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chore: replace unnecessarily complex sign extension implementation

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This commit is contained in:
Rekai Nyangadzayi Musuka
2022-02-28 20:38:50 -04:00
parent ddb68a7952
commit cb4d3a9a51
6 changed files with 19 additions and 41 deletions
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8
src/cpu/thumb/branch.zig
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@@ -3,13 +3,13 @@ const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
const checkCond = @import("../../cpu.zig").checkCond;
const u32SignExtend = @import("../../util.zig").u32SignExtend;
const sext = @import("../../util.zig").sext;
pub fn format16(comptime cond: u4) InstrFn {
return struct {
fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
// B
const offset = u32SignExtend(8, opcode & 0xFF) << 1;
const offset = sext(8, opcode & 0xFF) << 1;
const should_execute = switch (cond) {
0xE, 0xF => cpu.panic("[CPU/THUMB.16] Undefined conditional branch with condition {}", .{cond}),
@@ -27,7 +27,7 @@ pub fn format18() InstrFn {
return struct {
// B but conditional
fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
const offset = u32SignExtend(11, opcode & 0x7FF) << 1;
const offset = sext(11, opcode & 0x7FF) << 1;
cpu.r[15] = (cpu.r[15] + 2) +% offset;
}
}.inner;
@@ -47,7 +47,7 @@ pub fn format19(comptime is_low: bool) InstrFn {
cpu.r[14] = old_pc | 1;
} else {
// Instruction 1
cpu.r[14] = (cpu.r[15] + 2) +% (u32SignExtend(11, offset) << 12);
cpu.r[14] = (cpu.r[15] + 2) +% (sext(11, offset) << 12);
}
}
}.inner;