Add cygwin target.

Co-authored-by: Ookiineko <chiisaineko@protonmail.com>
Co-authored-by: nora <48135649+Noratrieb@users.noreply.github.com>
Co-authored-by: Jubilee <workingjubilee@gmail.com>

compiler/rustc_target/src/spec/base/cygwin.rs

@@ -0,0 +1,51 @@
+use std::borrow::Cow;
+
+use crate::spec::{Cc, DebuginfoKind, LinkerFlavor, Lld, SplitDebuginfo, TargetOptions, cvs};
+
+pub(crate) fn opts() -> TargetOptions {
+    let mut pre_link_args = TargetOptions::link_args(LinkerFlavor::Gnu(Cc::No, Lld::No), &[
+        // FIXME: Disable ASLR for now to fix relocation error
+        "--disable-dynamicbase",
+        "--enable-auto-image-base",
+    ]);
+    crate::spec::add_link_args(&mut pre_link_args, LinkerFlavor::Gnu(Cc::Yes, Lld::No), &[
+        // Tell GCC to avoid linker plugins, because we are not bundling
+        // them with Windows installer, and Rust does its own LTO anyways.
+        "-fno-use-linker-plugin",
+        "-Wl,--disable-dynamicbase",
+        "-Wl,--enable-auto-image-base",
+    ]);
+    let cygwin_libs = &["-lcygwin", "-lgcc", "-lcygwin", "-luser32", "-lkernel32", "-lgcc_s"];
+    let mut late_link_args =
+        TargetOptions::link_args(LinkerFlavor::Gnu(Cc::No, Lld::No), cygwin_libs);
+    crate::spec::add_link_args(
+        &mut late_link_args,
+        LinkerFlavor::Gnu(Cc::Yes, Lld::No),
+        cygwin_libs,
+    );
+    TargetOptions {
+        os: "cygwin".into(),
+        vendor: "pc".into(),
+        // FIXME(#13846) this should be enabled for cygwin
+        function_sections: false,
+        linker: Some("gcc".into()),
+        dynamic_linking: true,
+        dll_prefix: "".into(),
+        dll_suffix: ".dll".into(),
+        exe_suffix: ".exe".into(),
+        families: cvs!["unix"],
+        is_like_windows: true,
+        allows_weak_linkage: false,
+        pre_link_args,
+        late_link_args,
+        abi_return_struct_as_int: true,
+        emit_debug_gdb_scripts: false,
+        requires_uwtable: true,
+        eh_frame_header: false,
+        // FIXME(davidtwco): Support Split DWARF on Cygwin - may require LLVM changes to
+        // output DWO, despite using DWARF, doesn't use ELF..
+        debuginfo_kind: DebuginfoKind::Pdb,
+        supported_split_debuginfo: Cow::Borrowed(&[SplitDebuginfo::Off]),
+        ..Default::default()
+    }
+}

compiler/rustc_target/src/spec/base/mod.rs

@@ -3,6 +3,7 @@ pub(crate) mod android;
 pub(crate) mod apple;
 pub(crate) mod avr_gnu;
 pub(crate) mod bpf;
+pub(crate) mod cygwin;
 pub(crate) mod dragonfly;
 pub(crate) mod freebsd;
 pub(crate) mod fuchsia;

compiler/rustc_target/src/spec/mod.rs

@@ -2020,6 +2020,7 @@ supported_targets! {
     ("riscv64imac-unknown-nuttx-elf", riscv64imac_unknown_nuttx_elf),
     ("riscv64gc-unknown-nuttx-elf", riscv64gc_unknown_nuttx_elf),
 
+    ("x86_64-pc-cygwin", x86_64_pc_cygwin),
 }
 
 /// Cow-Vec-Str: Cow<'static, [Cow<'static, str>]>
@@ -3001,8 +3002,8 @@ impl Target {
         );
         check_eq!(
             self.is_like_windows,
-            self.os == "windows" || self.os == "uefi",
-            "`is_like_windows` must be set if and only if `os` is `windows` or `uefi`"
+            self.os == "windows" || self.os == "uefi" || self.os == "cygwin",
+            "`is_like_windows` must be set if and only if `os` is `windows`, `uefi` or `cygwin`"
         );
         check_eq!(
             self.is_like_wasm,

compiler/rustc_target/src/spec/targets/x86_64_pc_cygwin.rs

@@ -0,0 +1,32 @@
+use crate::spec::{Cc, LinkerFlavor, Lld, Target, base};
+
+pub(crate) fn target() -> Target {
+    let mut base = base::cygwin::opts();
+    base.cpu = "x86-64".into();
+    // FIXME: Disable ASLR for now to fix relocation error
+    base.add_pre_link_args(LinkerFlavor::Gnu(Cc::No, Lld::No), &[
+        "-m",
+        "i386pep",
+        "--disable-high-entropy-va",
+    ]);
+    base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &[
+        "-m64",
+        "-Wl,--disable-high-entropy-va",
+    ]);
+    base.max_atomic_width = Some(64);
+    base.linker = Some("x86_64-pc-cygwin-gcc".into());
+    Target {
+        llvm_target: "x86_64-pc-cygwin".into(),
+        pointer_width: 64,
+        data_layout:
+            "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128".into(),
+        arch: "x86_64".into(),
+        options: base,
+        metadata: crate::spec::TargetMetadata {
+            description: Some("64-bit x86 Cygwin".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: Some(true),
+        },
+    }
+}