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SPARC: optimize window underflow trap

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Save five instructions on underflow handling.

By using an optimized trap entry we can move instructions from
the window underflow function into the trap entry vector. By
setting WIM=0 and using RESTORE it is possible to move the
new WIM register content from the trapped window into the
to-be-restored register window. It is then possible to avoid
the WIM write delay.
This commit is contained in:
Daniel Hellstrom
2014-11-11 15:18:01 +01:00
parent 6930aa7f19
commit 0d3b5d4742
2 changed files with 16 additions and 9 deletions
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11
c/src/lib/libbsp/sparc/shared/start/start.S
View File

@@ -50,6 +50,15 @@
save; \
nop
/*
* Window Underflow optimized trap table entry
*/
#define WUTRAP(_vector, _handler) \
mov %wim, %l3 ; \
sethi %hi(_handler), %l4 ; \
jmp %l4+%lo(_handler); \
mov %g0, %wim ! WIM = 0, so that we can restore regardless of WIM
/*
* Software trap. Treat as BAD_TRAP for the time being...
*/
@@ -82,7 +91,7 @@ SYM(trap_table):
BAD_TRAP; ! 03 privileged instruction
BAD_TRAP; ! 04 fp disabled
WOTRAP(5, SYM(window_overflow_trap_handler)); ! 05 window overflow
TRAP( 6, SYM(window_underflow_trap_handler) );! 06 window underflow
WUTRAP(6, SYM(window_underflow_trap_handler));! 06 window underflow
BAD_TRAP; ! 07 memory address not aligned
BAD_TRAP; ! 08 fp exception
BAD_TRAP; ! 09 data access exception

14
c/src/lib/libcpu/sparc/reg_win/window.S
View File

@@ -74,9 +74,9 @@ SYM(window_overflow_trap_handler):
*
* On entry:
*
* l0 = psr (from trap table)
* l1 = pc
* l2 = npc
* l3 = wim (from trap table)
*/
PUBLIC(window_underflow_trap_handler)
@@ -96,17 +96,15 @@ SYM(window_underflow_trap_handler):
* register will result in the local register set changing.
*/
mov %wim, %l3 ! Calculate new WIM
! In WIM 3 write instruction delay. since WIM<=0 from trap entry
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) |
or %l5, %l4, %i5 ! %i5= (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
restore %o5, %g0, %l7 ! window to restore. Carry along new WIM
ldd [%sp + 0x00], %l0 ! First the local register set
mov %l7, %wim ! load the new WIM
ldd [%sp + 0x08], %l2
ldd [%sp + 0x10], %l4
ldd [%sp + 0x18], %l6
@@ -117,7 +115,7 @@ SYM(window_underflow_trap_handler):
save ! Get back to the trap window.
save
jmp %l1 ! Re-execute restore.
rett %l2
rett %l2
/*
* Flush All Windows trap handler.