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/*
* int swp(int r, int *p);
* uchar swpb(uchar r, uchar *p);
*
* int cas(uintptr *p, uintptr ov, uintptr nv);
*/
#define LDREX(a,r) WORD $(0xe<<28|0x01900f9f | (a)<<16 | (r)<<12)
#define STREX(a,v,r) WORD $(0xe<<28|0x01800f90 | (a)<<16 | (r)<<12 | (v)<<0)
TEXT cas+0(SB),0,$12 /* r0 holds p */
MOVW ov+4(FP), R1
MOVW nv+8(FP), R2
spin:
/* LDREX 0(R0),R3 */
LDREX(0,3)
CMP.S R3, R1
BNE fail
/* STREX 0(R0),R2,R4 */
STREX(0,2,4)
CMP.S $0, R4
BNE spin
MOVW $1, R0
RET
fail:
MOVW $0, R0
RET
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