add target feature ABI checks for SPARC

compiler/rustc_target/src/spec/mod.rs

@@ -987,12 +987,14 @@ crate::target_spec_enum! {
 crate::target_spec_enum! {
     /// The Rustc-specific variant of the ABI used for this target.
     pub enum RustcAbi {
+        /// On x86-32/64, aarch64, and S390x: do not use any FPU or SIMD registers for the ABI.
+        Softfloat = "softfloat",
         /// On x86-32 only: make use of SSE and SSE2 for ABI purposes.
         X86Sse2 = "x86-sse2",
         /// On PowerPC only: build for SPE.
         PowerPcSpe = "powerpc-spe",
-        /// On x86-32/64, aarch64, and S390x: do not use any FPU or SIMD registers for the ABI.
-        Softfloat = "softfloat",
+        /// On SPARC-32: use the V8+ ABI.
+        SparcV8Plus = "sparc-v8plus",
     }
 
     parse_error_type = "rustc abi";
@@ -2089,6 +2091,7 @@ crate::target_spec_enum! {
         VecDefault = "vec-default",
         VecExtAbi = "vec-extabi",
         X32 = "x32",
+        V8Plus = "v8plus",
         Unspecified = "",
     }
     other_variant = Other;
@@ -3596,6 +3599,36 @@ impl Target {
                     self.cfg_abi,
                 );
             }
+            Arch::Sparc => {
+                check!(
+                    self.llvm_abiname == LlvmAbi::Unspecified,
+                    "`llvm_abiname` is unused on SPARC"
+                );
+                check!(self.llvm_floatabi.is_none(), "`llvm_floatabi` is unused on SPARC");
+                check_matches!(
+                    (&self.rustc_abi, &self.cfg_abi),
+                    (Some(RustcAbi::SparcV8Plus), CfgAbi::V8Plus)
+                        | (None, CfgAbi::Unspecified | CfgAbi::Other(_)),
+                    "invalid SPARC Rust-specific ABI and `cfg(target_abi)` combination:\n\
+                    Rust-specific ABI: {:?}\n\
+                    cfg(target_abi): {}",
+                    self.rustc_abi,
+                    self.cfg_abi,
+                );
+            }
+            Arch::Sparc64 => {
+                check!(
+                    self.llvm_abiname == LlvmAbi::Unspecified,
+                    "`llvm_abiname` is unused on SPARC-64"
+                );
+                check!(self.llvm_floatabi.is_none(), "`llvm_floatabi` is unused on SPARC-64");
+                check!(self.rustc_abi.is_none(), "`rustc_abi` is unused on SPARC-64");
+                check_matches!(
+                    self.cfg_abi,
+                    CfgAbi::Unspecified | CfgAbi::Other(_),
+                    "invalid `target_abi` for SPARC-64"
+                );
+            }
             Arch::CSky => {
                 check!(
                     self.llvm_abiname == LlvmAbi::Unspecified,

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

@@ -1,6 +1,8 @@
 use rustc_abi::Endian;
 
-use crate::spec::{Arch, Cc, LinkerFlavor, Lld, Target, TargetMetadata, TargetOptions, base};
+use crate::spec::{
+    Arch, Cc, CfgAbi, LinkerFlavor, Lld, RustcAbi, Target, TargetMetadata, TargetOptions, base,
+};
 
 pub(crate) fn target() -> Target {
     Target {
@@ -16,13 +18,15 @@ pub(crate) fn target() -> Target {
         arch: Arch::Sparc,
         options: TargetOptions {
             features: "+v8plus".into(),
+            rustc_abi: Some(RustcAbi::SparcV8Plus),
             cpu: "v9".into(),
             endian: Endian::Big,
             late_link_args: TargetOptions::link_args(
                 LinkerFlavor::Gnu(Cc::Yes, Lld::No),
                 &["-mcpu=v9", "-m32"],
             ),
             max_atomic_width: Some(32),
+            cfg_abi: CfgAbi::V8Plus,
             ..base::linux_gnu::opts()
         },
     }

compiler/rustc_target/src/target_features.rs

@@ -937,6 +937,11 @@ const IBMZ_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
 const SPARC_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
     // tidy-alphabetical-start
     ("leoncasa", Unstable(sym::sparc_target_feature), &[]),
+    (
+        "soft-float",
+        Forbidden { reason: "unsupported ABI-configuration feature", hard_error: false },
+        &[],
+    ),
     ("v8plus", Unstable(sym::sparc_target_feature), &[]),
     ("v9", Unstable(sym::sparc_target_feature), &[]),
     // tidy-alphabetical-end
@@ -1414,6 +1419,26 @@ impl Target {
                 // to other targets above.)
                 FeatureConstraints { required: &["hard-float"], incompatible: &["spe"] }
             }
+            Arch::Sparc => {
+                // We currently don't have a soft-float target for SPARC.
+                // We need to pin down v8plus as it is a separate ABI (indicated in object files so
+                // things cannot be linked across ABI boundaries).
+                match self.rustc_abi {
+                    None => FeatureConstraints {
+                        required: &[],
+                        incompatible: &["soft-float", "v8plus"],
+                    },
+                    Some(RustcAbi::SparcV8Plus) => {
+                        FeatureConstraints { required: &["v8plus"], incompatible: &["soft-float"] }
+                    }
+                    _ => unreachable!(),
+                }
+            }
+            Arch::Sparc64 => {
+                // We currently don't have a soft-float target for SPARC64.
+                // v8plus is for 32bit SPARC only.
+                FeatureConstraints { required: &[], incompatible: &["soft-float", "v8plus"] }
+            }
             Arch::Avr => {
                 // We only support one ABI on AVR at the moment.
                 // SRAM is minimum requirement for C/C++ in both avr-gcc and Clang,

tests/ui/abi/sparcv8plus.rs

@@ -13,7 +13,7 @@
 //@ ignore-backends: gcc
 
 //[sparc_feature_v8plus,sparc_cpu_v9_feature_v8plus]~? WARN unstable feature specified for `-Ctarget-feature`
-//[sparc_feature_v8plus,sparc_cpu_v9_feature_v8plus]~? NOTE this feature is not stably supported; its behavior can change in the future
+//[sparc_feature_v8plus,sparc_cpu_v9_feature_v8plus]~? WARN `v8plus` must be disabled
 
 #![crate_type = "rlib"]
 #![feature(no_core, rustc_attrs, lang_items)]

tests/ui/abi/sparcv8plus.sparc_cpu_v9_feature_v8plus.stderr

@@ -2,11 +2,16 @@ warning: unstable feature specified for `-Ctarget-feature`: `v8plus`
    |
    = note: this feature is not stably supported; its behavior can change in the future
 
+warning: target feature `v8plus` must be disabled to ensure that the ABI of the current target can be implemented correctly
+   |
+   = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #116344 <https://github.com/rust-lang/rust/issues/116344>
+
 error: +v8plus,+v9
   --> $DIR/sparcv8plus.rs:35:1
    |
 LL | compile_error!("+v8plus,+v9");
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error; 2 warnings emitted
 

tests/ui/abi/sparcv8plus.sparc_feature_v8plus.stderr

@@ -2,11 +2,16 @@ warning: unstable feature specified for `-Ctarget-feature`: `v8plus`
    |
    = note: this feature is not stably supported; its behavior can change in the future
 
+warning: target feature `v8plus` must be disabled to ensure that the ABI of the current target can be implemented correctly
+   |
+   = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #116344 <https://github.com/rust-lang/rust/issues/116344>
+
 error: +v8plus,-v9 (FIXME)
   --> $DIR/sparcv8plus.rs:40:1
    |
 LL | compile_error!("+v8plus,-v9 (FIXME)");
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error; 2 warnings emitted
 

tests/ui/check-cfg/well-known-values.stderr

@@ -129,7 +129,7 @@ warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
 LL |     target_abi = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: expected values for `target_abi` are: ``, `abi64`, `abiv2`, `abiv2hf`, `eabi`, `eabihf`, `elfv1`, `elfv2`, `fortanix`, `ilp32`, `ilp32e`, `llvm`, `macabi`, `pauthtest`, `sim`, `softfloat`, `spe`, `uwp`, `vec-extabi`, and `x32`
+   = note: expected values for `target_abi` are: ``, `abi64`, `abiv2`, `abiv2hf`, `eabi`, `eabihf`, `elfv1`, `elfv2`, `fortanix`, `ilp32`, `ilp32e`, `llvm`, `macabi`, `pauthtest`, `sim`, `softfloat`, `spe`, `uwp`, `v8plus`, `vec-extabi`, and `x32`
    = 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`