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[AVR32] Optimize the TLB miss handler 

Reorder some instructions and change the register usage to reduce
the number of pipeline stalls. Also use the bfextu and bfins
instructions for bitfield manipulations instead of shifting and
masking.

This makes gzipping a 80MB file approximately 2% faster.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
This commit is contained in:
Haavard Skinnemoen 2007-03-14 13:59:13 +01:00
parent 9ca20a8366
commit c0c3e81608
1 changed files with 24 additions and 30 deletions
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54
arch/avr32/kernel/entry-avr32b.S
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@ -100,55 +100,49 @@ dtlb_miss_write:
.global tlb_miss_common
tlb_miss_common:
mfsr r0, SYSREG_PTBR
mfsr r1, SYSREG_TLBEAR
mfsr r0, SYSREG_TLBEAR
mfsr r1, SYSREG_PTBR
/* Is it the vmalloc space? */
bld r1, 31
bld r0, 31
brcs handle_vmalloc_miss
/* First level lookup */
pgtbl_lookup:
lsr r2, r1, PGDIR_SHIFT
ld.w r0, r0[r2 << 2]
bld r0, _PAGE_BIT_PRESENT
lsr r2, r0, PGDIR_SHIFT
ld.w r3, r1[r2 << 2]
bfextu r1, r0, PAGE_SHIFT, PGDIR_SHIFT - PAGE_SHIFT
bld r3, _PAGE_BIT_PRESENT
brcc page_table_not_present
/* TODO: Check access rights on page table if necessary */
/* Translate to virtual address in P1. */
andl r0, 0xf000
sbr r0, 31
andl r3, 0xf000
sbr r3, 31
/* Second level lookup */
lsl r1, (32 - PGDIR_SHIFT)
lsr r1, (32 - PGDIR_SHIFT) + PAGE_SHIFT
add r2, r0, r1 << 2
ld.w r1, r2[0]
bld r1, _PAGE_BIT_PRESENT
ld.w r2, r3[r1 << 2]
mfsr r0, SYSREG_TLBARLO
bld r2, _PAGE_BIT_PRESENT
brcc page_not_present
/* Mark the page as accessed */
sbr r1, _PAGE_BIT_ACCESSED
st.w r2[0], r1
sbr r2, _PAGE_BIT_ACCESSED
st.w r3[r1 << 2], r2
/* Drop software flags */
andl r1, _PAGE_FLAGS_HARDWARE_MASK & 0xffff
mtsr SYSREG_TLBELO, r1
andl r2, _PAGE_FLAGS_HARDWARE_MASK & 0xffff
mtsr SYSREG_TLBELO, r2
/* Figure out which entry we want to replace */
mfsr r0, SYSREG_TLBARLO
mfsr r1, SYSREG_MMUCR
clz r2, r0
brcc 1f
mov r1, -1 /* All entries have been accessed, */
mtsr SYSREG_TLBARLO, r1 /* so reset TLBAR */
mov r2, 0 /* and start at 0 */
1: mfsr r1, SYSREG_MMUCR
lsl r2, 14
andl r1, 0x3fff, COH
or r1, r2
mtsr SYSREG_MMUCR, r1
mov r3, -1 /* All entries have been accessed, */
mov r2, 0 /* so start at 0 */
mtsr SYSREG_TLBARLO, r3 /* and reset TLBAR */
1: bfins r1, r2, SYSREG_DRP_OFFSET, SYSREG_DRP_SIZE
mtsr SYSREG_MMUCR, r1
tlbw
tlbmiss_restore
@ -156,8 +150,8 @@ pgtbl_lookup:
handle_vmalloc_miss:
/* Simply do the lookup in init's page table */
mov r0, lo(swapper_pg_dir)
orh r0, hi(swapper_pg_dir)
mov r1, lo(swapper_pg_dir)
orh r1, hi(swapper_pg_dir)
rjmp pgtbl_lookup