diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s
index 77f4939b30f..e883f200455 100644
--- a/src/runtime/asm_amd64.s
+++ b/src/runtime/asm_amd64.s
@@ -1011,34 +1011,62 @@ done:
 
 // func memhash(p unsafe.Pointer, h, s uintptr) uintptr
 // hash function using AES hardware instructions
-TEXT runtime·memhash(SB),NOSPLIT,$0-32
+TEXT runtime·memhash<ABIInternal>(SB),NOSPLIT,$0-32
+#ifdef GOEXPERIMENT_regabiargs
+	// AX = ptr to data
+	// BX = seed
+	// CX = size
+#endif
 	CMPB	runtime·useAeshash(SB), $0
 	JEQ	noaes
+#ifndef GOEXPERIMENT_regabiargs
 	MOVQ	p+0(FP), AX	// ptr to data
 	MOVQ	s+16(FP), CX	// size
 	LEAQ	ret+24(FP), DX
+#endif
 	JMP	aeshashbody<>(SB)
 noaes:
-	JMP	runtime·memhashFallback(SB)
+	JMP	runtime·memhashFallback<ABIInternal>(SB)
 
 // func strhash(p unsafe.Pointer, h uintptr) uintptr
-TEXT runtime·strhash(SB),NOSPLIT,$0-24
+TEXT runtime·strhash<ABIInternal>(SB),NOSPLIT,$0-24
+#ifdef GOEXPERIMENT_regabiargs
+	// AX = ptr to string struct
+	// BX = seed
+#endif
 	CMPB	runtime·useAeshash(SB), $0
 	JEQ	noaes
+#ifndef GOEXPERIMENT_regabiargs
 	MOVQ	p+0(FP), AX	// ptr to string struct
+#endif
 	MOVQ	8(AX), CX	// length of string
 	MOVQ	(AX), AX	// string data
+#ifndef GOEXPERIMENT_regabiargs
 	LEAQ	ret+16(FP), DX
+#endif
 	JMP	aeshashbody<>(SB)
 noaes:
-	JMP	runtime·strhashFallback(SB)
+	JMP	runtime·strhashFallback<ABIInternal>(SB)
 
 // AX: data
+#ifdef GOEXPERIMENT_regabiargs
+// BX: hash seed
+#else
+// h+8(FP): hash seed
+#endif
 // CX: length
+#ifdef GOEXPERIMENT_regabiargs
+// At return: AX = return value
+#else
 // DX: address to put return value
+#endif
 TEXT aeshashbody<>(SB),NOSPLIT,$0-0
 	// Fill an SSE register with our seeds.
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	BX, X0				// 64 bits of per-table hash seed
+#else
 	MOVQ	h+8(FP), X0			// 64 bits of per-table hash seed
+#endif
 	PINSRW	$4, CX, X0			// 16 bits of length
 	PSHUFHW $0, X0, X0			// repeat length 4 times total
 	MOVO	X0, X1				// save unscrambled seed
@@ -1075,7 +1103,11 @@ final1:
 	AESENC	X1, X1	// scramble combo 3 times
 	AESENC	X1, X1
 	AESENC	X1, X1
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	X1, AX	// return X1
+#else
 	MOVQ	X1, (DX)
+#endif
 	RET
 
 endofpage:
@@ -1091,7 +1123,11 @@ endofpage:
 aes0:
 	// Return scrambled input seed
 	AESENC	X0, X0
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	X0, AX	// return X0
+#else
 	MOVQ	X0, (DX)
+#endif
 	RET
 
 aes16:
@@ -1121,7 +1157,11 @@ aes17to32:
 
 	// combine results
 	PXOR	X3, X2
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	X2, AX	// return X2
+#else
 	MOVQ	X2, (DX)
+#endif
 	RET
 
 aes33to64:
@@ -1163,7 +1203,11 @@ aes33to64:
 	PXOR	X6, X4
 	PXOR	X7, X5
 	PXOR	X5, X4
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	X4, AX	// return X4
+#else
 	MOVQ	X4, (DX)
+#endif
 	RET
 
 aes65to128:
@@ -1245,7 +1289,15 @@ aes65to128:
 	PXOR	X10, X8
 	PXOR	X11, X9
 	PXOR	X9, X8
+#ifdef GOEXPERIMENT_regabig
+	// X15 must be zero on return
+	PXOR	X15, X15
+#endif
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	X8, AX	// return X8
+#else
 	MOVQ	X8, (DX)
+#endif
 	RET
 
 aes129plus:
@@ -1361,38 +1413,73 @@ aesloop:
 	PXOR	X10, X8
 	PXOR	X11, X9
 	PXOR	X9, X8
+#ifdef GOEXPERIMENT_regabig
+	// X15 must be zero on return
+	PXOR	X15, X15
+#endif
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	X8, AX	// return X8
+#else
 	MOVQ	X8, (DX)
+#endif
 	RET
 
 // func memhash32(p unsafe.Pointer, h uintptr) uintptr
-TEXT runtime·memhash32(SB),NOSPLIT,$0-24
+// ABIInternal for performance.
+TEXT runtime·memhash32<ABIInternal>(SB),NOSPLIT,$0-24
+#ifdef GOEXPERIMENT_regabiargs
+	// AX = ptr to data
+	// BX = seed
+#endif
 	CMPB	runtime·useAeshash(SB), $0
 	JEQ	noaes
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	BX, X0	// X0 = seed
+#else
 	MOVQ	p+0(FP), AX	// ptr to data
 	MOVQ	h+8(FP), X0	// seed
+#endif
 	PINSRD	$2, (AX), X0	// data
 	AESENC	runtime·aeskeysched+0(SB), X0
 	AESENC	runtime·aeskeysched+16(SB), X0
 	AESENC	runtime·aeskeysched+32(SB), X0
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	X0, AX	// return X0
+#else
 	MOVQ	X0, ret+16(FP)
+#endif
 	RET
 noaes:
-	JMP	runtime·memhash32Fallback(SB)
+	JMP	runtime·memhash32Fallback<ABIInternal>(SB)
 
 // func memhash64(p unsafe.Pointer, h uintptr) uintptr
-TEXT runtime·memhash64(SB),NOSPLIT,$0-24
+// ABIInternal for performance.
+TEXT runtime·memhash64<ABIInternal>(SB),NOSPLIT,$0-24
+#ifdef GOEXPERIMENT_regabiargs
+	// AX = ptr to data
+	// BX = seed
+#else
+#endif
 	CMPB	runtime·useAeshash(SB), $0
 	JEQ	noaes
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	BX, X0	// X0 = seed
+#else
 	MOVQ	p+0(FP), AX	// ptr to data
 	MOVQ	h+8(FP), X0	// seed
+#endif
 	PINSRQ	$1, (AX), X0	// data
 	AESENC	runtime·aeskeysched+0(SB), X0
 	AESENC	runtime·aeskeysched+16(SB), X0
 	AESENC	runtime·aeskeysched+32(SB), X0
+#ifdef GOEXPERIMENT_regabiargs
+	MOVQ	X0, AX	// return X0
+#else
 	MOVQ	X0, ret+16(FP)
+#endif
 	RET
 noaes:
-	JMP	runtime·memhash64Fallback(SB)
+	JMP	runtime·memhash64Fallback<ABIInternal>(SB)
 
 // simple mask to get rid of data in the high part of the register.
 DATA masks<>+0x00(SB)/8, $0x0000000000000000
diff --git a/src/runtime/memclr_amd64.s b/src/runtime/memclr_amd64.s
index 37fe9745b1b..b4bc9988eca 100644
--- a/src/runtime/memclr_amd64.s
+++ b/src/runtime/memclr_amd64.s
@@ -12,9 +12,16 @@
 // See memclrNoHeapPointers Go doc for important implementation constraints.
 
 // func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)
-TEXT runtime·memclrNoHeapPointers(SB), NOSPLIT, $0-16
+// ABIInternal for performance.
+TEXT runtime·memclrNoHeapPointers<ABIInternal>(SB), NOSPLIT, $0-16
+#ifdef GOEXPERIMENT_regabiargs
+	// AX = ptr
+	// BX = n
+	MOVQ	AX, DI	// DI = ptr
+#else
 	MOVQ	ptr+0(FP), DI
 	MOVQ	n+8(FP), BX
+#endif
 	XORQ	AX, AX
 
 	// MOVOU seems always faster than REP STOSQ.
@@ -31,7 +38,9 @@ tail:
 	JE	_8
 	CMPQ	BX, $16
 	JBE	_9through16
-	PXOR	X0, X0
+#ifndef GOEXPERIMENT_regabig
+	PXOR	X15, X15
+#endif
 	CMPQ	BX, $32
 	JBE	_17through32
 	CMPQ	BX, $64
@@ -45,22 +54,22 @@ tail:
 	// TODO: for really big clears, use MOVNTDQ, even without AVX2.
 
 loop:
-	MOVOU	X0, 0(DI)
-	MOVOU	X0, 16(DI)
-	MOVOU	X0, 32(DI)
-	MOVOU	X0, 48(DI)
-	MOVOU	X0, 64(DI)
-	MOVOU	X0, 80(DI)
-	MOVOU	X0, 96(DI)
-	MOVOU	X0, 112(DI)
-	MOVOU	X0, 128(DI)
-	MOVOU	X0, 144(DI)
-	MOVOU	X0, 160(DI)
-	MOVOU	X0, 176(DI)
-	MOVOU	X0, 192(DI)
-	MOVOU	X0, 208(DI)
-	MOVOU	X0, 224(DI)
-	MOVOU	X0, 240(DI)
+	MOVOU	X15, 0(DI)
+	MOVOU	X15, 16(DI)
+	MOVOU	X15, 32(DI)
+	MOVOU	X15, 48(DI)
+	MOVOU	X15, 64(DI)
+	MOVOU	X15, 80(DI)
+	MOVOU	X15, 96(DI)
+	MOVOU	X15, 112(DI)
+	MOVOU	X15, 128(DI)
+	MOVOU	X15, 144(DI)
+	MOVOU	X15, 160(DI)
+	MOVOU	X15, 176(DI)
+	MOVOU	X15, 192(DI)
+	MOVOU	X15, 208(DI)
+	MOVOU	X15, 224(DI)
+	MOVOU	X15, 240(DI)
 	SUBQ	$256, BX
 	ADDQ	$256, DI
 	CMPQ	BX, $256
@@ -141,40 +150,40 @@ _9through16:
 	MOVQ	AX, -8(DI)(BX*1)
 	RET
 _17through32:
-	MOVOU	X0, (DI)
-	MOVOU	X0, -16(DI)(BX*1)
+	MOVOU	X15, (DI)
+	MOVOU	X15, -16(DI)(BX*1)
 	RET
 _33through64:
-	MOVOU	X0, (DI)
-	MOVOU	X0, 16(DI)
-	MOVOU	X0, -32(DI)(BX*1)
-	MOVOU	X0, -16(DI)(BX*1)
+	MOVOU	X15, (DI)
+	MOVOU	X15, 16(DI)
+	MOVOU	X15, -32(DI)(BX*1)
+	MOVOU	X15, -16(DI)(BX*1)
 	RET
 _65through128:
-	MOVOU	X0, (DI)
-	MOVOU	X0, 16(DI)
-	MOVOU	X0, 32(DI)
-	MOVOU	X0, 48(DI)
-	MOVOU	X0, -64(DI)(BX*1)
-	MOVOU	X0, -48(DI)(BX*1)
-	MOVOU	X0, -32(DI)(BX*1)
-	MOVOU	X0, -16(DI)(BX*1)
+	MOVOU	X15, (DI)
+	MOVOU	X15, 16(DI)
+	MOVOU	X15, 32(DI)
+	MOVOU	X15, 48(DI)
+	MOVOU	X15, -64(DI)(BX*1)
+	MOVOU	X15, -48(DI)(BX*1)
+	MOVOU	X15, -32(DI)(BX*1)
+	MOVOU	X15, -16(DI)(BX*1)
 	RET
 _129through256:
-	MOVOU	X0, (DI)
-	MOVOU	X0, 16(DI)
-	MOVOU	X0, 32(DI)
-	MOVOU	X0, 48(DI)
-	MOVOU	X0, 64(DI)
-	MOVOU	X0, 80(DI)
-	MOVOU	X0, 96(DI)
-	MOVOU	X0, 112(DI)
-	MOVOU	X0, -128(DI)(BX*1)
-	MOVOU	X0, -112(DI)(BX*1)
-	MOVOU	X0, -96(DI)(BX*1)
-	MOVOU	X0, -80(DI)(BX*1)
-	MOVOU	X0, -64(DI)(BX*1)
-	MOVOU	X0, -48(DI)(BX*1)
-	MOVOU	X0, -32(DI)(BX*1)
-	MOVOU	X0, -16(DI)(BX*1)
+	MOVOU	X15, (DI)
+	MOVOU	X15, 16(DI)
+	MOVOU	X15, 32(DI)
+	MOVOU	X15, 48(DI)
+	MOVOU	X15, 64(DI)
+	MOVOU	X15, 80(DI)
+	MOVOU	X15, 96(DI)
+	MOVOU	X15, 112(DI)
+	MOVOU	X15, -128(DI)(BX*1)
+	MOVOU	X15, -112(DI)(BX*1)
+	MOVOU	X15, -96(DI)(BX*1)
+	MOVOU	X15, -80(DI)(BX*1)
+	MOVOU	X15, -64(DI)(BX*1)
+	MOVOU	X15, -48(DI)(BX*1)
+	MOVOU	X15, -32(DI)(BX*1)
+	MOVOU	X15, -16(DI)(BX*1)
 	RET
diff --git a/src/runtime/memmove_amd64.s b/src/runtime/memmove_amd64.s
index d91641a8e82..f1e34035962 100644
--- a/src/runtime/memmove_amd64.s
+++ b/src/runtime/memmove_amd64.s
@@ -31,11 +31,20 @@
 // See memmove Go doc for important implementation constraints.
 
 // func memmove(to, from unsafe.Pointer, n uintptr)
-TEXT runtime·memmove(SB), NOSPLIT, $0-24
-
+// ABIInternal for performance.
+TEXT runtime·memmove<ABIInternal>(SB), NOSPLIT, $0-24
+#ifdef GOEXPERIMENT_regabiargs
+	// AX = to
+	// BX = from
+	// CX = n
+	MOVQ	AX, DI
+	MOVQ	BX, SI
+	MOVQ	CX, BX
+#else
 	MOVQ	to+0(FP), DI
 	MOVQ	from+8(FP), SI
 	MOVQ	n+16(FP), BX
+#endif
 
 	// REP instructions have a high startup cost, so we handle small sizes
 	// with some straightline code. The REP MOVSQ instruction is really fast
@@ -244,6 +253,10 @@ move_129through256:
 	MOVOU	X13, -48(DI)(BX*1)
 	MOVOU	X14, -32(DI)(BX*1)
 	MOVOU	X15, -16(DI)(BX*1)
+#ifdef GOEXPERIMENT_regabig
+	// X15 must be zero on return
+	PXOR	X15, X15
+#endif
 	RET
 move_256through2048:
 	SUBQ	$256, BX
@@ -283,6 +296,10 @@ move_256through2048:
 	LEAQ	256(SI), SI
 	LEAQ	256(DI), DI
 	JGE	move_256through2048
+#ifdef GOEXPERIMENT_regabig
+	// X15 must be zero on return
+	PXOR	X15, X15
+#endif
 	JMP	tail
 
 avxUnaligned:
diff --git a/src/runtime/stubs.go b/src/runtime/stubs.go
index f635d942e47..16d75832029 100644
--- a/src/runtime/stubs.go
+++ b/src/runtime/stubs.go
@@ -109,6 +109,9 @@ func reflect_memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr) {
 //go:noescape
 func memmove(to, from unsafe.Pointer, n uintptr)
 
+// Outside assembly calls memmove. Make sure it has ABI wrappers.
+//go:linkname memmove
+
 //go:linkname reflect_memmove reflect.memmove
 func reflect_memmove(to, from unsafe.Pointer, n uintptr) {
 	memmove(to, from, n)