runtime: add wasm bulk memory operations

The existing implementation uses loops to implement bulk memory
operations such as memcpy and memclr. Now that bulk memory operations
have been standardized and are implemented in all major browsers and
engines (see https://webassembly.org/roadmap/), we should use them
to improve performance.

Updates #28360

Change-Id: I28df0e0350287d5e7e1d1c09a4064ea1054e7575
Reviewed-on: https://go-review.googlesource.com/c/go/+/444935
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Richard Musiol <neelance@gmail.com>
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Richard Musiol <neelance@gmail.com>
Reviewed-by: Richard Musiol <neelance@gmail.com>

15 files changed, 59 insertions, 347 deletions

diff --git a/src/cmd/compile/internal/ir/symtab.go b/src/cmd/compile/internal/ir/symtab.go
index 2c89e677b4..bde7a4cfe4 100644
--- a/src/cmd/compile/internal/ir/symtab.go
+++ b/src/cmd/compile/internal/ir/symtab.go
@@ -58,10 +58,6 @@ var Syms struct {
 	// Wasm
 	WasmDiv *obj.LSym
 	// Wasm
-	WasmMove *obj.LSym
-	// Wasm
-	WasmZero *obj.LSym
-	// Wasm
 	WasmTruncS *obj.LSym
 	// Wasm
 	WasmTruncU *obj.LSym
diff --git a/src/cmd/compile/internal/ssa/_gen/Wasm.rules b/src/cmd/compile/internal/ssa/_gen/Wasm.rules
index 9e683b116c..a9ed82e456 100644
--- a/src/cmd/compile/internal/ssa/_gen/Wasm.rules
+++ b/src/cmd/compile/internal/ssa/_gen/Wasm.rules
@@ -234,24 +234,9 @@
 	(I64Store [s-8] dst (I64Load [s-8] src mem)
 		(I64Store dst (I64Load src mem) mem))
 
-// Adjust moves to be a multiple of 16 bytes.
-(Move [s] dst src mem)
-	&& s > 16 && s%16 != 0 && s%16 <= 8 =>
-	(Move [s-s%16]
-		(OffPtr <dst.Type> dst [s%16])
-		(OffPtr <src.Type> src [s%16])
-		(I64Store dst (I64Load src mem) mem))
-(Move [s] dst src mem)
-	&& s > 16 && s%16 != 0 && s%16 > 8 =>
-	(Move [s-s%16]
-		(OffPtr <dst.Type> dst [s%16])
-		(OffPtr <src.Type> src [s%16])
-		(I64Store [8] dst (I64Load [8] src mem)
-			(I64Store dst (I64Load src mem) mem)))
-
 // Large copying uses helper.
-(Move [s] dst src mem) && s%8 == 0 && logLargeCopy(v, s) =>
-	(LoweredMove [s/8] dst src mem)
+(Move [s] dst src mem) && logLargeCopy(v, s) =>
+	(LoweredMove [s] dst src mem)
 
 // Lowering Zero instructions
 (Zero [0] _ mem) => mem
@@ -274,7 +259,7 @@
 		(I64Store32 destptr (I64Const [0]) mem))
 
 // Strip off any fractional word zeroing.
-(Zero [s] destptr mem) && s%8 != 0 && s > 8 =>
+(Zero [s] destptr mem) && s%8 != 0 && s > 8 && s < 32 =>
 	(Zero [s-s%8] (OffPtr <destptr.Type> destptr [s%8])
 		(I64Store destptr (I64Const [0]) mem))
 
@@ -293,8 +278,8 @@
 				(I64Store destptr (I64Const [0]) mem))))
 
 // Large zeroing uses helper.
-(Zero [s] destptr mem) && s%8 == 0 && s > 32 =>
-	(LoweredZero [s/8] destptr mem)
+(Zero [s] destptr mem) =>
+	(LoweredZero [s] destptr mem)
 
 // Lowering constants
 (Const64 ...) => (I64Const ...)
diff --git a/src/cmd/compile/internal/ssa/_gen/WasmOps.go b/src/cmd/compile/internal/ssa/_gen/WasmOps.go
index 33529e729d..cd127b5f06 100644
--- a/src/cmd/compile/internal/ssa/_gen/WasmOps.go
+++ b/src/cmd/compile/internal/ssa/_gen/WasmOps.go
@@ -126,8 +126,8 @@ func init() {
 		{name: "LoweredInterCall", argLength: 2, reg: regInfo{inputs: []regMask{gp}, clobbers: callerSave}, aux: "CallOff", call: true},          // call fn by pointer. arg0=codeptr, arg1=mem, auxint=argsize, returns mem
 
 		{name: "LoweredAddr", argLength: 1, reg: gp11, aux: "SymOff", rematerializeable: true, symEffect: "Addr"}, // returns base+aux+auxint, arg0=base
-		{name: "LoweredMove", argLength: 3, reg: regInfo{inputs: []regMask{gp, gp}}, aux: "Int64"},                // large move. arg0=dst, arg1=src, arg2=mem, auxint=len/8, returns mem
-		{name: "LoweredZero", argLength: 2, reg: regInfo{inputs: []regMask{gp}}, aux: "Int64"},                    // large zeroing. arg0=start, arg1=mem, auxint=len/8, returns mem
+		{name: "LoweredMove", argLength: 3, reg: regInfo{inputs: []regMask{gp, gp}}, aux: "Int64"},                // large move. arg0=dst, arg1=src, arg2=mem, auxint=len, returns mem
+		{name: "LoweredZero", argLength: 2, reg: regInfo{inputs: []regMask{gp}}, aux: "Int64"},                    // large zeroing. arg0=start, arg1=mem, auxint=len, returns mem
 
 		{name: "LoweredGetClosurePtr", reg: gp01},                                                                          // returns wasm.REG_CTXT, the closure pointer
 		{name: "LoweredGetCallerPC", reg: gp01, rematerializeable: true},                                                   // returns the PC of the caller of the current function
diff --git a/src/cmd/compile/internal/ssa/rewriteWasm.go b/src/cmd/compile/internal/ssa/rewriteWasm.go
index 5b7f4a8e45..a5be7922a0 100644
--- a/src/cmd/compile/internal/ssa/rewriteWasm.go
+++ b/src/cmd/compile/internal/ssa/rewriteWasm.go
@@ -2141,76 +2141,18 @@ func rewriteValueWasm_OpMove(v *Value) bool {
 		return true
 	}
 	// match: (Move [s] dst src mem)
-	// cond: s > 16 && s%16 != 0 && s%16 <= 8
-	// result: (Move [s-s%16] (OffPtr <dst.Type> dst [s%16]) (OffPtr <src.Type> src [s%16]) (I64Store dst (I64Load src mem) mem))
+	// cond: logLargeCopy(v, s)
+	// result: (LoweredMove [s] dst src mem)
 	for {
 		s := auxIntToInt64(v.AuxInt)
 		dst := v_0
 		src := v_1
 		mem := v_2
-		if !(s > 16 && s%16 != 0 && s%16 <= 8) {
-			break
-		}
-		v.reset(OpMove)
-		v.AuxInt = int64ToAuxInt(s - s%16)
-		v0 := b.NewValue0(v.Pos, OpOffPtr, dst.Type)
-		v0.AuxInt = int64ToAuxInt(s % 16)
-		v0.AddArg(dst)
-		v1 := b.NewValue0(v.Pos, OpOffPtr, src.Type)
-		v1.AuxInt = int64ToAuxInt(s % 16)
-		v1.AddArg(src)
-		v2 := b.NewValue0(v.Pos, OpWasmI64Store, types.TypeMem)
-		v3 := b.NewValue0(v.Pos, OpWasmI64Load, typ.UInt64)
-		v3.AddArg2(src, mem)
-		v2.AddArg3(dst, v3, mem)
-		v.AddArg3(v0, v1, v2)
-		return true
-	}
-	// match: (Move [s] dst src mem)
-	// cond: s > 16 && s%16 != 0 && s%16 > 8
-	// result: (Move [s-s%16] (OffPtr <dst.Type> dst [s%16]) (OffPtr <src.Type> src [s%16]) (I64Store [8] dst (I64Load [8] src mem) (I64Store dst (I64Load src mem) mem)))
-	for {
-		s := auxIntToInt64(v.AuxInt)
-		dst := v_0
-		src := v_1
-		mem := v_2
-		if !(s > 16 && s%16 != 0 && s%16 > 8) {
-			break
-		}
-		v.reset(OpMove)
-		v.AuxInt = int64ToAuxInt(s - s%16)
-		v0 := b.NewValue0(v.Pos, OpOffPtr, dst.Type)
-		v0.AuxInt = int64ToAuxInt(s % 16)
-		v0.AddArg(dst)
-		v1 := b.NewValue0(v.Pos, OpOffPtr, src.Type)
-		v1.AuxInt = int64ToAuxInt(s % 16)
-		v1.AddArg(src)
-		v2 := b.NewValue0(v.Pos, OpWasmI64Store, types.TypeMem)
-		v2.AuxInt = int64ToAuxInt(8)
-		v3 := b.NewValue0(v.Pos, OpWasmI64Load, typ.UInt64)
-		v3.AuxInt = int64ToAuxInt(8)
-		v3.AddArg2(src, mem)
-		v4 := b.NewValue0(v.Pos, OpWasmI64Store, types.TypeMem)
-		v5 := b.NewValue0(v.Pos, OpWasmI64Load, typ.UInt64)
-		v5.AddArg2(src, mem)
-		v4.AddArg3(dst, v5, mem)
-		v2.AddArg3(dst, v3, v4)
-		v.AddArg3(v0, v1, v2)
-		return true
-	}
-	// match: (Move [s] dst src mem)
-	// cond: s%8 == 0 && logLargeCopy(v, s)
-	// result: (LoweredMove [s/8] dst src mem)
-	for {
-		s := auxIntToInt64(v.AuxInt)
-		dst := v_0
-		src := v_1
-		mem := v_2
-		if !(s%8 == 0 && logLargeCopy(v, s)) {
+		if !(logLargeCopy(v, s)) {
 			break
 		}
 		v.reset(OpWasmLoweredMove)
-		v.AuxInt = int64ToAuxInt(s / 8)
+		v.AuxInt = int64ToAuxInt(s)
 		v.AddArg3(dst, src, mem)
 		return true
 	}
@@ -4656,13 +4598,13 @@ func rewriteValueWasm_OpZero(v *Value) bool {
 		return true
 	}
 	// match: (Zero [s] destptr mem)
-	// cond: s%8 != 0 && s > 8
+	// cond: s%8 != 0 && s > 8 && s < 32
 	// result: (Zero [s-s%8] (OffPtr <destptr.Type> destptr [s%8]) (I64Store destptr (I64Const [0]) mem))
 	for {
 		s := auxIntToInt64(v.AuxInt)
 		destptr := v_0
 		mem := v_1
-		if !(s%8 != 0 && s > 8) {
+		if !(s%8 != 0 && s > 8 && s < 32) {
 			break
 		}
 		v.reset(OpZero)
@@ -4738,21 +4680,16 @@ func rewriteValueWasm_OpZero(v *Value) bool {
 		return true
 	}
 	// match: (Zero [s] destptr mem)
-	// cond: s%8 == 0 && s > 32
-	// result: (LoweredZero [s/8] destptr mem)
+	// result: (LoweredZero [s] destptr mem)
 	for {
 		s := auxIntToInt64(v.AuxInt)
 		destptr := v_0
 		mem := v_1
-		if !(s%8 == 0 && s > 32) {
-			break
-		}
 		v.reset(OpWasmLoweredZero)
-		v.AuxInt = int64ToAuxInt(s / 8)
+		v.AuxInt = int64ToAuxInt(s)
 		v.AddArg2(destptr, mem)
 		return true
 	}
-	return false
 }
 func rewriteValueWasm_OpZeroExt16to32(v *Value) bool {
 	v_0 := v.Args[0]
diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index 871530d7d5..7966cd4860 100644
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -206,8 +206,6 @@ func InitConfig() {
 	}
 
 	// Wasm (all asm funcs with special ABIs)
-	ir.Syms.WasmMove = typecheck.LookupRuntimeVar("wasmMove")
-	ir.Syms.WasmZero = typecheck.LookupRuntimeVar("wasmZero")
 	ir.Syms.WasmDiv = typecheck.LookupRuntimeVar("wasmDiv")
 	ir.Syms.WasmTruncS = typecheck.LookupRuntimeVar("wasmTruncS")
 	ir.Syms.WasmTruncU = typecheck.LookupRuntimeVar("wasmTruncU")
diff --git a/src/cmd/compile/internal/wasm/ssa.go b/src/cmd/compile/internal/wasm/ssa.go
index 765051c944..27ba98c9cd 100644
--- a/src/cmd/compile/internal/wasm/ssa.go
+++ b/src/cmd/compile/internal/wasm/ssa.go
@@ -149,14 +149,13 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		getValue32(s, v.Args[0])
 		getValue32(s, v.Args[1])
 		i32Const(s, int32(v.AuxInt))
-		p := s.Prog(wasm.ACall)
-		p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: ir.Syms.WasmMove}
+		s.Prog(wasm.AMemoryCopy)
 
 	case ssa.OpWasmLoweredZero:
 		getValue32(s, v.Args[0])
+		i32Const(s, 0)
 		i32Const(s, int32(v.AuxInt))
-		p := s.Prog(wasm.ACall)
-		p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: ir.Syms.WasmZero}
+		s.Prog(wasm.AMemoryFill)
 
 	case ssa.OpWasmLoweredNilCheck:
 		getValue64(s, v.Args[0])
diff --git a/src/cmd/internal/obj/wasm/a.out.go b/src/cmd/internal/obj/wasm/a.out.go
index 72ecaa9286..83ce0a6738 100644
--- a/src/cmd/internal/obj/wasm/a.out.go
+++ b/src/cmd/internal/obj/wasm/a.out.go
@@ -231,6 +231,17 @@ const (
 	AI64TruncSatF64S
 	AI64TruncSatF64U
 
+	AMemoryInit
+	ADataDrop
+	AMemoryCopy
+	AMemoryFill
+	ATableInit
+	AElemDrop
+	ATableCopy
+	ATableGrow
+	ATableSize
+	ATableFill
+
 	ALast // Sentinel: End of low-level WebAssembly instructions.
 
 	ARESUMEPOINT
diff --git a/src/cmd/internal/obj/wasm/anames.go b/src/cmd/internal/obj/wasm/anames.go
index 94123849ee..c9bc15d270 100644
--- a/src/cmd/internal/obj/wasm/anames.go
+++ b/src/cmd/internal/obj/wasm/anames.go
@@ -195,6 +195,16 @@ var Anames = []string{
 	"I64TruncSatF32U",
 	"I64TruncSatF64S",
 	"I64TruncSatF64U",
+	"MemoryInit",
+	"DataDrop",
+	"MemoryCopy",
+	"MemoryFill",
+	"TableInit",
+	"ElemDrop",
+	"TableCopy",
+	"TableGrow",
+	"TableSize",
+	"TableFill",
 	"Last",
 	"RESUMEPOINT",
 	"CALLNORESUME",
diff --git a/src/cmd/internal/obj/wasm/wasmobj.go b/src/cmd/internal/obj/wasm/wasmobj.go
index 59b2e7bddc..9b0aabe919 100644
--- a/src/cmd/internal/obj/wasm/wasmobj.go
+++ b/src/cmd/internal/obj/wasm/wasmobj.go
@@ -799,8 +799,6 @@ var notUsePC_B = map[string]bool{
 	"wasm_export_resume":     true,
 	"wasm_export_getsp":      true,
 	"wasm_pc_f_loop":         true,
-	"runtime.wasmMove":       true,
-	"runtime.wasmZero":       true,
 	"runtime.wasmDiv":        true,
 	"runtime.wasmTruncS":     true,
 	"runtime.wasmTruncU":     true,
@@ -844,7 +842,7 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
 	// Some functions use a special calling convention.
 	switch s.Name {
 	case "_rt0_wasm_js", "wasm_export_run", "wasm_export_resume", "wasm_export_getsp", "wasm_pc_f_loop",
-		"runtime.wasmMove", "runtime.wasmZero", "runtime.wasmDiv", "runtime.wasmTruncS", "runtime.wasmTruncU", "memeqbody":
+		"runtime.wasmDiv", "runtime.wasmTruncS", "runtime.wasmTruncU", "memeqbody":
 		varDecls = []*varDecl{}
 		useAssemblyRegMap()
 	case "memchr", "memcmp":
@@ -1088,7 +1086,11 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
 			writeUleb128(w, align(p.As))
 			writeUleb128(w, uint64(p.To.Offset))
 
-		case ACurrentMemory, AGrowMemory:
+		case ACurrentMemory, AGrowMemory, AMemoryFill:
+			w.WriteByte(0x00)
+
+		case AMemoryCopy:
+			w.WriteByte(0x00)
 			w.WriteByte(0x00)
 
 		}
diff --git a/src/cmd/link/internal/wasm/asm.go b/src/cmd/link/internal/wasm/asm.go
index 0aa065f99d..99018c8079 100644
--- a/src/cmd/link/internal/wasm/asm.go
+++ b/src/cmd/link/internal/wasm/asm.go
@@ -60,8 +60,6 @@ var wasmFuncTypes = map[string]*wasmFuncType{
 	"wasm_export_resume":     {Params: []byte{}},                                         //
 	"wasm_export_getsp":      {Results: []byte{I32}},                                     // sp
 	"wasm_pc_f_loop":         {Params: []byte{}},                                         //
-	"runtime.wasmMove":       {Params: []byte{I32, I32, I32}},                            // dst, src, len
-	"runtime.wasmZero":       {Params: []byte{I32, I32}},                                 // ptr, len
 	"runtime.wasmDiv":        {Params: []byte{I64, I64}, Results: []byte{I64}},           // x, y -> x/y
 	"runtime.wasmTruncS":     {Params: []byte{F64}, Results: []byte{I64}},                // x -> int(x)
 	"runtime.wasmTruncU":     {Params: []byte{F64}, Results: []byte{I64}},                // x -> uint(x)
diff --git a/src/runtime/asm_wasm.s b/src/runtime/asm_wasm.s
index d885da6e70..e075c72598 100644
--- a/src/runtime/asm_wasm.s
+++ b/src/runtime/asm_wasm.s
@@ -320,10 +320,8 @@ TEXT NAME(SB), WRAPPER, $MAXSIZE-48; \
 		I64Load stackArgs+16(FP); \
 		I32WrapI64; \
 		I64Load stackArgsSize+24(FP); \
-		I64Const $3; \
-		I64ShrU; \
 		I32WrapI64; \
-		Call runtime·wasmMove(SB); \
+		MemoryCopy; \
 	End; \
 	\
 	MOVD f+8(FP), CTXT; \
diff --git a/src/runtime/memclr_wasm.s b/src/runtime/memclr_wasm.s
index 5a053049f8..19d08ffbee 100644
--- a/src/runtime/memclr_wasm.s
+++ b/src/runtime/memclr_wasm.s
@@ -11,29 +11,10 @@ TEXT runtime·memclrNoHeapPointers(SB), NOSPLIT, $0-16
 	MOVD ptr+0(FP), R0
 	MOVD n+8(FP), R1
 
-loop:
-	Loop
-		Get R1
-		I64Eqz
-		If
-			RET
-		End
-
-		Get R0
-		I32WrapI64
-		I64Const $0
-		I64Store8 $0
-
-		Get R0
-		I64Const $1
-		I64Add
-		Set R0
-
-		Get R1
-		I64Const $1
-		I64Sub
-		Set R1
-
-		Br loop
-	End
-	UNDEF
+	Get R0
+	I32WrapI64
+	I32Const $0
+	Get R1
+	I32WrapI64
+	MemoryFill
+	RET
diff --git a/src/runtime/memmove_wasm.s b/src/runtime/memmove_wasm.s
index 8525fea35e..1be8487a99 100644
--- a/src/runtime/memmove_wasm.s
+++ b/src/runtime/memmove_wasm.s
@@ -13,142 +13,10 @@ TEXT runtime·memmove(SB), NOSPLIT, $0-24
 	MOVD n+16(FP), R2
 
 	Get R0
+	I32WrapI64
 	Get R1
-	I64LtU
-	If // forward
-exit_forward_64:
-		Block
-loop_forward_64:
-			Loop
-				Get R2
-				I64Const $8
-				I64LtU
-				BrIf exit_forward_64
-
-				MOVD 0(R1), 0(R0)
-
-				Get R0
-				I64Const $8
-				I64Add
-				Set R0
-
-				Get R1
-				I64Const $8
-				I64Add
-				Set R1
-
-				Get R2
-				I64Const $8
-				I64Sub
-				Set R2
-
-				Br loop_forward_64
-			End
-		End
-
-loop_forward_8:
-		Loop
-			Get R2
-			I64Eqz
-			If
-				RET
-			End
-
-			Get R0
-			I32WrapI64
-			I64Load8U (R1)
-			I64Store8 $0
-
-			Get R0
-			I64Const $1
-			I64Add
-			Set R0
-
-			Get R1
-			I64Const $1
-			I64Add
-			Set R1
-
-			Get R2
-			I64Const $1
-			I64Sub
-			Set R2
-
-			Br loop_forward_8
-		End
-
-	Else
-		// backward
-		Get R0
-		Get R2
-		I64Add
-		Set R0
-
-		Get R1
-		Get R2
-		I64Add
-		Set R1
-
-exit_backward_64:
-		Block
-loop_backward_64:
-			Loop
-				Get R2
-				I64Const $8
-				I64LtU
-				BrIf exit_backward_64
-
-				Get R0
-				I64Const $8
-				I64Sub
-				Set R0
-
-				Get R1
-				I64Const $8
-				I64Sub
-				Set R1
-
-				Get R2
-				I64Const $8
-				I64Sub
-				Set R2
-
-				MOVD 0(R1), 0(R0)
-
-				Br loop_backward_64
-			End
-		End
-
-loop_backward_8:
-		Loop
-			Get R2
-			I64Eqz
-			If
-				RET
-			End
-
-			Get R0
-			I64Const $1
-			I64Sub
-			Set R0
-
-			Get R1
-			I64Const $1
-			I64Sub
-			Set R1
-
-			Get R2
-			I64Const $1
-			I64Sub
-			Set R2
-
-			Get R0
-			I32WrapI64
-			I64Load8U (R1)
-			I64Store8 $0
-
-			Br loop_backward_8
-		End
-	End
-
-	UNDEF
+	I32WrapI64
+	Get R2
+	I32WrapI64
+	MemoryCopy
+	RET
diff --git a/src/runtime/sys_wasm.go b/src/runtime/sys_wasm.go
index e6e7f471ee..bf5756984a 100644
--- a/src/runtime/sys_wasm.go
+++ b/src/runtime/sys_wasm.go
@@ -16,10 +16,6 @@ type m0Stack struct {
 
 var wasmStack m0Stack
 
-func wasmMove()
-
-func wasmZero()
-
 func wasmDiv()
 
 func wasmTruncS()
diff --git a/src/runtime/sys_wasm.s b/src/runtime/sys_wasm.s
index 164dd16ec9..f706e00ab2 100644
--- a/src/runtime/sys_wasm.s
+++ b/src/runtime/sys_wasm.s
@@ -4,73 +4,6 @@
 
 #include "textflag.h"
 
-TEXT runtime·wasmMove(SB), NOSPLIT, $0-0
-loop:
-	Loop
-		// *dst = *src
-		Get R0
-		Get R1
-		I64Load $0
-		I64Store $0
-
-		// n--
-		Get R2
-		I32Const $1
-		I32Sub
-		Tee R2
-
-		// n == 0
-		I32Eqz
-		If
-			Return
-		End
-
-		// dst += 8
-		Get R0
-		I32Const $8
-		I32Add
-		Set R0
-
-		// src += 8
-		Get R1
-		I32Const $8
-		I32Add
-		Set R1
-
-		Br loop
-	End
-	UNDEF
-
-TEXT runtime·wasmZero(SB), NOSPLIT, $0-0
-loop:
-	Loop
-		// *dst = 0
-		Get R0
-		I64Const $0
-		I64Store $0
-
-		// n--
-		Get R1
-		I32Const $1
-		I32Sub
-		Tee R1
-
-		// n == 0
-		I32Eqz
-		If
-			Return
-		End
-
-		// dst += 8
-		Get R0
-		I32Const $8
-		I32Add
-		Set R0
-
-		Br loop
-	End
-	UNDEF
-
 TEXT runtime·wasmDiv(SB), NOSPLIT, $0-0
 	Get R0
 	I64Const $-0x8000000000000000