Update rustc_codegen_gcc rotate operation document
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rustc_codegen_gcc roate operation documentrustc_codegen_gcc rotate operation document
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GuillaumeGomez
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@GuillaumeGomez i noticed you and @antoyo are the only members of https://github.com/rust-lang/team/blob/main/teams/wg-gcc-backend.toml. Is there anything blocking you from r:ing and not just approving? |
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Just waiting for @antoyo to have a look. |
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…toyo Update `rustc_codegen_gcc` rotate operation document ## Description This PR resolves a TODO comment in the `rustc_codegen_gcc` backend by documenting that the rotate operations (`rotate_left` and `rotate_right`) already implement the optimized branchless algorithm from comment. The existing implementation already uses the optimal branchless rotation pattern: - For left rotation: `(x << n) | (x >> (-n & (width-1)))` - For right rotation: `(x >> n) | (x << (-n & (width-1)))` This pattern avoids branches and generates efficient machine code across different platforms, which was the goal mentioned in the original TODO. ## Changes - Removed the TODO comment that suggested implementing the algorithm from https://blog.regehr.org/archives/1063
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Rollup of 11 pull requests Successful merges: - #145278 (Update `rustc_codegen_gcc` rotate operation document) - #148825 (Add SystemTime::{MIN, MAX}) - #148837 (Use `let...else` instead of `match foo { ... _ => return };` and `if let ... else return`) - #149177 (Add proper suggestion for associated function with unknown field) - #149843 (Inherit attributes in delegation) - #149860 (Fix: Prevent macro-expanded extern crates from shadowing extern arguments) - #149874 (Weak for Arc pointer is marked as DynSend/DynSync) - #149903 (Remove unused code in `cfg_old`) - #149911 (bootstrap: Don't pass an unused `--color` to compiletest) - #149916 (Add a sanity check in case of any duplicate nodes) - #149924 (`declare_lint_pass` for `INLINE_ALWAYS_MISMATCHING_TARGET_FEATURES`) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup of 10 pull requests Successful merges: - #145278 (Update `rustc_codegen_gcc` rotate operation document) - #148837 (Use `let...else` instead of `match foo { ... _ => return };` and `if let ... else return`) - #149177 (Add proper suggestion for associated function with unknown field) - #149843 (Inherit attributes in delegation) - #149860 (Fix: Prevent macro-expanded extern crates from shadowing extern arguments) - #149874 (Weak for Arc pointer is marked as DynSend/DynSync) - #149903 (Remove unused code in `cfg_old`) - #149911 (bootstrap: Don't pass an unused `--color` to compiletest) - #149916 (Add a sanity check in case of any duplicate nodes) - #149924 (`declare_lint_pass` for `INLINE_ALWAYS_MISMATCHING_TARGET_FEATURES`) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of #145278 - notJoon:doc/rotate-operation, r=antoyo Update `rustc_codegen_gcc` rotate operation document ## Description This PR resolves a TODO comment in the `rustc_codegen_gcc` backend by documenting that the rotate operations (`rotate_left` and `rotate_right`) already implement the optimized branchless algorithm from comment. The existing implementation already uses the optimal branchless rotation pattern: - For left rotation: `(x << n) | (x >> (-n & (width-1)))` - For right rotation: `(x >> n) | (x << (-n & (width-1)))` This pattern avoids branches and generates efficient machine code across different platforms, which was the goal mentioned in the original TODO. ## Changes - Removed the TODO comment that suggested implementing the algorithm from https://blog.regehr.org/archives/1063
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Description
This PR resolves a TODO comment in the
rustc_codegen_gccbackend by documenting that the rotate operations (rotate_leftandrotate_right) already implement the optimized branchless algorithm from comment.The existing implementation already uses the optimal branchless rotation pattern:
(x << n) | (x >> (-n & (width-1)))(x >> n) | (x << (-n & (width-1)))This pattern avoids branches and generates efficient machine code across different platforms, which was the goal mentioned in the original TODO.
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