Extend attribute deduction to determine whether parameters using
indirect pass mode might have their address captured. Similarly to
the deduction of `readonly` attribute this information facilitates
memcpy optimizations.
cg_llvm: Use `LLVMDIBuilderCreateGlobalVariableExpression`
- Part of rust-lang/rust#134001
- Follow-up to rust-lang/rust#146763
---
This PR dismantles the somewhat complicated `LLVMRustDIBuilderCreateStaticVariable` function, and replaces it with equivalent calls to `LLVMDIBuilderCreateGlobalVariableExpression` and `LLVMGlobalSetMetadata`.
A key difference is that the new code does not replicate the attempted downcast of `InitVal`. As far as I can tell, those downcasts were actually dead, because `llvm::ConstantInt` and `llvm::ConstantFP` are not subclasses of `llvm::GlobalVariable`. I tried replacing those code paths with fatal errors, and was unable to induce failure in any of the relevant test suites I ran.
I have also confirmed that if the calls to `create_static_variable` are commented out, debuginfo tests will fail, demonstrating some amount of relevant test coverage.
The new `DIBuilder` methods have been added via an extension trait, not as inherent methods, to avoid impeding rust-lang/rust#142897.
Note that the code in `LLVMRustDIBuilderCreateStaticVariable` that tried to
downcast `InitVal` appears to have been dead, because `llvm::ConstantInt` and
`llvm::ConstantFP` are not subclasses of `llvm::GlobalVariable`.
refactor: Remove `LLVMRustInsertPrivateGlobal` and `define_private_global`
Since it can easily be implemented using the existing LLVM C API in
terms of `LLVMAddGlobal` and `LLVMSetLinkage` and `define_private_global`
was only used in one place.
Work towards https://github.com/rust-lang/rust/issues/46437
Since it can easily be implemented using the existing LLVM C API in
terms of `LLVMAddGlobal` and `LLVMSetLinkage` and `define_private_global`
was only used in one place.
cg_llvm: Replace some DIBuilder wrappers with LLVM-C API bindings (part 5)
- Part of rust-lang/rust#134001
- Follow-up to rust-lang/rust#146673
---
This is another batch of LLVMDIBuilder binding migrations, replacing some our own LLVMRust bindings with bindings to upstream LLVM-C APIs.
Some of these are a little more complex than most of the previous migrations, because they split one LLVMRust binding into multiple LLVM bindings, but nothing too fancy.
This appears to be the last of the low-hanging fruit. As noted in https://github.com/rust-lang/rust/issues/134001#issuecomment-2524979268, the remaining bindings are difficult or impossible to migrate at present.
LLVM change dfbd76bda01e removed separate remark support entirely, but
it turns out we can just drop the parameter and everything appears to
work fine.
Fixes 146912 as far as I can tell (the test passes.)
@rustbot label llvm-main
Use captures(address) instead of captures(none) for indirect args
While provenance cannot be captured through these arguments, the address / object identity can.
Fixes https://github.com/rust-lang/rust/issues/137668.
r? `@ghost`
The underlying implementation of `LLVMCreateConstantRangeAttribute` assumes
that each of `LowerWords` and `UpperWords` points to enough u64 values to
define an integer of the specified bit-length, and will encounter UB if that is
not the case.
Our safe wrapper function always passes pointers to `[u64; 2]` arrays,
regardless of the bit-length specified. That's fine in practice, because scalar
primitives never exceed 128 bits, but it is technically a soundness hole in a
safe function.
We can close the soundness hole by explicitly asserting `size_bits <= 128`.
This is effectively just a stricter version of the existing check that the
value must be small enough to fit in `c_uint`.
`&Freeze` parameters are not only `readonly` within the function,
but any captures of the pointer can also only be used for reads.
This can now be encoded using the `captures(address, read_provenance)`
attribute.
Set the dead_on_return attribute (added in LLVM 21) for arguments
that are passed indirectly, but not byval.
This indicates that the value of the argument on return does not
matter, enabling additional dead store elimination.
Implement support for `become` and explicit tail call codegen for the LLVM backend
This PR implements codegen of explicit tail calls via `become` in `rustc_codegen_ssa` and support within the LLVM backend. Completes a task on (https://github.com/rust-lang/rust/issues/112788). This PR implements all the necessary bits to make explicit tail calls usable, other backends have received stubs for now and will ICE if you use `become` on them. I suspect there is some bikeshedding to be done on how we should go about implementing this for other backends, but it should be relatively straightforward for GCC after this is merged.
During development I also put together a POC bytecode VM based on tail call dispatch to test these changes out and analyze the codegen to make sure it generates expected assembly. That is available [here](https://github.com/xacrimon/tcvm).
