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[/] [openrisc/] [trunk/] [rtos/] [rtems/] [c/] [src/] [lib/] [libcpu/] [sparc/] [reg_win/] [window.S] - Rev 173
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/*
* window.s
*
* This file contains the register window management routines for the
* SPARC architecture. Trap handlers for the following capabilities
* are included in this file:
*
* + Window Overflow
* + Window Underflow
* + Flushing All Windows
*
* COPYRIGHT:
*
* This file includes the window overflow and underflow handlers from
* the file srt0.s provided with the binary distribution of the SPARC
* Instruction Simulator (SIS) found at
* ftp://ftp.estec.esa.nl/pub/ws/wsd/erc32.
*
* COPYRIGHT (c) 1995. European Space Agency.
*
* This terms of the RTEMS license apply to this file.
*
* $Id: window.S,v 1.2 2001-09-27 12:01:39 chris Exp $
*/
#include <asm.h>
.seg "text"
/*
* Window overflow trap handler.
*
* On entry:
*
* l0 = psr (from trap table)
* l1 = pc
* l2 = npc
*/
PUBLIC(window_overflow_trap_handler)
SYM(window_overflow_trap_handler):
/*
* Calculate new WIM by "rotating" the valid bits in the WIM right
* by one position. The following shows how the bits move for a SPARC
* cpu implementation where SPARC_NUMBER_OF_REGISTER_WINDOWS is 8.
*
* OLD WIM = 76543210
* NEW WIM = 07654321
*
* NOTE: New WIM must be stored in a global register since the
* "save" instruction just prior to the load of the wim
* register will result in the local register set changing.
*/
mov %wim, %l3 ! l3 = WIM
mov %g1, %l7 ! save g1
srl %l3, 1, %g1 ! g1 = WIM >> 1
sll %l3, SPARC_NUMBER_OF_REGISTER_WINDOWS-1 , %l4
! l4 = WIM << (Number Windows - 1)
or %l4, %g1, %g1 ! g1 = (WIM >> 1) |
! (WIM << (Number Windows - 1))
save ! Get into window to be saved.
mov %g1, %wim ! load new WIM
nop; nop; nop ! 3 slot delay
std %l0, [%sp + 0x00] ! save local register set
std %l2, [%sp + 0x08]
std %l4, [%sp + 0x10]
std %l6, [%sp + 0x18]
std %i0, [%sp + 0x20] ! save input register set
std %i2, [%sp + 0x28]
std %i4, [%sp + 0x30]
std %i6, [%sp + 0x38]
restore ! Go back to trap window.
mov %l7, %g1 ! restore g1
jmp %l1 ! Re-execute save.
rett %l2
/*
* Window underflow trap handler.
*
* On entry:
*
* l0 = psr (from trap table)
* l1 = pc
* l2 = npc
*/
PUBLIC(window_underflow_trap_handler)
SYM(window_underflow_trap_handler):
/*
* Calculate new WIM by "rotating" the valid bits in the WIM left
* by one position. The following shows how the bits move for a SPARC
* cpu implementation where SPARC_NUMBER_OF_REGISTER_WINDOWS is 8.
*
* OLD WIM = 76543210
* NEW WIM = 07654321
*
* NOTE: New WIM must be stored in a global register since the
* "save" instruction just prior to the load of the wim
* register will result in the local register set changing.
*/
mov %wim, %l3 ! Calculate new WIM
sll %l3, 1, %l4 ! l4 = WIM << 1
srl %l3, SPARC_NUMBER_OF_REGISTER_WINDOWS-1, %l5
! l5 = WIM >> (Number Windows-1)
or %l5, %l4, %l5 ! l5 = (WIM << 1) |
! (WIM >> (Number Windows-1))
mov %l5, %wim ! load the new WIM
nop; nop; nop
restore ! Two restores to get into the
restore ! window to restore
ldd [%sp + 0x00], %l0 ! First the local register set
ldd [%sp + 0x08], %l2
ldd [%sp + 0x10], %l4
ldd [%sp + 0x18], %l6
ldd [%sp + 0x20], %i0 ! Then the input registers
ldd [%sp + 0x28], %i2
ldd [%sp + 0x30], %i4
ldd [%sp + 0x38], %i6
save ! Get back to the trap window.
save
jmp %l1 ! Re-execute restore.
rett %l2
/*
* Flush All Windows trap handler.
*
* Flush all windows with valid contents except the current one
* and the one we will be returning to.
*
* In examining the set register windows, one may logically divide
* the windows into sets (some of which may be empty) based on their
* current status:
*
* + current (i.e. in use),
* + used (i.e. a restore would not trap)
* + invalid (i.e. 1 in corresponding bit in WIM)
* + unused
*
* Either the used or unused set of windows may be empty.
*
* NOTE: We assume only one bit is set in the WIM at a time.
*
* Given a CWP of 5 and a WIM of 0x1, the registers are divided
* into sets as follows:
*
* + 0 - invalid
* + 1-4 - unused
* + 5 - current
* + 6-7 - used
*
* In this case, we only would save the used windows which we
* will not be returning to -- 6.
*
* Register Usage while saving the windows:
* g1 = current PSR
* g2 = current wim
* g3 = CWP
* g4 = wim scratch
* g5 = scratch
*
* On entry:
*
* l0 = psr (from trap table)
* l1 = pc
* l2 = npc
*/
PUBLIC(window_flush_trap_handler)
SYM(window_flush_trap_handler):
/*
* Save the global registers we will be using
*/
mov %g1, %l3
mov %g2, %l4
mov %g3, %l5
mov %g4, %l6
mov %g5, %l7
mov %l0, %g1 ! g1 = psr
mov %wim, %g2 ! g2 = wim
and %l0, SPARC_PSR_CWP_MASK, %g3 ! g3 = CWP
add %g3, 1, %g5 ! g5 = CWP + 1
and %g5, SPARC_NUMBER_OF_REGISTER_WINDOWS - 1, %g5
mov 1, %g4
sll %g4, %g5, %g4 ! g4 = WIM mask for CWP+1 invalid
restore ! go back one register window
save_frame_loop:
sll %g4, 1, %g5 ! rotate the "wim" left 1
srl %g4, SPARC_NUMBER_OF_REGISTER_WINDOWS - 1, %g4
or %g4, %g5, %g4 ! g4 = wim if we do one restore
/*
* If a restore would not underflow, then continue.
*/
andcc %g4, %g2, %g0 ! Any windows to flush?
bnz done_flushing ! No, then continue
nop
restore ! back one window
/*
* Now save the window just as if we overflowed to it.
*/
std %l0, [%sp + CPU_STACK_FRAME_L0_OFFSET]
std %l2, [%sp + CPU_STACK_FRAME_L2_OFFSET]
std %l4, [%sp + CPU_STACK_FRAME_L4_OFFSET]
std %l6, [%sp + CPU_STACK_FRAME_L6_OFFSET]
std %i0, [%sp + CPU_STACK_FRAME_I0_OFFSET]
std %i2, [%sp + CPU_STACK_FRAME_I2_OFFSET]
std %i4, [%sp + CPU_STACK_FRAME_I4_OFFSET]
std %i6, [%sp + CPU_STACK_FRAME_I6_FP_OFFSET]
ba save_frame_loop
nop
done_flushing:
add %g3, 2, %g3 ! calculate desired WIM
and %g3, SPARC_NUMBER_OF_REGISTER_WINDOWS - 1, %g3
mov 1, %g4
sll %g4, %g3, %g4 ! g4 = new WIM
mov %g4, %wim
mov %g1, %psr ! restore PSR
nop
nop
nop
/*
* Restore the global registers we used
*/
mov %l3, %g1
mov %l4, %g2
mov %l5, %g3
mov %l6, %g4
mov %l7, %g5
jmpl %l2, %g0
rett %l2 + 4
/* end of file */