piwalker/melonDS
1
0
Fork 0
mirror of https://github.com/melonDS-emu/melonDS.git synced 2024-11-14 05:17:40 -07:00
Code Issues Actions 3 Packages Projects Releases Wiki Activity

r15 writeback is very weird with ldr/str

Browse Source
This commit is contained in:
Jaklyy 2024-11-10 02:56:16 -05:00
parent fce0555a09
commit 9d92b8708a
2 changed files with 27 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/ARMInterpreter_Branch.cpp
View File

@ -104,7 +104,7 @@ void T_BL_LONG_1(ARM* cpu)
void T_BL_LONG_2(ARM* cpu)
{
if ((cpu->CurInstr & 0x1801) == 0x0801) // "BLX" with bit 0 set is an unvalid instruction.
if ((cpu->CurInstr & 0x1801) == 0x0801) // "BLX" with bit 0 set is an undefined instruction.
return T_UNK(cpu); // TODO: Check ARM7 for exceptions
s32 offset = (cpu->CurInstr & 0x7FF) << 1;

30
src/ARMInterpreter_LoadStore.cpp
View File

@ -67,7 +67,7 @@ enum class Writeback
};
template<bool signextend, int size, Writeback writeback>
void LoadSingle(ARM* cpu, u8 rd, u8 rn, s32 offset)
void LoadSingle(ARM* cpu, const u8 rd, const u8 rn, const s32 offset)
{
static_assert((size == 8) || (size == 16) || (size == 32), "dummy this function only takes 8/16/32 for size!!!");
@ -116,7 +116,19 @@ void LoadSingle(ARM* cpu, u8 rd, u8 rn, s32 offset)
if constexpr (writeback >= Writeback::Post) addr += offset;
if constexpr (writeback != Writeback::None) cpu->R[rn] = addr;
if constexpr (writeback != Writeback::None)
{
if (rn != 15) [[likely]] // r15 writeback fails on arm9
{
cpu->R[rn] = addr;
}
else if (cpu->Num == 1) // arm 7
{
// note that at no point does it actually write the value it loaded to a register...
cpu->JumpTo((addr+4) & ~1);
return;
}
}
if (rd == 15)
{
@ -127,7 +139,7 @@ void LoadSingle(ARM* cpu, u8 rd, u8 rn, s32 offset)
}
template<int size, Writeback writeback>
void StoreSingle(ARM* cpu, u8 rd, u8 rn, s32 offset)
void StoreSingle(ARM* cpu, const u8 rd, const u8 rn, const s32 offset)
{
static_assert((size == 8) || (size == 16) || (size == 32), "dummy this function only takes 8/16/32 for size!!!");
@ -163,7 +175,17 @@ void StoreSingle(ARM* cpu, u8 rd, u8 rn, s32 offset)
}
if constexpr (writeback >= Writeback::Post) addr += offset;
if constexpr (writeback != Writeback::None) cpu->R[rn] = addr;
if constexpr (writeback != Writeback::None)
{
if (rn != 15) [[likely]] // r15 writeback fails on arm9
{
cpu->R[rn] = addr;
}
else if (cpu->Num == 1) // arm 7
{
cpu->JumpTo(addr & ~1);
}
}
}