104 lines
2.0 KiB
ArmAsm
104 lines
2.0 KiB
ArmAsm
// Instruction prefixes: LOCK, REP and REPN. go tool asm encodes each
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// statement as a standalone one-byte instruction with a PC of its own (F0,
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// F3 and F2 respectively); the statement that follows is encoded unaware of
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// it, and nothing validates the pairing. The shapes are the runtime's
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// atomic read-modify-write family and the string moves, every result folded
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// back.
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#include "textflag.h"
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// func cas64(ptr *uint64, old, new uint64) bool
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TEXT ·cas64(SB), NOSPLIT, $0-25
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MOVQ ptr+0(FP), BX
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MOVQ old+8(FP), AX
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MOVQ new+16(FP), CX
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LOCK
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CMPXCHGQ CX, 0(BX)
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SETEQ ret+24(FP)
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RET
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// func casloop(addr *uint64, v uint64) uint64
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// The runtime's Or64 shape: a LOCK inside a branch loop, the backward jump
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// measuring over the prefix statement's own byte.
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TEXT ·casloop(SB), NOSPLIT, $0-24
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MOVQ addr+0(FP), BX
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MOVQ v+8(FP), CX
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loop:
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MOVQ CX, DX
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MOVQ (BX), AX
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ORQ AX, DX
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LOCK
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CMPXCHGQ DX, (BX)
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JNZ loop
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MOVQ AX, ret+16(FP)
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RET
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// func xadd64(p *uint64, v uint64) uint64
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TEXT ·xadd64(SB), NOSPLIT, $0-24
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MOVQ p+0(FP), AX
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MOVQ v+8(FP), BX
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LOCK
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XADDQ BX, (AX)
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MOVQ AX, ret+16(FP)
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RET
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// func xaddw(p *uint16, v uint16) uint16
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TEXT ·xaddw(SB), NOSPLIT, $0-12
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MOVQ p+0(FP), AX
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MOVW v+8(FP), BX
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LOCK
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XADDW BX, (AX)
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MOVW AX, ret+8(FP)
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RET
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// func lockarith(p *uint64)
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TEXT ·lockarith(SB), NOSPLIT, $0-8
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MOVQ p+0(FP), AX
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LOCK
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ORQ CX, (AX)
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LOCK
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ANDL CX, (AX)
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LOCK
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INCQ (AX)
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LOCK
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DECQ (AX)
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LOCK
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ORB BX, (AX)
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RET
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// func repstring(dst, src *byte, n int)
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// The memmove shapes: forward copy by quadwords, backward tails.
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TEXT ·repstring(SB), NOSPLIT, $0-24
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MOVQ dst+0(FP), DI
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MOVQ src+8(FP), SI
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REP
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MOVSQ
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REP
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MOVSB
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REPN
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MOVSB
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REP
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STOSQ
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REP
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STOSB
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RET
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// func pfxlabel()
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// Labels pinned on prefix statements' own bytes: pfx: sits on the LOCK,
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// mid: on the REPN.
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TEXT ·pfxlabel(SB), NOSPLIT, $0-0
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pfx:
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LOCK
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XCHGL BX, (AX)
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JMP done
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mid:
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REPN
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MOVSB
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done:
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REP
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STOSB
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RET
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