fix(cpu): fix PC offset when barrel shifter and bit 4 of DP is set

2022-01-24 17:52:01 -04:00
parent 038c0a9283
commit 95dd3e3df8
2 changed files with 7 additions and 1 deletions
--- a/src/cpu/arm/barrel_shifter.zig
+++ b/src/cpu/arm/barrel_shifter.zig
@@ -19,7 +19,7 @@ fn registerShift(comptime S: bool, cpu: *Arm7tdmi, opcode: u32) u32 {
    const rs = @truncate(u8, cpu.r[rs_idx]);

    const rm_idx = opcode & 0xF;
-    const rm = if (rm_idx == 0xF) cpu.fakePC() + 4 else cpu.r[rm_idx];
+    const rm = if (rm_idx == 0xF) cpu.fakePC() else cpu.r[rm_idx];

    return switch (@truncate(u2, opcode >> 5)) {
        0b00 => logicalLeft(S, &cpu.cpsr, rm, rs),