From ff5fdafc9e9702846480e0cea55ba861f72140a2 Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Fri, 19 Jan 2018 18:17:46 +0100 Subject: 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 Signed-off-by: Nicolas Pitre Acked-by: Ard Biesheuvel Acked-by: Arnd Bergmann Signed-off-by: Russell King --- arch/arm/lib/Makefile | 2 +- arch/arm/lib/memzero.S | 137 ------------------------------------------------- 2 files changed, 1 insertion(+), 138 deletions(-) delete mode 100644 arch/arm/lib/memzero.S (limited to 'arch/arm/lib') diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile index 4cb0b9624d8f..ad25fd1872c7 100644 --- 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 index 0eded952e089..000000000000 --- 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 -#include -#include - - .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) -- cgit v1.2.3