From 56fd37c60eb0d58ed4762340ddc85b74347bcd71 Mon Sep 17 00:00:00 2001
From: Jan Tuomi <jans.tuomi@gmail.com>
Date: Mon, 10 Apr 2023 17:30:25 +0300
Subject: Do stuff

---
 src/test_fibo.atk16 | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

(limited to 'src/test_fibo.atk16')

diff --git a/src/test_fibo.atk16 b/src/test_fibo.atk16
index 7f1abb9..a03f14b 100644
--- a/src/test_fibo.atk16
+++ b/src/test_fibo.atk16
@@ -1,9 +1,12 @@
 @opt stack_pointer RG
+@opt csr_scratch RF
+
+@use ext_std:*
 
 @label program
   ; call fibo subroutine with parameter 10
   ldi RA 10
-  csr fibo
+  csi fibo
   hlt
 
 @label fibo
@@ -13,24 +16,21 @@
   ; return value:
   ;  RA   fibo(n) : u16
 
-  spu RB                ; prelude
+  spu RB                 ; prelude
   spu RC
 
-  ldi RC 2              ; if n < 2, return n
-  sub RA RC RA
+  subi RA 2 RA           ; if n < 2, return n
   bri f_sign fibo_early
 
   spu RD                 ; prelude
-  spu RE
 
-  ldi RE 1               ; constant 1
   ldi RB 0               ; a = 0
   ldi RC 1               ; b = 1
 @label fibo_loop
   add RB RC RD           ; v = a + b
   mov RC RB              ; a = b
   mov RD RC              ; b = v
-  sub RA RE RA           ; n -= 1
+  dec RA                 ; n -= 1
   bri f_zero fibo_done   ; loop while n > 0
   jpi fibo_loop
 
@@ -39,9 +39,8 @@
   spo RB
   rsr
 @label fibo_done
-  ldr RD RA
-  spo RE
-  spo RD
+  mov RD RA
+  spo RD                 ; restore registers
   spo RC
   spo RB
   rsr
-- 
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