ref: 2b4a488762eb85495d0001cfa689f12b2c746a7a
dir: /sys/src/libc/arm/cas.s/
/* * 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