rustc_target: Sync with stdarch (important parts)

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

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]),

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]),

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()

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;

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,

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]),

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]),

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(),

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),

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),