Stage 2's softfloat support still had a couple of gaps, which were
preventing us from lowering `f16` on this target. With any luck,
this is enough to get PPC64 working as a Tier 2 target again.
Without the packed qualifier, the type layout that we use to
initialize doesn't match the correct layout of the underlying
storage, causing corrupted data and past-the-end writes.
When encountering a fn type that returns an error (union), a backend
that supports error return tracing will want the StackTrace struct and
its fields to be analyzed.
These const qualifiers on pointers to opaque types do not serve any
purpose. If anything they are misleading since the underlying pointers
very likely point to objects that are in fact mutated.
This commit does not change any behavior.
This bug manifested as a segfault in stage1 when calling this function.
The C++ code looks like this:
```c++
entry->llvm_di_type = ZigLLVMCreateDebugForwardDeclType(g->dbuilder,
ZigLLVMTag_DW_structure_type(), full_name,
import ? ZigLLVMFileToScope(import->data.structure.root_struct->di_file) : nullptr,
import ? import->data.structure.root_struct->di_file : nullptr,
line);
```
There is actually no problem here - what happened is that because
cross-language LTO was enabled between zig and c++ code, and because
Zig annotated the file parameter (3rd line) as being non-null, the C++
code assumed that parameter could not be null, and eagerly dereferenced
`import->...`, causing a segfault, since it was null.
I verified that this commit fixed the problem and I also verified this
hypothesis by disabling LTO and noticing that it indeed avoided the
problem.
Extern functions were missing attributes such as "readonly" on
non-optional pointers, and "byval" which is required to match C ABI.
Follow-up from bf28765a975355c27558eaa86cf00ccb29b663a7.
closes#12683
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
