This reverts commit 9f0359d78f9facc38418e32b0e8c1bf6f99f0d26 in an attempt to
make the tests pass again. The CI failure from that merge should be unrelated
to this commit.
This reverts commit b822e841cda0adabe3fec260ff51c18508f7ee32, reversing
changes made to 0c99ba1eab63865592bb084feb271cd4e4b0357e.
This caused a CI failure when it landed in master branch.
This function does not seem to differ in any interesting way from
`!typeRequiresComptime`, other than the `is_extern` param which is only
used in one place, and some differences did not seem correct anyway.
My reasoning for changing opaque types to be comptime-only is that
`explainWhyTypeIsComptime` is quite happy to explain why they are. :D
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
All tests have been manually verified which are now passing. This means that any remaining
TODO is an actual to-be-fixed or to-be-implemented test case.
* Sema: resolve type fully when emitting an alloc AIR instruction to
avoid tripping assertion for checking struct field alignment.
* LLVM backend: keep a reference to the LLVM target data alive during
lowering so that we can ask LLVM what it thinks the ABI alignment
and size of LLVM types are. We need this in order to lower tuples and
structs so that we can put in extra padding bytes when Zig disagrees
with LLVM about the size or alignment of something.
* LLVM backend: make the LLVM struct type packed that contains the most
aligned union field and the padding. This prevents the struct from
being too big according to LLVM. In the future, we may want to
consider instead emitting unions in a "flat" manner; putting the tag,
most aligned union field, and padding all in the same struct field
space.
* LLVM backend: make structs with 2 or fewer fields return isByRef=false.
This results in more efficient codegen. This required lowering of
bitcast to sometimes store the struct into an alloca, ptrcast, and
then load because LLVM does not allow bitcasting structs.
* enable more passing behavior tests.
