Clean-up of MMU routines: remove redundant register save/restore. More

indexing. Saves a few cycles here and there.

diff --git a/Kernel/platform-multicomp09/multicomp09.s b/Kernel/platform-multicomp09/multicomp09.s
index e7cb0f1..a49d295 100644 (file)
--- a/Kernel/platform-multicomp09/multicomp09.s
+++ b/Kernel/platform-multicomp09/multicomp09.s
@@ -165,7 +165,8 @@ loop@       lda     ,u+
        ;; low memory on reboot to bounce to the reset
        ;; vector.
 bounce@
-       ;; [NAC HACK 2016May01] todo
+       ;; [NAC HACK 2016May01] todo.. for multicomp need to re-enable the ROM.
+       ;; how to test this??
        lda     #0x06           ; reset GIME (map in internal 32k rom)
        sta     0xff90
        clr     0xff91
@@ -310,30 +311,29 @@ xinihw:   rts
 ;;;   into the userspace too.
 ;;;   takes: X = page table pointer
 ;;;   returns: nothing
-;;; [NAC HACK 2016May01] but.. X (page table pointer) not used??
-;;; [NAC HACK 2016May01] this can be smaller and tidier. Point to MMUADR and do indexed access.
-;;; [NAC HACK 2016May07] pushes x,u but uses neither. Could be smaller if we used X to point
-;;; to MMUADR... not so!! the indirect access grabs the value of X from the stack.
 _program_vectors:
        ;; copy the common section into user-space
-       pshs    x,u
+       pshs    y
+       ldy     #MMUADR
 
        ;; setup the null pointer / sentinal bytes in low process memory
-       lda     #(MMU_MAP1|8)
-       sta     MMUADR
-        ;; [NAC HACK 2016May07] access stacked X
-       lda     [0,s]        ; get process's blk address for address 0
-       sta     MMUDAT       ; put in our mmu ( at address 0 )
+       lda     #(MMU_MAP1|8)   ; stay in MAP1, select block 8
+       sta     ,y
+
+       lda     ,x              ; get process's blk address for address 0
+       sta     1,y             ; and put it in MMUDAT
        lda     #0x7E
        sta     0
 
        ;; restore the MMU mapping that we trampled on
-       lda     #(MMU_MAP1|8)
-       sta     MMUADR
+       ;; MMUADR still has MAP1, block 8 so no need to re-write it.
+
+       ;; retrieve value that used to be in MAP1, block 8
        lda     _krn_mmu_map
-       sta     MMUDAT
+       ;; and restore it
+       sta     1,y             ; MMUDAT
 
-       puls    pc,x,u       ; restore reg and return
+       puls    pc,y            ; restore reg and return
 
 
 
@@ -345,17 +345,19 @@ badswi_handler:
 
 
 ;;; Userspace mapping pages 7+  kernel mapping pages 3-5, first common 6
-;;; All registers preserved
+;;;   takes: nothing
+;;;   returns: nothing
+;;;   modifies: nothing - all registers preserved
 map_process_always:
-       pshs    x,y,u
+       pshs    x
        ldx     #U_DATA__U_PAGE
        jsr     map_process_2
-       puls    x,y,u,pc
+       puls    x,pc
 
 ;;; Maps a page table into cpu space
 ;;;   takes: X - pointer page table ( ptptr )
 ;;;   returns: nothing
-;;;   modifies: nothing
+;;;   modifies: nothing - all registers preserved
 map_process:
        cmpx    #0              ; is zero?
        bne     map_process_2   ; no then map process; else: map the kernel
@@ -364,7 +366,7 @@ map_process:
 ;;; Maps the Kernel into CPU space
 ;;;   takes: nothing
 ;;;   returns: nothing
-;;;   modifies: nothing
+;;;   modifies: nothing - all registers preserved
 ;;;    Map in the kernel below the current common, all registers preserved
 map_kernel:
        pshs    a
@@ -380,7 +382,7 @@ map_kernel:
 ;;; Maps a page table into the MMU
 ;;;   takes: X = pointer to page table
 ;;;   returns: nothing
-;;;   modifies: nothing
+;;;   modifies: nothing - all registers preserved
 map_process_2:
        pshs    x,y,a,b
 
@@ -388,27 +390,26 @@ map_process_2:
        ldy     #_usr_mmu_map
 
        lda     ,x+             ; get byte from page table
-       sta     ,y+             ; copy to usr_mmu_map
+       sta     0,y             ; copy to usr_mmu_map
        inca                    ; increment to get next 8K block
-       sta     ,y+             ; copy to usr_mmu_map
+       sta     1,y             ; copy to usr_mmu_map
 
        lda     ,x+             ; get byte from page table
-       sta     ,y+             ; copy to usr_mmu_map
+       sta     2,y             ; copy to usr_mmu_map
        inca                    ; increment to get next 8K block
-       sta     ,y+             ; copy to usr_mmu_map
+       sta     3,y             ; copy to usr_mmu_map
 
        lda     ,x+             ; get byte from page table
-       sta     ,y+             ; copy to usr_mmu_map
+       sta     4,y             ; copy to usr_mmu_map
        inca                    ; increment to get next 8K block
-       sta     ,y+             ; copy to usr_mmu_map
+       sta     5,y             ; copy to usr_mmu_map
 
        lda     ,x+             ; bank all but common memory
-       sta     ,y              ;
+       sta     6,y             ;
 
        ;; now, update MMU with those values
        lda     #(MMU_MAP1|0)   ; stay in map1, select mapsel=0
        ldx     #MMUADR
-       ldy     #_usr_mmu_map   ; go back to start [NAC HACK 2016May07] or could use offsets above..
 
        ldb     ,y+             ; page from usr_mmu_map
        std     ,x              ; Write A to MMUADR to set MAPSEL=8, then write B to MMUDAT
@@ -475,11 +476,6 @@ map_for_swap
        sta     MMUDAT
        rts
 
-;;; multicomp09 HW registers
-;;; vdu/virtual UART
-UARTDAT        equ $ffd1
-UARTSTA        equ $ffd0
-
 ;;;  Print a character to debugging
 ;;;   takes: A = character
 ;;;   returns: nothing

diff --git a/Kernel/platform-multicomp09/platform.def b/Kernel/platform-multicomp09/platform.def
index c2c185a..a9ac230 100644 (file)
--- a/Kernel/platform-multicomp09/platform.def
+++ b/Kernel/platform-multicomp09/platform.def
@@ -38,4 +38,9 @@ SDDATA         equ $FFD8
 SDCTL          equ $FFD9
 SDLBA0         equ $FFDA       ; not used here
 SDLBA1         equ $FFDB       ; not used here
-SDLBA2         equ $FFDC       ; not used here
+SDLBA2        equ $FFDC        ; not used here
+
+
+;;; vdu/virtual UART registers
+UARTDAT                equ $ffd1
+UARTSTA                equ $ffd0