1 files changed, 70 insertions, 0 deletions
diff --git a/src/luma/cpu/compare.rs b/src/luma/cpu/compare.rs
new file mode 100644
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+++ b/src/luma/cpu/compare.rs
@@ -0,0 +1,70 @@
+/*
+	Copyright 2021-2023 Gabriel Jensen.
+
+	This file is part of Luma.
+
+	Luma is free software: you can redistribute it
+	and/or modify it under the terms of the GNU
+	Affero General Public License as published by
+	the Free Software Foundation, either version 3
+	of the License, or (at your option) any later
+	version.
+
+	Luma is distributed in the hope that it will be
+	useful, but WITHOUT ANY WARRANTY; without even
+	the implied warranty of MERCHANTABILITY or
+	FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	Affero General Public License for more details.
+
+	You should have received a copy of the GNU
+	Affero General Public License along with Luma.
+	If not, see <https://www.gnu.org/licenses/>.
+*/
+
+use crate::luma::log;
+use crate::luma::cpu::Cpu;
+
+impl Cpu {
+	pub(super) fn compare_immediate(&mut self, register: u8, immediate: u32) {
+		log(&format!("cmp r{register}, {immediate:#X}"));
+
+		let mut state = self.state.lock().unwrap();
+
+		let register_value = state.read_register(register);
+
+		let (temporary, c) = register_value.overflowing_sub(immediate);
+
+		let v = false; // ???
+		let z = temporary == 0x0;
+		let n = temporary & 0b10000000000000000000000000000000 != 0x0;
+
+		let mut cpsr = state.read_cpsr() & 0b00001111111111111111111111111111;
+		cpsr |= (v as u32) << 0x1C;
+		cpsr |= (c as u32) << 0x1D;
+		cpsr |= (z as u32) << 0x1E;
+		cpsr |= (n as u32) << 0x1F;
+		state.write_cpsr(cpsr);
+	}
+
+	pub(super) fn compare_register(&mut self, left: u8, right: u8) {
+		log(&format!("cmp r{left}, r{right}"));
+
+		let mut state = self.state.lock().unwrap();
+
+		let left_value  = state.read_register(left);
+		let right_value = state.read_register(right);
+
+		let (temporary, c) = left_value.overflowing_sub(right_value);
+
+		let v = false; // ???
+		let z = temporary == 0x0;
+		let n = temporary & 0b10000000000000000000000000000000 != 0x0;
+
+		let mut cpsr = state.read_cpsr() & 0b00001111111111111111111111111111;
+		cpsr |= (v as u32) << 0x1C;
+		cpsr |= (c as u32) << 0x1D;
+		cpsr |= (z as u32) << 0x1E;
+		cpsr |= (n as u32) << 0x1F;
+		state.write_cpsr(cpsr);
+	}
+}