log2: implement using left rotate through carry

2019-10-19 12:51:11 +00:00 · 2019-10-19 12:51:11 +00:00 · 6f7fc05171
commit 6f7fc05171
parent 6c23ec2fed
1 changed files with 7 additions and 6 deletions
--- a/lib/log2.asm
+++ b/lib/log2.asm
@ -3,12 +3,13 @@
 ; OUT	AX	dual logarithm
 log2:
  push cx
-  mov cx, 16
+  mov cx, 15
 .loop:
-  sar ax, 1
-  loopnz .loop
-  xchg ax, cx
+  rcl ax, 1
+  jc .ret
+  loop .loop
+.ret:
+  cmc
+  mov ax, cx
  pop cx
-  neg ax
-  add ax, 15
  ret