From a32c50a6bc4e8e23e9f8e3178304fc4c9717aaa6 Mon Sep 17 00:00:00 2001
From: Piotr Fusik <fox@scene.pl>
Date: Wed, 7 Mar 2018 20:45:50 +0100
Subject: [PATCH 1/3] Optimize deceaxy.

---
 libsrc/runtime/ldec.s | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/libsrc/runtime/ldec.s b/libsrc/runtime/ldec.s
index 53b60095d..ee7ed3fd4 100644
--- a/libsrc/runtime/ldec.s
+++ b/libsrc/runtime/ldec.s
@@ -1,5 +1,6 @@
 ;
-; Ullrich von Bassewitz, 29.12.1999
+; Piotr Fusik, 07.03.2018
+; originally by Ullrich von Bassewitz
 ;
 ; CC65 runtime: Decrement eax by value in Y
 ;
@@ -11,16 +12,13 @@ deceaxy:
         sty     tmp1
         sec
         sbc     tmp1
-        sta     tmp1
-        txa
-        sbc     #0
-        tax
-        lda     sreg
-        sbc     #0
-        sta     sreg
-        lda     sreg+1
-        sbc     #0
-        sta     sreg+1
-        lda     tmp1
-        rts
+        bcs     @L9
+        dex
+        cpx     #$ff
+        bne     @L9
+        dec     sreg
+        cpx     sreg
+        bne     @L9
+        dec     sreg+1
+@L9:    rts
 

From 970c5f6184ca48a6db7118063ce284855cc63787 Mon Sep 17 00:00:00 2001
From: Piotr Fusik <fox@scene.pl>
Date: Thu, 8 Mar 2018 22:10:11 +0100
Subject: [PATCH 2/3] Add comments.

---
 libsrc/runtime/ldec.s | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libsrc/runtime/ldec.s b/libsrc/runtime/ldec.s
index ee7ed3fd4..e7e891119 100644
--- a/libsrc/runtime/ldec.s
+++ b/libsrc/runtime/ldec.s
@@ -13,12 +13,15 @@ deceaxy:
         sec
         sbc     tmp1
         bcs     @L9
+; borrow from X
         dex
         cpx     #$ff
         bne     @L9
+; X wrapped from zero to $ff, borrow from sreg
         dec     sreg
         cpx     sreg
         bne     @L9
+; sreg wrapped from zero to $ff, borrow from sreg+1
         dec     sreg+1
 @L9:    rts
 

From 18ada212e7dda94d30e7df9b00f58f856bb8fc50 Mon Sep 17 00:00:00 2001
From: Piotr Fusik <fox@scene.pl>
Date: Fri, 9 Mar 2018 18:48:24 +0100
Subject: [PATCH 3/3] Fix coding style.

---
 libsrc/runtime/ldec.s | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/libsrc/runtime/ldec.s b/libsrc/runtime/ldec.s
index e7e891119..f8e59d5c0 100644
--- a/libsrc/runtime/ldec.s
+++ b/libsrc/runtime/ldec.s
@@ -1,5 +1,5 @@
 ;
-; Piotr Fusik, 07.03.2018
+; Piotr Fusik, 09.03.2018
 ; originally by Ullrich von Bassewitz
 ;
 ; CC65 runtime: Decrement eax by value in Y
@@ -13,15 +13,24 @@ deceaxy:
         sec
         sbc     tmp1
         bcs     @L9
-; borrow from X
+
+; Borrow from X.
+
         dex
-        cpx     #$ff
+        cpx     #$FF
         bne     @L9
-; X wrapped from zero to $ff, borrow from sreg
+
+; X wrapped from zero to $FF, borrow from sreg.
+
         dec     sreg
         cpx     sreg
         bne     @L9
-; sreg wrapped from zero to $ff, borrow from sreg+1
+
+; sreg wrapped from zero to $FF, borrow from sreg+1.
+
         dec     sreg+1
+
+; Done.
+
 @L9:    rts