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2022-03-07Auto merge of #94690 - nnethercote:clarify-Layout-interning, r=fee1-deadbors-7/+7
Clarify `Layout` interning. `Layout` is another type that is sometimes interned, sometimes not, and we always use references to refer to it so we can't take any advantage of the uniqueness properties for hashing or equality checks. This commit renames `Layout` as `LayoutS`, and then introduces a new `Layout` that is a newtype around an `Interned<LayoutS>`. It also interns more layouts than before. Previously layouts within layouts (via the `variants` field) were never interned, but now they are. Hence the lifetime on the new `Layout` type. Unlike other interned types, these ones are in `rustc_target` instead of `rustc_middle`. This reflects the existing structure of the code, which does layout-specific stuff in `rustc_target` while `TyAndLayout` is generic over the `Ty`, allowing the type-specific stuff to occur in `rustc_middle`. The commit also adds a `HashStable` impl for `Interned`, which was needed. It hashes the contents, unlike the `Hash` impl which hashes the pointer. r? `@fee1-dead`
2022-03-07Clarify `Layout` interning.Nicholas Nethercote-7/+7
`Layout` is another type that is sometimes interned, sometimes not, and we always use references to refer to it so we can't take any advantage of the uniqueness properties for hashing or equality checks. This commit renames `Layout` as `LayoutS`, and then introduces a new `Layout` that is a newtype around an `Interned<LayoutS>`. It also interns more layouts than before. Previously layouts within layouts (via the `variants` field) were never interned, but now they are. Hence the lifetime on the new `Layout` type. Unlike other interned types, these ones are in `rustc_target` instead of `rustc_middle`. This reflects the existing structure of the code, which does layout-specific stuff in `rustc_target` while `TyAndLayout` is generic over the `Ty`, allowing the type-specific stuff to occur in `rustc_middle`. The commit also adds a `HashStable` impl for `Interned`, which was needed. It hashes the contents, unlike the `Hash` impl which hashes the pointer.
2022-03-07Auto merge of #94638 - erikdesjardins:noextranull, r=nagisabors-30/+18
cleanup: remove unused ability to have LLVM null-terminate const strings (and the copied function in rustc_codegen_gcc) Noticed this while writing https://github.com/rust-lang/rust/pull/94450#issuecomment-1059687348. r? `@nagisa`
2022-03-06Auto merge of #94597 - nnethercote:ConstAllocation, r=fee1-deadbors-9/+13
Introduce `ConstAllocation`. Currently some `Allocation`s are interned, some are not, and it's very hard to tell at a use point which is which. This commit introduces `ConstAllocation` for the known-interned ones, which makes the division much clearer. `ConstAllocation::inner()` is used to get the underlying `Allocation`. In some places it's natural to use an `Allocation`, in some it's natural to use a `ConstAllocation`, and in some places there's no clear choice. I've tried to make things look as nice as possible, while generally favouring `ConstAllocation`, which is the type that embodies more information. This does require quite a few calls to `inner()`. The commit also tweaks how `PartialOrd` works for `Interned`. The previous code was too clever by half, building on `T: Ord` to make the code shorter. That caused problems with deriving `PartialOrd` and `Ord` for `ConstAllocation`, so I changed it to build on `T: PartialOrd`, which is slightly more verbose but much more standard and avoided the problems. r? `@fee1-dead`
2022-03-07Introduce `ConstAllocation`.Nicholas Nethercote-9/+13
Currently some `Allocation`s are interned, some are not, and it's very hard to tell at a use point which is which. This commit introduces `ConstAllocation` for the known-interned ones, which makes the division much clearer. `ConstAllocation::inner()` is used to get the underlying `Allocation`. In some places it's natural to use an `Allocation`, in some it's natural to use a `ConstAllocation`, and in some places there's no clear choice. I've tried to make things look as nice as possible, while generally favouring `ConstAllocation`, which is the type that embodies more information. This does require quite a few calls to `inner()`. The commit also tweaks how `PartialOrd` works for `Interned`. The previous code was too clever by half, building on `T: Ord` to make the code shorter. That caused problems with deriving `PartialOrd` and `Ord` for `ConstAllocation`, so I changed it to build on `T: PartialOrd`, which is slightly more verbose but much more standard and avoided the problems.
2022-03-06Auto merge of #94679 - matthiaskrgr:rollup-9vd7w6a, r=matthiaskrgrbors-1/+1
Rollup of 3 pull requests Successful merges: - #94659 (explain why shift with signed offset works the way it does) - #94671 (fix pin doc typo) - #94672 (Improved error message for failed bitcode load) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
2022-03-06cleanup: remove unused ability to have LLVM null-terminate const stringsErik Desjardins-30/+18
2022-03-06Improved error message for failed bitcode loadJoe-1/+1
"bc" is an unnecessary shorthand that obfuscates the compilation error
2022-03-04Always include global target features in function attributesTomasz Miąsko-7/+6
This ensures that information about target features configured with `-C target-feature=...` or detected with `-C target-cpu=native` is retained for subsequent consumers of LLVM bitcode. This is crucial for linker plugin LTO, since this information is not conveyed to the plugin otherwise.
2022-03-04Use SmallStr when building target-features LLVM attributeTomasz Miąsko-1/+2
2022-03-04Auto merge of #94539 - tmiasko:string-attributes, r=nikicbors-37/+47
Pass LLVM string attributes as string slices
2022-03-04Auto merge of #94159 - erikdesjardins:align-load, r=nikicbors-8/+31
Add !align metadata on loads of &/&mut/Box Note that this refers to the alignment of what the loaded value points to, _not_ the alignment of the loaded value itself. r? `@ghost` (blocked on #94158)
2022-03-03all: fix some typoscuishuang-5/+5
Signed-off-by: cuishuang <imcusg@gmail.com>
2022-03-03Rollup merge of #94529 - GuillaumeGomez:unused-doc-comments-blocks, r=estebankDylan DPC-2/+2
Unused doc comments blocks Fixes #77030.
2022-03-03Pass LLVM string attributes as string slicesTomasz Miąsko-37/+47
2022-03-02Fix unused_doc_comments lint errorsGuillaume Gomez-2/+2
2022-03-02rename ErrorReported -> ErrorGuaranteedmark-3/+3
2022-03-02Auto merge of #94229 - erikdesjardins:rem2, r=nikicbors-61/+13
Remove LLVM attribute removal This was necessary before, because `declare_raw_fn` would always apply the default optimization attributes to every declared function. Then `attributes::from_fn_attrs` would have to remove the default attributes in the case of, e.g. `#[optimize(speed)]` in a `-Os` build. (see [`src/test/codegen/optimize-attr-1.rs`](https://github.com/rust-lang/rust/blob/03a8cc7df1d65554a4d40825b0490c93ac0f0236/src/test/codegen/optimize-attr-1.rs#L33)) However, every relevant callsite of `declare_raw_fn` (i.e. where we actually generate code for the function, and not e.g. a call to an intrinsic, where optimization attributes don't [?] matter) calls `from_fn_attrs`, so we can remove the attribute setting from `declare_raw_fn`, and rely on `from_fn_attrs` to apply the correct attributes all at once. r? `@ghost` (blocked on #94221) `@rustbot` label S-blocked
2022-03-02Auto merge of #87402 - nagisa:nagisa/request-feature-requests-for-features, ↵bors-89/+158
r=estebank Direct users towards using Rust target feature names in CLI This PR consists of a couple of changes on how we handle target features. In particular there is a bug-fix wherein we avoid passing through features that aren't prefixed by `+` or `-` to LLVM. These appear to be causing LLVM to assert, which is pretty poor a behaviour (and also makes it pretty clear we expect feature names to be prefixed). The other commit, I anticipate to be somewhat more controversial is outputting a warning when users specify a LLVM-specific, or otherwise unknown, feature name on the CLI. In those situations we request users to either replace it with a known Rust feature name (e.g. `bmi` -> `bmi1`) or file a feature request. I've a couple motivations for this: first of all, if users are specifying these features on the command line, I'm pretty confident there is also a need for these features to be usable via `#[cfg(target_feature)]` machinery. And second, we're growing a fair number of backends recently and having ability to provide some sort of unified-ish interface in this place seems pretty useful to me. Sponsored by: standard.ai
2022-03-01Auto merge of #94402 - erikdesjardins:revert-coldland, r=nagisabors-22/+3
Revert "Auto merge of #92419 - erikdesjardins:coldland, r=nagisa" Should fix (untested) #94390 Reopens #46515, #87055 r? `@ehuss`
2022-02-28Add !align metadata on loads of &/&mut/BoxErik Desjardins-8/+31
Note that this refers to the alignment of what the loaded value points to, _not_ the alignment of the loaded value itself.
2022-03-01Querify `global_backend_features`Simonas Kazlauskas-17/+31
At the very least this serves to deduplicate the diagnostics that are output about unknown target features provided via CLI.
2022-03-01Direct users towards using Rust feature names in CLISimonas Kazlauskas-75/+131
If they are trying to use features rustc doesn't yet know about, request a feature request. Additionally, also warn against using feature names without leading `+` or `-` signs.
2022-02-28Rollup merge of #94365 - mati865:fix-mingw-detection-for-rawdylib, ↵Matthias Krüger-1/+3
r=michaelwoerister Fix MinGW target detection in raw-dylib LLVM target doesn't have to be the same as Rust target so relying on it is wrong. It was one of concerns in https://github.com/rust-lang/rust/pull/88801 that was not fixed in https://github.com/rust-lang/rust/pull/90782.
2022-02-28Remove LLVM attribute removalErik Desjardins-61/+13
This was necessary before, because `declare_raw_fn` would always apply the default optimization attributes to every declared function, and then `attributes::from_fn_attrs` would have to remove the default attributes in the case of, e.g. `#[optimize(speed)]` in a `-Os` build. However, every relevant callsite of `declare_raw_fn` (i.e. where we actually generate code for the function, and not e.g. a call to an intrinsic, where optimization attributes don't [?] matter) calls `from_fn_attrs`, so we can simply remove the attribute setting from `declare_raw_fn`, and rely on `from_fn_attrs` to apply the correct attributes all at once.
2022-02-27Revert "Auto merge of #92419 - erikdesjardins:coldland, r=nagisa"Erik Desjardins-22/+3
This reverts commit 4f49627c6fe2a32d1fed6310466bb0e1c535c0c0, reversing changes made to 028c6f1454787c068ff5117e9000a1de4fd98374.
2022-02-27Do not pass through features without +/- prefixSimonas Kazlauskas-17/+16
LLVM really dislikes this and will assert, saying something along the lines of: ``` rustc: llvm/lib/MC/MCSubtargetInfo.cpp:60: void ApplyFeatureFlag( llvm::FeatureBitset&, llvm::StringRef, llvm::ArrayRef<llvm::SubtargetFeatureKV> ): Assertion `SubtargetFeatures::hasFlag(Feature) && "Feature flags should start with '+' or '-'"` failed. ```
2022-02-27Apply noundef metadata to loads of types that do not permit raw initErik Desjardins-0/+15
This matches the noundef attributes we apply on arguments/return types.
2022-02-27Auto merge of #94221 - erikdesjardins:addattr, r=nikicbors-334/+354
Add LLVM attributes in batches instead of individually This should improve performance. ~r? `@ghost` (blocked on #94127)~
2022-02-26just put smallvec lengths in the signatureErik Desjardins-11/+8
2022-02-26Auto merge of #93516 - nagisa:branch-protection, r=cjgillotbors-30/+30
No branch protection metadata unless enabled Even if we emit metadata disabling branch protection, this metadata may conflict with other modules (e.g. during LTO) that have different branch protection metadata set. This is an unstable flag and feature, so ideally the flag not being specified should act as if the feature wasn't implemented in the first place. Additionally this PR also ensures we emit an error if `-Zbranch-protection` is set on targets other than the supported aarch64. For now the error is being output from codegen, but ideally it should be moved to earlier in the pipeline before stabilization.
2022-02-26Add LLVM attributes in batches instead of individuallyErik Desjardins-334/+357
This should improve performance.
2022-02-26Auto merge of #94127 - erikdesjardins:debugattr, r=nikicbors-49/+60
At opt-level=0, apply only ABI-affecting attributes to functions This should provide a small perf improvement for debug builds, and should more than cancel out the perf regression from adding noundef (https://github.com/rust-lang/rust/pull/93670#issuecomment-1038347581, #94106). r? `@nikic`
2022-02-25Auto merge of #94290 - Mark-Simulacrum:bump-bootstrap, r=pietroalbinibors-1/+1
Bump bootstrap to 1.60 This bumps the bootstrap compiler to 1.60 and cleans up cfgs and Span's rustc_pass_by_value (enabled by the bootstrap bump).
2022-02-25Fix MinGW target detection in raw-dylibMateusz Mikuła-1/+3
LLVM target doesn't have to be the same as Rust target so relying on it is wrong.
2022-02-25Switch bootstrap cfgsMark Rousskov-1/+1
2022-02-25Auto merge of #93644 - michaelwoerister:simpler-debuginfo-typemap, r=wesleywiserbors-351/+251
debuginfo: Simplify TypeMap used during LLVM debuginfo generation. This PR simplifies the TypeMap that is used in `rustc_codegen_llvm::debuginfo::metadata`. It was unnecessarily complicated because it was originally implemented when types were not yet normalized before codegen. So it did it's own normalization and kept track of multiple unnormalized types being mapped to a single unique id. This PR is based on https://github.com/rust-lang/rust/pull/93503, which is not merged yet. The PR also removes the arena used for allocating string ids and instead uses `InlinableString` from the [inlinable_string](https://crates.io/crates/inlinable_string) crate. That might not be the best choice, since that crate does not seem to be very actively maintained. The [flexible-string](https://crates.io/crates/flexible-string) crate would be an alternative. r? `@ghost`
2022-02-25debuginfo: Simplify TypeMap used during LLVM debuginfo generation -- address ↵Michael Woerister-8/+23
review comments.
2022-02-25Auto merge of #94130 - erikdesjardins:partially, r=nikicbors-22/+19
Use undef for (some) partially-uninit constants There needs to be some limit to avoid perf regressions on large arrays with undef in each element (see comment in the code). Fixes: #84565 Original PR: #83698 Depends on LLVM 14: #93577
2022-02-24Rollup merge of #94242 - compiler-errors:fat-uninhabitable-pointer, ↵Dylan DPC-18/+20
r=michaelwoerister properly handle fat pointers to uninhabitable types Calculate the pointee metadata size by using `tcx.struct_tail_erasing_lifetimes` instead of duplicating the logic in `fat_pointer_kind`. Open to alternatively suggestions on how to fix this. Fixes #94149 r? ````@michaelwoerister```` since you touched this code last, I think!
2022-02-24Auto merge of #94123 - bjorn3:cg_ssa_singleton_builder, r=tmiaskobors-91/+97
Partially move cg_ssa towards using a single builder Not all codegen backends can handle hopping between blocks well. For example Cranelift requires blocks to be terminated before switching to building a new block. Rust-gpu requires a `RefCell` to allow hopping between blocks and cg_gcc currently has a buggy implementation of hopping between blocks. This PR reduces the amount of cases where cg_ssa switches between blocks before they are finished and mostly fixes the block hopping in cg_gcc. (~~only `scalar_to_backend` doesn't handle it correctly yet in cg_gcc~~ fixed that one.) `@antoyo` please review the cg_gcc changes.
2022-02-24Introduce Bx::switch_to_blockbjorn3-75/+69
2022-02-24Rollup merge of #89887 - arlosi:char-debug, r=wesleywiserMatthias Krüger-2/+2
Change `char` type in debuginfo to DW_ATE_UTF Rust previously encoded the `char` type as DW_ATE_unsigned_char. The more appropriate encoding is `DW_ATE_UTF`. Clang also uses the DW_ATE_UTF for `char32_t` in C++. This fixes the display of the `char` type in the Windows debuggers. Without this change, the variable did not show in the locals window. ![image](https://user-images.githubusercontent.com/704597/137368067-9b3e4dc8-a075-44ba-a687-bf3810a44e5a.png) LLDB 13 is also able to display the char value, when before it failed with `need to add support for DW_TAG_base_type 'char' encoded with DW_ATE = 0x8, bit_size = 32` r? `@wesleywiser`
2022-02-23Change `char` type in debuginfo to DW_ATE_UTFArlo Siemsen-2/+2
Rust previously encoded the `char` type as DW_ATE_unsigned_char. The more appropriate encoding is DW_ATE_UTF. Clang uses this same debug encoding for char32_t. This fixes the display of `char` types in Windows debuggers as well as LLDB.
2022-02-23properly handle fat pointers to uninhabitable typesMichael Goulet-18/+20
2022-02-22Reapply cg_llvm: `fewer_names` in `uncached_llvm_type`David Wood-1/+10
Co-authored-by: Erik Desjardins <erikdesjardins@users.noreply.github.com> Co-authored-by: Tomasz Miąsko <tomasz.miasko@gmail.com>
2022-02-21debuginfo: Simplify TypeMap used during LLVM debuginfo generation.Michael Woerister-350/+235
The previous implementation was written before types were properly normalized for code generation and had to assume a more complicated relationship between types and their debuginfo -- generating separate identifiers for debuginfo nodes that were based on normalized types. Since types are now already normalized, we can use them as identifiers for debuginfo nodes.
2022-02-21use `List<Ty<'tcx>>` for tupleslcnr-3/+2
2022-02-20Auto merge of #93678 - steffahn:better_unsafe_diagnostics, r=nagisabors-7/+5
Improve `unused_unsafe` lint I’m going to add some motivation and explanation below, particularly pointing the changes in behavior from this PR. _Edit:_ Looking for existing issues, looks like this PR fixes #88260. _Edit2:_ Now also contains code that closes #90776.
2022-02-20Improve `unused_unsafe` lintFrank Steffahn-7/+5
Main motivation: Fixes some issues with the current behavior. This PR is more-or-less completely re-implementing the unused_unsafe lint; it’s also only done in the MIR-version of the lint, the set of tests for the `-Zthir-unsafeck` version no longer succeeds (and is thus disabled, see `lint-unused-unsafe.rs`). On current nightly, ```rs unsafe fn unsf() {} fn inner_ignored() { unsafe { #[allow(unused_unsafe)] unsafe { unsf() } } } ``` doesn’t create any warnings. This situation is not unrealistic to come by, the inner `unsafe` block could e.g. come from a macro. Actually, this PR even includes removal of one unused `unsafe` in the standard library that was missed in a similar situation. (The inner `unsafe` coming from an external macro hides the warning, too.) The reason behind this problem is how the check currently works: * While generating MIR, it already skips nested unsafe blocks (i.e. unsafe nested in other unsafe) so that the inner one is always the one considered unused * To differentiate the cases of no unsafe operations inside the `unsafe` vs. a surrounding `unsafe` block, there’s some ad-hoc magic walking up the HIR to look for surrounding used `unsafe` blocks. There’s a lot of problems with this approach besides the one presented above. E.g. the MIR-building uses checks for `unsafe_op_in_unsafe_fn` lint to decide early whether or not `unsafe` blocks in an `unsafe fn` are redundant and ought to be removed. ```rs unsafe fn granular_disallow_op_in_unsafe_fn() { unsafe { #[deny(unsafe_op_in_unsafe_fn)] { unsf(); } } } ``` ``` error: call to unsafe function is unsafe and requires unsafe block (error E0133) --> src/main.rs:13:13 | 13 | unsf(); | ^^^^^^ call to unsafe function | note: the lint level is defined here --> src/main.rs:11:16 | 11 | #[deny(unsafe_op_in_unsafe_fn)] | ^^^^^^^^^^^^^^^^^^^^^^ = note: consult the function's documentation for information on how to avoid undefined behavior warning: unnecessary `unsafe` block --> src/main.rs:10:5 | 9 | unsafe fn granular_disallow_op_in_unsafe_fn() { | --------------------------------------------- because it's nested under this `unsafe` fn 10 | unsafe { | ^^^^^^ unnecessary `unsafe` block | = note: `#[warn(unused_unsafe)]` on by default ``` Here, the intermediate `unsafe` was ignored, even though it contains a unsafe operation that is not allowed to happen in an `unsafe fn` without an additional `unsafe` block. Also closures were problematic and the workaround/algorithms used on current nightly didn’t work properly. (I skipped trying to fully understand what it was supposed to do, because this PR uses a completely different approach.) ```rs fn nested() { unsafe { unsafe { unsf() } } } ``` ``` warning: unnecessary `unsafe` block --> src/main.rs:10:9 | 9 | unsafe { | ------ because it's nested under this `unsafe` block 10 | unsafe { unsf() } | ^^^^^^ unnecessary `unsafe` block | = note: `#[warn(unused_unsafe)]` on by default ``` vs ```rs fn nested() { let _ = || unsafe { let _ = || unsafe { unsf() }; }; } ``` ``` warning: unnecessary `unsafe` block --> src/main.rs:9:16 | 9 | let _ = || unsafe { | ^^^^^^ unnecessary `unsafe` block | = note: `#[warn(unused_unsafe)]` on by default warning: unnecessary `unsafe` block --> src/main.rs:10:20 | 10 | let _ = || unsafe { unsf() }; | ^^^^^^ unnecessary `unsafe` block ``` *note that this warning kind-of suggests that **both** unsafe blocks are redundant* -------------------------------------------------------------------------------- I also dislike the fact that it always suggests keeping the outermost `unsafe`. E.g. for ```rs fn granularity() { unsafe { unsafe { unsf() } unsafe { unsf() } unsafe { unsf() } } } ``` I prefer if `rustc` suggests removing the more-course outer-level `unsafe` instead of the fine-grained inner `unsafe` blocks, which it currently does on nightly: ``` warning: unnecessary `unsafe` block --> src/main.rs:10:9 | 9 | unsafe { | ------ because it's nested under this `unsafe` block 10 | unsafe { unsf() } | ^^^^^^ unnecessary `unsafe` block | = note: `#[warn(unused_unsafe)]` on by default warning: unnecessary `unsafe` block --> src/main.rs:11:9 | 9 | unsafe { | ------ because it's nested under this `unsafe` block 10 | unsafe { unsf() } 11 | unsafe { unsf() } | ^^^^^^ unnecessary `unsafe` block warning: unnecessary `unsafe` block --> src/main.rs:12:9 | 9 | unsafe { | ------ because it's nested under this `unsafe` block ... 12 | unsafe { unsf() } | ^^^^^^ unnecessary `unsafe` block ``` -------------------------------------------------------------------------------- Needless to say, this PR addresses all these points. For context, as far as my understanding goes, the main advantage of skipping inner unsafe blocks was that a test case like ```rs fn top_level_used() { unsafe { unsf(); unsafe { unsf() } unsafe { unsf() } unsafe { unsf() } } } ``` should generate some warning because there’s redundant nested `unsafe`, however every single `unsafe` block _does_ contain some statement that uses it. Of course this PR doesn’t aim change the warnings on this kind of code example, because the current behavior, warning on all the inner `unsafe` blocks, makes sense in this case. As mentioned, during MIR building all the unsafe blocks *are* kept now, and usage is attributed to them. The way to still generate a warning like ``` warning: unnecessary `unsafe` block --> src/main.rs:11:9 | 9 | unsafe { | ------ because it's nested under this `unsafe` block 10 | unsf(); 11 | unsafe { unsf() } | ^^^^^^ unnecessary `unsafe` block | = note: `#[warn(unused_unsafe)]` on by default warning: unnecessary `unsafe` block --> src/main.rs:12:9 | 9 | unsafe { | ------ because it's nested under this `unsafe` block ... 12 | unsafe { unsf() } | ^^^^^^ unnecessary `unsafe` block warning: unnecessary `unsafe` block --> src/main.rs:13:9 | 9 | unsafe { | ------ because it's nested under this `unsafe` block ... 13 | unsafe { unsf() } | ^^^^^^ unnecessary `unsafe` block ``` in this case is by emitting a `unused_unsafe` warning for all of the `unsafe` blocks that are _within a **used** unsafe block_. The previous code had a little HIR traversal already anyways to collect a set of all the unsafe blocks (in order to afterwards determine which ones are unused afterwards). This PR uses such a traversal to do additional things including logic like _always_ warn for an `unsafe` block that’s inside of another **used** unsafe block. The traversal is expanded to include nested closures in the same go, this simplifies a lot of things. The whole logic around `unsafe_op_in_unsafe_fn` is a little complicated, there’s some test cases of corner-cases in this PR. (The implementation involves differentiating between whether a used unsafe block was used exclusively by operations where `allow(unsafe_op_in_unsafe_fn)` was active.) The main goal was to make sure that code should compile successfully if all the `unused_unsafe`-warnings are addressed _simultaneously_ (by removing the respective `unsafe` blocks) no matter how complicated the patterns of `unsafe_op_in_unsafe_fn` being disallowed and allowed throughout the function are. -------------------------------------------------------------------------------- One noteworthy design decision I took here: An `unsafe` block with `allow(unused_unsafe)` **is considered used** for the purposes of linting about redundant contained unsafe blocks. So while ```rs fn granularity() { unsafe { //~ ERROR: unnecessary `unsafe` block unsafe { unsf() } unsafe { unsf() } unsafe { unsf() } } } ``` warns for the outer `unsafe` block, ```rs fn top_level_ignored() { #[allow(unused_unsafe)] unsafe { #[deny(unused_unsafe)] { unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block } } } ``` warns on the inner ones.