoid calling `analyzeRef` if it can be helped.
For example in the case of field_val and elem_val, there should never be
a reason to create a temporary (alloc or decl). Recent previous commits
made progress along that front.
There is a new abstraction in Sema, which looks like this:
var anon_decl = try block.startAnonDecl();
defer anon_decl.deinit();
// here 'anon_decl.arena()` may be used
const decl = try anon_decl.finish(ty, val);
// decl is typically now used with `decl_ref`.
This pattern is used to upgrade `ref_val` usages to `decl_ref` usages.
Additional improvements:
* Sema: fix source location resolution for calling convention
expression.
* Sema: properly report "unable to resolve comptime value" for loads of
global variables. There is now a set of functions which can be
called if the callee wants to obtain the Value even if the tag is
`variable` (indicating comptime-known address but runtime-known value).
* Sema: `coerce` resolves builtin types before checking equality.
* Sema: fix `u1_type` missing from `addType`, making this type have a
slightly more efficient representation in AIR.
* LLVM backend: fix `genTypedValue` for tags `decl_ref` and `variable`
to properly do an LLVMConstBitCast.
* Remove unused parameter from `Value.toEnum`.
After this commit, some test cases are no longer passing. This is due to
the more principled approach to comptime references causing more
anonymous decls to get sent to the linker for codegen. However, in all
these cases the decls are not actually referenced by the runtime machine
code. A future commit in this branch will implement garbage collection
of decls so that unused decls do not get sent to the linker for codegen.
This will make the tests go back to passing.
* Add AIR instruction: struct_field_val
- This is part of an effort to eliminate the AIR instruction `ref`.
- It's implemented for C backend and LLVM backend so far.
* Rename `resolvePossiblyUndefinedValue` to `resolveMaybeUndefVal` just
to save some columns on long lines.
* Sema: add `fieldVal` alongside `fieldPtr` (renamed from
`namedFieldPtr`). This is part of an effort to eliminate the AIR
instruction `ref`. The idea is to avoid unnecessary loads, stores,
stack usage, and IR instructions, by paying a DRY cost.
LLVM backend improvements:
* internal linkage vs exported linkage is implemented, along with
aliases. There is an issue with incremental updates due to missing
LLVM API for deleting aliases; see the relevant comment in this commit.
- `updateDeclExports` is hooked up to the LLVM backend now.
* Fix usage of `Type.tag() == .noreturn` rather than calling `isNoReturn()`.
* Properly mark global variables as mutable/constant.
* Fix llvm type generation of function pointers
* Fix codegen for calls of function pointers
* Implement llvm type generation of error unions and error sets.
* Implement AIR instructions: addwrap, subwrap, mul, mulwrap, div,
bit_and, bool_and, bit_or, bool_or, xor, struct_field_ptr,
struct_field_val, unwrap_errunion_err, add for floats, sub for
floats.
After this commit, `zig test` on a file with `test "example" {}`
correctly generates and executes a test binary. However the
`test_functions` slice is undefined and just happens to be going into
the .bss section, causing the length to be 0. The next step towards
`zig test` will be replacing the `test_functions` Decl Value with the
set of test function pointers, before it is sent to linker/codegen.
@select(
comptime T: type,
pred: std.meta.Vector(len, bool),
a: std.meta.Vector(len, T),
b: std.meta.Vector(len, T)
) std.meta.Vector(len, T)
Constructs a vector from a & b, based on the values in the predicate vector. For indices where the predicate value is true, the corresponding
element from the a vector is selected, and otherwise from b.
* There is now a main_pkg in addition to root_pkg. They are usually the
same. When using `zig test`, main_pkg is the user's source file and
root_pkg has the test runner.
* scanDecl no longer looks for test decls outside the package being
tested. honoring `--test-filter` is still TODO.
* test runner main function has a void return value rather than
`anyerror!void`
* Sema is improved to generate better AIR for for loops on slices.
* Sema: fix incorrect capacity calculation in zirBoolBr
* Sema: add compile errors for trying to use slice fields as an lvalue.
* Sema: fix type coercion for error unions
* Sema: fix analyzeVarRef generating garbage AIR
* C codegen: fix renderValue for error unions with 0 bit payload
* C codegen: implement function pointer calls
* CLI: fix usage text
Adds 4 new AIR instructions:
* slice_len, slice_ptr: to get the ptr and len fields of a slice.
* slice_elem_val, ptr_slice_elem_val: to get the element value of
a slice, and a pointer to a slice.
AstGen gains a new functionality:
* One of the unused flags of struct decls is now used to indicate
structs that are known to have non-zero size based on the AST alone.
When updating the code, I accidentally made it look at the fact that the
error set operands were a `type` rather than looking at exactly which error
set types they were.
Now supports multiple items pointing to the same body. This is a common
pattern even when using a jump table, with multiple cases pointing to
the same block of code.
In the case of a range specified, the items are moved to branches in the
else body. A future improvement may make it possible to have jump table
items as well as ranges pointing to the same block of code.
- Get correct types in wasm backend.
- `arg` is already a `Ref`, therefore simply use `@intToEnum`.
- Fix regression in `zirBoolBr, where the order of insertion was incorrect.
* Breaking language change: inline assembly must use string literal
syntax. This is in preparation for inline assembly improvements that
involve more integration with the Zig language. This means we cannot
rely on text substitution.
* Liveness: properly handle inline assembly and function calls with
more than 3 operands.
- More than 35 operands is not yet supported. This is a low priority
to implement.
- This required implementation in codegen.zig as well.
* Liveness: fix bug causing incorrect tomb bits.
* Sema: enable switch expressions that are evaluated at compile-time.
- Runtime switch instructions still need to be reworked in this
branch. There was a TODO left here (by me) with a suggestion to do
some bigger changes as part of the AIR memory reworking. Now that
time has come and I plan to honor the suggestion in a future commit
before merging this branch.
* AIR printing: fix missing ')' on alive instructions.
We're back to "hello world" working for the x86_64 backend.
* some instructions are not implemented yet
* fix off-by-1 in Air.getMainBody
* Compilation: use `@import("builtin")` rather than `std.builtin`
for the values that are different for different build configurations.
* Sema: avoid calling `addType` in between
air_instructions.ensureUnusedCapacity and corresponding
appendAssumeCapacity because it can possibly add an instruction.
* Value: functions print their names
