From eae158ae732fe6ea4e8d09ba587f0a9fe212e5f5 Mon Sep 17 00:00:00 2001
From: aaaaaa123456789 <aaaaaa123456789@acidch.at>
Date: Tue, 30 Jul 2019 08:18:26 -0300
Subject: [PATCH] QoL #13: Faster multiplication (AddNTimes)

---
 engine/math/math.asm | 30 +++++++++++++++---------------
 home/array.asm       | 12 +++++++++++-
 2 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/engine/math/math.asm b/engine/math/math.asm
index d5df3c34..9a5bcada 100644
--- a/engine/math/math.asm
+++ b/engine/math/math.asm
@@ -30,7 +30,7 @@ _Multiply::
 
 	ldh a, [hMathBuffer + 2]
 	ld c, a
-	ldh a, [hMultiplicand + 0]
+	ldh a, [hMultiplicand]
 	adc c
 	ldh [hMathBuffer + 2], a
 
@@ -54,9 +54,9 @@ _Multiply::
 	rla
 	ldh [hMultiplicand + 1], a
 
-	ldh a, [hMultiplicand + 0]
+	ldh a, [hMultiplicand]
 	rla
-	ldh [hMultiplicand + 0], a
+	ldh [hMultiplicand], a
 
 	ldh a, [hMultiplicand - 1]
 	rla
@@ -75,13 +75,13 @@ _Multiply::
 	ldh [hProduct + 1], a
 
 	ldh a, [hMathBuffer + 1]
-	ldh [hProduct + 0], a
+	ldh [hProduct], a
 
 	ret
 
 _Divide::
 	xor a
-	ldh [hMathBuffer + 0], a
+	ldh [hMathBuffer], a
 	ldh [hMathBuffer + 1], a
 	ldh [hMathBuffer + 2], a
 	ldh [hMathBuffer + 3], a
@@ -91,7 +91,7 @@ _Divide::
 	ld e, a
 
 .loop
-	ldh a, [hMathBuffer + 0]
+	ldh a, [hMathBuffer]
 	ld c, a
 	ldh a, [hDividend + 1]
 	sub c
@@ -99,11 +99,11 @@ _Divide::
 
 	ldh a, [hDivisor]
 	ld c, a
-	ldh a, [hDividend + 0]
+	ldh a, [hDividend]
 	sbc c
 	jr c, .next
 
-	ldh [hDividend + 0], a
+	ldh [hDividend], a
 
 	ld a, d
 	ldh [hDividend + 1], a
@@ -139,13 +139,13 @@ _Divide::
 	jr nz, .next2
 
 	ld e, 8
-	ldh a, [hMathBuffer + 0]
+	ldh a, [hMathBuffer]
 	ldh [hDivisor], a
 	xor a
-	ldh [hMathBuffer + 0], a
+	ldh [hMathBuffer], a
 
 	ldh a, [hDividend + 1]
-	ldh [hDividend + 0], a
+	ldh [hDividend], a
 
 	ldh a, [hDividend + 2]
 	ldh [hDividend + 1], a
@@ -164,9 +164,9 @@ _Divide::
 	srl a
 	ldh [hDivisor], a
 
-	ldh a, [hMathBuffer + 0]
-	rr a
-	ldh [hMathBuffer + 0], a
+	ldh a, [hMathBuffer]
+	rra
+	ldh [hMathBuffer], a
 
 	jr .loop
 
@@ -184,6 +184,6 @@ _Divide::
 	ldh [hQuotient + 1], a
 
 	ldh a, [hMathBuffer + 1]
-	ldh [hQuotient + 0], a
+	ldh [hQuotient], a
 
 	ret
diff --git a/home/array.asm b/home/array.asm
index 0abf9b7d..af59c45e 100644
--- a/home/array.asm
+++ b/home/array.asm
@@ -35,10 +35,20 @@ SkipNames::
 
 AddNTimes::
 ; Add bc * a to hl.
+; Preserves bc
 	and a
 	ret z
+
+	push bc
 .loop
+	rra ; and a from below and above resets carry
+	jr nc, .noadd
 	add hl, bc
-	dec a
+.noadd
+	sla c
+	rl b
+	and a
 	jr nz, .loop
+.done
+	pop bc
 	ret