X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=doc%2Fchoices.txt;h=1442eca452e5bed8306897b5062f5c87fce84d0b;hb=d08e6df2202ed3f19b681221b502dedb3c6c8a28;hp=fd6cbab859d01cca36a164247512711ee00c6bab;hpb=57781964418caea528f9018cace1acb4a789d71c;p=fw%2Fsdcc

diff --git a/doc/choices.txt b/doc/choices.txt
index fd6cbab8..1442eca4 100644
--- a/doc/choices.txt
+++ b/doc/choices.txt
@@ -192,3 +192,51 @@ Pending optimisations:
         ...
         push    iTemp4
 
+Swaps:
+        ld      hl,bc           ; 8
+        ld      bc,de           ; 8
+        ld      de,hl           ; 8
+
+vs
+        push    bc		; 11
+        ld      bc,de           ; 8
+        pop     de              ; 11
+
+Swaps 2:
+        ld      a,h
+        ld      h,b
+        ld      b,a
+        ld      a,l
+        ld      l,c
+        ld      c,aq            ; 6*4 = 24
+
+Cleaning up the arguments to a call:
+         ld     iy,#n           ; 14
+         add    iy,sp           ; 15
+         ld     sp,iy           ; 10 = 39
+
+         pop    af              ; 5/byte
+
+
+So for 8 bytes and above use the first form.
+
+Pointer assign:
+        ld      hl,bc           ; 4+4
+        ld      e,(hl)          ; 7
+        inc     hl              ; 6
+        ld      d,(hl)          ; 7
+
+vs:
+        ld      a,(bc)          ; 7
+        ld      e,a             ; 4
+        inc     bc              ; 6
+        ld      a,(bc)          ; 7
+        ld      d,a             ; 4
+
+Same cost.  Not worth it, although is does free up HL.
+
+Shift left signed on HL
+      sla  l
+      rl   h                    ; 8+8 = 16
+
+      add  hl,hl                ; 11