[lldb][LoongArch] Fix the incorrect floating-point register dwarf number

According to the documentation described at
https://github.com/loongson/la-abi-specs/blob/release/ladwarf.adoc, the
dwarf numbers for floating-point registers range from 32 to 63.

An incorrect dwarf number will prevent the register values from being
properly restored during unwinding.

This test reflects this problem:

```
loongson@linux:~$ cat test.c

void foo() {
  asm volatile ("movgr2fr.d $fs2, $ra":::"$fs2");
}
int main() {
  asm volatile ("movgr2fr.d $fs2, $sp":::"$fs2");
  foo();
  return 0;
}

loongson@linux:~$ clang -g test.c  -o test

```
Without this patch:
```
loongson@linux:~$ ./_build/bin/lldb ./t
(lldb) target create "./t"
Current executable set to
'/home/loongson/llvm-project/_build_lldb/t' (loongarch64).
(lldb) b foo
Breakpoint 1: where = t`foo + 20 at test.c:4:1, address =
0x0000000000000714
(lldb) r
Process 2455626 launched: '/home/loongson/llvm-project/_build_lldb/t' (loongarch64)
Process 2455626 stopped
* thread #1, name = 't', stop reason = breakpoint 1.1
    frame #0: 0x0000555555554714 t`foo at test.c:4:1
   1    #include <stdio.h>
   2
   3    void foo() {
-> 4    asm volatile ("movgr2fr.d $fs2, $ra":::"$fs2");
   5    }
   6    int main() {
   7    asm volatile ("movgr2fr.d $fs2, $sp":::"$fs2");
(lldb) si
Process 2455626 stopped
* thread #1, name = 't', stop reason = instruction step into
    frame #0: 0x0000555555554718 t`foo at test.c:4:1
   1    #include <stdio.h>
   2
   3    void foo() {
-> 4    asm volatile ("movgr2fr.d $fs2, $ra":::"$fs2");
   5    }
   6    int main() {
   7    asm volatile ("movgr2fr.d $fs2, $sp":::"$fs2");
(lldb) f 1
frame #1: 0x0000555555554768 t`main at test.c:8:1
   5    }
   6    int main() {
   7    asm volatile ("movgr2fr.d $fs2, $sp":::"$fs2");
-> 8    foo();
   9    return 0;
   10   }
(lldb) register read -a
General Purpose Registers:
        r1 = 0x0000555555554768  t`main + 40 at test.c:8:1
        r3 = 0x00007ffffffef780
       r22 = 0x00007ffffffef7b0
       r23 = 0x00007ffffffef918
       r24 = 0x0000000000000001
       r25 = 0x0000000000000000
       r26 = 0x000055555555be08  t`__do_global_dtors_aux_fini_array_entry
       r27 = 0x0000555555554740  t`main at test.c:6
       r28 = 0x00007ffffffef928
       r29 = 0x00007ffff7febc88  ld-linux-loongarch-lp64d.so.1`_rtld_global_ro
       r30 = 0x000055555555be08  t`__do_global_dtors_aux_fini_array_entry
        pc = 0x0000555555554768  t`main + 40 at test.c:8:1
33 registers were unavailable.

Floating Point Registers:
       f13 = 0x00007ffffffef780 !!!!! wrong register
       f24 = 0xffffffffffffffff
       f25 = 0xffffffffffffffff
       f26 = 0x0000555555554768  t`main + 40 at test.c:8:1
       f27 = 0xffffffffffffffff
       f28 = 0xffffffffffffffff
       f29 = 0xffffffffffffffff
       f30 = 0xffffffffffffffff
       f31 = 0xffffffffffffffff
32 registers were unavailable.
```
With this patch:
```
The previous operations are the same.
(lldb) register read -a
General Purpose Registers:
        r1 = 0x0000555555554768  t`main + 40 at test.c:8:1
        r3 = 0x00007ffffffef780
       r22 = 0x00007ffffffef7b0
       r23 = 0x00007ffffffef918
       r24 = 0x0000000000000001
       r25 = 0x0000000000000000
       r26 = 0x000055555555be08  t`__do_global_dtors_aux_fini_array_entry
       r27 = 0x0000555555554740  t`main at test.c:6
       r28 = 0x00007ffffffef928
       r29 = 0x00007ffff7febc88  ld-linux-loongarch-lp64d.so.1`_rtld_global_ro
       r30 = 0x000055555555be08  t`__do_global_dtors_aux_fini_array_entry
        pc = 0x0000555555554768  t`main + 40 at test.c:8:1
33 registers were unavailable.

Floating Point Registers:
       f24 = 0xffffffffffffffff
       f25 = 0xffffffffffffffff
       f26 = 0x00007ffffffef780
       f27 = 0xffffffffffffffff
       f28 = 0xffffffffffffffff
       f29 = 0xffffffffffffffff
       f30 = 0xffffffffffffffff
       f31 = 0xffffffffffffffff
33 registers were unavailable.
```

Reviewed By: SixWeining

Pull Request: llvm#120391

lldb/source/Utility/LoongArch_DWARF_Registers.h

@@ -47,22 +47,7 @@ enum {
   dwarf_gpr_r30,
   dwarf_gpr_r31 = 31,
 
-  dwarf_gpr_orig_a0,
-  dwarf_gpr_pc,
-  dwarf_gpr_badv,
-
-  dwarf_gpr_reserved0 = 35,
-  dwarf_gpr_reserved1,
-  dwarf_gpr_reserved2,
-  dwarf_gpr_reserved3,
-  dwarf_gpr_reserved4,
-  dwarf_gpr_reserved5,
-  dwarf_gpr_reserved6,
-  dwarf_gpr_reserved7,
-  dwarf_gpr_reserved8,
-  dwarf_gpr_reserved9,
-
-  dwarf_fpr_f0 = 45,
+  dwarf_fpr_f0 = 32,
   dwarf_fpr_f1,
   dwarf_fpr_f2,
   dwarf_fpr_f3,
@@ -93,7 +78,7 @@ enum {
   dwarf_fpr_f28,
   dwarf_fpr_f29,
   dwarf_fpr_f30,
-  dwarf_fpr_f31 = 76,
+  dwarf_fpr_f31 = 63,
 
   dwarf_fpr_fcc0,
   dwarf_fpr_fcc1,
@@ -170,6 +155,23 @@ enum {
   dwarf_fpr_fs5 = dwarf_fpr_f29,
   dwarf_fpr_fs6 = dwarf_fpr_f30,
   dwarf_fpr_fs7 = dwarf_fpr_f31,
+
+  // mock pc regnum
+  dwarf_gpr_pc = 57005,
+
+  // fake registers are only used to define `RegisterInfo`
+  dwarf_gpr_orig_a0,
+  dwarf_gpr_badv,
+  dwarf_gpr_reserved0,
+  dwarf_gpr_reserved1,
+  dwarf_gpr_reserved2,
+  dwarf_gpr_reserved3,
+  dwarf_gpr_reserved4,
+  dwarf_gpr_reserved5,
+  dwarf_gpr_reserved6,
+  dwarf_gpr_reserved7,
+  dwarf_gpr_reserved8,
+  dwarf_gpr_reserved9,
 };
 
 } // namespace loongarch_dwarf