[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>

diff --git a/arch/avr32/kernel/entry-avr32b.S b/arch/avr32/kernel/entry-avr32b.S
index 484e08310f1512651af5fffb5d932ed9296ab30f..42657f1703b2773dc3532eaf3a5bf99efcf7e26a 100644 (file)
--- a/arch/avr32/kernel/entry-avr32b.S
+++ b/arch/avr32/kernel/entry-avr32b.S
@@ -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