Hacked bug re: pointer get.

[fw/sdcc] / doc / choices.txt

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+Some of the implementation choices
+----------------------------------
+
+gbz80:
+
+Load from direct space:
+  Alternatives:
+  1.  Via HL
+       ld hl,#dir
+       ld x,(hl)
+       inc hl
+       ld y,(hl)
+  2.  Via a
+       ld a,(dir)
+       ld x,a
+       ld a,(dir+1)
+       ld x,a
+  1 is bad when x or y involve HL (1b)
+                                       8       16      32
+     1 = 12 + n*(8+8) - 8              20      36      68
+     1b = n*(12+12+8)                  32      64      128
+     2 = n*(16+4)                      20      40      80
+  So choose 2.
+
+  Hmm.  (2) is too hard to support in the current model.
+
+On stack word push
+   1.   lda  hl,x(sp)
+        ld   a,(hl+)
+        ld   h,(hl)
+        ld   l,a
+        push hl
+   2.   lda  hl,x(sp)
+        ld   e,(hl)
+        inc  hl
+        ld   d,(hl)
+   1 = d + 8 + 8 + 4
+   2 = d + 8 + 8 + 8
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