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Speed up target feature computation
The LLVM backend calls `LLVMRustHasFeature` twice for every feature. In short-running rustc invocations, this accounts for a surprising amount of work.
r? `@bjorn3`
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Clean up various LLVM FFI things in codegen_llvm
cc ```@ZuseZ4``` I touched some autodiff parts
The major change of this PR is [bfd88ce](https://github.com/rust-lang/rust/pull/137549/commits/bfd88cead0dd79717f123ad7e9a26ecad88653cb) which makes `CodegenCx` generic just like `GenericBuilder`
The other commits mostly took advantage of the new feature of making extern functions safe, but also just used some wrappers that were already there and shrunk unsafe blocks.
best reviewed commit-by-commit
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Currently it is called twice, once with `allow_unstable` set to true and
once with it set to false. This results in some duplicated work. Most
notably, for the LLVM backend, `LLVMRustHasFeature` is called twice for
every feature, and it's moderately slow. For very short running
compilations on platforms with many features (e.g. a `check` build of
hello-world on x86) this is a significant fraction of runtime.
This commit changes `target_features_cfg` so it is only called once, and
it now returns a pair of feature sets. This halves the number of
`LLVMRustHasFeature` calls.
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This reverts commit a7a6c64a657f68113301c2ffe0745b49a16442d1, reversing
changes made to ebbe63891f1fae21734cb97f2f863b08b1d44bf8.
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The embedded bitcode should always be prepared for LTO/ThinLTO
Fixes #115344. Fixes #117220.
There are currently two methods for generating bitcode that used for LTO. One method involves using `-C linker-plugin-lto` to emit object files as bitcode, which is the typical setting used by cargo. The other method is through `-C embed-bitcode=yes`.
When using with `-C embed-bitcode=yes -C lto=no`, we run a complete non-LTO LLVM pipeline to obtain bitcode, then the bitcode is used for LTO. We run the Call Graph Profile Pass twice on the same module.
This PR is doing something similar to LLVM's `buildFatLTODefaultPipeline`, obtaining the bitcode for embedding after running `buildThinLTOPreLinkDefaultPipeline`.
r? nikic
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The implementation of the `type_has_metadata` function is duplicated in
`rustc_codegen_ssa` and `rustc_monomorphize`, so move this to
`rustc_middle`.
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Emit getelementptr inbounds nuw for pointer::add()
Lower pointer::add (via intrinsic::offset with unsigned offset) to getelementptr inbounds nuw on LLVM versions that support it. This lets LLVM make use of the pre-condition that the offset addition does not wrap in an unsigned sense. Together with inbounds, this also implies that the offset is non-negative.
Fixes https://github.com/rust-lang/rust/issues/137217.
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things which are already immediates
That means it stops trying to truncate things that are already `i1`s.
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- For shifts this shrinks the IR by no longer needing an `assume` while still providing the UB information
- Having this on the `i8`→`i1` truncations will hopefully help with some places that have to load `i8`s or pass those in LLVM structs without range information
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improve cold_path()
#120370 added a new instrinsic `cold_path()` and used it to fix `likely` and `unlikely`
However, in order to limit scope, the information about cold code paths is only used in 2-target switch instructions. This is sufficient for `likely` and `unlikely`, but limits usefulness of `cold_path` for idiomatic rust. For example, code like this:
```
if let Some(x) = y { ... }
```
may generate 3-target switch:
```
switch y.discriminator:
0 => true branch
1 = > false branch
_ => unreachable
```
and therefore marking a branch as cold will have no effect.
This PR improves `cold_path()` to work with arbitrary switch instructions.
Note that for 2-target switches, we can use `llvm.expect`, but for multiple targets we need to manually emit branch weights. I checked Clang and it also emits weights in this situation. The Clang's weight calculation is more complex that this PR, which I believe is mainly because `switch` in `C/C++` can have multiple cases going to the same target.
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Set both `nuw` and `nsw` in slice size calculation
There's an old note in the code to do this, and now that [LLVM-C has an API for it](https://github.com/llvm/llvm-project/blob/f0b8ff12519270adcfef93410abff76ab073476a/llvm/include/llvm-c/Core.h#L4403-L4408), we might as well. And it's been there since what looks like LLVM 17 https://github.com/llvm/llvm-project/commit/de9b6aa341d8951625d62ae3dac8670ebb3eb006 so doesn't even need to be conditional.
(There's other places, like `RawVecInner` or `Layout`, that might want to do things like this too, but I'll leave those for a future PR.)
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There's an old note in the code to do this, and now that LLVM-C has an API for it, we might as well.
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Previously it only did integer-ABI things, but this way it does data pointers too. That gives more information in general to the backend, and allows slightly simplifying one of the helpers in slice iterators.
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Separate Builder methods from tcx
As part of the autodiff upstreaming we noticed, that it would be nice to have various builder methods available without the TypeContext, which prevents the normal CodegenCx to be passed around between threads.
We introduce a SimpleCx which just owns the llvm module and llvm context, to encapsulate them.
The previous CodegenCx now implements deref and forwards access to the llvm module or context to it's SimpleCx sub-struct. This gives us a bit more flexibility, because now we can pass (or construct) the SimpleCx in locations where we don't have enough information to construct a CodegenCx, or are not able to pass it around due to the tcx lifetimes (and it not implementing send/sync).
This also introduces an SBuilder, similar to the SimpleCx. The SBuilder uses a SimpleCx, whereas the existing Builder uses the larger CodegenCx. I will push updates to make implementations generic (where possible) to be implemented once and work for either of the two. I'll also clean up the leftover code.
`call` is a bit tricky, because it requires a tcx, I probably need to duplicate it after all.
Tracking:
- https://github.com/rust-lang/rust/issues/124509
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Co-authored-by: Oli Scherer <github35764891676564198441@oli-obk.de>
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Update our range `assume`s to the format that LLVM prefers
I found out in https://github.com/llvm/llvm-project/issues/123278#issuecomment-2597440158 that the way I started emitting the `assume`s in #109993 was suboptimal, and as seen in that LLVM issue the way we're doing it -- with two `assume`s sometimes -- can at times lead to CVP/SCCP not realize what's happening because one of them turns into a `ne` instead of conveying a range.
So this updates how it's emitted from
```
assume( x >= LOW );
assume( x <= HIGH );
```
or
```
// (for ranges that wrap the range)
assume( (x <= LOW) | (x >= HIGH) );
```
to
```
assume( (x - LOW) <= (HIGH - LOW) );
```
so that we don't need multiple `icmp`s nor multiple `assume`s for a single value, and both wrappping and non-wrapping ranges emit the same shape.
(And we don't bother emitting the subtraction if `LOW` is zero, since that's trivial for us to check too.)
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`rustc_span::symbol` defines some things that are re-exported from
`rustc_span`, such as `Symbol` and `sym`. But it doesn't re-export some
closely related things such as `Ident` and `kw`. So you can do `use
rustc_span::{Symbol, sym}` but you have to do `use
rustc_span::symbol::{Ident, kw}`, which is inconsistent for no good
reason.
This commit re-exports `Ident`, `kw`, and `MacroRulesNormalizedIdent`,
and changes many `rustc_span::symbol::` qualifiers in `compiler/` to
`rustc_span::`. This is a 200+ net line of code reduction, mostly
because many files with two `use rustc_span` items can be reduced to
one.
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forbid toggling x87 and fpregs on hard-float targets
Part of https://github.com/rust-lang/rust/issues/116344, follow-up to https://github.com/rust-lang/rust/pull/129884:
The `x87` target feature on x86 and the `fpregs` target feature on ARM must not be disabled on a hardfloat target, as that would change the float ABI. However, *enabling* `fpregs` on ARM is [explicitly requested](https://github.com/rust-lang/rust/issues/130988) as it seems to be useful. Therefore, we need to refine the distinction of "forbidden" target features and "allowed" target features: all (un)stable target features can determine on a per-target basis whether they should be allowed to be toggled or not. `fpregs` then checks whether the current target has the `soft-float` feature, and if yes, `fpregs` is permitted -- otherwise, it is not. (Same for `x87` on x86).
Also fixes https://github.com/rust-lang/rust/issues/132351. Since `fpregs` and `x87` can be enabled on some builds and disabled on others, it would make sense that one can query it via `cfg`. Therefore, I made them behave in `cfg` like any other unstable target feature.
The first commit prepares the infrastructure, but does not change behavior. The second commit then wires up `fpregs` and `x87` with that new infrastructure.
r? `@workingjubilee`
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codegen `#[naked]` functions using global asm
tracking issue: https://github.com/rust-lang/rust/issues/90957
Fixes #124375
This implements the approach suggested in the tracking issue: use the existing global assembly infrastructure to emit the body of `#[naked]` functions. The main advantage is that we now have full control over what gets generated, and are no longer dependent on LLVM not sneakily messing with our output (inlining, adding extra instructions, etc).
I discussed this approach with `@Amanieu` and while I think the general direction is correct, there is probably a bunch of stuff that needs to change or move around here. I'll leave some inline comments on things that I'm not sure about.
Combined with https://github.com/rust-lang/rust/pull/127853, if both accepted, I think that resolves all steps from the tracking issue.
r? `@Amanieu`
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be invalid to toggle
Also rename some things for extra clarity
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It was inconsistently done (sometimes even within a single function) and
most of the rest of the compiler uses fatal errors instead, which need
to be caught using catch_with_exit_code anyway. Using fatal errors
instead of ErrorGuaranteed everywhere in the driver simplifies things a
bit.
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use intra-doc links so there'll be a doc gen fail next time this becomes
wrong
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the behavior of the type system not only depends on the current
assumptions, but also the currentnphase of the compiler. This is
mostly necessary as we need to decide whether and how to reveal
opaque types. We track this via the `TypingMode`.
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CFI: Append debug location to CFI blocks
Currently we're not appending debug locations to the inserted CFI blocks. This shows up in #132615 and #100783. This change fixes that by passing down the debug location to the CFI type-test generation and appending it to the blocks.
Credits also belong to `@jakos-sec` who worked with me on this.
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After link_binary the temporary files referenced by CodegenResults are
deleted, so calling link_binary again with the same CodegenResults
should not be allowed.
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As a side effect this should add raw-dylib support to cg_gcc as the
default ArchiveBuilderBuilder that is used implements
create_dll_import_lib. I haven't tested if the raw-dylib support
actually works however.
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The initial naming of "Abi" was an awful mistake, conveying wrong ideas
about how psABIs worked and even more about what the enum meant.
It was only meant to represent the way the value would be described to
a codegen backend as it was lowered to that intermediate representation.
It was never meant to mean anything about the actual psABI handling!
The conflation is because LLVM typically will associate a certain form
with a certain ABI, but even that does not hold when the special cases
that actually exist arise, plus the IR annotations that modify the ABI.
Reframe `rustc_abi::Abi` as the `BackendRepr` of the type, and rename
`BackendRepr::Aggregate` as `BackendRepr::Memory`. Unfortunately, due to
the persistent misunderstandings, this too is now incorrect:
- Scattered ABI-relevant code is entangled with BackendRepr
- We do not always pre-compute a correct BackendRepr that reflects how
we "actually" want this value to be handled, so we leave the backend
interface to also inject various special-cases here
- In some cases `BackendRepr::Memory` is a "real" aggregate, but in
others it is in fact using memory, and in some cases it is a scalar!
Our rustc-to-backend lowering code handles this sort of thing right now.
That will eventually be addressed by lifting duplicated lowering code
to either rustc_codegen_ssa or rustc_target as appropriate.
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llvm: replace some deprecated functions
`LLVMMDStringInContext` and `LLVMMDNodeInContext` are deprecated, replace them with `LLVMMDStringInContext2` and `LLVMMDNodeInContext2`.
Also replace `Value` with `Metadata` in some function signatures for better consistency.
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