git.y1.nz

commit 01777708810b347f83994b9486bacd6009800b4c
parent 2f8d3304c9f733229c04dcbda0936e655a215a2a
Author: Phidias618 <126189685+Phidias618@users.noreply.github.com>
Date:   Thu,  7 May 2026 12:35:43 +0200

refactor memset() for the sm83
Diffstat:
M
gbdk-lib/include/asm/sm83/string.h
2
+-
M
gbdk-lib/libc/asm/sm83/_memset.s
61
++++++++++++++++++++++++++-----------------------------------

2 files changed, 27 insertions(+), 36 deletions(-)
diff --git a/gbdk-lib/include/asm/sm83/string.h b/gbdk-lib/include/asm/sm83/string.h
@@ -51,7 +51,7 @@ void *memmove (void *dest, const void *src, size_t n);
     @param c         char value to fill with (truncated from int)
     @param n         Number of bytes to fill
 */
-void *memset (void *s, int c, size_t n) OLDCALL PRESERVES_REGS(b, c);
+void *memset (void *s, int c, size_t n);
 
 /** Reverses the characters in a string
 
diff --git a/gbdk-lib/libc/asm/sm83/_memset.s b/gbdk-lib/libc/asm/sm83/_memset.s
@@ -4,49 +4,40 @@
 
 ; void *memset (void *s, int c, size_t n)
 _memset::
-        lda     hl,7(sp)
-        ld      a,(hl-)
-        ld      d, a
-        ld      a,(hl-)
-        ld      e, a
-        or      d
-        jr      z,6$
+        ld a, c
+
+        pop hl                ; pop return address
+        pop bc                ; pop n
+        push hl               ; push return address
         
-        dec     hl
-        ld      a,(hl-)
-        push    af
-        ld      a,(hl-)
-        ld      l,(hl)
-        ld      h,a
-        pop     af
+        ld h, d
+        ld l, e
         
-        srl     d
-        rr      e
-        jr      nc,4$
-        ld      (hl+),a
-4$:     
-        srl     d
-        rr      e
-        jr      nc,5$
+        srl     b
+        rr      c
+        jr      nc,0$
         ld      (hl+),a
-        ld      (hl+),a
-5$:             
-        inc     d
-        inc     e
-        jr      2$
+0$:     
+        srl     b
+        inc     b
+        rr      c
+        
+        jr      c,2$
+        jr      z,3$
 1$:     
+        dec     c
         ld      (hl+),a
         ld      (hl+),a
+2$:
         ld      (hl+),a
         ld      (hl+),a
-2$:
-        dec     e
         jr      nz,1$
-        dec     d
+3$:
+        dec     b
         jr      nz,1$
-6$:
-        lda     hl,2(sp)
-        ld      a,(hl+)
-        ld      e,a
-        ld      d,(hl)
+
+        ; return s in bc
+        ld b, d
+        ld c, e
+        
         ret

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