sh: __copy_user() optimizations for small copies.

This implements a fast-path for small (less than 12 bytes) copies,
with the existing path treated as the slow-path and left as the default
behaviour for all other copy sizes.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 108 insertions, 61 deletions

diff --git a/arch/sh/mm/copy_page.S b/arch/sh/mm/copy_page.S
index ae039f2da162..a81dbdb05596 100644
--- a/arch/sh/mm/copy_page.S
+++ b/arch/sh/mm/copy_page.S
@@ -141,47 +141,38 @@ ENTRY(__copy_user_page)
         .long 9999b, 6000f      ;       \
         .previous
 ENTRY(__copy_user)
-        tst     r6,r6           ! Check explicitly for zero
-        bf      1f
-        rts
-         mov    #0,r0           ! normal return
-1:
-        mov.l   r10,@-r15
-        mov.l   r9,@-r15
-        mov.l   r8,@-r15
+        ! Check if small number of bytes
+        mov     #11,r0
         mov     r4,r3
-        add     r6,r3           ! last destination address
-        mov     #12,r0          ! Check if small number of bytes
-        cmp/gt  r0,r6
-        bt      2f
-        bra     .L_cleanup_loop
-         nop
-2:
-        neg     r5,r0           ! Calculate bytes needed to align source
+        cmp/gt  r0,r6           ! r6 (len) > r0 (11)
+        bf/s    .L_cleanup_loop_no_pop
+         add    r6,r3           ! last destination address
+
+        ! Calculate bytes needed to align to src
+        mov.l   r11,@-r15
+        neg     r5,r0
+        mov.l   r10,@-r15
         add     #4,r0
+        mov.l   r9,@-r15
         and     #3,r0
+        mov.l   r8,@-r15
         tst     r0,r0
-        bt      .L_jump
-        mov     r0,r1
+        bt      2f
 
-.L_loop1:
-        ! Copy bytes to align source
-EX(     mov.b   @r5+,r0         )
-        dt      r1
-EX(     mov.b   r0,@r4          )
+1:
+        ! Copy bytes to long word align src
+EX(     mov.b   @r5+,r1         )
+        dt      r0
         add     #-1,r6
-        bf/s    .L_loop1
+EX(     mov.b   r1,@r4          )
+        bf/s    1b
          add    #1,r4
 
-.L_jump:
-        mov     r6,r2           ! Calculate number of longwords to copy
+        ! Jump to appropriate routine depending on dest
+2:      mov     #3,r1
+        mov     r6, r2
+        and     r4,r1
         shlr2   r2
-        tst     r2,r2
-        bt      .L_cleanup
-
-        mov     r4,r0           ! Jump to appropriate routine
-        and     #3,r0
-        mov     r0,r1
         shll2   r1
         mova    .L_jump_tbl,r0
         mov.l   @(r0,r1),r1
@@ -195,43 +186,97 @@ EX(	mov.b	r0,@r4		)
         .long   .L_dest10
         .long   .L_dest11
 
+/*
+ * Come here if there are less than 12 bytes to copy
+ *
+ * Keep the branch target close, so the bf/s callee doesn't overflow
+ * and result in a more expensive branch being inserted. This is the
+ * fast-path for small copies, the jump via the jump table will hit the
+ * default slow-path cleanup. -PFM.
+ */
+.L_cleanup_loop_no_pop:
+        tst     r6,r6           ! Check explicitly for zero
+        bt      1f
+
+2:
+EX(     mov.b   @r5+,r0         )
+        dt      r6
+EX(     mov.b   r0,@r4          )
+        bf/s    2b
+         add    #1,r4
+
+1:      mov     #0,r0           ! normal return
+5000:
+
+# Exception handler:
+.section .fixup, "ax"
+6000:
+        mov.l   8000f,r1
+        mov     r3,r0
+        jmp     @r1
+         sub    r4,r0
+        .align  2
+8000:   .long   5000b
+
+.previous
+        rts
+         nop
+
 ! Destination = 00
 
 .L_dest00:
-        mov     r2,r7
-        shlr2   r7
-        shlr    r7
-        tst     r7,r7
-        mov     #7,r0
-        bt/s    1f
-         and    r0,r2
-        .align 2
+        ! Skip the large copy for small transfers
+        mov     #(32+32-4), r0
+        cmp/gt  r6, r0          ! r0 (60) > r6 (len)
+        bt      1f
+
+        ! Align dest to a 32 byte boundary
+        neg     r4,r0
+        add     #0x20, r0
+        and     #0x1f, r0
+        tst     r0, r0
+        bt      2f
+
+        sub     r0, r6
+        shlr2   r0
+3:
+EX(     mov.l   @r5+,r1         )
+        dt      r0
+EX(     mov.l   r1,@r4          )
+        bf/s    3b
+         add    #4,r4
+
 2:
 EX(     mov.l   @r5+,r0         )
+EX(     mov.l   @r5+,r1         )
+EX(     mov.l   @r5+,r2         )
+EX(     mov.l   @r5+,r7         )
 EX(     mov.l   @r5+,r8         )
 EX(     mov.l   @r5+,r9         )
 EX(     mov.l   @r5+,r10        )
-EX(     mov.l   r0,@r4          )
-EX(     mov.l   r8,@(4,r4)      )
-EX(     mov.l   r9,@(8,r4)      )
-EX(     mov.l   r10,@(12,r4)    )
-EX(     mov.l   @r5+,r0         )
-EX(     mov.l   @r5+,r8         )
-EX(     mov.l   @r5+,r9         )
-EX(     mov.l   @r5+,r10        )
-        dt      r7
-EX(     mov.l   r0,@(16,r4)     )
-EX(     mov.l   r8,@(20,r4)     )
-EX(     mov.l   r9,@(24,r4)     )
-EX(     mov.l   r10,@(28,r4)    )
+EX(     mov.l   @r5+,r11        )
+EX(     movca.l r0,@r4          )
+        add     #-32, r6
+EX(     mov.l   r1,@(4,r4)      )
+        mov     #32, r0
+EX(     mov.l   r2,@(8,r4)      )
+        cmp/gt  r6, r0          ! r0 (32) > r6 (len)
+EX(     mov.l   r7,@(12,r4)     )
+EX(     mov.l   r8,@(16,r4)     )
+EX(     mov.l   r9,@(20,r4)     )
+EX(     mov.l   r10,@(24,r4)    )
+EX(     mov.l   r11,@(28,r4)    )
         bf/s    2b
          add    #32,r4
-        tst     r2,r2
+
+1:      mov     r6, r0
+        shlr2   r0
+        tst     r0, r0
         bt      .L_cleanup
 1:
-EX(     mov.l   @r5+,r0         )
-        dt      r2
-EX(     mov.l   r0,@r4          )
+EX(     mov.l   @r5+,r1         )
+        dt      r0
+EX(     mov.l   r1,@r4          )
         bf/s    1b
          add    #4,r4
 
@@ -250,7 +295,7 @@ EX(	mov.l	r0,@r4		)
          and    r0,r2
 2:
         dt      r7
-#ifdef __LITTLE_ENDIAN__
+#ifdef CONFIG_CPU_LITTLE_ENDIAN
 EX(     mov.l   @r5+,r0         )
 EX(     mov.l   @r5+,r1         )
 EX(     mov.l   @r5+,r8         )
@@ -320,7 +365,7 @@ EX(	mov.w	r0,@(2,r4)	)
 1:      ! Read longword, write two words per iteration
 EX(     mov.l   @r5+,r0         )
         dt      r2
-#ifdef __LITTLE_ENDIAN__
+#ifdef CONFIG_CPU_LITTLE_ENDIAN
 EX(     mov.w   r0,@r4          )
         shlr16  r0
 EX(     mov.w   r0,@(2,r4)      )
@@ -342,7 +387,7 @@ EX(	mov.w	r0,@r4		)
         ! Read longword, write byte, word, byte per iteration
 EX(     mov.l   @r5+,r0         )
         dt      r2
-#ifdef __LITTLE_ENDIAN__
+#ifdef CONFIG_CPU_LITTLE_ENDIAN
 EX(     mov.b   r0,@r4          )
         shlr8   r0
         add     #1,r4
@@ -379,6 +424,7 @@ EX(	mov.b	r0,@r4		)
 
 .L_exit:
         mov     #0,r0           ! normal return
+
 5000:
 
 # Exception handler:
@@ -394,5 +440,6 @@ EX(	mov.b	r0,@r4		)
 .previous
         mov.l   @r15+,r8
         mov.l   @r15+,r9
+        mov.l   @r15+,r10
         rts
-         mov.l  @r15+,r10
+         mov.l  @r15+,r11