Ensure strings created with `const_str` get the `unnamed_addr` attribute
This function (`const_str`) is only used when we need to invent a string during codegen -- for example, for a panic message to pass when codegening some of the assert/panic/etc terminators (for stuff like divide by zero).
AFAICT all other consts, such as the user-defined ones from const eval, should already be getting this attribute (things that come from a ConstAllocation do, for example). Which means that the "unnamed" part is even more true than usual here, these aren't strings that even exist as far as the user can tell.
~~Setting this attribute allows LLVM to merge these constants, leading to significant binary size savings (much more than I would expect). On x86_64-unknown-linux-gnu, t takes a build of ripgrep (release without debug info) from 9.7MiB to 6.0MiB (a savings of over 30%!?), and a build of rustc_driver's shared object from 123MiB to 112MiB (less drastic, but still over 10% reduced).~~
~~The effect on ripgrep is substantially reduced on macOS for reasons beyond me (I may have fucked up the test), only saving around 0.2MiB, although rustc_driver is still around 10MB or smaller than it had been previously.~~
~~This raises some questions, such as "does that mean 1/3 of ripgrep was made of division by zero complaints?" I'm not sure, that may be the case. The output of `strings path/to/rg` is \~2MB smaller, so it seems like a lot of it was. Allowing these to be merged presumably also allow functions that contain them to be merged (if the addresses had semantic meaning, then it stands).~~
~~I intend to do some more analysis here, but I got this up as soon as I realized that this attribute was only missing for internal const strings, and all other ones already get it.~~
Edit: The wins are much more marginal, but there's some argument to do this for the sake of consistency.
Add -Z llvm_module_flag
Allow adding values to the `!llvm.module.flags` metadata for a generated module. The syntax is
`-Z llvm_module_flag=<name>:<type>:<value>:<behavior>`
Currently only u32 values are supported but the type is required to be specified for forward compatibility. The `behavior` element must match one of the named LLVM metadata behaviors.viors.
This flag is expected to be perma-unstable.
Allow adding values to the `!llvm.module.flags` metadata for a generated
module. The syntax is
`-Z llvm_module_flag=<name>:<type>:<value>:<behavior>`
Currently only u32 values are supported but the type is required to be
specified for forward compatibility. The `behavior` element must match
one of the named LLVM metadata behaviors.viors.
This flag is expected to be perma-unstable.
consts: remove dead code around `i1` constant values
`LLVMConstZext` recently got deleted, and it turns out (thanks to `@nikic` for knowing!) that this is dead code. Tests all pass for me without this logic, and per nikic:
> We always generate constants in "relocatable bag of bytes"
> representation, so you're never going to get a plain bool.
So this should be a safe thing to do.
r? `@nikic`
`@rustbot` label: +llvm-main
`LLVMConstZext` recently got deleted, and it turns out (thanks to @nikic
for knowing!) that this is dead code. Tests all pass for me without this
logic, and per nikic:
> We always generate constants in "relocatable bag of bytes"
> representation, so you're never going to get a plain bool.
So this should be a safe thing to do.
r? @nikic
@rustbot label: +llvm-main
Most notably, this commit changes the `pub use crate::*;` in that file
to `use crate::*;`. This requires a lot of `use` items in other crates
to be adjusted, because everything defined within `rustc_span::*` was
also available via `rustc_span::source_map::*`, which is bizarre.
The commit also removes `SourceMap::span_to_relative_line_string`, which
is unused.
- Sort dependencies and features sections.
- Add `tidy` markers to the sorted sections so they stay sorted.
- Remove empty `[lib`] sections.
- Remove "See more keys..." comments.
Excluded files:
- rustc_codegen_{cranelift,gcc}, because they're external.
- rustc_lexer, because it has external use.
- stable_mir, because it has external use.
coverage: Consistently remove unused counter IDs from expressions/mappings
If some coverage counters were removed by MIR optimizations, we need to take care not to refer to those counter IDs in coverage mappings, and instead replace them with a constant zero value. If we don't, `llvm-cov` might see a too-large counter ID and silently discard the entire function from its coverage reports.
Fixes#117012.
report `unused_import` for empty reexports even it is pub
Fixes#116032
An easy fix. r? `@petrochenkov`
(Discovered this issue while reviewing #115993.)
Most coverage metadata is encoded into two sections in the final executable.
The `__llvm_covmap` section mostly just contains a list of filenames, while the
`__llvm_covfun` section contains encoded coverage maps for each instrumented
function.
The catch is that each per-function record also needs to contain a hash of the
filenames list that it refers to. Historically this was handled by assembling
most of the per-function data into a temporary list, then assembling the
filenames buffer, then using the filenames hash to emit the per-function data,
and then finally emitting the filenames table itself.
However, now that we build the filenames table up-front (via a separate
traversal of the per-function data), we can hash and emit that part first, and
then emit each of the per-function records immediately after building. This
removes the awkwardness of having to temporarily store nearly-complete
per-function records.
The main change here is that `VirtualFileMapping` now uses an internal hashmap
to de-duplicate incoming global file IDs. That removes the need for
`encode_mappings_for_function` to re-sort its mappings by filename in order to
de-duplicate them.
(We still de-duplicate runs of identical filenames to save work, but this is
not load-bearing for correctness, so a sort is not necessary.)
The combined `get_expressions_and_counter_regions` method was an artifact of
having to prepare the expressions and mappings at the same time, to avoid
ownership/lifetime problems with temporary data used by both.
Now that we have an explicit transition from `FunctionCoverageCollector` to the
final `FunctionCoverage`, we can prepare any shared data during that step and
store it in the final struct.
This gives us a clearly-defined place to run code after the instance's MIR has
been traversed by codegen, but before we emit its `__llvm_covfun` record.
This query has a name that sounds general-purpose, but in fact it has
coverage-specific semantics, and (fortunately) is only used by coverage code.
Because it is only ever called once (from one designated CGU), it doesn't need
to be a query, and we can change it to a regular function instead.
Implement rustc part of RFC 3127 trim-paths
This PR implements (or at least tries to) [RFC 3127 trim-paths](https://github.com/rust-lang/rust/issues/111540), the rustc part. That is `-Zremap-path-scope` with all of it's components/scopes.
`@rustbot` label: +F-trim-paths
Even though expression details are now stored in the info structure, we still
need to inject `ExpressionUsed` statements into MIR, because if one is missing
during codegen then we know that it was optimized out and we can remap all of
its associated code regions to zero.
Previously, mappings were attached to individual coverage statements in MIR.
That necessitated special handling in MIR optimizations to avoid deleting those
statements, since otherwise codegen would be unable to reassemble the original
list of mappings.
With this change, a function's list of mappings is now attached to its MIR
body, and survives intact even if individual statements are deleted by
optimizations.
Instead of modifying the accumulated expressions in-place, we now build a set
of expressions that are known to be zero, and then consult that set on the fly
when converting the expression data for FFI.
This will be necessary when moving mappings and expression data into function
coverage info, which can't be mutated during codegen.
Coverage codegen can now allocate arrays based on the number of
counters/expressions originally used by the instrumentor.
The existing query that inspects coverage statements is still used for
determining the number of counters passed to `llvm.instrprof.increment`. If
some high-numbered counters were removed by MIR optimizations, the instrumented
binary can potentially use less memory and disk space at runtime.
This allows coverage information to be attached to the function as a whole when
appropriate, instead of being smuggled through coverage statements in the
function's basic blocks.
As an example, this patch moves the `function_source_hash` value out of
individual `CoverageKind::Counter` statements and into the per-function info.
When synthesizing unused functions for coverage purposes, the absence of this
info is taken to indicate that a function was not eligible for coverage and
should not be synthesized.
Remove cgu_reuse_tracker from Session
This removes a bit of global mutable state.
It will now miss post-lto cgu reuse when ThinLTO determines that a cgu doesn't get changed, but there weren't any tests for this anyway and a test for it would be fragile to the exact implementation of ThinLTO in LLVM.
Copy 1-element arrays as scalars, not vectors
For `[T; 1]` it's silly to copy as `<1 x T>` when we can just copy as `T`.
Inspired by https://github.com/rust-lang/rust/issues/101210#issuecomment-1732470941, which pointed out that `Option<[u8; 1]>` was codegenning worse than `Option<u8>`.
(I'm not sure *why* LLVM doesn't optimize out `<1 x u8>`, but might as well just not emit it in the first place in this codepath.)
---
I think I bit off too much in #116479; let me try just the scalar case first.
r? `@ghost`
Prototype using const generic for simd_shuffle IDX array
cc https://github.com/rust-lang/rust/issues/85229
r? `@workingjubilee` on the design
TLDR: there is now a `fn simd_shuffle_generic<T, U, const IDX: &'static [u32]>(x: T, y: T) -> U;` intrinsic that allows replacing
```rust
simd_shuffle(a, b, const { stuff })
```
with
```rust
simd_shuffle_generic::<_, _, {&stuff}>(a, b)
```
which makes the compiler implementations much simpler, if we manage to at some point eliminate `simd_shuffle`.
There are some issues with this today though (can't do math without bubbling it up in the generic arguments). With this change, we can start porting the simple cases and get better data on the others.
subst -> instantiate
continues #110793, there are still quite a few uses of `subst` and `substitute`, but changing them all in the same PR was a bit too much, so I've stopped here for now.
The LLVM API that we use to encode coverage mappings already has its own code
for removing unused coverage expressions and renumbering the rest.
This lets us get rid of our own complex renumbering code, making it easier to
change our coverage code in other ways.
After coverage instrumentation and MIR transformations, we can sometimes end up
with coverage expressions that always have a value of zero. Any expression
operand that refers to an always-zero expression can be replaced with a literal
`Operand::Zero`, making the emitted coverage mapping data smaller and simpler.
This simplification step is mostly redundant with the simplifications performed
inline in `expressions_with_regions`, except that it does a slightly more
thorough job in some cases (because it checks for always-zero expressions
*after* other simplifications).
However, adding this simplification step will then let us greatly simplify that
code, without affecting the quality of the emitted coverage maps.
treat host effect params as erased in codegen
This fixes the changes brought to codegen tests when effect params are added to libcore, by not attempting to monomorphize functions that get the host param by being `const fn`.
r? `@oli-obk`
This fixes the changes brought to codegen tests when effect params are
added to libcore, by not attempting to monomorphize functions that get
the host param by being `const fn`.
Rework `no_coverage` to `coverage(off)`
As discussed at the tail of https://github.com/rust-lang/rust/issues/84605 this replaces the `no_coverage` attribute with a `coverage` attribute that takes sub-parameters (currently `off` and `on`) to control the coverage instrumentation.
Allows future-proofing for things like `coverage(off, reason="Tested live", issue="#12345")` or similar.
Remove `verbose_generic_activity_with_arg`
This removes `verbose_generic_activity_with_arg` and changes users to `generic_activity_with_arg`. This keeps the output of `-Z time` readable while these repeated events are still available with the self profiling mechanism.
Instead of writing coverage mappings into a supplied `&RustString`, this
function can just create the buffer itself and return the resulting vector of
bytes.
If two or more mappings cover exactly the same region, their relative order
will now be preserved from `get_expressions_and_counter_regions`, rather than
being disturbed by implementation details of an unstable sort.
The current order is: counter mappings, expression mappings, zero mappings.
(LLVM will also perform its own stable sort on these mappings, but that sort
only compares file ID, start location, and `RegionKind`.)
This struct was only being used to hold the global file table, and one of its
methods didn't even use the table. Changing its methods to ordinary functions
makes it easier to see where the table is mutated.
debuginfo: add compiler option to allow compressed debuginfo sections
LLVM already supports emitting compressed debuginfo. In debuginfo=full builds, the debug section is often a large amount of data, and it typically compresses very well (3x is not unreasonable.) We add a new knob to allow debuginfo to be compressed when the matching LLVM functionality is present. Like clang, if a known-but-disabled compression mechanism is requested, we disable compression and emit uncompressed debuginfo sections.
The API is different enough on older LLVMs we just pretend the support
is missing on LLVM older than 16.
Use the same DISubprogram for each instance of the same inlined function within a caller
# Issue Details:
The call to `panic` within a function like `Option::unwrap` is translated to LLVM as a `tail call` (as it will never return), when multiple calls to the same function like this are inlined LLVM will notice the common `tail call` block (i.e., loading the same panic string + location info and then calling `panic`) and merge them together.
When merging these instructions together, LLVM will also attempt to merge the debug locations as well, but this fails (i.e., debug info is dropped) as Rust emits a new `DISubprogram` at each inline site thus LLVM doesn't recognize that these are actually the same function and so thinks that there isn't a common debug location.
As an example of this, consider the following program:
```rust
#[no_mangle]
fn add_numbers(x: &Option<i32>, y: &Option<i32>) -> i32 {
let x1 = x.unwrap();
let y1 = y.unwrap();
x1 + y1
}
```
When building for x86_64 Windows using 1.72 it generates (note the lack of `.cv_loc` before the call to `panic`, thus it will be attributed to the same line at the `addq` instruction):
```llvm
.cv_loc 0 1 3 0 # src\lib.rs:3:0
addq $40, %rsp
retq
leaq .Lalloc_f570dea0a53168780ce9a91e67646421(%rip), %rcx
leaq .Lalloc_629ace53b7e5b76aaa810d549cc84ea3(%rip), %r8
movl $43, %edx
callq _ZN4core9panicking5panic17h12e60b9063f6dee8E
int3
```
# Fix Details:
Cache the `DISubprogram` emitted for each inlined function instance within a caller so that this can be reused if that instance is encountered again.
Ideally, we would also deduplicate child scopes and variables, however my attempt to do that with #114643 resulted in asserts when building for Linux (#115156) which would require some deep changes to Rust to fix (#115455).
Instead, when using an inlined function as a debug scope, we will also create a new child scope such that subsequent child scopes and variables do not collide (from LLVM's perspective).
After this change the above assembly now (with <https://reviews.llvm.org/D159226> as well) shows the `panic!` was inlined from `unwrap` in `option.rs` at line 935 into the current function in `lib.rs` at line 0 (line 0 is emitted since it is ambiguous which line to use as there were two inline sites that lead to this same code):
```llvm
.cv_loc 0 1 3 0 # src\lib.rs:3:0
addq $40, %rsp
retq
.cv_inline_site_id 6 within 0 inlined_at 1 0 0
.cv_loc 6 2 935 0 # library\core\src\option.rs:935:0
leaq .Lalloc_5f55955de67e57c79064b537689facea(%rip), %rcx
leaq .Lalloc_e741d4de8cb5801e1fd7a6c6795c1559(%rip), %r8
movl $43, %edx
callq _ZN4core9panicking5panic17hde1558f32d5b1c04E
int3
```
lto: load bitcode sections by name
Upstream change
llvm/llvm-project@6b539f5eb8 changed `isSectionBitcode` works and it now only respects `.llvm.lto` sections instead of also `.llvmbc`, which it says was never intended to be used for LTO. We instead load sections by name, and sniff for raw bitcode by hand.
This is an alternative approach to #115136, where we tried the same thing using the `object` crate, but it got too fraught to continue.
r? `@nikic`
`@rustbot` label: +llvm-main
Use `Freeze` for `SourceFile`
This uses the `Freeze` type in `SourceFile` to let accessing `external_src` and `lines` be lock-free.
Behavior of `add_external_src` is changed to set `ExternalSourceKind::AbsentErr` on a hash mismatch which matches the documentation. `ExternalSourceKind::Unneeded` was removed as it's unused.
Based on https://github.com/rust-lang/rust/pull/115401.
LLVM already supports emitting compressed debuginfo. In debuginfo=full
builds, the debug section is often a large amount of data, and it
typically compresses very well (3x is not unreasonable.) We add a new
knob to allow debuginfo to be compressed when the matching LLVM
functionality is present. Like clang, if a known-but-disabled
compression mechanism is requested, we disable compression and emit
uncompressed debuginfo sections.
The API is different enough on older LLVMs we just pretend the support
is missing on LLVM older than 16.
Upstream change
llvm/llvm-project@6b539f5eb8 changed
`isSectionBitcode` works and it now only respects `.llvm.lto` sections
instead of also `.llvmbc`, which it says was never intended to be used
for LTO. We instead load sections by name, and sniff for raw bitcode by
hand.
r? @nikic
@rustbot label: +llvm-main
Add CL and CMD into to pdb debug info
Partial fix for https://github.com/rust-lang/rust/issues/96475
The Arg0 and CommandLineArgs of the MCTargetOptions cpp class are not set within bb548f9645/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp (L378)
This causes LLVM to not neither output any compiler path (cl) nor the arguments that were used when invoking it (cmd) in the PDB file.
This fix adds the missing information to the target machine so LLVM can use it.
