Apply ABI attributes on return types in `rustc_codegen_cranelift` #142389

beetrees · 2025-06-11T23:52:56Z

The x86-64 System V ABI standard doesn't sign/zero-extend integer arguments or return types.
But the de-facto standard as implemented by Clang and GCC is to sign/zero-extend arguments to 32 bits (but not return types).
Additionally, Apple targets sign/zero-extend both arguments and return values to 32 bits.
However, the rustc_target ABI adjustment code currently unconditionally extends both arguments and return values to 32 bits on all targets.
This doesn't cause a miscompilation when compiling with LLVM as LLVM will ignore the signext/zeroext attribute when applied to return types on non-Apple x86-64 targets.
Cranelift, however, does not have a similar special case, requiring rustc to set the argument extension attribute correctly.
However, rustc_codegen_cranelift doesn't currently apply ABI attributes to return types at all, meaning rustc_codegen_cranelift will currently miscompile i8/u8/i16/u16 returns on x86-64 Apple targets as those targets require sign/zero-extension of return types.

This PR fixes the bug(s) by making the rustc_target x86-64 System V ABI only mark return types as sign/zero-extended on Apple platforms, while also making rustc_codegen_cranelift apply ABI attributes to return types. The RISC-V and s390x C ABIs also require sign/zero extension of return types, so this will fix those targets when building with rustc_codegen_cranelift too.

r? @bjorn3

rustbot · 2025-06-11T23:53:02Z

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

bjorn3 · 2025-06-12T16:12:38Z

@bors2 try jobs=x86_64-apple-*

rust-bors · 2025-06-12T16:12:41Z

⌛ Trying commit eb472e7 with merge 6a4c445…

To cancel the try build, run the command @bors2 try cancel.

Apply ABI attributes on return types in `rustc_codegen_cranelift` - The [x86-64 System V ABI standard](https://gitlab.com/x86-psABIs/x86-64-ABI/-/jobs/artifacts/master/raw/x86-64-ABI/abi.pdf?job=build) doesn't sign/zero-extend integer arguments or return types. - But the de-facto standard as implemented by Clang and GCC is to sign/zero-extend arguments to 32 bits (but not return types). - Additionally, Apple targets [sign/zero-extend both arguments and return values to 32 bits](https://developer.apple.com/documentation/xcode/writing-64-bit-intel-code-for-apple-platforms#Pass-arguments-to-functions-correctly). - However, the `rustc_target` ABI adjustment code currently [unconditionally extends both arguments and return values to 32 bits](https://github.com/rust-lang/rust/blame/e703dff8fe220b78195c53478e83fb2f68d8499c/compiler/rustc_target/src/callconv/x86_64.rs#L240) on all targets. - This doesn't cause a miscompilation when compiling with LLVM as LLVM will ignore the `signext`/`zeroext` attribute when applied to return types on non-Apple x86-64 targets. - Cranelift, however, does not have a similar special case, requiring `rustc` to set the argument extension attribute correctly. - However, `rustc_codegen_cranelift` doesn't currently apply ABI attributes to return types at all, meaning `rustc_codegen_cranelift` will currently miscompile `i8`/`u8`/`i16`/`u16` returns on x86-64 Apple targets as those targets require sign/zero-extension of return types. This PR fixes the bug(s) by making the `rustc_target` x86-64 System V ABI only mark return types as sign/zero-extended on Apple platforms, while also making `rustc_codegen_cranelift` apply ABI attributes to return types. The RISC-V and s390x C ABIs also require sign/zero extension of return types, so this will fix those targets when building with `rustc_codegen_cranelift` too. try-job: `x86_64-apple-*` r? `@bjorn3` try-job: x86_64-apple-*

rust-bors · 2025-06-12T18:28:21Z

☀️ Try build successful (CI)
Build commit: 6a4c445 (6a4c445322019216b3977c8391f73f8ba182585a, parent: 6c8138de8f1c96b2f66adbbc0e37c73525444750)

bjorn3 · 2025-06-14T09:59:43Z

@bors r+

bors · 2025-06-14T09:59:45Z

📌 Commit eb472e7 has been approved by bjorn3

It is now in the queue for this repository.

Apply ABI attributes on return types in `rustc_codegen_cranelift` - The [x86-64 System V ABI standard](https://gitlab.com/x86-psABIs/x86-64-ABI/-/jobs/artifacts/master/raw/x86-64-ABI/abi.pdf?job=build) doesn't sign/zero-extend integer arguments or return types. - But the de-facto standard as implemented by Clang and GCC is to sign/zero-extend arguments to 32 bits (but not return types). - Additionally, Apple targets [sign/zero-extend both arguments and return values to 32 bits](https://developer.apple.com/documentation/xcode/writing-64-bit-intel-code-for-apple-platforms#Pass-arguments-to-functions-correctly). - However, the `rustc_target` ABI adjustment code currently [unconditionally extends both arguments and return values to 32 bits](https://github.com/rust-lang/rust/blame/e703dff8fe220b78195c53478e83fb2f68d8499c/compiler/rustc_target/src/callconv/x86_64.rs#L240) on all targets. - This doesn't cause a miscompilation when compiling with LLVM as LLVM will ignore the `signext`/`zeroext` attribute when applied to return types on non-Apple x86-64 targets. - Cranelift, however, does not have a similar special case, requiring `rustc` to set the argument extension attribute correctly. - However, `rustc_codegen_cranelift` doesn't currently apply ABI attributes to return types at all, meaning `rustc_codegen_cranelift` will currently miscompile `i8`/`u8`/`i16`/`u16` returns on x86-64 Apple targets as those targets require sign/zero-extension of return types. This PR fixes the bug(s) by making the `rustc_target` x86-64 System V ABI only mark return types as sign/zero-extended on Apple platforms, while also making `rustc_codegen_cranelift` apply ABI attributes to return types. The RISC-V and s390x C ABIs also require sign/zero extension of return types, so this will fix those targets when building with `rustc_codegen_cranelift` too. r? `@bjorn3`

Rollup of 10 pull requests Successful merges: - #133952 (Remove wasm legacy abi) - #134661 (Reduce precedence of expressions that have an outer attr) - #141769 (Move metadata object generation for dylibs to the linker code ) - #141864 (Handle win32 separator for cygwin paths) - #142347 (Async drop - fix for StorageLive/StorageDead codegen for pinned future) - #142377 (Try unremapping compiler sources) - #142389 (Apply ABI attributes on return types in `rustc_codegen_cranelift`) - #142470 (Add some missing mailmap entries) - #142481 (Add `f16` inline asm support for LoongArch) - #142509 (bump std libc dependency) r? `@ghost` `@rustbot` modify labels: rollup

Apply ABI attributes on return types in `rustc_codegen_cranelift` - The [x86-64 System V ABI standard](https://gitlab.com/x86-psABIs/x86-64-ABI/-/jobs/artifacts/master/raw/x86-64-ABI/abi.pdf?job=build) doesn't sign/zero-extend integer arguments or return types. - But the de-facto standard as implemented by Clang and GCC is to sign/zero-extend arguments to 32 bits (but not return types). - Additionally, Apple targets [sign/zero-extend both arguments and return values to 32 bits](https://developer.apple.com/documentation/xcode/writing-64-bit-intel-code-for-apple-platforms#Pass-arguments-to-functions-correctly). - However, the `rustc_target` ABI adjustment code currently [unconditionally extends both arguments and return values to 32 bits](https://github.com/rust-lang/rust/blame/e703dff8fe220b78195c53478e83fb2f68d8499c/compiler/rustc_target/src/callconv/x86_64.rs#L240) on all targets. - This doesn't cause a miscompilation when compiling with LLVM as LLVM will ignore the `signext`/`zeroext` attribute when applied to return types on non-Apple x86-64 targets. - Cranelift, however, does not have a similar special case, requiring `rustc` to set the argument extension attribute correctly. - However, `rustc_codegen_cranelift` doesn't currently apply ABI attributes to return types at all, meaning `rustc_codegen_cranelift` will currently miscompile `i8`/`u8`/`i16`/`u16` returns on x86-64 Apple targets as those targets require sign/zero-extension of return types. This PR fixes the bug(s) by making the `rustc_target` x86-64 System V ABI only mark return types as sign/zero-extended on Apple platforms, while also making `rustc_codegen_cranelift` apply ABI attributes to return types. The RISC-V and s390x C ABIs also require sign/zero extension of return types, so this will fix those targets when building with `rustc_codegen_cranelift` too. r? ``@bjorn3``

Rollup of 9 pull requests Successful merges: - #133952 (Remove wasm legacy abi) - #141769 (Move metadata object generation for dylibs to the linker code ) - #141864 (Handle win32 separator for cygwin paths) - #142347 (Async drop - fix for StorageLive/StorageDead codegen for pinned future) - #142377 (Try unremapping compiler sources) - #142389 (Apply ABI attributes on return types in `rustc_codegen_cranelift`) - #142470 (Add some missing mailmap entries) - #142481 (Add `f16` inline asm support for LoongArch) - #142509 (bump std libc dependency) r? `@ghost` `@rustbot` modify labels: rollup

Apply ABI attributes on return types in `rustc_codegen_cranelift` - The [x86-64 System V ABI standard](https://gitlab.com/x86-psABIs/x86-64-ABI/-/jobs/artifacts/master/raw/x86-64-ABI/abi.pdf?job=build) doesn't sign/zero-extend integer arguments or return types. - But the de-facto standard as implemented by Clang and GCC is to sign/zero-extend arguments to 32 bits (but not return types). - Additionally, Apple targets [sign/zero-extend both arguments and return values to 32 bits](https://developer.apple.com/documentation/xcode/writing-64-bit-intel-code-for-apple-platforms#Pass-arguments-to-functions-correctly). - However, the `rustc_target` ABI adjustment code currently [unconditionally extends both arguments and return values to 32 bits](https://github.com/rust-lang/rust/blame/e703dff8fe220b78195c53478e83fb2f68d8499c/compiler/rustc_target/src/callconv/x86_64.rs#L240) on all targets. - This doesn't cause a miscompilation when compiling with LLVM as LLVM will ignore the `signext`/`zeroext` attribute when applied to return types on non-Apple x86-64 targets. - Cranelift, however, does not have a similar special case, requiring `rustc` to set the argument extension attribute correctly. - However, `rustc_codegen_cranelift` doesn't currently apply ABI attributes to return types at all, meaning `rustc_codegen_cranelift` will currently miscompile `i8`/`u8`/`i16`/`u16` returns on x86-64 Apple targets as those targets require sign/zero-extension of return types. This PR fixes the bug(s) by making the `rustc_target` x86-64 System V ABI only mark return types as sign/zero-extended on Apple platforms, while also making `rustc_codegen_cranelift` apply ABI attributes to return types. The RISC-V and s390x C ABIs also require sign/zero extension of return types, so this will fix those targets when building with `rustc_codegen_cranelift` too. r? ```@bjorn3```

Rollup of 8 pull requests Successful merges: - #133952 (Remove wasm legacy abi) - #141769 (Move metadata object generation for dylibs to the linker code ) - #141864 (Handle win32 separator for cygwin paths) - #142347 (Async drop - fix for StorageLive/StorageDead codegen for pinned future) - #142389 (Apply ABI attributes on return types in `rustc_codegen_cranelift`) - #142470 (Add some missing mailmap entries) - #142481 (Add `f16` inline asm support for LoongArch) - #142509 (bump std libc dependency) r? `@ghost` `@rustbot` modify labels: rollup

Apply ABI attributes on return types in `rustc_codegen_cranelift` - The [x86-64 System V ABI standard](https://gitlab.com/x86-psABIs/x86-64-ABI/-/jobs/artifacts/master/raw/x86-64-ABI/abi.pdf?job=build) doesn't sign/zero-extend integer arguments or return types. - But the de-facto standard as implemented by Clang and GCC is to sign/zero-extend arguments to 32 bits (but not return types). - Additionally, Apple targets [sign/zero-extend both arguments and return values to 32 bits](https://developer.apple.com/documentation/xcode/writing-64-bit-intel-code-for-apple-platforms#Pass-arguments-to-functions-correctly). - However, the `rustc_target` ABI adjustment code currently [unconditionally extends both arguments and return values to 32 bits](https://github.com/rust-lang/rust/blame/e703dff8fe220b78195c53478e83fb2f68d8499c/compiler/rustc_target/src/callconv/x86_64.rs#L240) on all targets. - This doesn't cause a miscompilation when compiling with LLVM as LLVM will ignore the `signext`/`zeroext` attribute when applied to return types on non-Apple x86-64 targets. - Cranelift, however, does not have a similar special case, requiring `rustc` to set the argument extension attribute correctly. - However, `rustc_codegen_cranelift` doesn't currently apply ABI attributes to return types at all, meaning `rustc_codegen_cranelift` will currently miscompile `i8`/`u8`/`i16`/`u16` returns on x86-64 Apple targets as those targets require sign/zero-extension of return types. This PR fixes the bug(s) by making the `rustc_target` x86-64 System V ABI only mark return types as sign/zero-extended on Apple platforms, while also making `rustc_codegen_cranelift` apply ABI attributes to return types. The RISC-V and s390x C ABIs also require sign/zero extension of return types, so this will fix those targets when building with `rustc_codegen_cranelift` too. r? ````@bjorn3````

Rollup of 9 pull requests Successful merges: - #133952 (Remove wasm legacy abi) - #134661 (Reduce precedence of expressions that have an outer attr) - #141769 (Move metadata object generation for dylibs to the linker code ) - #141864 (Handle win32 separator for cygwin paths) - #141937 (Report never type lints in dependencies) - #142347 (Async drop - fix for StorageLive/StorageDead codegen for pinned future) - #142389 (Apply ABI attributes on return types in `rustc_codegen_cranelift`) - #142470 (Add some missing mailmap entries) - #142481 (Add `f16` inline asm support for LoongArch) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 10 pull requests Successful merges: - #133952 (Remove wasm legacy abi) - #134661 (Reduce precedence of expressions that have an outer attr) - #141769 (Move metadata object generation for dylibs to the linker code ) - #141937 (Report never type lints in dependencies) - #142347 (Async drop - fix for StorageLive/StorageDead codegen for pinned future) - #142389 (Apply ABI attributes on return types in `rustc_codegen_cranelift`) - #142470 (Add some missing mailmap entries) - #142481 (Add `f16` inline asm support for LoongArch) - #142499 (Remove check run bootstrap) - #142543 (Suggest adding semicolon in user code rather than macro impl details) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #142389 - beetrees:cranelift-arg-ext, r=bjorn3 Apply ABI attributes on return types in `rustc_codegen_cranelift` - The [x86-64 System V ABI standard](https://gitlab.com/x86-psABIs/x86-64-ABI/-/jobs/artifacts/master/raw/x86-64-ABI/abi.pdf?job=build) doesn't sign/zero-extend integer arguments or return types. - But the de-facto standard as implemented by Clang and GCC is to sign/zero-extend arguments to 32 bits (but not return types). - Additionally, Apple targets [sign/zero-extend both arguments and return values to 32 bits](https://developer.apple.com/documentation/xcode/writing-64-bit-intel-code-for-apple-platforms#Pass-arguments-to-functions-correctly). - However, the `rustc_target` ABI adjustment code currently [unconditionally extends both arguments and return values to 32 bits](https://github.com/rust-lang/rust/blame/e703dff8fe220b78195c53478e83fb2f68d8499c/compiler/rustc_target/src/callconv/x86_64.rs#L240) on all targets. - This doesn't cause a miscompilation when compiling with LLVM as LLVM will ignore the `signext`/`zeroext` attribute when applied to return types on non-Apple x86-64 targets. - Cranelift, however, does not have a similar special case, requiring `rustc` to set the argument extension attribute correctly. - However, `rustc_codegen_cranelift` doesn't currently apply ABI attributes to return types at all, meaning `rustc_codegen_cranelift` will currently miscompile `i8`/`u8`/`i16`/`u16` returns on x86-64 Apple targets as those targets require sign/zero-extension of return types. This PR fixes the bug(s) by making the `rustc_target` x86-64 System V ABI only mark return types as sign/zero-extended on Apple platforms, while also making `rustc_codegen_cranelift` apply ABI attributes to return types. The RISC-V and s390x C ABIs also require sign/zero extension of return types, so this will fix those targets when building with `rustc_codegen_cranelift` too. r? `````@bjorn3`````

Apply ABI attributes on return types in `rustc_codegen_cranelift` - The [x86-64 System V ABI standard](https://gitlab.com/x86-psABIs/x86-64-ABI/-/jobs/artifacts/master/raw/x86-64-ABI/abi.pdf?job=build) doesn't sign/zero-extend integer arguments or return types. - But the de-facto standard as implemented by Clang and GCC is to sign/zero-extend arguments to 32 bits (but not return types). - Additionally, Apple targets [sign/zero-extend both arguments and return values to 32 bits](https://developer.apple.com/documentation/xcode/writing-64-bit-intel-code-for-apple-platforms#Pass-arguments-to-functions-correctly). - However, the `rustc_target` ABI adjustment code currently [unconditionally extends both arguments and return values to 32 bits](https://github.com/rust-lang/rust/blame/e703dff8fe220b78195c53478e83fb2f68d8499c/compiler/rustc_target/src/callconv/x86_64.rs#L240) on all targets. - This doesn't cause a miscompilation when compiling with LLVM as LLVM will ignore the `signext`/`zeroext` attribute when applied to return types on non-Apple x86-64 targets. - Cranelift, however, does not have a similar special case, requiring `rustc` to set the argument extension attribute correctly. - However, `rustc_codegen_cranelift` doesn't currently apply ABI attributes to return types at all, meaning `rustc_codegen_cranelift` will currently miscompile `i8`/`u8`/`i16`/`u16` returns on x86-64 Apple targets as those targets require sign/zero-extension of return types. This PR fixes the bug(s) by making the `rustc_target` x86-64 System V ABI only mark return types as sign/zero-extended on Apple platforms, while also making `rustc_codegen_cranelift` apply ABI attributes to return types. The RISC-V and s390x C ABIs also require sign/zero extension of return types, so this will fix those targets when building with `rustc_codegen_cranelift` too. r? `````@bjorn3`````

Apply ABI attributes on return types in rustc_codegen_cranelift

eb472e7

rustbot assigned bjorn3 Jun 11, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 11, 2025

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 14, 2025

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bors merged commit 1615266 into rust-lang:master Jun 16, 2025
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Apply ABI attributes on return types in `rustc_codegen_cranelift` #142389

Apply ABI attributes on return types in `rustc_codegen_cranelift` #142389

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Apply ABI attributes on return types in `rustc_codegen_cranelift` #142389

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