From 5097e15f86517db3ca4daf557a64360a512e7336 Mon Sep 17 00:00:00 2001
From: user <none>
Date: Fri, 18 Aug 2023 20:08:23 -0500
Subject: [PATCH] Add unsigned div and mod instructions

---
 asm_2/bytecode.txt |  4 +--
 asm_2/interp.asm   | 62 ++++++++++++++++++++++++++++++++++++++++++++--
 asm_2/tbc.inc      | 16 ++++++++++++
 3 files changed, 78 insertions(+), 4 deletions(-)

diff --git a/asm_2/bytecode.txt b/asm_2/bytecode.txt
index 121da15..8496459 100644
--- a/asm_2/bytecode.txt
+++ b/asm_2/bytecode.txt
@@ -34,7 +34,7 @@ FXYN
 0XY8	div
 0XY9	cmp
 0XYA	test
-0XYB
+0XYB	mod
 0XYC
 0XYD
 0XYE
@@ -52,7 +52,7 @@ FXYN
 1XY8	div
 1XY9	cmp
 1XYA	test
-1XYB
+1XYB	mod
 1XYC
 1XYD
 1XYE
diff --git a/asm_2/interp.asm b/asm_2/interp.asm
index 3bf677f..7c42281 100644
--- a/asm_2/interp.asm
+++ b/asm_2/interp.asm
@@ -492,7 +492,7 @@ alu_dispatch_jumptable:
 	rjmp	exec_div
 	rjmp	exec_cmp
 	rjmp	exec_test
-	rjmp	exec_nop
+	rjmp	exec_mod
 	rjmp	exec_nop
 	rjmp	exec_nop
 	rjmp	exec_nop
@@ -720,10 +720,68 @@ exec_mul:
 
 
 exec_div:
-	; TODO
+	; Call/ret take more than three clock cycles, so they can't be used
+	ldi	ZL, LOW(_div_done)
+	ldi	ZH, HIGH(_div_done)
+	rjmp	div_subroutine
+_div_done:
+
 	rjmp	_dispatch_done_writeback_flags
 
 
+exec_mod:
+	; Call/ret take more than three clock cycles, so they can't be used
+	ldi	ZL, LOW(_mod_done)
+	ldi	ZH, HIGH(_mod_done)
+	rjmp	div_subroutine
+_mod_done:
+
+	movw	r6, r22
+	movw	r8, r24
+
+	rjmp	_dispatch_done_writeback_flags
+
+
+div_subroutine:
+	; r22:r23:r24:r25 - remainder
+	; r6 :r7 :r8 :r9  - dividend/result
+	; r10:r11:r12:r13 - divisor
+	; r21             - loop counter
+
+	clr	r22
+	clr	r23
+	clr	r24
+	clr	r25
+	ldi	r21, 32
+_div_loop:
+	lsl	r6
+	rol	r7
+	rol	r8
+	rol	r9
+	rol	r22
+	rol	r23
+	rol	r24
+	rol	r25
+
+	cp	r22, r10
+	cpc	r23, r11
+	cpc	r24, r12
+	cpc	r25, r13
+
+	brlo	_div_next
+	sub	r22, r10
+	sbc	r23, r11
+	sbc	r24, r12
+	sbc	r25, r13
+	inc	r6
+_div_next:
+
+	dec	r21
+	brne	_div_loop
+
+	ijmp
+
+
 exec_cmp:
 	movw	r22, r6
 	movw	r24, r8
diff --git a/asm_2/tbc.inc b/asm_2/tbc.inc
index 739c982..35bbc65 100644
--- a/asm_2/tbc.inc
+++ b/asm_2/tbc.inc
@@ -223,6 +223,13 @@
 	.dw	(0x0 << 12) | (@0 << 8) | (@1 << 4) | (0xa)
 .endmacro
 
+.macro T_MOD
+	.if @0 < 0 || @0 > 0xf || @1 < 0 || @1 > 0xf
+	.error "Tortoise Bytecode: invalid variable register"
+	.endif
+	.dw	(0x0 << 12) | (@0 << 8) | (@1 << 4) | (0xb)
+.endmacro
+
 .macro T_JALR
 	.if @0 < 0 || @0 > 0xf || @1 < 0 || @1 > 0xf
 	.error "Tortoise Bytecode: invalid variable register"
@@ -336,6 +343,15 @@
 	.dw	HWRD(@1)
 .endmacro
 
+.macro T_MODI
+	.if @0 < 0 || @0 > 0xf
+	.error "Tortoise Bytecode: invalid variable register"
+	.endif
+	.dw	(0x1 << 12) | (@0 << 8) | (0 << 4) | (0xb)
+	.dw	LWRD(@1)
+	.dw	HWRD(@1)
+.endmacro
+
 .macro T_JALI
 	.if @0 < 0 || @0 > 0xf
 	.error "Tortoise Bytecode: invalid variable register"
-- 
2.43.0