Rollup merge of #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 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

Author: GuillaumeGomez

compiler/rustc_span/src/symbol.rs

@@ -1611,6 +1611,7 @@ symbols! {
         repr_simd,
         repr_transparent,
         require,
+        reserve_x18: "reserve-x18",
         residual,
         result,
         result_ffi_guarantees,

compiler/rustc_target/src/asm/aarch64.rs

@@ -1,7 +1,7 @@
 use std::fmt;
 
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_span::Symbol;
+use rustc_span::{Symbol, sym};
 
 use super::{InlineAsmArch, InlineAsmType, ModifierInfo};
 use crate::spec::{RelocModel, Target};
@@ -71,18 +71,26 @@ impl AArch64InlineAsmRegClass {
     }
 }
 
-pub(crate) fn target_reserves_x18(target: &Target) -> bool {
-    target.os == "android" || target.os == "fuchsia" || target.is_like_osx || target.is_like_windows
+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)
 }
 
 fn reserved_x18(
     _arch: InlineAsmArch,
     _reloc_model: RelocModel,
-    _target_features: &FxIndexSet<Symbol>,
+    target_features: &FxIndexSet<Symbol>,
     target: &Target,
     _is_clobber: bool,
 ) -> Result<(), &'static str> {
-    if target_reserves_x18(target) {
+    if target_reserves_x18(target, target_features) {
         Err("x18 is a reserved register on this target")
     } else {
         Ok(())

compiler/rustc_target/src/asm/mod.rs

@@ -965,11 +965,13 @@ impl InlineAsmClobberAbi {
                 _ => Err(&["C", "system", "efiapi", "aapcs"]),
             },
             InlineAsmArch::AArch64 => match name {
-                "C" | "system" | "efiapi" => Ok(if aarch64::target_reserves_x18(target) {
-                    InlineAsmClobberAbi::AArch64NoX18
-                } else {
-                    InlineAsmClobberAbi::AArch64
-                }),
+                "C" | "system" | "efiapi" => {
+                    Ok(if aarch64::target_reserves_x18(target, target_features) {
+                        InlineAsmClobberAbi::AArch64NoX18
+                    } else {
+                        InlineAsmClobberAbi::AArch64
+                    })
+                }
                 _ => Err(&["C", "system", "efiapi"]),
             },
             InlineAsmArch::Arm64EC => match name {

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

@@ -16,7 +16,6 @@ pub(crate) fn target() -> Target {
         data_layout: "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: "aarch64".into(),
         options: TargetOptions {
-            features: "+reserve-x18".into(),
             mcount: "\u{1}_mcount".into(),
             stack_probes: StackProbeType::Inline,
             supported_sanitizers: SanitizerSet::ADDRESS

compiler/rustc_target/src/target_features.rs

@@ -228,6 +228,12 @@ const AARCH64_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
     ("rcpc3", Unstable(sym::aarch64_unstable_target_feature), &["rcpc2"]),
     // FEAT_RDM
     ("rdm", Stable, &["neon"]),
+    // This is needed for inline assembly, but shouldn't be stabilized as-is
+    // since it should be enabled globally using -Zfixed-x18, not
+    // #[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), &[]),
     // FEAT_SB
     ("sb", Stable, &[]),
     // FEAT_SHA1 & FEAT_SHA256

tests/codegen/asm/aarch64-clobbers.rs

@@ -0,0 +1,51 @@
+//@ revisions: aarch64 aarch64_fixed_x18 aarch64_no_x18 aarch64_reserve_x18 arm64ec
+//@[aarch64] compile-flags: --target aarch64-unknown-linux-gnu
+//@[aarch64] needs-llvm-components: aarch64
+//@[aarch64_fixed_x18] compile-flags: --target aarch64-unknown-linux-gnu -Zfixed-x18
+//@[aarch64_fixed_x18] needs-llvm-components: aarch64
+//@[aarch64_no_x18] compile-flags: --target aarch64-pc-windows-msvc
+//@[aarch64_no_x18] needs-llvm-components: aarch64
+// aarch64-unknown-trusty uses aarch64-unknown-unknown-musl which doesn't
+// reserve x18 by default as llvm_target, and pass +reserve-x18 in target-spec.
+//@[aarch64_reserve_x18] compile-flags: --target aarch64-unknown-trusty
+//@[aarch64_reserve_x18] needs-llvm-components: aarch64
+//@[arm64ec] compile-flags: --target arm64ec-pc-windows-msvc
+//@[arm64ec] needs-llvm-components: aarch64
+// ignore-tidy-linelength
+
+#![crate_type = "rlib"]
+#![feature(no_core, rustc_attrs, lang_items)]
+#![no_core]
+
+#[lang = "sized"]
+trait Sized {}
+
+#[rustc_builtin_macro]
+macro_rules! asm {
+    () => {};
+}
+
+// CHECK-LABEL: @cc_clobber
+// CHECK: call void asm sideeffect "", "~{cc}"()
+#[no_mangle]
+pub unsafe fn cc_clobber() {
+    asm!("", options(nostack, nomem));
+}
+
+// CHECK-LABEL: @no_clobber
+// CHECK: call void asm sideeffect "", ""()
+#[no_mangle]
+pub unsafe fn no_clobber() {
+    asm!("", options(nostack, nomem, preserves_flags));
+}
+
+// CHECK-LABEL: @clobber_abi
+// aarch64: asm sideeffect "", "={w0},={w1},={w2},={w3},={w4},={w5},={w6},={w7},={w8},={w9},={w10},={w11},={w12},={w13},={w14},={w15},={w16},={w17},={w18},={w30},={q0},={q1},={q2},={q3},={q4},={q5},={q6},={q7},={q8},={q9},={q10},={q11},={q12},={q13},={q14},={q15},={q16},={q17},={q18},={q19},={q20},={q21},={q22},={q23},={q24},={q25},={q26},={q27},={q28},={q29},={q30},={q31},~{p0},~{p1},~{p2},~{p3},~{p4},~{p5},~{p6},~{p7},~{p8},~{p9},~{p10},~{p11},~{p12},~{p13},~{p14},~{p15},~{ffr}"()
+// aarch64_fixed_x18: asm sideeffect "", "={w0},={w1},={w2},={w3},={w4},={w5},={w6},={w7},={w8},={w9},={w10},={w11},={w12},={w13},={w14},={w15},={w16},={w17},={w30},={q0},={q1},={q2},={q3},={q4},={q5},={q6},={q7},={q8},={q9},={q10},={q11},={q12},={q13},={q14},={q15},={q16},={q17},={q18},={q19},={q20},={q21},={q22},={q23},={q24},={q25},={q26},={q27},={q28},={q29},={q30},={q31},~{p0},~{p1},~{p2},~{p3},~{p4},~{p5},~{p6},~{p7},~{p8},~{p9},~{p10},~{p11},~{p12},~{p13},~{p14},~{p15},~{ffr}"()
+// aarch64_no_x18: asm sideeffect "", "={w0},={w1},={w2},={w3},={w4},={w5},={w6},={w7},={w8},={w9},={w10},={w11},={w12},={w13},={w14},={w15},={w16},={w17},={w30},={q0},={q1},={q2},={q3},={q4},={q5},={q6},={q7},={q8},={q9},={q10},={q11},={q12},={q13},={q14},={q15},={q16},={q17},={q18},={q19},={q20},={q21},={q22},={q23},={q24},={q25},={q26},={q27},={q28},={q29},={q30},={q31},~{p0},~{p1},~{p2},~{p3},~{p4},~{p5},~{p6},~{p7},~{p8},~{p9},~{p10},~{p11},~{p12},~{p13},~{p14},~{p15},~{ffr}"()
+// aarch64_reserve_x18: asm sideeffect "", "={w0},={w1},={w2},={w3},={w4},={w5},={w6},={w7},={w8},={w9},={w10},={w11},={w12},={w13},={w14},={w15},={w16},={w17},={w30},={q0},={q1},={q2},={q3},={q4},={q5},={q6},={q7},={q8},={q9},={q10},={q11},={q12},={q13},={q14},={q15},={q16},={q17},={q18},={q19},={q20},={q21},={q22},={q23},={q24},={q25},={q26},={q27},={q28},={q29},={q30},={q31},~{p0},~{p1},~{p2},~{p3},~{p4},~{p5},~{p6},~{p7},~{p8},~{p9},~{p10},~{p11},~{p12},~{p13},~{p14},~{p15},~{ffr}"()
+// arm64ec: asm sideeffect "", "={w0},={w1},={w2},={w3},={w4},={w5},={w6},={w7},={w8},={w9},={w10},={w11},={w12},={w15},={w16},={w17},={w30},={q0},={q1},={q2},={q3},={q4},={q5},={q6},={q7},={q8},={q9},={q10},={q11},={q12},={q13},={q14},={q15}"()
+#[no_mangle]
+pub unsafe fn clobber_abi() {
+    asm!("", clobber_abi("C"), options(nostack, nomem, preserves_flags));
+}

tests/codegen/asm/arm64ec-clobbers.rs

@@ -251,7 +251,7 @@ warning: unexpected `cfg` condition value: `zebra`
 LL |     cfg!(target_feature = "zebra");
    |          ^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: expected values for `target_feature` are: `10e60`, `2e3`, `3e3r1`, `3e3r2`, `3e3r3`, `3e7`, `7e10`, `a`, `aclass`, `adx`, `aes`, `altivec`, `alu32`, `amx-bf16`, `amx-complex`, `amx-fp16`, `amx-int8`, `amx-tile`, `atomics`, `avx`, `avx2`, `avx512bf16`, `avx512bitalg`, `avx512bw`, `avx512cd`, `avx512dq`, `avx512f`, `avx512fp16`, `avx512ifma`, `avx512vbmi`, `avx512vbmi2`, `avx512vl`, `avx512vnni`, `avx512vp2intersect`, and `avx512vpopcntdq` and 251 more
+   = note: expected values for `target_feature` are: `10e60`, `2e3`, `3e3r1`, `3e3r2`, `3e3r3`, `3e7`, `7e10`, `a`, `aclass`, `adx`, `aes`, `altivec`, `alu32`, `amx-bf16`, `amx-complex`, `amx-fp16`, `amx-int8`, `amx-tile`, `atomics`, `avx`, `avx2`, `avx512bf16`, `avx512bitalg`, `avx512bw`, `avx512cd`, `avx512dq`, `avx512f`, `avx512fp16`, `avx512ifma`, `avx512vbmi`, `avx512vbmi2`, `avx512vl`, `avx512vnni`, `avx512vp2intersect`, and `avx512vpopcntdq` and 252 more
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: 27 warnings emitted

tests/ui/check-cfg/mix.stderr

@@ -174,7 +174,7 @@ warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
 LL |     target_feature = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: expected values for `target_feature` are: `10e60`, `2e3`, `3e3r1`, `3e3r2`, `3e3r3`, `3e7`, `7e10`, `a`, `aclass`, `adx`, `aes`, `altivec`, `alu32`, `amx-bf16`, `amx-complex`, `amx-fp16`, `amx-int8`, `amx-tile`, `atomics`, `avx`, `avx2`, `avx512bf16`, `avx512bitalg`, `avx512bw`, `avx512cd`, `avx512dq`, `avx512f`, `avx512fp16`, `avx512ifma`, `avx512vbmi`, `avx512vbmi2`, `avx512vl`, `avx512vnni`, `avx512vp2intersect`, `avx512vpopcntdq`, `avxifma`, `avxneconvert`, `avxvnni`, `avxvnniint16`, `avxvnniint8`, `backchain`, `bf16`, `bmi1`, `bmi2`, `bti`, `bulk-memory`, `c`, `cache`, `cmpxchg16b`, `crc`, `crt-static`, `cssc`, `d`, `d32`, `dit`, `doloop`, `dotprod`, `dpb`, `dpb2`, `dsp`, `dsp1e2`, `dspe60`, `e`, `e1`, `e2`, `ecv`, `edsp`, `elrw`, `ermsb`, `exception-handling`, `extended-const`, `f`, `f16c`, `f32mm`, `f64mm`, `faminmax`, `fcma`, `fdivdu`, `fhm`, `flagm`, `flagm2`, `float1e2`, `float1e3`, `float3e4`, `float7e60`, `floate1`, `fma`, `fp-armv8`, `fp16`, `fp64`, `fp8`, `fp8dot2`, `fp8dot4`, `fp8fma`, `fpuv2_df`, `fpuv2_sf`, `fpuv3_df`, `fpuv3_hf`, `fpuv3_hi`, `fpuv3_sf`, `frecipe`, `frintts`, `fxsr`, `gfni`, `hard-float`, `hard-float-abi`, `hard-tp`, `hbc`, `high-registers`, `hvx`, `hvx-length128b`, `hwdiv`, `i8mm`, `jsconv`, `lahfsahf`, `lasx`, `lbt`, `leoncasa`, `lor`, `lse`, `lse128`, `lse2`, `lsx`, `lut`, `lvz`, `lzcnt`, `m`, `mclass`, `mops`, `movbe`, `mp`, `mp1e2`, `msa`, `mte`, `multivalue`, `mutable-globals`, `neon`, `nontrapping-fptoint`, `nvic`, `paca`, `pacg`, `pan`, `partword-atomics`, `pauth-lr`, `pclmulqdq`, `pmuv3`, `popcnt`, `power10-vector`, `power8-altivec`, `power8-vector`, `power9-altivec`, `power9-vector`, `prfchw`, `quadword-atomics`, `rand`, `ras`, `rclass`, `rcpc`, `rcpc2`, `rcpc3`, `rdm`, `rdrand`, `rdseed`, `reference-types`, `relax`, `relaxed-simd`, `rtm`, `sb`, `sha`, `sha2`, `sha3`, `sha512`, `sign-ext`, `simd128`, `sm3`, `sm4`, `sme`, `sme-b16b16`, `sme-f16f16`, `sme-f64f64`, `sme-f8f16`, `sme-f8f32`, `sme-fa64`, `sme-i16i64`, `sme-lutv2`, `sme2`, `sme2p1`, `spe`, `ssbs`, `sse`, `sse2`, `sse3`, `sse4.1`, `sse4.2`, `sse4a`, `ssse3`, `ssve-fp8dot2`, `ssve-fp8dot4`, `ssve-fp8fma`, `sve`, `sve-b16b16`, `sve2`, `sve2-aes`, `sve2-bitperm`, `sve2-sha3`, `sve2-sm4`, `sve2p1`, `tail-call`, `tbm`, `thumb-mode`, `thumb2`, `tme`, `trust`, `trustzone`, `ual`, `unaligned-scalar-mem`, `v`, `v5te`, `v6`, `v6k`, `v6t2`, `v7`, `v8`, `v8.1a`, `v8.2a`, `v8.3a`, `v8.4a`, `v8.5a`, `v8.6a`, `v8.7a`, `v8.8a`, `v8.9a`, `v8plus`, `v9`, `v9.1a`, `v9.2a`, `v9.3a`, `v9.4a`, `v9.5a`, `v9a`, `vaes`, `vdsp2e60f`, `vdspv1`, `vdspv2`, `vector`, `vfp2`, `vfp3`, `vfp4`, `vh`, `virt`, `virtualization`, `vpclmulqdq`, `vsx`, `wfxt`, `wide-arithmetic`, `xop`, `xsave`, `xsavec`, `xsaveopt`, `xsaves`, `zaamo`, `zabha`, `zalrsc`, `zba`, `zbb`, `zbc`, `zbkb`, `zbkc`, `zbkx`, `zbs`, `zdinx`, `zfh`, `zfhmin`, `zfinx`, `zhinx`, `zhinxmin`, `zk`, `zkn`, `zknd`, `zkne`, `zknh`, `zkr`, `zks`, `zksed`, `zksh`, and `zkt`
+   = note: expected values for `target_feature` are: `10e60`, `2e3`, `3e3r1`, `3e3r2`, `3e3r3`, `3e7`, `7e10`, `a`, `aclass`, `adx`, `aes`, `altivec`, `alu32`, `amx-bf16`, `amx-complex`, `amx-fp16`, `amx-int8`, `amx-tile`, `atomics`, `avx`, `avx2`, `avx512bf16`, `avx512bitalg`, `avx512bw`, `avx512cd`, `avx512dq`, `avx512f`, `avx512fp16`, `avx512ifma`, `avx512vbmi`, `avx512vbmi2`, `avx512vl`, `avx512vnni`, `avx512vp2intersect`, `avx512vpopcntdq`, `avxifma`, `avxneconvert`, `avxvnni`, `avxvnniint16`, `avxvnniint8`, `backchain`, `bf16`, `bmi1`, `bmi2`, `bti`, `bulk-memory`, `c`, `cache`, `cmpxchg16b`, `crc`, `crt-static`, `cssc`, `d`, `d32`, `dit`, `doloop`, `dotprod`, `dpb`, `dpb2`, `dsp`, `dsp1e2`, `dspe60`, `e`, `e1`, `e2`, `ecv`, `edsp`, `elrw`, `ermsb`, `exception-handling`, `extended-const`, `f`, `f16c`, `f32mm`, `f64mm`, `faminmax`, `fcma`, `fdivdu`, `fhm`, `flagm`, `flagm2`, `float1e2`, `float1e3`, `float3e4`, `float7e60`, `floate1`, `fma`, `fp-armv8`, `fp16`, `fp64`, `fp8`, `fp8dot2`, `fp8dot4`, `fp8fma`, `fpuv2_df`, `fpuv2_sf`, `fpuv3_df`, `fpuv3_hf`, `fpuv3_hi`, `fpuv3_sf`, `frecipe`, `frintts`, `fxsr`, `gfni`, `hard-float`, `hard-float-abi`, `hard-tp`, `hbc`, `high-registers`, `hvx`, `hvx-length128b`, `hwdiv`, `i8mm`, `jsconv`, `lahfsahf`, `lasx`, `lbt`, `leoncasa`, `lor`, `lse`, `lse128`, `lse2`, `lsx`, `lut`, `lvz`, `lzcnt`, `m`, `mclass`, `mops`, `movbe`, `mp`, `mp1e2`, `msa`, `mte`, `multivalue`, `mutable-globals`, `neon`, `nontrapping-fptoint`, `nvic`, `paca`, `pacg`, `pan`, `partword-atomics`, `pauth-lr`, `pclmulqdq`, `pmuv3`, `popcnt`, `power10-vector`, `power8-altivec`, `power8-vector`, `power9-altivec`, `power9-vector`, `prfchw`, `quadword-atomics`, `rand`, `ras`, `rclass`, `rcpc`, `rcpc2`, `rcpc3`, `rdm`, `rdrand`, `rdseed`, `reference-types`, `relax`, `relaxed-simd`, `reserve-x18`, `rtm`, `sb`, `sha`, `sha2`, `sha3`, `sha512`, `sign-ext`, `simd128`, `sm3`, `sm4`, `sme`, `sme-b16b16`, `sme-f16f16`, `sme-f64f64`, `sme-f8f16`, `sme-f8f32`, `sme-fa64`, `sme-i16i64`, `sme-lutv2`, `sme2`, `sme2p1`, `spe`, `ssbs`, `sse`, `sse2`, `sse3`, `sse4.1`, `sse4.2`, `sse4a`, `ssse3`, `ssve-fp8dot2`, `ssve-fp8dot4`, `ssve-fp8fma`, `sve`, `sve-b16b16`, `sve2`, `sve2-aes`, `sve2-bitperm`, `sve2-sha3`, `sve2-sm4`, `sve2p1`, `tail-call`, `tbm`, `thumb-mode`, `thumb2`, `tme`, `trust`, `trustzone`, `ual`, `unaligned-scalar-mem`, `v`, `v5te`, `v6`, `v6k`, `v6t2`, `v7`, `v8`, `v8.1a`, `v8.2a`, `v8.3a`, `v8.4a`, `v8.5a`, `v8.6a`, `v8.7a`, `v8.8a`, `v8.9a`, `v8plus`, `v9`, `v9.1a`, `v9.2a`, `v9.3a`, `v9.4a`, `v9.5a`, `v9a`, `vaes`, `vdsp2e60f`, `vdspv1`, `vdspv2`, `vector`, `vfp2`, `vfp3`, `vfp4`, `vh`, `virt`, `virtualization`, `vpclmulqdq`, `vsx`, `wfxt`, `wide-arithmetic`, `xop`, `xsave`, `xsavec`, `xsaveopt`, `xsaves`, `zaamo`, `zabha`, `zalrsc`, `zba`, `zbb`, `zbc`, `zbkb`, `zbkc`, `zbkx`, `zbs`, `zdinx`, `zfh`, `zfhmin`, `zfinx`, `zhinx`, `zhinxmin`, `zk`, `zkn`, `zknd`, `zkne`, `zknh`, `zkr`, `zks`, `zksed`, `zksh`, and `zkt`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`