libc/arm: implement _tas() with LDREX/STREX, execute memory barrier on smp systems (zynq)
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cinap_lenrek
parent
5458506881
commit
6506147066
5 changed files with 127 additions and 64 deletions
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@ -1,58 +1,50 @@
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#define CLREX WORD $0xf57ff01f
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#define LDREX(a,r) WORD $(0xe<<28|0x01900f9f | (a)<<16 | (r)<<12)
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/* `The order of operands is from left to right in dataflow order' - asm man */
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#define STREX(v,a,r) WORD $(0xe<<28|0x01800f90 | (a)<<16 | (r)<<12 | (v)<<0)
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/*
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* int cas(ulong *p, ulong ov, ulong nv);
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* int cas32(u32int *p, u32int ov, u32int nv);
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* int cas(uint *p, int ov, int nv);
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* int casp(void **p, void *ov, void *nv);
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* int casl(ulong *p, ulong ov, ulong nv);
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*/
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TEXT cas+0(SB),0,$0 /* r0 holds p */
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TEXT casp+0(SB),0,$0 /* r0 holds p */
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TEXT cas32(SB), 1, $-4
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TEXT cas(SB), 1, $-4
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TEXT casp(SB), 1, $-4
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TEXT casl(SB), 1, $-4
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MOVW ov+4(FP), R1
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MOVW nv+8(FP), R2
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spincas:
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LDREX(0,3) /* LDREX 0(R0),R3 */
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LDREX (R0), R3
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CMP.S R3, R1
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BNE fail
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STREX(2,0,4) /* STREX 0(R0),R2,R4 */
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STREX R2, (R0), R4
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CMP.S $0, R4
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BNE spincas
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MOVW $1, R0
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RET
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MOVW _barrier(SB), R5
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B (R5)
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fail:
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CLREX
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MOVW $0, R0
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RET
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TEXT _xinc(SB), $0 /* void _xinc(long *); */
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TEXT ainc(SB), $0 /* long ainc(long *); */
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TEXT _xinc(SB), 1, $-4 /* void _xinc(long *); */
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TEXT ainc(SB), 1, $-4 /* long ainc(long *); */
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spinainc:
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LDREX(0,3) /* LDREX 0(R0),R3 */
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LDREX (R0), R3
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ADD $1,R3
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STREX(3,0,4) /* STREX 0(R0),R3,R4 */
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STREX R3, (R0), R4
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CMP.S $0, R4
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BNE spinainc
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MOVW R3, R0
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RET
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MOVW _barrier(SB), R5
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B (R5)
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TEXT _xdec(SB), $0 /* long _xdec(long *); */
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TEXT adec(SB), $0 /* long adec(long *); */
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TEXT _xdec(SB), 1, $-4 /* long _xdec(long *); */
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TEXT adec(SB), 1, $-4 /* long adec(long *); */
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spinadec:
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LDREX(0,3) /* LDREX 0(R0),R3 */
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LDREX (R0), R3
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SUB $1,R3
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STREX(3,0,4) /* STREX 0(R0),R3,R4 */
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STREX R3, (R0), R4
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CMP.S $0, R4
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BNE spinadec
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MOVW R3, R0
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RET
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TEXT loadlinked(SB), $0 /* long loadlinked(long *); */
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LDREX(0,0) /* LDREX 0(R0),R0 */
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RET
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TEXT storecond(SB), $0 /* int storecond(long *, long); */
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MOVW ov+4(FP), R3
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STREX(3,0,0) /* STREX 0(R0),R3,R0 */
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RSB $1, R0
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RET
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MOVW _barrier(SB), R5
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B (R5)
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@ -1,28 +0,0 @@
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/*
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* int swp(int r, int *p);
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* uchar swpb(uchar r, uchar *p);
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*
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* int cas(uintptr *p, uintptr ov, uintptr nv);
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*/
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#define LDREX(a,r) WORD $(0xe<<28|0x01900f9f | (a)<<16 | (r)<<12)
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#define STREX(a,v,r) WORD $(0xe<<28|0x01800f90 | (a)<<16 | (r)<<12 | (v)<<0)
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TEXT cas+0(SB),0,$12 /* r0 holds p */
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MOVW ov+4(FP), R1
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MOVW nv+8(FP), R2
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spin:
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/* LDREX 0(R0),R3 */
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LDREX(0,3)
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CMP.S R3, R1
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BNE fail
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/* STREX 0(R0),R2,R4 */
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STREX(0,2,4)
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CMP.S $0, R4
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BNE spin
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MOVW $1, R0
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RET
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fail:
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MOVW $0, R0
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RET
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89
sys/src/libc/arm/lock.c
Normal file
89
sys/src/libc/arm/lock.c
Normal file
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@ -0,0 +1,89 @@
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#include <u.h>
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#include <libc.h>
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static long lockinit(long);
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/*
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* barrier is called from atom.s and tas.s assembly
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* to execute memory barrier.
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*/
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long (*_barrier)(long) = lockinit;
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static int
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cpus(void)
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{
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char buf[256], *p;
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int f, n;
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f = open("#c/sysstat", OREAD);
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if(f < 0)
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return -1;
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n = read(f, buf, sizeof(buf)-1);
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close(f);
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if(n <= 0)
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return -1;
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buf[n] = '\0';
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n = 0;
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p = buf;
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while(*p != '\0'){
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if(*p == '\n')
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n++;
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p++;
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}
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return n;
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}
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long _dmb(long);
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static long
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_nop(long r0)
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{
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return r0;
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}
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static long
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lockinit(long r0)
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{
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if(cpus() > 1)
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_barrier = _dmb;
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else
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_barrier = _nop;
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return (*_barrier)(r0);
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}
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void
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lock(Lock *lk)
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{
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int i;
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/* once fast */
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if(!_tas(&lk->val))
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return;
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/* a thousand times pretty fast */
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for(i=0; i<1000; i++){
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if(!_tas(&lk->val))
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return;
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sleep(0);
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}
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/* now nice and slow */
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for(i=0; i<1000; i++){
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if(!_tas(&lk->val))
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return;
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sleep(100);
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}
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/* take your time */
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while(_tas(&lk->val))
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sleep(1000);
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}
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int
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canlock(Lock *lk)
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{
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return _tas(&lk->val) == 0;
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}
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void
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unlock(Lock *lk)
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{
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lk->val = (*_barrier)(0);
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}
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@ -23,6 +23,7 @@ CFILES=\
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cycles.c\
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notejmp.c\
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vlrt.c\
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lock.c\
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HFILES=/sys/include/libc.h
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@ -1,5 +1,14 @@
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TEXT _tas(SB), 1, $-4
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MOVW R0,R1
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MOVW $1,R0
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SWPW R0,(R1) /* fix: deprecated in armv7 */
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TEXT _tas(SB), 1, $-4
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MOVW $1, R2
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_tas1:
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LDREX (R0), R1
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STREX R2, (R0), R3
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CMP.S $0, R3
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BNE _tas1
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MOVW R1, R0
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MOVW _barrier(SB), R4
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B (R4)
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TEXT _dmb(SB), 1, $-4
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WORD $0xf57ff05f
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RET
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