There are some `@panic("TODO")` in there but I'm trying to get the
branch to the point where collaborators can jump in.
Next is to repair the seam between LazySrcLoc and codegen's expected
absolute file offsets.
Next up is reworking the seam between the LazySrcLoc emitted by Sema
and the byte offsets currently expected by codegen.
And then the big one: updating astgen.zig to use the new memory layout.
Add a new allocated_registers bitmap to keep track of all callee-saved
registers allocated during generation of this function.
Function(.arm).gen uses this data to generate instructions in the
function prologue and epilogue to push and pop these registers
respectively.
Previously, this would reuse an operand even if reuseOperand returned
false for both operands.
genArmBinOpCode was also changed to be more Three-address code oriented
in the process.
on the break instruction operands. This involves a new TZIR instruction,
br_block_flat, which represents a break instruction where the operand is
the result of a flat block. See the doc comments on the instructions for
more details.
How it works: when adding break instructions in semantic analysis, the
underlying allocation is slightly padded so that it is the size of a
br_block_flat instruction, which allows the break instruction to later
be converted without removing instructions inside the parent body. The
extra type coercion instructions go into the body of the br_block_flat,
and backends are responsible for dispatching the instruction correctly
(it should map to the same function calls for related instructions).
Motivating test case:
```zig
export fn _start() noreturn {
var x: u64 = 1;
var y: u32 = 2;
var thing: u32 = 1;
const result = if (thing == 1) x else y;
exit();
}
```
The main idea here is for astgen to output ideal ZIR depending on
whether or not the sub-expressions of a block consume the result
location. Here, neither `x` nor `y` consume the result location of the
conditional expression block, and so the ZIR should communicate the
result of the condbr using break instructions, not with the result
location pointer.
With this commit, this is accomplished:
```
%22 = alloc_inferred()
%23 = block({
%24 = const(TypedValue{ .ty = type, .val = bool})
%25 = deref(%18)
%26 = const(TypedValue{ .ty = comptime_int, .val = 1})
%27 = cmp_eq(%25, %26)
%28 = as(%24, %27)
%29 = condbr(%28, {
%30 = deref(%4)
< there is no longer a store instruction here >
%31 = break("label_23", %30)
}, {
%32 = deref(%11)
< there is no longer a store instruction here >
%33 = break("label_23", %32)
})
})
%34 = store_to_inferred_ptr(%22, %23) <-- the store is only here
%35 = resolve_inferred_alloc(%22)
```
However if the result location gets consumed, the break instructions
change to break_void, and the result value is communicated only by the
stores, not by the break instructions.
Implementation:
* The GenZIR scope that conditional branches uses now has an optional
result location pointer field and a count of how many times the
result location ended up being an rvalue (not consumed).
* When rvalue() is called on a result location for a block, it
increments this counter. After generating the branches of a block,
astgen for the conditional branch checks this count and if it is 2
then the store_to_block_ptr instructions are elided and it calls
rvalue() using the block result (which will account for peer type
resolution on the break operands).
astgen has many functions disabled until they can be reworked with these
new semantics. That will be done before merging the branch.
There are some new rules for astgen to follow regarding result locations
and what you are allowed/required to do depending on which one is passed
to expr(). See the updated doc comments of ResultLoc for details.
I also changed naming conventions of stuff in this commit, sorry about
that.
* fix wrong pointer const-ness when unwrapping optionals
* allow grouped expressions and orelse as lvalues
* ZIR for unwrapping optionals: no redundant deref
- add notes to please don't use rlWrapPtr, this function should be
deleted
* catch and orelse: better ZIR for non-lvalue: no redundant deref;
operate entirely on values. lvalue case still works properly.
- properly propagate the result location into the target expression
* Test harness: better output when tests fail due to compile errors.
* TZIR: add instruction variants. These allow fewer TZIR instructions to
be emitted from zir_sema. See the commit diff for per-instruction
documentation.
- is_null
- is_non_null
- is_null_ptr
- is_non_null_ptr
- is_err
- is_err_ptr
- optional_payload
- optional_payload_ptr
* TZIR: removed old naming convention instructions:
- isnonnull
- isnull
- iserr
- unwrap_optional
* ZIR: add instruction variants. These allow fewer ZIR instructions to
be emitted from astgen. See the commit diff for per-instruction
documentation.
- is_non_null
- is_null
- is_non_null_ptr
- is_null_ptr
- is_err
- is_err_ptr
- optional_payload_safe
- optional_payload_unsafe
- optional_payload_safe_ptr
- optional_payload_unsafe_ptr
- err_union_payload_safe
- err_union_payload_unsafe
- err_union_payload_safe_ptr
- err_union_payload_unsafe_ptr
- err_union_code
- err_union_code_ptr
* ZIR: removed old naming convention instructions:
- isnonnull
- isnull
- iserr
- unwrap_optional_safe
- unwrap_optional_unsafe
- unwrap_err_safe
- unwrap_err_unsafe
- unwrap_err_code
* Implement error notes
- note: other symbol exported here
- note: previous else prong is here
- note: previous '_' prong is here
* Add Compilation.CObject.ErrorMsg. This object properly converts to
AllErrors.Message when the time comes.
* Add Compilation.CObject.failure_retryable. Properly handles
out-of-memory and other transient failures.
* Introduce Module.SrcLoc which has not only a byte offset but also
references the file which the byte offset applies to.
* Scope.Block now contains both a pointer to the "owner" Decl and the
"source" Decl. As an example, during inline function call, the
"owner" will be the Decl of the caller and the "source" will be the
Decl of the callee.
* Module.ErrorMsg now sports a `file_scope` field so that notes can
refer to source locations in a file other than the parent error
message.
* Some instances where a `*Scope` was stored, now store a
`*Scope.Container`.
* Some methods in the `Scope` namespace were moved to the more specific
type, since there was only an implementation for one particular tag.
- `removeDecl` moved to `Scope.Container`
- `destroy` moved to `Scope.File`
* Two kinds of Scope deleted:
- zir_module
- decl
* astgen: properly use DeclVal / DeclRef. DeclVal was incorrectly
changed to be a reference; this commit fixes it. Fewer ZIR
instructions processed as a result.
- declval_in_module is renamed to declval
- previous declval ZIR instruction is deleted; it was only for .zir
files.
* Test harness: friendlier diagnostics when an unexpected set of errors
is encountered.
* zir_sema: fix analyzeInstBlockFlat by properly calling resolvingInst
on the last zir instruction in the block.
Compile log implementation:
* Write to a buffer rather than directly to stderr.
* Only keep track of 1 callsite per Decl.
* No longer mutate the ZIR Inst struct data.
* "Compile log statement found" errors are only emitted when there are
no other compile errors.
-femit-zir and support for .zir source files is regressed. If we wanted
to support this again, outputting .zir would need to be done as yet
another backend rather than in the haphazard way it was previously
implemented.
For parsing .zir, it was implemented previously in a way that was not
helpful for debugging. We need tighter integration with the test harness
for it to be useful; so clearly a rewrite is needed. Given that a
rewrite is needed, and it was getting in the way of progress and
organization of the rest of stage2, I regressed the feature.
Previously, the x86_64 backend would remove code for exitlude relocs
if the jump amount were 0. This causes issues as earlier jumps rely on
the jump being present at the same address.
