Rollup merge of rust-lang#96971 - zhaixiaojuan:master, r=wesleywiser

Initial support for loongarch64-unknown-linux-gnu

Hi, We hope to add a new port in rust for LoongArch.

LoongArch intro
LoongArch is a RISC style ISA which is independently designed by Loongson
Technology in China. It is divided into two versions, the 32-bit version (LA32)
and the 64-bit version (LA64). LA64 applications have application-level
backward binary compatibility with LA32 applications. LoongArch is composed of
a basic part (Loongson Base) and an expanded part. The expansion part includes
Loongson Binary Translation (LBT), Loongson VirtualiZation (LVZ), Loongson SIMD
EXtension (LSX) and Loongson Advanced SIMD EXtension(LASX).

Currently the LA464 processor core supports LoongArch ISA and the Loongson
3A5000 processor integrates 4 64-bit LA464 cores. LA464 is a four-issue 64-bit
high-performance processor core. It can be used as a single core for high-end
embedded and desktop applications, or as a basic processor core to form an
on-chip multi-core system for server and high-performance machine applications.

Documentations:
ISA:
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html
ABI:
https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html
More docs can be found at:
https://loongson.github.io/LoongArch-Documentation/README-EN.html

Since last year, we have locally adapted two versions of rust, rust1.41 and rust1.57, and completed the test locally.
I'm not sure if I'm submitting all the patches at once, so I split up the patches and here's one of the commits

Author: compiler-errors

compiler/rustc_codegen_gcc/example/alloc_system.rs

@@ -15,6 +15,7 @@
 const MIN_ALIGN: usize = 8;
 #[cfg(any(target_arch = "x86_64",
               target_arch = "aarch64",
+              target_arch = "loongarch64",
               target_arch = "mips64",
               target_arch = "s390x",
               target_arch = "sparc64"))]

compiler/rustc_codegen_ssa/src/back/metadata.rs

@@ -127,6 +127,7 @@ pub(crate) fn create_object_file(sess: &Session) -> Option<write::Object<'static
         "msp430" => Architecture::Msp430,
         "hexagon" => Architecture::Hexagon,
         "bpf" => Architecture::Bpf,
+        "loongarch64" => Architecture::LoongArch64,
         // Unsupported architecture.
         _ => return None,
     };
@@ -190,6 +191,10 @@ pub(crate) fn create_object_file(sess: &Session) -> Option<write::Object<'static
             }
             e_flags
         }
+        Architecture::LoongArch64 => {
+            // Source: https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html#_e_flags_identifies_abi_type_and_version
+            elf::EF_LARCH_OBJABI_V1 | elf::EF_LARCH_ABI_DOUBLE_FLOAT
+        }
         _ => 0,
     };
     // adapted from LLVM's `MCELFObjectTargetWriter::getOSABI`

compiler/rustc_llvm/build.rs

@@ -10,6 +10,7 @@ const OPTIONAL_COMPONENTS: &[&str] = &[
     "aarch64",
     "amdgpu",
     "avr",
+    "loongarch",
     "m68k",
     "mips",
     "powerpc",

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -146,6 +146,12 @@ extern "C" void LLVMTimeTraceProfilerFinish(const char* FileName) {
 #define SUBTARGET_HEXAGON
 #endif
 
+#ifdef LLVM_COMPONENT_LOONGARCH
+#define SUBTARGET_LOONGARCH SUBTARGET(LoongArch)
+#else
+#define SUBTARGET_LOONGARCH
+#endif
+
 #define GEN_SUBTARGETS                                                         \
   SUBTARGET_X86                                                                \
   SUBTARGET_ARM                                                                \
@@ -159,6 +165,7 @@ extern "C" void LLVMTimeTraceProfilerFinish(const char* FileName) {
   SUBTARGET_SPARC                                                              \
   SUBTARGET_HEXAGON                                                            \
   SUBTARGET_RISCV                                                              \
+  SUBTARGET_LOONGARCH                                                          \
 
 #define SUBTARGET(x)                                                           \
   namespace llvm {                                                             \

compiler/rustc_llvm/src/lib.rs

@@ -102,6 +102,14 @@ pub fn initialize_available_targets() {
         LLVMInitializeM68kAsmPrinter,
         LLVMInitializeM68kAsmParser
     );
+    init_target!(
+        llvm_component = "loongarch",
+        LLVMInitializeLoongArchTargetInfo,
+        LLVMInitializeLoongArchTarget,
+        LLVMInitializeLoongArchTargetMC,
+        LLVMInitializeLoongArchAsmPrinter,
+        LLVMInitializeLoongArchAsmParser
+    );
     init_target!(
         llvm_component = "mips",
         LLVMInitializeMipsTargetInfo,

compiler/rustc_target/src/spec/loongarch64_unknown_linux_gnu.rs

@@ -0,0 +1,17 @@
+use crate::spec::{Target, TargetOptions};
+
+pub fn target() -> Target {
+    Target {
+        llvm_target: "loongarch64-unknown-linux-gnu".into(),
+        pointer_width: 64,
+        data_layout: "e-m:e-p:64:64-i64:64-i128:128-n64-S128".into(),
+        arch: "loongarch64".into(),
+        options: TargetOptions {
+            cpu: "generic".into(),
+            features: "+f,+d".into(),
+            llvm_abiname: "lp64d".into(),
+            max_atomic_width: Some(64),
+            ..super::linux_gnu_base::opts()
+        },
+    }
+}

compiler/rustc_target/src/spec/mod.rs

@@ -1021,6 +1021,7 @@ supported_targets! {
     ("x86_64-unknown-linux-gnux32", x86_64_unknown_linux_gnux32),
     ("i686-unknown-linux-gnu", i686_unknown_linux_gnu),
     ("i586-unknown-linux-gnu", i586_unknown_linux_gnu),
+    ("loongarch64-unknown-linux-gnu", loongarch64_unknown_linux_gnu),
     ("m68k-unknown-linux-gnu", m68k_unknown_linux_gnu),
     ("mips-unknown-linux-gnu", mips_unknown_linux_gnu),
     ("mips64-unknown-linux-gnuabi64", mips64_unknown_linux_gnuabi64),

config.example.toml

@@ -88,7 +88,7 @@ changelog-seen = 2
 # the resulting rustc being unable to compile for the disabled architectures.
 #
 # To add support for new targets, see https://rustc-dev-guide.rust-lang.org/building/new-target.html.
-#targets = "AArch64;ARM;BPF;Hexagon;MSP430;Mips;NVPTX;PowerPC;RISCV;Sparc;SystemZ;WebAssembly;X86"
+#targets = "AArch64;ARM;BPF;Hexagon;LoongArch;MSP430;Mips;NVPTX;PowerPC;RISCV;Sparc;SystemZ;WebAssembly;X86"
 
 # LLVM experimental targets to build support for. These targets are specified in
 # the same format as above, but since these targets are experimental, they are

library/std/src/env.rs

@@ -895,6 +895,7 @@ pub mod consts {
     /// - x86_64
     /// - arm
     /// - aarch64
+    /// - loongarch64
     /// - m68k
     /// - mips
     /// - mips64

library/std/src/os/linux/raw.rs

@@ -231,6 +231,7 @@ mod arch {
 }
 
 #[cfg(any(
+    target_arch = "loongarch64",
     target_arch = "mips64",
     target_arch = "s390x",
     target_arch = "sparc64",