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diff --git a/src/runtime/internal/atomic/atomic_riscv64.s b/src/runtime/internal/atomic/atomic_riscv64.s
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+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// RISC-V's atomic operations have two bits, aq ("acquire") and rl ("release"),
+// which may be toggled on and off. Their precise semantics are defined in
+// section 6.3 of the specification, but the basic idea is as follows:
+//
+//   - If neither aq nor rl is set, the CPU may reorder the atomic arbitrarily.
+//     It guarantees only that it will execute atomically.
+//
+//   - If aq is set, the CPU may move the instruction backward, but not forward.
+//
+//   - If rl is set, the CPU may move the instruction forward, but not backward.
+//
+//   - If both are set, the CPU may not reorder the instruction at all.
+//
+// These four modes correspond to other well-known memory models on other CPUs.
+// On ARM, aq corresponds to a dmb ishst, aq+rl corresponds to a dmb ish. On
+// Intel, aq corresponds to an lfence, rl to an sfence, and aq+rl to an mfence
+// (or a lock prefix).
+//
+// Go's memory model requires that
+//   - if a read happens after a write, the read must observe the write, and
+//     that
+//   - if a read happens concurrently with a write, the read may observe the
+//     write.
+// aq is sufficient to guarantee this, so that's what we use here. (This jibes
+// with ARM, which uses dmb ishst.)
+
+#include "textflag.h"
+
+// Atomically:
+//      if(*val == *old){
+//              *val = new;
+//              return 1;
+//      } else {
+//              return 0;
+//      }
+
+TEXT ·Cas(SB), NOSPLIT, $0-17
+	MOV	ptr+0(FP), A0
+	MOVW	old+8(FP), A1
+	MOVW	new+12(FP), A2
+cas_again:
+	LRW	(A0), A3
+	BNE	A3, A1, cas_fail
+	SCW	A2, (A0), A4
+	BNE	A4, ZERO, cas_again
+	MOV	$1, A0
+	MOVB	A0, ret+16(FP)
+	RET
+cas_fail:
+	MOV	$0, A0
+	MOV	A0, ret+16(FP)
+	RET
+
+// func Cas64(ptr *uint64, old, new uint64) bool
+TEXT ·Cas64(SB), NOSPLIT, $0-25
+	MOV	ptr+0(FP), A0
+	MOV	old+8(FP), A1
+	MOV	new+16(FP), A2
+cas_again:
+	LRD	(A0), A3
+	BNE	A3, A1, cas_fail
+	SCD	A2, (A0), A4
+	BNE	A4, ZERO, cas_again
+	MOV	$1, A0
+	MOVB	A0, ret+24(FP)
+	RET
+cas_fail:
+	MOVB	ZERO, ret+24(FP)
+	RET
+
+// func Load(ptr *uint32) uint32
+TEXT ·Load(SB),NOSPLIT|NOFRAME,$0-12
+	MOV	ptr+0(FP), A0
+	LRW	(A0), A0
+	MOVW	A0, ret+8(FP)
+	RET
+
+// func Load8(ptr *uint8) uint8
+TEXT ·Load8(SB),NOSPLIT|NOFRAME,$0-9
+	MOV	ptr+0(FP), A0
+	FENCE
+	MOVBU	(A0), A1
+	FENCE
+	MOVB	A1, ret+8(FP)
+	RET
+
+// func Load64(ptr *uint64) uint64
+TEXT ·Load64(SB),NOSPLIT|NOFRAME,$0-16
+	MOV	ptr+0(FP), A0
+	LRD	(A0), A0
+	MOV	A0, ret+8(FP)
+	RET
+
+// func Store(ptr *uint32, val uint32)
+TEXT ·Store(SB), NOSPLIT, $0-12
+	MOV	ptr+0(FP), A0
+	MOVW	val+8(FP), A1
+	AMOSWAPW A1, (A0), ZERO
+	RET
+
+// func Store8(ptr *uint8, val uint8)
+TEXT ·Store8(SB), NOSPLIT, $0-9
+	MOV	ptr+0(FP), A0
+	MOVBU	val+8(FP), A1
+	FENCE
+	MOVB	A1, (A0)
+	FENCE
+	RET
+
+// func Store64(ptr *uint64, val uint64)
+TEXT ·Store64(SB), NOSPLIT, $0-16
+	MOV	ptr+0(FP), A0
+	MOV	val+8(FP), A1
+	AMOSWAPD A1, (A0), ZERO
+	RET
+
+TEXT ·Casp1(SB), NOSPLIT, $0-25
+	JMP	·Cas64(SB)
+
+TEXT ·Casuintptr(SB),NOSPLIT,$0-25
+	JMP	·Cas64(SB)
+
+TEXT ·CasRel(SB), NOSPLIT, $0-17
+	JMP	·Cas(SB)
+
+TEXT ·Loaduintptr(SB),NOSPLIT,$0-16
+	JMP	·Load64(SB)
+
+TEXT ·Storeuintptr(SB),NOSPLIT,$0-16
+	JMP	·Store64(SB)
+
+TEXT ·Loaduint(SB),NOSPLIT,$0-16
+	JMP ·Loaduintptr(SB)
+
+TEXT ·Loadint64(SB),NOSPLIT,$0-16
+	JMP ·Loaduintptr(SB)
+
+TEXT ·Xaddint64(SB),NOSPLIT,$0-24
+	MOV	ptr+0(FP), A0
+	MOV	delta+8(FP), A1
+	AMOADDD A1, (A0), A0
+	ADD	A0, A1, A0
+	MOVW	A0, ret+16(FP)
+	RET
+
+TEXT ·LoadAcq(SB),NOSPLIT|NOFRAME,$0-12
+	JMP	·Load(SB)
+
+TEXT ·LoadAcq64(SB),NOSPLIT|NOFRAME,$0-16
+	JMP	·Load64(SB)
+
+TEXT ·LoadAcquintptr(SB),NOSPLIT|NOFRAME,$0-16
+	JMP	·Load64(SB)
+
+// func Loadp(ptr unsafe.Pointer) unsafe.Pointer
+TEXT ·Loadp(SB),NOSPLIT,$0-16
+	JMP	·Load64(SB)
+
+// func StorepNoWB(ptr unsafe.Pointer, val unsafe.Pointer)
+TEXT ·StorepNoWB(SB), NOSPLIT, $0-16
+	JMP	·Store64(SB)
+
+TEXT ·StoreRel(SB), NOSPLIT, $0-12
+	JMP	·Store(SB)
+
+TEXT ·StoreRel64(SB), NOSPLIT, $0-16
+	JMP	·Store64(SB)
+
+TEXT ·StoreReluintptr(SB), NOSPLIT, $0-16
+	JMP	·Store64(SB)
+
+// func Xchg(ptr *uint32, new uint32) uint32
+TEXT ·Xchg(SB), NOSPLIT, $0-20
+	MOV	ptr+0(FP), A0
+	MOVW	new+8(FP), A1
+	AMOSWAPW A1, (A0), A1
+	MOVW	A1, ret+16(FP)
+	RET
+
+// func Xchg64(ptr *uint64, new uint64) uint64
+TEXT ·Xchg64(SB), NOSPLIT, $0-24
+	MOV	ptr+0(FP), A0
+	MOV	new+8(FP), A1
+	AMOSWAPD A1, (A0), A1
+	MOV	A1, ret+16(FP)
+	RET
+
+// Atomically:
+//      *val += delta;
+//      return *val;
+
+// func Xadd(ptr *uint32, delta int32) uint32
+TEXT ·Xadd(SB), NOSPLIT, $0-20
+	MOV	ptr+0(FP), A0
+	MOVW	delta+8(FP), A1
+	AMOADDW A1, (A0), A2
+	ADD	A2,A1,A0
+	MOVW	A0, ret+16(FP)
+	RET
+
+// func Xadd64(ptr *uint64, delta int64) uint64
+TEXT ·Xadd64(SB), NOSPLIT, $0-24
+	MOV	ptr+0(FP), A0
+	MOV	delta+8(FP), A1
+	AMOADDD A1, (A0), A2
+	ADD	A2, A1, A0
+	MOV	A0, ret+16(FP)
+	RET
+
+// func Xadduintptr(ptr *uintptr, delta uintptr) uintptr
+TEXT ·Xadduintptr(SB), NOSPLIT, $0-24
+	JMP	·Xadd64(SB)
+
+// func Xchguintptr(ptr *uintptr, new uintptr) uintptr
+TEXT ·Xchguintptr(SB), NOSPLIT, $0-24
+	JMP	·Xchg64(SB)
+
+// func And8(ptr *uint8, val uint8)
+TEXT ·And8(SB), NOSPLIT, $0-9
+	MOV	ptr+0(FP), A0
+	MOVBU	val+8(FP), A1
+	AND	$3, A0, A2
+	AND	$-4, A0
+	SLL	$3, A2
+	XOR	$255, A1
+	SLL	A2, A1
+	XOR	$-1, A1
+	AMOANDW A1, (A0), ZERO
+	RET
+
+// func Or8(ptr *uint8, val uint8)
+TEXT ·Or8(SB), NOSPLIT, $0-9
+	MOV	ptr+0(FP), A0
+	MOVBU	val+8(FP), A1
+	AND	$3, A0, A2
+	AND	$-4, A0
+	SLL	$3, A2
+	SLL	A2, A1
+	AMOORW	A1, (A0), ZERO
+	RET
+
+// func And(ptr *uint32, val uint32)
+TEXT ·And(SB), NOSPLIT, $0-12
+	MOV	ptr+0(FP), A0
+	MOVW	val+8(FP), A1
+	AMOANDW	A1, (A0), ZERO
+	RET
+
+// func Or(ptr *uint32, val uint32)
+TEXT ·Or(SB), NOSPLIT, $0-12
+	MOV	ptr+0(FP), A0
+	MOVW	val+8(FP), A1
+	AMOORW	A1, (A0), ZERO
+	RET