Fix handling of x18 in AArch64 inline assembly on ohos/trusty or with -Zfixed-x18 by taiki-e · Pull Request #133463 · rust-lang/rust

taiki-e · 2024-11-25T17:13:47Z

Currently AArch64 inline assembly allows using x18 on ohos/trusty or with -Zfixed-x18.

rust/compiler/rustc_target/src/asm/aarch64.rs

Lines 74 to 76 in 7db7489

    
           pub(crate) fn target_reserves_x18(target: &Target) -> bool { 
        
               target.os == "android" || target.os == "fuchsia" || target.is_like_osx || target.is_like_windows 
        
           }

However, x18 is reserved in these environments and should not be allowed in the input/output operands of inline assemblies as it is in Android, Windows, etc..

rust/compiler/rustc_target/src/spec/targets/aarch64_unknown_linux_ohos.rs

Line 19 in 7db7489

features: "+reserve-x18".into(),

rust/compiler/rustc_target/src/spec/targets/aarch64_unknown_trusty.rs

Line 18 in 7db7489

features: "+neon,+fp-armv8,+reserve-x18".into(),

rust/compiler/rustc_codegen_llvm/src/llvm_util.rs

Lines 764 to 771 in 7db7489

    
           // -Zfixed-x18 
        
           if sess.opts.unstable_opts.fixed_x18 { 
        
               if sess.target.arch != "aarch64" { 
        
                   sess.dcx().emit_fatal(FixedX18InvalidArch { arch: &sess.target.arch }); 
        
               } else { 
        
                   features.push("+reserve-x18".into()); 
        
               } 
        
           }

(As for ohos, +reserve-x18 is redundant since 7a966b9 that starting using llvm's ohos targets. So removed it from target-spec.)

This fix may potentially break the code for tier 2 target (aarch64-unknown-linux-ohos). (As for others, aarch64-unknown-trusty is tier 3 and -Zfixed-x18 is unstable so breaking them should be fine.)
However, in any case, it seems suspicious that the code that is broken by this was sound.

r? @Amanieu

@rustbot label O-AArch64 +A-inline-assembly

rustbot · 2024-11-25T17:13:57Z

These commits modify compiler targets.
(See the Target Tier Policy.)

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

taiki-e · 2024-11-25T17:38:22Z

cc @Darksonn (who added -Zfixed-x18 in #124655)
cc @randomPoison (who added aarch64-unknown-trusty in #129490)

… -Zfixed-x18

Darksonn · 2024-11-26T09:51:43Z

compiler/rustc_target/src/asm/aarch64.rs

+pub(crate) fn target_reserves_x18(target: &Target, target_features: &FxIndexSet<Symbol>) -> bool {
+    // See isX18ReservedByDefault in LLVM for targets reserve x18 by default:
+    // https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/TargetParser/AArch64TargetParser.cpp#L102-L105
+    // Note that +reserve-x18 is currently not set for the above targets.
+    target.os == "android"
+        || target.os == "fuchsia"
+        || target.env == "ohos"
+        || target.is_like_osx
+        || target.is_like_windows
+        || target_features.contains(&sym::reserve_x18)


Is it possible to avoid duplicating this logic? It seems prone to getting out of sync with llvm.

I can't think of a good way to avoid the duplication unfortunately.

randomPoison · 2024-11-26T18:06:55Z

This seems correct as far as Trusty is concerned, thanks @taiki-e for addressing this ❤️ I wasn't aware of this when I added the Trusty targets, but as far as I know we don't directly use the x18 register in inline assembly from Rust, so this shouldn't introduce any problems for Trusty 👍

Amanieu · 2024-11-28T00:58:14Z

@bors r+

bors · 2024-11-28T00:58:17Z

📌 Commit 687dc19 has been approved by Amanieu

It is now in the queue for this repository.

…llaumeGomez Rollup of 7 pull requests Successful merges: - rust-lang#133358 (Don't type error if we fail to coerce `Pin<T>` because it doesnt contain a ref) - rust-lang#133422 (Fix clobber_abi in RV32E and RV64E inline assembly) - rust-lang#133452 (Support predicate registers (clobber-only) in Hexagon inline assembly) - rust-lang#133463 (Fix handling of x18 in AArch64 inline assembly on ohos/trusty or with -Zfixed-x18) - rust-lang#133487 (fix confusing diagnostic for reserved `##`) - rust-lang#133557 (Small doc fixes in `rustc_codegen_ssa`) - rust-lang#133560 (Trim extra space in 'repeated `mut`' diagnostic) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#133463 - taiki-e:aarch64-asm-x18, r=Amanieu Fix handling of x18 in AArch64 inline assembly on ohos/trusty or with -Zfixed-x18 Currently AArch64 inline assembly allows using x18 on ohos/trusty or with -Zfixed-x18. https://github.com/rust-lang/rust/blob/7db7489f9bc274cb60c4956bfa56de0185eb1b9b/compiler/rustc_target/src/asm/aarch64.rs#L74-L76 However, x18 is reserved in these environments and should not be allowed in the input/output operands of inline assemblies as it is in Android, Windows, etc.. https://github.com/rust-lang/rust/blob/7db7489f9bc274cb60c4956bfa56de0185eb1b9b/compiler/rustc_target/src/spec/targets/aarch64_unknown_linux_ohos.rs#L19 https://github.com/rust-lang/rust/blob/7db7489f9bc274cb60c4956bfa56de0185eb1b9b/compiler/rustc_target/src/spec/targets/aarch64_unknown_trusty.rs#L18 https://github.com/rust-lang/rust/blob/7db7489f9bc274cb60c4956bfa56de0185eb1b9b/compiler/rustc_codegen_llvm/src/llvm_util.rs#L764-L771 (As for ohos, +reserve-x18 is [redundant](llvm/llvm-project@c417b7a#diff-0ddf23e0bf2b28b2d05f842f087d1e6f694e8e06d1765e8d0f10d47fddcdff9c) since rust-lang@7a966b9 that starting using llvm's ohos targets. So removed it from target-spec.) This fix may potentially break the code for tier 2 target (aarch64-unknown-linux-ohos). (As for others, aarch64-unknown-trusty is tier 3 and -Zfixed-x18 is unstable so breaking them should be fine.) However, in any case, it seems suspicious that the code that is broken by this was sound. r? `@Amanieu` `@rustbot` label O-AArch64 +A-inline-assembly

Fix handling of x18 in AArch64 inline assembly on ohos/trusty or with -Zfixed-x18 Currently AArch64 inline assembly allows using x18 on ohos/trusty or with -Zfixed-x18. https://github.com/rust-lang/rust/blob/7db7489f9bc274cb60c4956bfa56de0185eb1b9b/compiler/rustc_target/src/asm/aarch64.rs#L74-L76 However, x18 is reserved in these environments and should not be allowed in the input/output operands of inline assemblies as it is in Android, Windows, etc.. https://github.com/rust-lang/rust/blob/7db7489f9bc274cb60c4956bfa56de0185eb1b9b/compiler/rustc_target/src/spec/targets/aarch64_unknown_linux_ohos.rs#L19 https://github.com/rust-lang/rust/blob/7db7489f9bc274cb60c4956bfa56de0185eb1b9b/compiler/rustc_target/src/spec/targets/aarch64_unknown_trusty.rs#L18 https://github.com/rust-lang/rust/blob/7db7489f9bc274cb60c4956bfa56de0185eb1b9b/compiler/rustc_codegen_llvm/src/llvm_util.rs#L764-L771 (As for ohos, +reserve-x18 is [redundant](llvm/llvm-project@c417b7a#diff-0ddf23e0bf2b28b2d05f842f087d1e6f694e8e06d1765e8d0f10d47fddcdff9c) since rust-lang@7a966b9 that starting using llvm's ohos targets. So removed it from target-spec.) This fix may potentially break the code for tier 2 target (aarch64-unknown-linux-ohos). (As for others, aarch64-unknown-trusty is tier 3 and -Zfixed-x18 is unstable so breaking them should be fine.) However, in any case, it seems suspicious that the code that is broken by this was sound. r? `@Amanieu` `@rustbot` label O-AArch64 +A-inline-assembly

RalfJung · 2025-06-13T22:52:00Z

compiler/rustc_target/src/target_features.rs

+    // #[target_feature].
+    // Note that cfg(target_feature = "reserve-x18") is currently not set for
+    // targets that reserve x18 by default.
+    ("reserve-x18", Unstable(sym::aarch64_unstable_target_feature), &[]),


Is there any cleaner way this could be done? This really should be listed as Forbidden, just like the retpoline flags.

It seems like it just needs things to be listed in unstable_target_features? That does include "forbidden" target features, so listing it here as forbidden might actually just work.

rustbot assigned Amanieu Nov 25, 2024

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 Nov 25, 2024

rustbot added A-inline-assembly Area: Inline assembly (`asm!(…)`) O-AArch64 Armv8-A or later processors in AArch64 mode labels Nov 25, 2024

taiki-e force-pushed the aarch64-asm-x18 branch from a43aa35 to 0c8db6e Compare November 25, 2024 17:16

taiki-e mentioned this pull request Nov 25, 2024

Reflect rust#133422 & rust#133587 to inline assembly documentation rust-lang/reference#1683

Closed

This comment has been minimized.

Sign in to view

taiki-e force-pushed the aarch64-asm-x18 branch from 0c8db6e to 85b9750 Compare November 25, 2024 17:29

This comment has been minimized.

Sign in to view

taiki-e force-pushed the aarch64-asm-x18 branch from 85b9750 to f4b01b5 Compare November 25, 2024 17:40

This comment has been minimized.

Sign in to view

Fix handling of x18 in AArch64 inline assembly on ohos/trusty or with…

687dc19

… -Zfixed-x18

taiki-e force-pushed the aarch64-asm-x18 branch from f4b01b5 to 687dc19 Compare November 25, 2024 18:10

Darksonn reviewed Nov 26, 2024

View reviewed changes

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 Nov 28, 2024

GuillaumeGomez mentioned this pull request Nov 28, 2024

Rollup of 7 pull requests #133568

Merged

bors merged commit 23bab15 into rust-lang:master Nov 28, 2024

rustbot added this to the 1.85.0 milestone Nov 28, 2024

taiki-e deleted the aarch64-asm-x18 branch November 28, 2024 14:23

RalfJung reviewed Jun 13, 2025

View reviewed changes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Fix handling of x18 in AArch64 inline assembly on ohos/trusty or with -Zfixed-x18#133463

Fix handling of x18 in AArch64 inline assembly on ohos/trusty or with -Zfixed-x18#133463
bors merged 1 commit intorust-lang:masterfrom
taiki-e:aarch64-asm-x18

taiki-e commented Nov 25, 2024

Uh oh!

rustbot commented Nov 25, 2024

Uh oh!

This comment has been minimized.

taiki-e commented Nov 25, 2024

Uh oh!

This comment has been minimized.

This comment has been minimized.

Darksonn Nov 26, 2024

Uh oh!

Amanieu Nov 28, 2024

Uh oh!

randomPoison commented Nov 26, 2024

Uh oh!

Amanieu commented Nov 28, 2024

Uh oh!

bors commented Nov 28, 2024

Uh oh!

RalfJung Jun 13, 2025

Uh oh!

RalfJung Jun 13, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

8 participants

	pub(crate) fn target_reserves_x18(target: &Target) -> bool {
	target.os == "android" \|\| target.os == "fuchsia" \|\| target.is_like_osx \|\| target.is_like_windows
	}

	// -Zfixed-x18
	if sess.opts.unstable_opts.fixed_x18 {
	if sess.target.arch != "aarch64" {
	sess.dcx().emit_fatal(FixedX18InvalidArch { arch: &sess.target.arch });
	} else {
	features.push("+reserve-x18".into());
	}
	}

Uh oh!

Conversation

taiki-e commented Nov 25, 2024

Uh oh!

rustbot commented Nov 25, 2024

Uh oh!

This comment has been minimized.

taiki-e commented Nov 25, 2024

Uh oh!

This comment has been minimized.

This comment has been minimized.

Darksonn Nov 26, 2024

Choose a reason for hiding this comment

Uh oh!

Amanieu Nov 28, 2024

Choose a reason for hiding this comment

Uh oh!

randomPoison commented Nov 26, 2024

Uh oh!

Amanieu commented Nov 28, 2024

Uh oh!

bors commented Nov 28, 2024

Uh oh!

RalfJung Jun 13, 2025

Choose a reason for hiding this comment

Uh oh!

RalfJung Jun 13, 2025

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

8 participants