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>
This commit is contained in:
Nicolas Pitre
Russell King
parent
ec80eb4671
commit
ff5fdafc9e
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@ -130,8 +130,3 @@ void *memset(void *s, int c, size_t count)
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*xs++ = c;
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return s;
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}
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void __memzero(void *s, size_t count)
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{
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memset(s, 0, count);
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}
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@ -39,18 +39,4 @@ static inline void *memset64(uint64_t *p, uint64_t v, __kernel_size_t n)
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return __memset64(p, v, n * 8, v >> 32);
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}
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extern void __memzero(void *ptr, __kernel_size_t n);
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#define memset(p,v,n) \
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({ \
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void *__p = (p); size_t __n = n; \
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if ((__n) != 0) { \
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if (__builtin_constant_p((v)) && (v) == 0) \
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__memzero((__p),(__n)); \
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else \
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memset((__p),(v),(__n)); \
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} \
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(__p); \
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})
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#endif
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@ -92,7 +92,6 @@ EXPORT_SYMBOL(__memset64);
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EXPORT_SYMBOL(memcpy);
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EXPORT_SYMBOL(memmove);
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EXPORT_SYMBOL(memchr);
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EXPORT_SYMBOL(__memzero);
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EXPORT_SYMBOL(mmioset);
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EXPORT_SYMBOL(mmiocpy);
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@ -105,8 +105,9 @@ __mmap_switched:
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ARM( ldmia r4!, {r0, r1, sp} )
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THUMB( ldmia r4!, {r0, r1, r3} )
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THUMB( mov sp, r3 )
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sub r1, r1, r0
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bl __memzero @ clear .bss
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sub r2, r1, r0
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mov r1, #0
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bl memset @ clear .bss
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ldmia r4, {r0, r1, r2, r3}
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str r9, [r0] @ Save processor ID
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@ -8,7 +8,7 @@
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lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \
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csumpartialcopy.o csumpartialcopyuser.o clearbit.o \
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delay.o delay-loop.o findbit.o memchr.o memcpy.o \
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memmove.o memset.o memzero.o setbit.o \
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memmove.o memset.o setbit.o \
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strchr.o strrchr.o \
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testchangebit.o testclearbit.o testsetbit.o \
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ashldi3.o ashrdi3.o lshrdi3.o muldi3.o \
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@ -1,137 +0,0 @@
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/*
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* linux/arch/arm/lib/memzero.S
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*
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* Copyright (C) 1995-2000 Russell King
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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#include <asm/unwind.h>
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.text
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.align 5
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.word 0
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/*
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* Align the pointer in r0. r3 contains the number of bytes that we are
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* mis-aligned by, and r1 is the number of bytes. If r1 < 4, then we
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* don't bother; we use byte stores instead.
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*/
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UNWIND( .fnstart )
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1: subs r1, r1, #4 @ 1 do we have enough
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blt 5f @ 1 bytes to align with?
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cmp r3, #2 @ 1
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strltb r2, [r0], #1 @ 1
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strleb r2, [r0], #1 @ 1
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strb r2, [r0], #1 @ 1
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add r1, r1, r3 @ 1 (r1 = r1 - (4 - r3))
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/*
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* The pointer is now aligned and the length is adjusted. Try doing the
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* memzero again.
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*/
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ENTRY(__memzero)
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mov r2, #0 @ 1
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ands r3, r0, #3 @ 1 unaligned?
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bne 1b @ 1
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/*
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* r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
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*/
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cmp r1, #16 @ 1 we can skip this chunk if we
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blt 4f @ 1 have < 16 bytes
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#if ! CALGN(1)+0
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/*
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* We need an extra register for this loop - save the return address and
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* use the LR
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*/
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str lr, [sp, #-4]! @ 1
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UNWIND( .fnend )
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UNWIND( .fnstart )
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UNWIND( .save {lr} )
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mov ip, r2 @ 1
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mov lr, r2 @ 1
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3: subs r1, r1, #64 @ 1 write 32 bytes out per loop
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stmgeia r0!, {r2, r3, ip, lr} @ 4
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stmgeia r0!, {r2, r3, ip, lr} @ 4
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stmgeia r0!, {r2, r3, ip, lr} @ 4
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stmgeia r0!, {r2, r3, ip, lr} @ 4
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bgt 3b @ 1
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ldmeqfd sp!, {pc} @ 1/2 quick exit
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/*
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* No need to correct the count; we're only testing bits from now on
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*/
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tst r1, #32 @ 1
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stmneia r0!, {r2, r3, ip, lr} @ 4
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stmneia r0!, {r2, r3, ip, lr} @ 4
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tst r1, #16 @ 1 16 bytes or more?
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stmneia r0!, {r2, r3, ip, lr} @ 4
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ldr lr, [sp], #4 @ 1
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UNWIND( .fnend )
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#else
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/*
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* This version aligns the destination pointer in order to write
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* whole cache lines at once.
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*/
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stmfd sp!, {r4-r7, lr}
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UNWIND( .fnend )
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UNWIND( .fnstart )
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UNWIND( .save {r4-r7, lr} )
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mov r4, r2
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mov r5, r2
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mov r6, r2
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mov r7, r2
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mov ip, r2
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mov lr, r2
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cmp r1, #96
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andgts ip, r0, #31
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ble 3f
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rsb ip, ip, #32
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sub r1, r1, ip
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movs ip, ip, lsl #(32 - 4)
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stmcsia r0!, {r4, r5, r6, r7}
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stmmiia r0!, {r4, r5}
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movs ip, ip, lsl #2
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strcs r2, [r0], #4
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3: subs r1, r1, #64
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stmgeia r0!, {r2-r7, ip, lr}
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stmgeia r0!, {r2-r7, ip, lr}
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bgt 3b
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ldmeqfd sp!, {r4-r7, pc}
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tst r1, #32
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stmneia r0!, {r2-r7, ip, lr}
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tst r1, #16
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stmneia r0!, {r4-r7}
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ldmfd sp!, {r4-r7, lr}
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UNWIND( .fnend )
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#endif
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UNWIND( .fnstart )
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4: tst r1, #8 @ 1 8 bytes or more?
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stmneia r0!, {r2, r3} @ 2
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tst r1, #4 @ 1 4 bytes or more?
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strne r2, [r0], #4 @ 1
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/*
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* When we get here, we've got less than 4 bytes to zero. We
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* may have an unaligned pointer as well.
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*/
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5: tst r1, #2 @ 1 2 bytes or more?
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strneb r2, [r0], #1 @ 1
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strneb r2, [r0], #1 @ 1
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tst r1, #1 @ 1 a byte left over
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strneb r2, [r0], #1 @ 1
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ret lr @ 1
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UNWIND( .fnend )
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ENDPROC(__memzero)
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@ -765,7 +765,7 @@ static int imxdma_alloc_chan_resources(struct dma_chan *chan)
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desc = kzalloc(sizeof(*desc), GFP_KERNEL);
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if (!desc)
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break;
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__memzero(&desc->desc, sizeof(struct dma_async_tx_descriptor));
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memset(&desc->desc, 0, sizeof(struct dma_async_tx_descriptor));
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dma_async_tx_descriptor_init(&desc->desc, chan);
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desc->desc.tx_submit = imxdma_tx_submit;
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/* txd.flags will be overwritten in prep funcs */
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