8080: preserve BC on switches as required by the compiler ABI

diff --git a/Kernel/lib/8080fixedbank-core.s b/Kernel/lib/8080fixedbank-core.s
index 0c7cb83..bdff5b9 100644 (file)
--- a/Kernel/lib/8080fixedbank-core.s
+++ b/Kernel/lib/8080fixedbank-core.s
@@ -12,8 +12,7 @@
 .define _platform_switchout
 
 !
-!      Verify ABI exact rules but I think we don't need to stack any
-!      register state.
+!      The ABI requires we preserve BC
 !
 
 !
@@ -22,6 +21,7 @@
 _platform_switchout:
        lxi h,0
        push h                  ! Save a 0 argment
+       push b
        dad sp
        shld U_DATA__U_SP       ! Save the sp for a switch in
        call map_process_always_di
@@ -142,8 +142,9 @@ skip_copyback:
        lhld U_DATA__U_SP
        sphl
        !
-       !       Recover our return code
+       !       Recover our parent frame pointer and return code
        !
+       pop b
        pop h
        lda U_DATA__U_ININTERRUPT
        sta _int_disabled
@@ -184,8 +185,9 @@ _dofork:
        mov h,m
        mov l,a
        !
-       ! We don't have any state to save but the pid
+       ! We don't have any state to save but the pid and framepointer 
        !
+       push b
        push h
        lxi h,0
        dad sp
@@ -228,6 +230,10 @@ _dofork:
        !
        lxi h,0
        shld _runticks
+       !
+       !       Frame pointer
+       !
+       pop b
        ret
 
 .define bouncebuffer