6502/cc65
1
0
Fork 0
mirror of https://github.com/cc65/cc65.git synced 2024-06-01 13:41:34 +00:00
Code Issues Projects Releases Wiki Activity

Load INITBSS segment from disk.

Browse Source 
Conceptually the INITBSS segment is not initialized in any way. Therefore it makes sense to not load it from disk. However the INIT segment has to be loaded from disk and therefore moved to its run location above the INITBSS segment. The necessary move routine increases runtime RAM usage :-(

Therefore we now "unnecessarily" load the INITBSS segment from disk too meaning that the INIT segment is loaded at its run location. Therefore there's no need for the move routine anymore.

After all we trade disk space for (runtime) RAM space - an easy decision ;-)

Notes:

- The code allowing to re-run a program without re-load present so far could not have worked as far as I can see as it only avoided to re-run the move routine but still tried to re-run the code in the INIT segment that was clobbered by zeroing the BSS. Therefore I removed the code in question altogether. I'm personally not into this "dirty re-run" but if someone wants to add an actually working solution I won't block that.

- INITBSS is intentionally not just merged with the DATA segment as ROM-based targets can't reuse the INIT segment for the BSS and therefore have no reason to place the INIT segment above INITBSS.

- Because ROM-based targets don't copy INITBSS from the ROM (like it is done with the DATA segment) all users of INITBSS _MUST_NOT_ presume INITBSS to be initialized with zeros!
This commit is contained in:
Oliver Schmidt 2016-02-28 19:29:37 +01:00
parent 25f4482641
commit 3d08abcfa8
4 changed files with 51 additions and 119 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

61
cfg/c64-overlay.cfg
View File

@ -15,8 +15,7 @@ MEMORY {
LOADADDR: file = %O, start = %S - 2, size = $0002;
HEADER: file = %O, define = yes, start = %S, size = $000D;
MAIN: file = %O, define = yes, start = __HEADER_LAST__, size = __OVERLAYSTART__ - __STACKSIZE__ - __HEADER_LAST__;
MOVE: file = %O, start = __INITBSS_LOAD__, size = __HIMEM__ - __BSS_RUN__;
INIT: file = "", start = __BSS_RUN__, size = __HIMEM__ - __BSS_RUN__;
INIT: file = %O, start = __BSS_RUN__, size = __HIMEM__ - __BSS_RUN__;
OVL1ADDR: file = "%O.1", start = __OVERLAYSTART__ - 2, size = $0002;
OVL1: file = "%O.1", start = __OVERLAYSTART__, size = __OVERLAYSIZE__;
OVL2ADDR: file = "%O.2", start = __OVERLAYSTART__ - 2, size = $0002;
@ -37,35 +36,35 @@ MEMORY {
OVL9: file = "%O.9", start = __OVERLAYSTART__, size = __OVERLAYSIZE__;
}
SEGMENTS {
ZEROPAGE: load = ZP, type = zp;
LOADADDR: load = LOADADDR, type = ro;
EXEHDR: load = HEADER, type = ro;
STARTUP: load = MAIN, type = ro;
LOWCODE: load = MAIN, type = ro, optional = yes;
CODE: load = MAIN, type = ro;
RODATA: load = MAIN, type = ro;
DATA: load = MAIN, type = rw;
INITBSS: load = MAIN, type = bss, define = yes;
BSS: load = MAIN, type = bss, define = yes;
INIT: load = MOVE, run = INIT, type = ro, define = yes;
OVL1ADDR: load = OVL1ADDR, type = ro;
OVERLAY1: load = OVL1, type = ro, define = yes, optional = yes;
OVL2ADDR: load = OVL2ADDR, type = ro;
OVERLAY2: load = OVL2, type = ro, define = yes, optional = yes;
OVL3ADDR: load = OVL3ADDR, type = ro;
OVERLAY3: load = OVL3, type = ro, define = yes, optional = yes;
OVL4ADDR: load = OVL4ADDR, type = ro;
OVERLAY4: load = OVL4, type = ro, define = yes, optional = yes;
OVL5ADDR: load = OVL5ADDR, type = ro;
OVERLAY5: load = OVL5, type = ro, define = yes, optional = yes;
OVL6ADDR: load = OVL6ADDR, type = ro;
OVERLAY6: load = OVL6, type = ro, define = yes, optional = yes;
OVL7ADDR: load = OVL7ADDR, type = ro;
OVERLAY7: load = OVL7, type = ro, define = yes, optional = yes;
OVL8ADDR: load = OVL8ADDR, type = ro;
OVERLAY8: load = OVL8, type = ro, define = yes, optional = yes;
OVL9ADDR: load = OVL9ADDR, type = ro;
OVERLAY9: load = OVL9, type = ro, define = yes, optional = yes;
ZEROPAGE: load = ZP, type = zp;
LOADADDR: load = LOADADDR, type = ro;
EXEHDR: load = HEADER, type = ro;
STARTUP: load = MAIN, type = ro;
LOWCODE: load = MAIN, type = ro, optional = yes;
CODE: load = MAIN, type = ro;
RODATA: load = MAIN, type = ro;
DATA: load = MAIN, type = rw;
INITBSS: load = MAIN, type = rw;
BSS: load = MAIN, type = bss, define = yes;
INIT: load = INIT, type = ro;
OVL1ADDR: load = OVL1ADDR, type = ro;
OVERLAY1: load = OVL1, type = ro, define = yes, optional = yes;
OVL2ADDR: load = OVL2ADDR, type = ro;
OVERLAY2: load = OVL2, type = ro, define = yes, optional = yes;
OVL3ADDR: load = OVL3ADDR, type = ro;
OVERLAY3: load = OVL3, type = ro, define = yes, optional = yes;
OVL4ADDR: load = OVL4ADDR, type = ro;
OVERLAY4: load = OVL4, type = ro, define = yes, optional = yes;
OVL5ADDR: load = OVL5ADDR, type = ro;
OVERLAY5: load = OVL5, type = ro, define = yes, optional = yes;
OVL6ADDR: load = OVL6ADDR, type = ro;
OVERLAY6: load = OVL6, type = ro, define = yes, optional = yes;
OVL7ADDR: load = OVL7ADDR, type = ro;
OVERLAY7: load = OVL7, type = ro, define = yes, optional = yes;
OVL8ADDR: load = OVL8ADDR, type = ro;
OVERLAY8: load = OVL8, type = ro, define = yes, optional = yes;
OVL9ADDR: load = OVL9ADDR, type = ro;
OVERLAY9: load = OVL9, type = ro, define = yes, optional = yes;
}
FEATURES {
CONDES: type = constructor,

25
cfg/c64.cfg
View File

@ -12,21 +12,20 @@ MEMORY {
LOADADDR: file = %O, start = %S - 2, size = $0002;
HEADER: file = %O, define = yes, start = %S, size = $000D;
MAIN: file = %O, define = yes, start = __HEADER_LAST__, size = __HIMEM__ - __STACKSIZE__ - __HEADER_LAST__;
MOVE: file = %O, start = __INITBSS_LOAD__, size = __HIMEM__ - __BSS_RUN__;
INIT: file = "", start = __BSS_RUN__, size = __HIMEM__ - __BSS_RUN__;
INIT: file = %O, start = __BSS_RUN__, size = __HIMEM__ - __BSS_RUN__;
}
SEGMENTS {
ZEROPAGE: load = ZP, type = zp;
LOADADDR: load = LOADADDR, type = ro;
EXEHDR: load = HEADER, type = ro;
STARTUP: load = MAIN, type = ro;
LOWCODE: load = MAIN, type = ro, optional = yes;
CODE: load = MAIN, type = ro;
RODATA: load = MAIN, type = ro;
DATA: load = MAIN, type = rw;
INITBSS: load = MAIN, type = bss, define = yes;
BSS: load = MAIN, type = bss, define = yes;
INIT: load = MOVE, run = INIT, type = ro, define = yes;
ZEROPAGE: load = ZP, type = zp;
LOADADDR: load = LOADADDR, type = ro;
EXEHDR: load = HEADER, type = ro;
STARTUP: load = MAIN, type = ro;
LOWCODE: load = MAIN, type = ro, optional = yes;
CODE: load = MAIN, type = ro;
RODATA: load = MAIN, type = ro;
DATA: load = MAIN, type = rw;
INITBSS: load = MAIN, type = rw;
BSS: load = MAIN, type = bss, define = yes;
INIT: load = INIT, type = ro, define = yes;
}
FEATURES {
CONDES: type = constructor,

39
libsrc/c64/crt0.s
View File

@ -6,7 +6,7 @@
.export __STARTUP__ : absolute = 1 ; Mark as startup
.import initlib, donelib
.import moveinit, zerobss, callmain
.import zerobss, callmain
.import BSOUT
.import __MAIN_START__, __MAIN_SIZE__ ; Linker generated
.import __STACKSIZE__ ; from configure file
@ -23,11 +23,6 @@
Start:
; Switch to the second charset.
lda #14
jsr BSOUT
; Switch off the BASIC ROM.
lda $01
@ -39,22 +34,10 @@ Start:
tsx
stx spsave ; Save the system stack ptr
; Allow some re-entrancy by skipping the next task if it already was done.
; This sometimes can let us rerun the program without reloading it.
ldx move_init
beq L0
; Move the INIT segment from where it was loaded (over the bss segments)
; into where it must be run (over the BSS segment).
jsr moveinit
dec move_init ; Set to false
; Save space by putting some of the start-up code in the INIT segment,
; which can be re-used by the BSS segment, the heap and the C stack.
L0: jsr runinit
jsr init
; Clear the BSS data.
@ -98,7 +81,7 @@ L2: lda zpsave,x
.segment "INIT"
runinit:
init:
; Save the zero-page locations that we need.
@ -115,6 +98,11 @@ L1: lda sp,x
sta sp
stx sp+1 ; Set argument stack ptr
; Switch to the second charset.
lda #14
jsr BSOUT
; Call the module constructors.
jmp initlib
@ -123,17 +111,8 @@ L1: lda sp,x
; ------------------------------------------------------------------------
; Data
.data
; These two variables were moved out of the BSS segment, and into DATA, because
; we need to use them before INIT is moved off of BSS, and before BSS is zeroed.
.segment "INITBSS"
mmusave:.res 1
spsave: .res 1
move_init:
.byte 1
.segment "INITBSS"
zpsave: .res zpspace

45
libsrc/common/moveinit.s
View File

@ -1,45 +0,0 @@
;
; 2015-10-07, Greg King
;
.export moveinit
.import __INIT_LOAD__, __INIT_RUN__, __INIT_SIZE__ ; Linker-generated
.macpack cpu
.macpack generic
; Put this in the DATA segment because it is self-modifying code.
.data
; Move the INIT segment from where it was loaded (over the bss segments)
; into where it must be run (over the BSS segment). The two areas might overlap;
; and, the segment is moved upwards. Therefore, this code starts at the highest
; address, and decrements to the lowest address. The low bytes of the starting
; pointers are not sums. The high bytes are sums; but, they do not include the
; carry. Both the low-byte sums and the carries will be done when the pointers
; are indexed by the .Y register.
moveinit:
; First, move the last, partial page.
; Then, move all of the full pages.
ldy #<__INIT_SIZE__ ; size of partial page
ldx #>__INIT_SIZE__ + (<__INIT_SIZE__ <> 0) ; number of pages, including partial
L1: dey
init_load:
lda __INIT_LOAD__ + (__INIT_SIZE__ & $FF00) - $0100 * (<__INIT_SIZE__ = 0),y
init_run:
sta __INIT_RUN__ + (__INIT_SIZE__ & $FF00) - $0100 * (<__INIT_SIZE__ = 0),y
tya
bnz L1 ; page not finished
dec init_load+2
dec init_run+2
dex
bnz L1 ; move next page
rts