This is problematic because in practice it depends on whether the
compiler backend supports it too, as evidenced by the TODO comment about
LLVM not supporting some architectures that in fact do support tail
calls.
Instead this logic is organized strategically in src/target.zig, part of
the internal compiler source code, and the behavior tests in question
duplicate some logic for deciding whether to proceed with the test.
The proper place to expose this flag is in `@import("builtin")` - the
generated source file - so that third party compilers can advertise
whether they support tail calls.
Previously, when lowering AIR instructions `wrap_errunion_payload`,
`wrap_errunion_err`, and `wrap_optional`, the LLVM backend would create
an alloca instruction to store the result, but did not set the alignment
on it. This caused UB which went undetected for a long time until we
started enabling the stack protector.
Closes#12594
Unblocks #12508
Inspires #12634
Tests passed locally:
* test-behavior
* test-cases
Previously, Zig had inconsistent semantics for an enum like this:
`enum(u8){zero = 0}`
Although in theory this can only hold one possible value, the tag
`zero`, Zig no longer will treat the type this way. It will do loads and
stores, as if the type has runtime bits.
Closes#12619
Tests passed locally:
* test-behavior
* test-cases
Removed the copy of param_names inside of Fn and changed to
implementation of getParamName to fetch to parameter name from the ZIR.
The signature of getParamName was also changed to take an additional
*Module argument.
This change provides a basic implementation of #2349 for stage2. There's
still quite a lot of work before this logic is as complete as what's in
Clang (b364535304/clang/lib/CodeGen/CGStmt.cpp (L2304-L2795)),
particularly considering the diversity of constraints across targets.
It's probably not worth doing the complete work until there's a clearer
picture for constraints in Zig's future dedicated ASM syntax, but at
least this gives us a small improvement for now.
As a bonus, this also fixes a bug with how we were handling `_`
identifiers.
When lowering the return type for Wasm if the calling convention is `C`,
it now correctly lower it according to what clang does as specified in:
https://github.com/WebAssembly/tool-conventions/blob/main/BasicCABI.md
This makes use of the same logic as the Wasm backend, ensuring the
generated code does not diverge in function signatures.
When passing arguments accross the C-ABI for the Wasm target,
we want slightly different behavior than x86_64.
For instance: a struct with multiple fields must always be passed
by reference, even if its ABI size fits in a single integer.
However, we do pass larger integers such as 128bit by value,
which LLVM will correctly lower to use double arguments instead.
When lowering a struct type to an LLVM struct type, keep track of
whether there are any underaligned fields. If so, then make it a packed
llvm struct. This works because we already insert manual padding bytes
regardless.
We could unconditionally use an LLVM packed struct; the reason we bother
checking for underaligned fields is that it is a conservative choice, in
case LLVM handles packed structs less optimally. A future improvement
could simplify this code by unconditionally using packed LLVM structs
and then make sure measure perf is unaffected.
closes#12190
This is a possible workaround for
https://github.com/llvm/llvm-project/issues/56585
On my computer it makes stage3-release go from false positive
compilation errors on the behavior tests to "segmentation fault".
Is this forwards progress or backwards progress? I have no idea.
See #11450
This is a workaround for https://github.com/llvm/llvm-project/issues/56585
which causes writes to i1 in memory to be optimized to an incorrect value.
Unfortunately, this does not save users from running into this bug with u1
in their own types.
However, this does seem to be enough to get the behavior tests working.
This resolves#11450 on my machine.
Previously, the Zig ABI size and LLVM ABI size of these types disagreed
sometimes. This code also corrects the logging messages to not trigger
LLVM assertions.
This reverts commit 2eaef84ebe.
Here is a motivating example:
```zig
const E = union(enum) {
A: [9]u8,
B: u64,
};
```
```llvm
%test2.E = type { { i64, [1 x i8] }, i1, [6 x i8] }
```
```
error(codegen): when lowering test2.E, Zig ABI size = 16 but LLVM ABI size = 24
```
For calling convention ABI purposes, integer attributes and return
values need to have an LLVM attribute signext or zeroext added
sometimes. This commit implements that logic.
It also implements a proof-of-concept of moving the F16T type from
being a compiler_rt hack to being how the compiler lowers f16 in
functions that need to match certain calling conventions.
Closes#12054
For some targets, Clang unconditionally adds some clobbers to all inline assembly.
While this is probably not strictly necessary, if we don't follow Clang's lead
here then we may risk tripping LLVM bugs since anything not used by Clang tends
to be buggy and regress often.
LLVM does not properly handle debug info for f16 on the aarch64-windows
target, causing "fatal error: unknown codeview register H1". The
previous workaround checked only for f16 but was still vulnerable if a
type was a byval struct or tuple which had an f16 field in it.
Now I have filed an upstream issue (see
https://github.com/llvm/llvm-project/issues/56484) and broadened the
workaround to always skip debug values for this target.
Our lowerings for various LLVM types assume that we can anticipate the
alignment/layout that LLVM will generate. Among other things, this
requires that we keep the alignment of our lowered LLVM types
synchronized with their expected alignment in Zig.
- Arrays were using packed struct types, which is seems to be
incorrect since array elements are supposed to be self-aligned.
- Unions were using packed struct types for their payload, which causes
layout divergence between what stage2 expects and what LLVM generates
Consider this lowered union type:
```llvm
%Value = type { <{ i64, [8 x i8] }>, i1, [7 x i8] } ; 24 bytes, align(1)
%ErrorUnion = type { %Value, i16 } ; 26 bytes, align(2)
```
Zig expects Value to be align(8) and, by extension, for ErrorUnion to be
size 32.
