ARM: 8745/1: get rid of __memzero()

The __memzero assembly code is almost identical to memset's except for
two orr instructions. The runtime performance of __memset(p, n) and
memset(p, 0, n) is accordingly almost identical.

However, the memset() macro used to guard against a zero length and to
call __memzero at compile time when the fill value is a constant zero
interferes with compiler optimizations.

Arnd found tha the test against a zero length brings up some new
warnings with gcc v8:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82103

And successively rremoving the test against a zero length and the call
to __memzero optimization produces the following kernel sizes for
defconfig with gcc 6:

    text     data     bss       dec       hex  filename
12248142  6278960  413588  18940690   1210312  vmlinux.orig
12244474  6278960  413588  18937022   120f4be  vmlinux.no_zero_test
12239160  6278960  413588  18931708   120dffc  vmlinux.no_memzero

So it is probably not worth keeping __memzero around given that the
compiler can do a better job at inlining trivial memset(p,0,n) on its
own. And the memset code already handles a zero length just fine.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

diff --git a/arch/arm/boot/compressed/string.c b/arch/arm/boot/compressed/string.c
index 309e1bbad75d57870fcb16ae6fc92a7343c8a0e2..13c90abc68d68a9c5a73502beacb17aef1c89132 100644 (file)
--- a/arch/arm/boot/compressed/string.c
+++ b/arch/arm/boot/compressed/string.c
@@ -130,8 +130,3 @@ void *memset(void *s, int c, size_t count)
                *xs++ = c;
        return s;
 }
-
-void __memzero(void *s, size_t count)
-{
-       memset(s, 0, count);
-}

diff --git a/arch/arm/include/asm/string.h b/arch/arm/include/asm/string.h
index f54a3136aac6e36efbc3a809c1937fa401b39a8f..111a1d8a41ddfad3c8fd64e79f0df6d8c74af31b 100644 (file)
--- a/arch/arm/include/asm/string.h
+++ b/arch/arm/include/asm/string.h
@@ -39,18 +39,4 @@ static inline void *memset64(uint64_t *p, uint64_t v, __kernel_size_t n)
        return __memset64(p, v, n * 8, v >> 32);
 }
 
-extern void __memzero(void *ptr, __kernel_size_t n);
-
-#define memset(p,v,n)                                                  \
-       ({                                                              \
-               void *__p = (p); size_t __n = n;                        \
-               if ((__n) != 0) {                                       \
-                       if (__builtin_constant_p((v)) && (v) == 0)      \
-                               __memzero((__p),(__n));                 \
-                       else                                            \
-                               memset((__p),(v),(__n));                \
-               }                                                       \
-               (__p);                                                  \
-       })
-
 #endif

diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c
index 5266fd9ad6b41402dceafcdf1991776f39fbe57b..783fbb4de5f95eabbd136f2880f8f40471120bcb 100644 (file)
--- a/arch/arm/kernel/armksyms.c
+++ b/arch/arm/kernel/armksyms.c
@@ -92,7 +92,6 @@ EXPORT_SYMBOL(__memset64);
 EXPORT_SYMBOL(memcpy);
 EXPORT_SYMBOL(memmove);
 EXPORT_SYMBOL(memchr);
-EXPORT_SYMBOL(__memzero);
 
 EXPORT_SYMBOL(mmioset);
 EXPORT_SYMBOL(mmiocpy);

diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 21dde771a7dd8d1465a73145f6351db0dfe922b4..6e0375e7db055bc82cf0674b37b74646e2d64ff0 100644 (file)
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -105,8 +105,9 @@ __mmap_switched:
    ARM(        ldmia   r4!, {r0, r1, sp} )
  THUMB(        ldmia   r4!, {r0, r1, r3} )
  THUMB(        mov     sp, r3 )
-       sub     r1, r1, r0
-       bl      __memzero                       @ clear .bss
+       sub     r2, r1, r0
+       mov     r1, #0
+       bl      memset                          @ clear .bss
 
        ldmia   r4, {r0, r1, r2, r3}
        str     r9, [r0]                        @ Save processor ID

diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 4cb0b9624d8ff6bd017a25c28475e33c94cd7231..ad25fd1872c7d7dd5c6c837e9f579b284dec2c15 100644 (file)
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -8,7 +8,7 @@
 lib-y          := backtrace.o changebit.o csumipv6.o csumpartial.o   \
                   csumpartialcopy.o csumpartialcopyuser.o clearbit.o \
                   delay.o delay-loop.o findbit.o memchr.o memcpy.o   \
-                  memmove.o memset.o memzero.o setbit.o              \
+                  memmove.o memset.o setbit.o                        \
                   strchr.o strrchr.o                                 \
                   testchangebit.o testclearbit.o testsetbit.o        \
                   ashldi3.o ashrdi3.o lshrdi3.o muldi3.o             \

diff --git a/arch/arm/lib/memzero.S b/arch/arm/lib/memzero.S
deleted file mode 100644 (file)
index 0eded95..0000000
--- a/arch/arm/lib/memzero.S
+++ /dev/null
@@ -1,137 +0,0 @@
-/*
- *  linux/arch/arm/lib/memzero.S
- *
- *  Copyright (C) 1995-2000 Russell King
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-#include <linux/linkage.h>
-#include <asm/assembler.h>
-#include <asm/unwind.h>
-
-       .text
-       .align  5
-       .word   0
-/*
- * Align the pointer in r0.  r3 contains the number of bytes that we are
- * mis-aligned by, and r1 is the number of bytes.  If r1 < 4, then we
- * don't bother; we use byte stores instead.
- */
-UNWIND(        .fnstart                        )
-1:     subs    r1, r1, #4              @ 1 do we have enough
-       blt     5f                      @ 1 bytes to align with?
-       cmp     r3, #2                  @ 1
-       strltb  r2, [r0], #1            @ 1
-       strleb  r2, [r0], #1            @ 1
-       strb    r2, [r0], #1            @ 1
-       add     r1, r1, r3              @ 1 (r1 = r1 - (4 - r3))
-/*
- * The pointer is now aligned and the length is adjusted.  Try doing the
- * memzero again.
- */
-
-ENTRY(__memzero)
-       mov     r2, #0                  @ 1
-       ands    r3, r0, #3              @ 1 unaligned?
-       bne     1b                      @ 1
-/*
- * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
- */
-       cmp     r1, #16                 @ 1 we can skip this chunk if we
-       blt     4f                      @ 1 have < 16 bytes
-
-#if ! CALGN(1)+0
-
-/*
- * We need an extra register for this loop - save the return address and
- * use the LR
- */
-       str     lr, [sp, #-4]!          @ 1
-UNWIND(        .fnend                          )
-UNWIND(        .fnstart                        )
-UNWIND(        .save   {lr}                    )
-       mov     ip, r2                  @ 1
-       mov     lr, r2                  @ 1
-
-3:     subs    r1, r1, #64             @ 1 write 32 bytes out per loop
-       stmgeia r0!, {r2, r3, ip, lr}   @ 4
-       stmgeia r0!, {r2, r3, ip, lr}   @ 4
-       stmgeia r0!, {r2, r3, ip, lr}   @ 4
-       stmgeia r0!, {r2, r3, ip, lr}   @ 4
-       bgt     3b                      @ 1
-       ldmeqfd sp!, {pc}               @ 1/2 quick exit
-/*
- * No need to correct the count; we're only testing bits from now on
- */
-       tst     r1, #32                 @ 1
-       stmneia r0!, {r2, r3, ip, lr}   @ 4
-       stmneia r0!, {r2, r3, ip, lr}   @ 4
-       tst     r1, #16                 @ 1 16 bytes or more?
-       stmneia r0!, {r2, r3, ip, lr}   @ 4
-       ldr     lr, [sp], #4            @ 1
-UNWIND(        .fnend                          )
-
-#else
-
-/*
- * This version aligns the destination pointer in order to write
- * whole cache lines at once.
- */
-
-       stmfd   sp!, {r4-r7, lr}
-UNWIND(        .fnend                 )
-UNWIND(        .fnstart               )
-UNWIND(        .save   {r4-r7, lr}    )
-       mov     r4, r2
-       mov     r5, r2
-       mov     r6, r2
-       mov     r7, r2
-       mov     ip, r2
-       mov     lr, r2
-
-       cmp     r1, #96
-       andgts  ip, r0, #31
-       ble     3f
-
-       rsb     ip, ip, #32
-       sub     r1, r1, ip
-       movs    ip, ip, lsl #(32 - 4)
-       stmcsia r0!, {r4, r5, r6, r7}
-       stmmiia r0!, {r4, r5}
-       movs    ip, ip, lsl #2
-       strcs   r2, [r0], #4
-
-3:     subs    r1, r1, #64
-       stmgeia r0!, {r2-r7, ip, lr}
-       stmgeia r0!, {r2-r7, ip, lr}
-       bgt     3b
-       ldmeqfd sp!, {r4-r7, pc}
-
-       tst     r1, #32
-       stmneia r0!, {r2-r7, ip, lr}
-       tst     r1, #16
-       stmneia r0!, {r4-r7}
-       ldmfd   sp!, {r4-r7, lr}
-UNWIND(        .fnend                 )
-
-#endif
-
-UNWIND(        .fnstart                        )
-4:     tst     r1, #8                  @ 1 8 bytes or more?
-       stmneia r0!, {r2, r3}           @ 2
-       tst     r1, #4                  @ 1 4 bytes or more?
-       strne   r2, [r0], #4            @ 1
-/*
- * When we get here, we've got less than 4 bytes to zero.  We
- * may have an unaligned pointer as well.
- */
-5:     tst     r1, #2                  @ 1 2 bytes or more?
-       strneb  r2, [r0], #1            @ 1
-       strneb  r2, [r0], #1            @ 1
-       tst     r1, #1                  @ 1 a byte left over
-       strneb  r2, [r0], #1            @ 1
-       ret     lr                      @ 1
-UNWIND(        .fnend                          )
-ENDPROC(__memzero)

diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
index 331f863c605ea928b766122a1226d598e6a0ec15..715b39ae5a46b70ef9ca700eb7932064bd34409c 100644 (file)
--- a/drivers/dma/imx-dma.c
+++ b/drivers/dma/imx-dma.c
@@ -765,7 +765,7 @@ static int imxdma_alloc_chan_resources(struct dma_chan *chan)
                desc = kzalloc(sizeof(*desc), GFP_KERNEL);
                if (!desc)
                        break;
-               __memzero(&desc->desc, sizeof(struct dma_async_tx_descriptor));
+               memset(&desc->desc, 0, sizeof(struct dma_async_tx_descriptor));
                dma_async_tx_descriptor_init(&desc->desc, chan);
                desc->desc.tx_submit = imxdma_tx_submit;
                /* txd.flags will be overwritten in prep funcs */