rustc_target: Remove fpmr target feature

FEAT_FPMR has been removed from upstream LLVM as of LLVM 19.
Remove the feature from the target features list and explicitly enable
it in target specs.

Author: mrkajetanp

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -306,6 +306,9 @@ pub fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFeature<'a
         ("x86", s) if get_version().0 >= 18 && s.starts_with("avx512") => {
             Some(LLVMFeature::with_dependency(s, TargetFeatureFoldStrength::EnableOnly("evex512")))
         }
+        // FPMR is no longer a Rust target feature but instead is enabled by default through target specs
+        // It only exists as a feature in LLVM 18, cannot be passed down for any other version
+        ("aarch64", "fpmr") if get_version().0 != 18 => None,
         (_, s) => Some(LLVMFeature::new(s)),
     }
 }

compiler/rustc_target/src/spec/targets/aarch64_be_unknown_linux_gnu.rs

@@ -14,7 +14,7 @@ pub fn target() -> Target {
         data_layout: "E-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: "aarch64".into(),
         options: TargetOptions {
-            features: "+v8a,+outline-atomics".into(),
+            features: "+v8a,+outline-atomics,+fpmr".into(),
             max_atomic_width: Some(128),
             stack_probes: StackProbeType::Inline,
             mcount: "\u{1}_mcount".into(),

compiler/rustc_target/src/spec/targets/aarch64_be_unknown_linux_gnu_ilp32.rs

@@ -18,7 +18,7 @@ pub fn target() -> Target {
         arch: "aarch64".into(),
         options: TargetOptions {
             abi: "ilp32".into(),
-            features: "+v8a,+outline-atomics".into(),
+            features: "+v8a,+outline-atomics,+fpmr".into(),
             stack_probes: StackProbeType::Inline,
             mcount: "\u{1}_mcount".into(),
             endian: Endian::Big,

compiler/rustc_target/src/spec/targets/aarch64_kmc_solid_asp3.rs

@@ -15,7 +15,7 @@ pub fn target() -> Target {
         arch: "aarch64".into(),
         options: TargetOptions {
             linker: Some("aarch64-kmc-elf-gcc".into()),
-            features: "+v8a,+neon,+fp-armv8".into(),
+            features: "+v8a,+neon,+fp-armv8,+fpmr".into(),
             relocation_model: RelocModel::Static,
             disable_redzone: true,
             max_atomic_width: Some(128),

compiler/rustc_target/src/spec/targets/aarch64_linux_android.rs

@@ -19,7 +19,7 @@ pub fn target() -> Target {
             max_atomic_width: Some(128),
             // As documented in https://developer.android.com/ndk/guides/cpu-features.html
             // the neon (ASIMD) and FP must exist on all android aarch64 targets.
-            features: "+v8a,+neon,+fp-armv8".into(),
+            features: "+v8a,+neon,+fp-armv8,+fpmr".into(),
             stack_probes: StackProbeType::Inline,
             supported_sanitizers: SanitizerSet::CFI
                 | SanitizerSet::HWADDRESS

compiler/rustc_target/src/spec/targets/aarch64_nintendo_switch_freestanding.rs

@@ -18,7 +18,7 @@ pub fn target() -> Target {
         data_layout: "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: "aarch64".into(),
         options: TargetOptions {
-            features: "+v8a".into(),
+            features: "+v8a,+fpmr".into(),
             linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::Yes),
             linker: Some("rust-lld".into()),
             link_script: Some(LINKER_SCRIPT.into()),

compiler/rustc_target/src/spec/targets/aarch64_pc_windows_gnullvm.rs

@@ -3,7 +3,7 @@ use crate::spec::{base, Target};
 pub fn target() -> Target {
     let mut base = base::windows_gnullvm::opts();
     base.max_atomic_width = Some(128);
-    base.features = "+v8a,+neon,+fp-armv8".into();
+    base.features = "+v8a,+neon,+fp-armv8,+fpmr".into();
     base.linker = Some("aarch64-w64-mingw32-clang".into());
 
     Target {

compiler/rustc_target/src/spec/targets/aarch64_pc_windows_msvc.rs

@@ -3,7 +3,7 @@ use crate::spec::{base, Target};
 pub fn target() -> Target {
     let mut base = base::windows_msvc::opts();
     base.max_atomic_width = Some(128);
-    base.features = "+v8a,+neon,+fp-armv8".into();
+    base.features = "+v8a,+neon,+fp-armv8,+fpmr".into();
 
     Target {
         llvm_target: "aarch64-pc-windows-msvc".into(),

compiler/rustc_target/src/spec/targets/aarch64_unknown_freebsd.rs

@@ -13,7 +13,7 @@ pub fn target() -> Target {
         data_layout: "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: "aarch64".into(),
         options: TargetOptions {
-            features: "+v8a".into(),
+            features: "+v8a,+fpmr".into(),
             max_atomic_width: Some(128),
             stack_probes: StackProbeType::Inline,
             supported_sanitizers: SanitizerSet::ADDRESS

compiler/rustc_target/src/spec/targets/aarch64_unknown_fuchsia.rs

@@ -13,7 +13,7 @@ pub fn target() -> Target {
         data_layout: "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: "aarch64".into(),
         options: TargetOptions {
-            features: "+v8a".into(),
+            features: "+v8a,+fpmr".into(),
             max_atomic_width: Some(128),
             stack_probes: StackProbeType::Inline,
             supported_sanitizers: SanitizerSet::ADDRESS