From 56a1431db813bf97833c493ed97f08783e916ab7 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Thu, 27 Feb 2020 21:00:35 +0100
Subject: [PATCH] increased floating point multiplication precision

---
 c64/basic/math/mul_FAC2_FAC1_shift.s | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/c64/basic/math/mul_FAC2_FAC1_shift.s b/c64/basic/math/mul_FAC2_FAC1_shift.s
index 2f3c8acf..6aed5169 100644
--- a/c64/basic/math/mul_FAC2_FAC1_shift.s
+++ b/c64/basic/math/mul_FAC2_FAC1_shift.s
@@ -8,6 +8,16 @@
 
 mul_FAC2_FAC1_shift:
 
+	// Check if rounding is needed
+
+	php
+	clc
+	lda RESHO+4
+	bpl !+
+	sec
+!:
+	// Copy bytes
+
 	lda RESHO+3
 	sta RESHO+4
 	lda RESHO+2
@@ -18,5 +28,19 @@ mul_FAC2_FAC1_shift:
 	sta RESHO+1
 	lda #$00
 	sta RESHO+0
+	bcc !+
 
+	// Perform rounding
+
+	inc RESHO+4
+	bne !+
+	inc RESHO+3
+	bne !+
+	inc RESHO+2
+	bne !+
+	inc RESHO+1
+	bne !+
+	inc RESHO+0
+!:
+	plp
 	rts