[LLDB][LoongArch] Add LoongArch ArchSpec and subtype detection

Define LoongArch architecture subtypes, add the LoongArch ArchSpec bits,
and inspect the ELF header to detect the right subtype based on ELF class.

Here is a simple test:

```
[loongson@linux ~]$ cat hello.c

int main()
{
	printf("Hello, World!\n");
	return 0;
}
[loongson@linux ~]$ clang hello.c -g -o hello
```

Without this patch:

```
[loongson@linux ~]$ llvm-project/llvm/build/bin/lldb hello
(lldb) target create "hello"
error: '/home/loongson/hello' doesn't contain any 'host' platform architectures: unknown
```

With this patch:

```
[loongson@linux ~]$ llvm-project/llvm/build/bin/lldb hello
(lldb) target create "hello"
Current executable set to '/home/loongson/hello' (loongarch64).
(lldb) run
Process 735167 launched: '/home/loongson/hello' (loongarch64)
Hello, World!
Process 735167 exited with status = 0 (0x00000000)
(lldb) quit
[loongson@linux ~]$ llvm-project/llvm/build/bin/llvm-lit llvm-project/lldb/test/Shell/ObjectFile/ELF/loongarch-arch.yaml
llvm-lit: /home/loongson/llvm-project/llvm/utils/lit/lit/llvm/config.py:456: note: using clang: /home/loongson/llvm-project/llvm/build/bin/clang
-- Testing: 1 tests, 1 workers --
PASS: lldb-shell :: ObjectFile/ELF/loongarch-arch.yaml (1 of 1)

Testing Time: 0.09s
  Passed: 1
```

Reviewed By: SixWeining, xen0n, DavidSpickett

Differential Revision: https://reviews.llvm.org/D137057

1 files changed, 14 insertions, 0 deletions

diff --git a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
index af1b093..cf1b375 100644
--- a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
+++ b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
@@ -320,6 +320,18 @@ static uint32_t ppc64VariantFromElfFlags(const elf::ELFHeader &header) {
     return ArchSpec::eCore_ppc64_generic;
 }
 
+static uint32_t loongarchVariantFromElfFlags(const elf::ELFHeader &header) {
+  uint32_t fileclass = header.e_ident[EI_CLASS];
+  switch (fileclass) {
+  case llvm::ELF::ELFCLASS32:
+    return ArchSpec::eLoongArchSubType_loongarch32;
+  case llvm::ELF::ELFCLASS64:
+    return ArchSpec::eLoongArchSubType_loongarch64;
+  default:
+    return ArchSpec::eLoongArchSubType_unknown;
+  }
+}
+
 static uint32_t subTypeFromElfHeader(const elf::ELFHeader &header) {
   if (header.e_machine == llvm::ELF::EM_MIPS)
     return mipsVariantFromElfFlags(header);
@@ -327,6 +339,8 @@ static uint32_t subTypeFromElfHeader(const elf::ELFHeader &header) {
     return ppc64VariantFromElfFlags(header);
   else if (header.e_machine == llvm::ELF::EM_RISCV)
     return riscvVariantFromElfFlags(header);
+  else if (header.e_machine == llvm::ELF::EM_LOONGARCH)
+    return loongarchVariantFromElfFlags(header);
 
   return LLDB_INVALID_CPUTYPE;
 }