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

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

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

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

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

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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

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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

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

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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

taiki-e commented Nov 25, 2024

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Darksonn Nov 26, 2024

Amanieu Nov 28, 2024

randomPoison commented Nov 26, 2024

Amanieu commented Nov 28, 2024

bors commented Nov 28, 2024

	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());
	}
	}

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

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