You can encode a shifted 12-bit immediate in an ADD instruction on
ARM64. If the negated constant fits in this range, we can exploit this
to avoid materializing the immediate.
This approach saves an instruction if it does not need to be
materialized in a register afterwards. Otherwise, we just materialize
it later and the total number of instructions stays the same.
Before:
0x52bff01a mov w26, #-0x800000 ; =-8388608
0x93407f1b sxtw x27, w24
0xcb3ac37b sub x27, x27, w26, sxtw
After:
0x93407f1b sxtw x27, w24
0x9160037b add x27, x27, #0x800, lsl #12 ; =0x800000
You can encode a 12-bit immediate in an ADD instruction on ARM64. If the
negated constant fits in this range, we can exploit this to avoid
materializing the immediate.
This approach saves an instruction if it does not need to be
materialized in a register afterwards. Otherwise, we just materialize
it later and the total number of instructions stays the same.
Before:
0x12800019 mov w25, #-0x1 ; =-1
0x93407f5b sxtw x27, w26
0xcb39c37b sub x27, x27, w25, sxtw
After:
0x93407f5b sxtw x27, w26
0x9100077b add x27, x27, #0x1
You can encode a shifted 12-bit immediate in a SUB instruction on ARM64.
Constants in this range do not need to be sign extended, so we can
exploit this to avoid materializing the immediate.
This approach saves an instruction if it does not need to be
materialized in a register afterwards. Otherwise, we just materialize
it later and the total number of instructions stays the same.
Before:
0x52a00099 mov w25, #0x40000 ; =262144
0x93407f7a sxtw x26, w27
0xcb39c35a sub x26, x26, w25, sxtw
After:
0x93407f7a sxtw x26, w27
0xd141035a sub x26, x26, #0x40, lsl #12 ; =0x40000
You can encode a 12-bit immediate in a SUB instruction on ARM64.
Constants in this range do not need to be sign extended, so we can
exploit this to avoid materializing the immediate.
This approach saves an instruction if it does not need to be
materialized in a register afterwards. Otherwise, we just materialize
it later and the total number of instructions stays the same.
Before:
0x52800416 mov w22, #0x20 ; =32
0x93407f78 sxtw x24, w27
0xcb36c318 sub x24, x24, w22, sxtw
After:
0x93407f78 sxtw x24, w27
0xd1008318 sub x24, x24, #0x20
A number of settings in the `debugger` group were wrongly using a newly
constructed `QSettings` object instead of the singleton object that
`GetQSettings()` provides.
This made the application create a spurious, extra configuration file in
the user directory:
```
~/.config/Dolphin Emulator/dolphin-emu.conf
```
Notice that, by default, the application configuration files are stored
in `~/.config/dolphin-emu`; not in `~/.config/Dolphin Emulator`.
