dragon-nx32: (MOOH) Optimized fork copy bank routine

Around twice as fast. Now about 0.24 s for a 24KB large sh.

Signed-off-by: Tormod Volden <debian.tormod@gmail.com>

diff --git a/Kernel/platform-dragon-nx32/mem-nx32-mooh.s b/Kernel/platform-dragon-nx32/mem-nx32-mooh.s
index 256bbb0..5f24f6d 100644 (file)
--- a/Kernel/platform-dragon-nx32/mem-nx32-mooh.s
+++ b/Kernel/platform-dragon-nx32/mem-nx32-mooh.s
@@ -157,32 +157,71 @@ map_restore
 ; fast bank copy for fork
 ; src bank in A, dst bank in B, start in X, end in U
 ; FIXME support internal bank (SAM map 1)
-; FIXME optimize copy loop, should have only one cmp
+
+; Since we have 32KB banks we cannot map two whole banks in so
+; we are operating in a copying window that holds one source
+; and one destination MMU block at a time.
+
+; Start address must be >= 0x8000 because of the window location
+; and bank shifting tricks, and it will be 16-byte aligned (rounded down)
+; to avoid potential window overflow in the unrolled loop.
+
+; Gets called with PROGBASE (0x8000) or with u_syscall_sp from fork_copy()
 
 copybank
+       pshs a,b        ; map/bank # = MMU block mapped at 0x8000
        stu endaddr
-       stb $FFA4       ; map dst at 0x8000
-       sta $FFA5       ; map src at 0xa000
-copyf   cmpx #0x9fff   ; address in block? FIXME for non-aligned
-       bhi nxtblk
-       ldu 0x2000,x    ; read from src bank
-       stu ,x++        ; write to dst bank
+       stb 0xFFA4      ; map dst at 0x8000
+       sta 0xFFA5      ; map src at 0xA000
+       tfr x,d
+       andb #0xF0      ; align start address to 16-byte (unrolling size)
+       tfr d,x
+
+calcend        cmpx #0xA000    ; address inside window?
+       bhs nxtblk      ; shift bank down until it is
+       cmpu #0xA000    ; end address inside window?
+       bls lastb
+       ldu #0xA000
+lastb  stu endblk      ; endblk = MIN(endaddr, 0xA000)
+       leau 0x2000,x
+
+copylp ldd ,u++        ; read from src bank
+       std ,x++        ; write to dst bank
+       ldd ,u++
+       std ,x++
+       ldd ,u++
+       std ,x++
+       ldd ,u++
+       std ,x++
+       ldd ,u++
+       std ,x++
+       ldd ,u++
+       std ,x++
+       ldd ,u++
+       std ,x++
+       ldd ,u++
+       std ,x++
+       cmpx endblk
+       blo copylp
+
        cmpx endaddr
-       blo copyf
-       bra copydone
-nxtblk  inc $FFA4      ; next 8KB block
-       inc $FFA5
+       bhs cpdone
+       ldu endaddr
+       bra calcend
+
+nxtblk inc 0xFFA4      ; next 8KB block in bank
+       inc 0xFFA5
+       leax -0x2000,x
        ldu endaddr
        leau -0x2000,u
        stu endaddr
-       leax -0x2000,x
-       bra copyf
-copydone
-       exg b,a         ; leave with dst mapped
+       bra calcend
+cpdone
+       lda 1,s         ; map destination bank
        jsr map_process_a
-       exg b,a
-       rts
+       puls a,b,pc
 
+endblk         .dw 0
 endaddr                .dw 0
 map_store      .db 0
 map_copy       .db 0