* Disable 128-bit atomics for x86_64 generic (currently also baseline)
because they require heavy abi agreement to correctly lower.
** This is a breaking change **
* Enable 128-bit atomics for aarch64 in Sema since it just works.
Since the Zig language documentation claims support for `.Min` and
`.Max` in `@atomicRmw` with floats, allow in Sema and implement for both
the llvm and C backends.
* CompileStep: Avoid calling producesPdbFile() to determine whether the
option should be respected. If the user asks for it, put it on the
command line and let the Zig CLI deal with it appropriately.
* Make the namespace of `std.dwarf.Format.dwarf32` no longer have a
redundant "dwarf" in it.
* Add `zig cc` integration for `-gdwarf32` and `-gdwarf64`.
* Toss in a bonus bug fix for `-gdwarf-2`, `-gdwarf-3`, etc.
* Avoid using default init values for struct fields unnecessarily.
* Add missing cache hash addition for the new option.
This commit enables producing 64-bit DWARF format for Zig executables
that are produced through the LLVM backend. This is achieved by exposing
both command-line flags and CompileStep flags. The production of the
64-bit format only affects binaries that use the DWARF format and it is
disabled on MacOS due to it being problematic. This commit, despite
generating the interface for the Zig user to be able to tell the compile
which format is wanted, is just implemented for the LLVM backend, so
clang and the self-hosted backends will need this to be implemented in a
future commit.
This is an effort to work around #7962, since the emission of the 64-bit
format automatically produces 64-bit relocations. Further investigation
will be needed to make DWARF 32-bit format to emit bigger relocations
when needed and not make the linker angry.
Uses the new liveness behaviour. This also removes useless calls
to `processDeath` on branches that were just initialized. Branch
consolidation and processing deaths on branches inside `condbr`
is still a TODO, just like before.
This also skips var_args on other native backends as they do not
support this feature yet.
Backends want to avoid emitting unused instructions which do not have
side effects: to that end, they all have `Liveness.isUnused` checks for
many instructions. However, checking this in the backends avoids a lot
of potential optimizations. For instance, if a nested field is loaded,
then the first field access would still be emitted, since its result is
used by the next access (which is then unreferenced).
To elide more instructions, Liveness can track this data instead. For
operands which do not have to be lowered (i.e. are not side effecting
and are not something special like `arg), Liveness can ignore their
operand usages, and push the unused information further up, potentially
marking many more instructions as unreferenced.
In doing this, I also uncovered a bug in the LLVM backend relating to
discarding the result of `@cVaArg`, which this change fixes. A behaviour
test has been added to cover it.
This is a partial rewrite of Liveness, so has some other notable changes:
- A proper multi-pass system to prevent code duplication
- Better logging
- Minor bugfixes
