rustc_target: RISC-V: add base "I"-related important extensions

Of RISC-V features defined in stdarch, this commit adds extensions
satisfying following criteria:

*   Formerly a part of the "I" extension and splitted thereafter
    (now ratified as "I" + "Zifencei" + "Zicsr" + "Zicntr" + "Zihpm") or
*   Dicoverable from newer versions of the Linux kernel ("Zihintpause").

This is based on the latest ratified ISA Manuals (version 20240411).

Additional (1):

One of those, "Zicsr", is a dependency of many other ISA extensions and
this commit adds correct dependencies to "Zicsr" except "V"
(due to an ongoing PR).

Additional (2):

In RISC-V, "G" is an abbreviation of following extensions:

*   "I"
*   "M"
*   "A"
*   "F"
*   "D"
*   "Zicsr" (although implied by "F")
*   "Zifencei"

and all targets with either "riscv32gc" or "riscv64gc" are updated
accordingly.

Author: a4lg

Diff for: compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_gnu.rs

@@ -17,7 +17,7 @@ pub(crate) fn target() -> Target {
         options: TargetOptions {
             code_model: Some(CodeModel::Medium),
             cpu: "generic-rv32".into(),
-            features: "+m,+a,+f,+d,+c".into(),
+            features: "+m,+a,+f,+d,+c,+zicsr,+zifencei".into(),
             llvm_abiname: "ilp32d".into(),
             max_atomic_width: Some(32),
             supported_split_debuginfo: Cow::Borrowed(&[SplitDebuginfo::Off]),

Diff for: compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs

@@ -19,7 +19,7 @@ pub(crate) fn target() -> Target {
         options: TargetOptions {
             code_model: Some(CodeModel::Medium),
             cpu: "generic-rv32".into(),
-            features: "+m,+a,+f,+d,+c".into(),
+            features: "+m,+a,+f,+d,+c,+zicsr,+zifencei".into(),
             llvm_abiname: "ilp32d".into(),
             max_atomic_width: Some(32),
             supported_split_debuginfo: Cow::Borrowed(&[SplitDebuginfo::Off]),

Diff for: compiler/rustc_target/src/spec/targets/riscv64gc_unknown_freebsd.rs

@@ -15,7 +15,7 @@ pub(crate) fn target() -> Target {
         options: TargetOptions {
             code_model: Some(CodeModel::Medium),
             cpu: "generic-rv64".into(),
-            features: "+m,+a,+f,+d,+c".into(),
+            features: "+m,+a,+f,+d,+c,+zicsr,+zifencei".into(),
             llvm_abiname: "lp64d".into(),
             max_atomic_width: Some(64),
             ..base::freebsd::opts()

Diff for: compiler/rustc_target/src/spec/targets/riscv64gc_unknown_fuchsia.rs

@@ -4,7 +4,7 @@ pub(crate) fn target() -> Target {
     let mut base = base::fuchsia::opts();
     base.code_model = Some(CodeModel::Medium);
     base.cpu = "generic-rv64".into();
-    base.features = "+m,+a,+f,+d,+c".into();
+    base.features = "+m,+a,+f,+d,+c,+zicsr,+zifencei".into();
     base.llvm_abiname = "lp64d".into();
     base.max_atomic_width = Some(64);
     base.stack_probes = StackProbeType::Inline;

Diff for: compiler/rustc_target/src/spec/targets/riscv64gc_unknown_hermit.rs

@@ -14,7 +14,7 @@ pub(crate) fn target() -> Target {
         data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".into(),
         options: TargetOptions {
             cpu: "generic-rv64".into(),
-            features: "+m,+a,+f,+d,+c".into(),
+            features: "+m,+a,+f,+d,+c,+zicsr,+zifencei".into(),
             relocation_model: RelocModel::Pic,
             code_model: Some(CodeModel::Medium),
             tls_model: TlsModel::LocalExec,

Diff for: compiler/rustc_target/src/spec/targets/riscv64gc_unknown_linux_gnu.rs

@@ -17,7 +17,7 @@ pub(crate) fn target() -> Target {
         options: TargetOptions {
             code_model: Some(CodeModel::Medium),
             cpu: "generic-rv64".into(),
-            features: "+m,+a,+f,+d,+c".into(),
+            features: "+m,+a,+f,+d,+c,+zicsr,+zifencei".into(),
             llvm_abiname: "lp64d".into(),
             max_atomic_width: Some(64),
             supported_split_debuginfo: Cow::Borrowed(&[SplitDebuginfo::Off]),

Diff for: compiler/rustc_target/src/spec/targets/riscv64gc_unknown_linux_musl.rs

@@ -17,7 +17,7 @@ pub(crate) fn target() -> Target {
         options: TargetOptions {
             code_model: Some(CodeModel::Medium),
             cpu: "generic-rv64".into(),
-            features: "+m,+a,+f,+d,+c".into(),
+            features: "+m,+a,+f,+d,+c,+zicsr,+zifencei".into(),
             llvm_abiname: "lp64d".into(),
             max_atomic_width: Some(64),
             supported_split_debuginfo: Cow::Borrowed(&[SplitDebuginfo::Off]),

Diff for: compiler/rustc_target/src/spec/targets/riscv64gc_unknown_netbsd.rs

@@ -15,7 +15,7 @@ pub(crate) fn target() -> Target {
         options: TargetOptions {
             code_model: Some(CodeModel::Medium),
             cpu: "generic-rv64".into(),
-            features: "+m,+a,+f,+d,+c".into(),
+            features: "+m,+a,+f,+d,+c,+zicsr,+zifencei".into(),
             llvm_abiname: "lp64d".into(),
             max_atomic_width: Some(64),
             mcount: "__mcount".into(),

Diff for: compiler/rustc_target/src/spec/targets/riscv64gc_unknown_none_elf.rs

@@ -22,7 +22,7 @@ pub(crate) fn target() -> Target {
             llvm_abiname: "lp64d".into(),
             cpu: "generic-rv64".into(),
             max_atomic_width: Some(64),
-            features: "+m,+a,+f,+d,+c".into(),
+            features: "+m,+a,+f,+d,+c,+zicsr,+zifencei".into(),
             panic_strategy: PanicStrategy::Abort,
             relocation_model: RelocModel::Static,
             code_model: Some(CodeModel::Medium),

Diff for: compiler/rustc_target/src/spec/targets/riscv64gc_unknown_nuttx_elf.rs

@@ -24,7 +24,7 @@ pub(crate) fn target() -> Target {
             llvm_abiname: "lp64d".into(),
             cpu: "generic-rv64".into(),
             max_atomic_width: Some(64),
-            features: "+m,+a,+f,+d,+c".into(),
+            features: "+m,+a,+f,+d,+c,+zicsr,+zifencei".into(),
             panic_strategy: PanicStrategy::Abort,
             relocation_model: RelocModel::Static,
             code_model: Some(CodeModel::Medium),

Diff for: compiler/rustc_target/src/spec/targets/riscv64gc_unknown_openbsd.rs

@@ -15,7 +15,7 @@ pub(crate) fn target() -> Target {
         options: TargetOptions {
             code_model: Some(CodeModel::Medium),
             cpu: "generic-rv64".into(),
-            features: "+m,+a,+f,+d,+c".into(),
+            features: "+m,+a,+f,+d,+c,+zicsr,+zifencei".into(),
             llvm_abiname: "lp64d".into(),
             max_atomic_width: Some(64),
             ..base::openbsd::opts()

Diff for: compiler/rustc_target/src/target_features.rs

@@ -488,7 +488,7 @@ static RISCV_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
     ("c", Stable, &[]),
     ("d", Unstable(sym::riscv_target_feature), &["f"]),
     ("e", Unstable(sym::riscv_target_feature), &[]),
-    ("f", Unstable(sym::riscv_target_feature), &[]),
+    ("f", Unstable(sym::riscv_target_feature), &["zicsr"]),
     (
         "forced-atomics",
         Stability::Forbidden { reason: "unsound because it changes the ABI of atomic operations" },
@@ -516,15 +516,20 @@ static RISCV_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
     ("zdinx", Unstable(sym::riscv_target_feature), &["zfinx"]),
     ("zfh", Unstable(sym::riscv_target_feature), &["zfhmin"]),
     ("zfhmin", Unstable(sym::riscv_target_feature), &["f"]),
-    ("zfinx", Unstable(sym::riscv_target_feature), &[]),
+    ("zfinx", Unstable(sym::riscv_target_feature), &["zicsr"]),
     ("zhinx", Unstable(sym::riscv_target_feature), &["zhinxmin"]),
     ("zhinxmin", Unstable(sym::riscv_target_feature), &["zfinx"]),
+    ("zicntr", Unstable(sym::riscv_target_feature), &["zicsr"]),
+    ("zicsr", Unstable(sym::riscv_target_feature), &[]),
+    ("zifencei", Unstable(sym::riscv_target_feature), &[]),
+    ("zihintpause", Unstable(sym::riscv_target_feature), &[]),
+    ("zihpm", Unstable(sym::riscv_target_feature), &["zicsr"]),
     ("zk", Stable, &["zkn", "zkr", "zkt"]),
     ("zkn", Stable, &["zbkb", "zbkc", "zbkx", "zkne", "zknd", "zknh"]),
     ("zknd", Stable, &[]),
     ("zkne", Stable, &[]),
     ("zknh", Stable, &[]),
-    ("zkr", Stable, &[]),
+    ("zkr", Stable, &["zicsr"]),
     ("zks", Stable, &["zbkb", "zbkc", "zbkx", "zksed", "zksh"]),
     ("zksed", Stable, &[]),
     ("zksh", Stable, &[]),

Diff for: tests/ui/check-cfg/target_feature.stderr

@@ -317,6 +317,11 @@ LL |     cfg!(target_feature = "_UNEXPECTED_VALUE");
 `zfinx`
 `zhinx`
 `zhinxmin`
+`zicntr`
+`zicsr`
+`zifencei`
+`zihintpause`
+`zihpm`
 `zk`
 `zkn`
 `zknd`