Rollup merge of rust-lang#63165 - xen0n:mips64-musl-targets, r=alexcrichton

Add builtin targets for mips64(el)-unknown-linux-musl

This is prerequisite for rust-lang/libc#1449.

Tested locally to produce working static and dynamic binaries, ~~but CI config is untested for now~~ CI is to be added in a follow-up PR.

*edit: dynamic binaries also confirmed working!*

Author: Centril

src/librustc_target/spec/mips64_unknown_linux_musl.rs

@@ -0,0 +1,25 @@
+use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
+
+pub fn target() -> TargetResult {
+    let mut base = super::linux_musl_base::opts();
+    base.cpu = "mips64r2".to_string();
+    base.features = "+mips64r2".to_string();
+    base.max_atomic_width = Some(64);
+    base.crt_static_default = false;
+    Ok(Target {
+        llvm_target: "mips64-unknown-linux-musl".to_string(),
+        target_endian: "big".to_string(),
+        target_pointer_width: "64".to_string(),
+        target_c_int_width: "32".to_string(),
+        data_layout: "E-m:e-i8:8:32-i16:16:32-i64:64-n32:64-S128".to_string(),
+        arch: "mips64".to_string(),
+        target_os: "linux".to_string(),
+        target_env: "musl".to_string(),
+        target_vendor: "unknown".to_string(),
+        linker_flavor: LinkerFlavor::Gcc,
+        options: TargetOptions {
+            target_mcount: "_mcount".to_string(),
+            .. base
+        },
+    })
+}

src/librustc_target/spec/mips64el_unknown_linux_musl.rs

@@ -0,0 +1,25 @@
+use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
+
+pub fn target() -> TargetResult {
+    let mut base = super::linux_musl_base::opts();
+    base.cpu = "mips64r2".to_string();
+    base.features = "+mips64r2".to_string();
+    base.max_atomic_width = Some(64);
+    base.crt_static_default = false;
+    Ok(Target {
+        llvm_target: "mips64el-unknown-linux-musl".to_string(),
+        target_endian: "little".to_string(),
+        target_pointer_width: "64".to_string(),
+        target_c_int_width: "32".to_string(),
+        data_layout: "e-m:e-i8:8:32-i16:16:32-i64:64-n32:64-S128".to_string(),
+        arch: "mips64".to_string(),
+        target_os: "linux".to_string(),
+        target_env: "musl".to_string(),
+        target_vendor: "unknown".to_string(),
+        linker_flavor: LinkerFlavor::Gcc,
+        options: TargetOptions {
+            target_mcount: "_mcount".to_string(),
+            .. base
+        },
+    })
+}

src/librustc_target/spec/mod.rs

@@ -371,6 +371,8 @@ supported_targets! {
     ("i586-unknown-linux-musl", i586_unknown_linux_musl),
     ("mips-unknown-linux-musl", mips_unknown_linux_musl),
     ("mipsel-unknown-linux-musl", mipsel_unknown_linux_musl),
+    ("mips64-unknown-linux-musl", mips64_unknown_linux_musl),
+    ("mips64el-unknown-linux-musl", mips64el_unknown_linux_musl),
     ("hexagon-unknown-linux-musl", hexagon_unknown_linux_musl),
 
     ("mips-unknown-linux-uclibc", mips_unknown_linux_uclibc),