cmd/compile: add wasm architecture

This commit adds the wasm architecture to the compile command.
A later commit will contain the corresponding linker changes.

Design doc: https://docs.google.com/document/d/131vjr4DH6JFnb-blm_uRdaC0_Nv3OUwjEY5qVCxCup4

The following files are generated:
- src/cmd/compile/internal/ssa/opGen.go
- src/cmd/compile/internal/ssa/rewriteWasm.go
- src/cmd/internal/obj/wasm/anames.go

Updates #18892

Change-Id: Ifb4a96a3e427aac2362a1c97967d5667450fba3b
Reviewed-on: https://go-review.googlesource.com/103295
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

9 files changed, 1434 insertions, 2 deletions

diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index ea11294000..2fbbf6cb25 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -364,6 +364,7 @@ const (
 	ABaseARM64
 	ABaseMIPS
 	ABaseS390X
+	ABaseWasm
 
 	AllowedOpCodes = 1 << 11            // The number of opcodes available for any given architecture.
 	AMask          = AllowedOpCodes - 1 // AND with this to use the opcode as an array index.
@@ -595,7 +596,7 @@ func (ctxt *Link) Logf(format string, args ...interface{}) {
 // the hardware stack pointer and the local variable area.
 func (ctxt *Link) FixedFrameSize() int64 {
 	switch ctxt.Arch.Family {
-	case sys.AMD64, sys.I386:
+	case sys.AMD64, sys.I386, sys.Wasm:
 		return 0
 	case sys.PPC64:
 		// PIC code on ppc64le requires 32 bytes of stack, and it's easier to
diff --git a/src/cmd/internal/obj/stringer.go b/src/cmd/internal/obj/stringer.go
index c4b3712359..1c7a962e57 100644
--- a/src/cmd/internal/obj/stringer.go
+++ b/src/cmd/internal/obj/stringer.go
@@ -26,7 +26,7 @@ var (
 	pkg    = flag.String("p", "", "package name")
 )
 
-var Are = regexp.MustCompile(`^\tA([A-Z0-9]+)`)
+var Are = regexp.MustCompile(`^\tA([A-Za-z0-9]+)`)
 
 func main() {
 	flag.Parse()
diff --git a/src/cmd/internal/obj/util.go b/src/cmd/internal/obj/util.go
index 89d481e726..98475d00ca 100644
--- a/src/cmd/internal/obj/util.go
+++ b/src/cmd/internal/obj/util.go
@@ -394,6 +394,7 @@ const (
 	RBaseARM64 = 8 * 1024  // range [8k, 13k)
 	RBaseMIPS  = 13 * 1024 // range [13k, 14k)
 	RBaseS390X = 14 * 1024 // range [14k, 15k)
+	RBaseWasm  = 16 * 1024
 )
 
 // RegisterRegister binds a pretty-printer (Rconv) for register
diff --git a/src/cmd/internal/obj/wasm/a.out.go b/src/cmd/internal/obj/wasm/a.out.go
new file mode 100644
index 0000000000..9c04be2609
--- /dev/null
+++ b/src/cmd/internal/obj/wasm/a.out.go
@@ -0,0 +1,288 @@
+// Copyright 2018 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.
+
+package wasm
+
+import "cmd/internal/obj"
+
+//go:generate go run ../stringer.go -i $GOFILE -o anames.go -p wasm
+
+const (
+	/* mark flags */
+	DONE          = 1 << iota
+	PRESERVEFLAGS // not allowed to clobber flags
+)
+
+/*
+ *	wasm
+ */
+const (
+	ACallImport = obj.ABaseWasm + obj.A_ARCHSPECIFIC + iota
+	AGet
+	ASet
+	ATee
+	ANot // alias for I32Eqz
+
+	// The following are low-level WebAssembly instructions.
+	// Their order matters, since it matches the opcode encoding.
+	// Gaps in the encoding are indicated by comments.
+
+	AUnreachable // opcode 0x00
+	ANop
+	ABlock
+	ALoop
+	AIf
+	AElse
+
+	AEnd // opcode 0x0B
+	ABr
+	ABrIf
+	ABrTable
+	// ACall and AReturn are WebAssembly instructions. obj.ACALL and obj.ARET are higher level instructions
+	// with Go semantics, e.g. they manipulate the Go stack on the linear memory.
+	AReturn
+	ACall
+	ACallIndirect
+
+	ADrop // opcode 0x1A
+	ASelect
+
+	AI32Load // opcode 0x28
+	AI64Load
+	AF32Load
+	AF64Load
+	AI32Load8S
+	AI32Load8U
+	AI32Load16S
+	AI32Load16U
+	AI64Load8S
+	AI64Load8U
+	AI64Load16S
+	AI64Load16U
+	AI64Load32S
+	AI64Load32U
+	AI32Store
+	AI64Store
+	AF32Store
+	AF64Store
+	AI32Store8
+	AI32Store16
+	AI64Store8
+	AI64Store16
+	AI64Store32
+	ACurrentMemory
+	AGrowMemory
+
+	AI32Const
+	AI64Const
+	AF32Const
+	AF64Const
+
+	AI32Eqz
+	AI32Eq
+	AI32Ne
+	AI32LtS
+	AI32LtU
+	AI32GtS
+	AI32GtU
+	AI32LeS
+	AI32LeU
+	AI32GeS
+	AI32GeU
+
+	AI64Eqz
+	AI64Eq
+	AI64Ne
+	AI64LtS
+	AI64LtU
+	AI64GtS
+	AI64GtU
+	AI64LeS
+	AI64LeU
+	AI64GeS
+	AI64GeU
+
+	AF32Eq
+	AF32Ne
+	AF32Lt
+	AF32Gt
+	AF32Le
+	AF32Ge
+
+	AF64Eq
+	AF64Ne
+	AF64Lt
+	AF64Gt
+	AF64Le
+	AF64Ge
+
+	AI32Clz
+	AI32Ctz
+	AI32Popcnt
+	AI32Add
+	AI32Sub
+	AI32Mul
+	AI32DivS
+	AI32DivU
+	AI32RemS
+	AI32RemU
+	AI32And
+	AI32Or
+	AI32Xor
+	AI32Shl
+	AI32ShrS
+	AI32ShrU
+	AI32Rotl
+	AI32Rotr
+
+	AI64Clz
+	AI64Ctz
+	AI64Popcnt
+	AI64Add
+	AI64Sub
+	AI64Mul
+	AI64DivS
+	AI64DivU
+	AI64RemS
+	AI64RemU
+	AI64And
+	AI64Or
+	AI64Xor
+	AI64Shl
+	AI64ShrS
+	AI64ShrU
+	AI64Rotl
+	AI64Rotr
+
+	AF32Abs
+	AF32Neg
+	AF32Ceil
+	AF32Floor
+	AF32Trunc
+	AF32Nearest
+	AF32Sqrt
+	AF32Add
+	AF32Sub
+	AF32Mul
+	AF32Div
+	AF32Min
+	AF32Max
+	AF32Copysign
+
+	AF64Abs
+	AF64Neg
+	AF64Ceil
+	AF64Floor
+	AF64Trunc
+	AF64Nearest
+	AF64Sqrt
+	AF64Add
+	AF64Sub
+	AF64Mul
+	AF64Div
+	AF64Min
+	AF64Max
+	AF64Copysign
+
+	AI32WrapI64
+	AI32TruncSF32
+	AI32TruncUF32
+	AI32TruncSF64
+	AI32TruncUF64
+	AI64ExtendSI32
+	AI64ExtendUI32
+	AI64TruncSF32
+	AI64TruncUF32
+	AI64TruncSF64
+	AI64TruncUF64
+	AF32ConvertSI32
+	AF32ConvertUI32
+	AF32ConvertSI64
+	AF32ConvertUI64
+	AF32DemoteF64
+	AF64ConvertSI32
+	AF64ConvertUI32
+	AF64ConvertSI64
+	AF64ConvertUI64
+	AF64PromoteF32
+	AI32ReinterpretF32
+	AI64ReinterpretF64
+	AF32ReinterpretI32
+	AF64ReinterpretI64
+
+	// End of low-level WebAssembly instructions.
+
+	ARESUMEPOINT
+	// ACALLNORESUME is a call which is not followed by a resume point.
+	// It is allowed inside of WebAssembly blocks, whereas obj.ACALL is not.
+	// However, it is not allowed to switch goroutines while inside of an ACALLNORESUME call.
+	ACALLNORESUME
+
+	AMOVB
+	AMOVH
+	AMOVW
+	AMOVD
+
+	AWORD
+	ALAST
+)
+
+const (
+	REG_NONE = 0
+)
+
+const (
+	// globals
+	REG_PC_F = obj.RBaseWasm + iota
+	REG_PC_B
+	REG_SP // SP is currently 32-bit, until 64-bit memory operations are available
+	REG_CTXT
+	REG_g
+	// RET* are used by runtime.return0 and runtime.reflectcall. These functions pass return values in registers.
+	REG_RET0
+	REG_RET1
+	REG_RET2
+	REG_RET3
+
+	// locals
+	REG_R0
+	REG_R1
+	REG_R2
+	REG_R3
+	REG_R4
+	REG_R5
+	REG_R6
+	REG_R7
+	REG_R8
+	REG_R9
+	REG_R10
+	REG_R11
+	REG_R12
+	REG_R13
+	REG_R14
+	REG_R15
+	REG_F0
+	REG_F1
+	REG_F2
+	REG_F3
+	REG_F4
+	REG_F5
+	REG_F6
+	REG_F7
+	REG_F8
+	REG_F9
+	REG_F10
+	REG_F11
+	REG_F12
+	REG_F13
+	REG_F14
+	REG_F15
+
+	MAXREG
+
+	MINREG  = REG_PC_F
+	REGSP   = REG_SP
+	REGCTXT = REG_CTXT
+	REGG    = REG_g
+)
diff --git a/src/cmd/internal/obj/wasm/anames.go b/src/cmd/internal/obj/wasm/anames.go
new file mode 100644
index 0000000000..20d04446d0
--- /dev/null
+++ b/src/cmd/internal/obj/wasm/anames.go
@@ -0,0 +1,189 @@
+// Generated by stringer -i a.out.go -o anames.go -p wasm
+// Do not edit.
+
+package wasm
+
+import "cmd/internal/obj"
+
+var Anames = []string{
+	obj.A_ARCHSPECIFIC: "CallImport",
+	"Get",
+	"Set",
+	"Tee",
+	"Not",
+	"Unreachable",
+	"Nop",
+	"Block",
+	"Loop",
+	"If",
+	"Else",
+	"End",
+	"Br",
+	"BrIf",
+	"BrTable",
+	"Return",
+	"Call",
+	"CallIndirect",
+	"Drop",
+	"Select",
+	"I32Load",
+	"I64Load",
+	"F32Load",
+	"F64Load",
+	"I32Load8S",
+	"I32Load8U",
+	"I32Load16S",
+	"I32Load16U",
+	"I64Load8S",
+	"I64Load8U",
+	"I64Load16S",
+	"I64Load16U",
+	"I64Load32S",
+	"I64Load32U",
+	"I32Store",
+	"I64Store",
+	"F32Store",
+	"F64Store",
+	"I32Store8",
+	"I32Store16",
+	"I64Store8",
+	"I64Store16",
+	"I64Store32",
+	"CurrentMemory",
+	"GrowMemory",
+	"I32Const",
+	"I64Const",
+	"F32Const",
+	"F64Const",
+	"I32Eqz",
+	"I32Eq",
+	"I32Ne",
+	"I32LtS",
+	"I32LtU",
+	"I32GtS",
+	"I32GtU",
+	"I32LeS",
+	"I32LeU",
+	"I32GeS",
+	"I32GeU",
+	"I64Eqz",
+	"I64Eq",
+	"I64Ne",
+	"I64LtS",
+	"I64LtU",
+	"I64GtS",
+	"I64GtU",
+	"I64LeS",
+	"I64LeU",
+	"I64GeS",
+	"I64GeU",
+	"F32Eq",
+	"F32Ne",
+	"F32Lt",
+	"F32Gt",
+	"F32Le",
+	"F32Ge",
+	"F64Eq",
+	"F64Ne",
+	"F64Lt",
+	"F64Gt",
+	"F64Le",
+	"F64Ge",
+	"I32Clz",
+	"I32Ctz",
+	"I32Popcnt",
+	"I32Add",
+	"I32Sub",
+	"I32Mul",
+	"I32DivS",
+	"I32DivU",
+	"I32RemS",
+	"I32RemU",
+	"I32And",
+	"I32Or",
+	"I32Xor",
+	"I32Shl",
+	"I32ShrS",
+	"I32ShrU",
+	"I32Rotl",
+	"I32Rotr",
+	"I64Clz",
+	"I64Ctz",
+	"I64Popcnt",
+	"I64Add",
+	"I64Sub",
+	"I64Mul",
+	"I64DivS",
+	"I64DivU",
+	"I64RemS",
+	"I64RemU",
+	"I64And",
+	"I64Or",
+	"I64Xor",
+	"I64Shl",
+	"I64ShrS",
+	"I64ShrU",
+	"I64Rotl",
+	"I64Rotr",
+	"F32Abs",
+	"F32Neg",
+	"F32Ceil",
+	"F32Floor",
+	"F32Trunc",
+	"F32Nearest",
+	"F32Sqrt",
+	"F32Add",
+	"F32Sub",
+	"F32Mul",
+	"F32Div",
+	"F32Min",
+	"F32Max",
+	"F32Copysign",
+	"F64Abs",
+	"F64Neg",
+	"F64Ceil",
+	"F64Floor",
+	"F64Trunc",
+	"F64Nearest",
+	"F64Sqrt",
+	"F64Add",
+	"F64Sub",
+	"F64Mul",
+	"F64Div",
+	"F64Min",
+	"F64Max",
+	"F64Copysign",
+	"I32WrapI64",
+	"I32TruncSF32",
+	"I32TruncUF32",
+	"I32TruncSF64",
+	"I32TruncUF64",
+	"I64ExtendSI32",
+	"I64ExtendUI32",
+	"I64TruncSF32",
+	"I64TruncUF32",
+	"I64TruncSF64",
+	"I64TruncUF64",
+	"F32ConvertSI32",
+	"F32ConvertUI32",
+	"F32ConvertSI64",
+	"F32ConvertUI64",
+	"F32DemoteF64",
+	"F64ConvertSI32",
+	"F64ConvertUI32",
+	"F64ConvertSI64",
+	"F64ConvertUI64",
+	"F64PromoteF32",
+	"I32ReinterpretF32",
+	"I64ReinterpretF64",
+	"F32ReinterpretI32",
+	"F64ReinterpretI64",
+	"RESUMEPOINT",
+	"CALLNORESUME",
+	"MOVB",
+	"MOVH",
+	"MOVW",
+	"MOVD",
+	"WORD",
+	"LAST",
+}
diff --git a/src/cmd/internal/obj/wasm/wasmobj.go b/src/cmd/internal/obj/wasm/wasmobj.go
new file mode 100644
index 0000000000..2b7e12a93f
--- /dev/null
+++ b/src/cmd/internal/obj/wasm/wasmobj.go
@@ -0,0 +1,934 @@
+// Copyright 2018 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.
+
+package wasm
+
+import (
+	"bytes"
+	"cmd/internal/obj"
+	"cmd/internal/objabi"
+	"cmd/internal/sys"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"math"
+)
+
+var Register = map[string]int16{
+	"PC_F": REG_PC_F,
+	"PC_B": REG_PC_B,
+	"SP":   REG_SP,
+	"CTXT": REG_CTXT,
+	"g":    REG_g,
+	"RET0": REG_RET0,
+	"RET1": REG_RET1,
+	"RET2": REG_RET2,
+	"RET3": REG_RET3,
+
+	"R0":  REG_R0,
+	"R1":  REG_R1,
+	"R2":  REG_R2,
+	"R3":  REG_R3,
+	"R4":  REG_R4,
+	"R5":  REG_R5,
+	"R6":  REG_R6,
+	"R7":  REG_R7,
+	"R8":  REG_R8,
+	"R9":  REG_R9,
+	"R10": REG_R10,
+	"R11": REG_R11,
+	"R12": REG_R12,
+	"R13": REG_R13,
+	"R14": REG_R14,
+	"R15": REG_R15,
+
+	"F0":  REG_F0,
+	"F1":  REG_F1,
+	"F2":  REG_F2,
+	"F3":  REG_F3,
+	"F4":  REG_F4,
+	"F5":  REG_F5,
+	"F6":  REG_F6,
+	"F7":  REG_F7,
+	"F8":  REG_F8,
+	"F9":  REG_F9,
+	"F10": REG_F10,
+	"F11": REG_F11,
+	"F12": REG_F12,
+	"F13": REG_F13,
+	"F14": REG_F14,
+	"F15": REG_F15,
+}
+
+var registerNames []string
+
+func init() {
+	obj.RegisterRegister(MINREG, MAXREG, rconv)
+	obj.RegisterOpcode(obj.ABaseWasm, Anames)
+
+	registerNames = make([]string, MAXREG-MINREG)
+	for name, reg := range Register {
+		registerNames[reg-MINREG] = name
+	}
+}
+
+func rconv(r int) string {
+	return registerNames[r-MINREG]
+}
+
+var unaryDst = map[obj.As]bool{
+	ASet:          true,
+	ATee:          true,
+	ACall:         true,
+	ACallIndirect: true,
+	ACallImport:   true,
+	ABr:           true,
+	ABrIf:         true,
+	ABrTable:      true,
+	AI32Store:     true,
+	AI64Store:     true,
+	AF32Store:     true,
+	AF64Store:     true,
+	AI32Store8:    true,
+	AI32Store16:   true,
+	AI64Store8:    true,
+	AI64Store16:   true,
+	AI64Store32:   true,
+	ACALLNORESUME: true,
+}
+
+var Linkwasm = obj.LinkArch{
+	Arch:       sys.ArchWasm,
+	Init:       instinit,
+	Preprocess: preprocess,
+	Assemble:   assemble,
+	UnaryDst:   unaryDst,
+}
+
+var (
+	morestack       *obj.LSym
+	morestackNoCtxt *obj.LSym
+	gcWriteBarrier  *obj.LSym
+	sigpanic        *obj.LSym
+	deferreturn     *obj.LSym
+	jmpdefer        *obj.LSym
+)
+
+const (
+	/* mark flags */
+	WasmImport = 1 << 0
+)
+
+func instinit(ctxt *obj.Link) {
+	morestack = ctxt.Lookup("runtime.morestack")
+	morestackNoCtxt = ctxt.Lookup("runtime.morestack_noctxt")
+	gcWriteBarrier = ctxt.Lookup("runtime.gcWriteBarrier")
+	sigpanic = ctxt.Lookup("runtime.sigpanic")
+	deferreturn = ctxt.Lookup("runtime.deferreturn")
+	jmpdefer = ctxt.Lookup(`"".jmpdefer`)
+}
+
+func preprocess(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
+	appendp := func(p *obj.Prog, as obj.As, args ...obj.Addr) *obj.Prog {
+		if p.As != obj.ANOP {
+			p2 := obj.Appendp(p, newprog)
+			p2.Pc = p.Pc
+			p = p2
+		}
+		p.As = as
+		switch len(args) {
+		case 0:
+			p.From = obj.Addr{}
+			p.To = obj.Addr{}
+		case 1:
+			if unaryDst[as] {
+				p.From = obj.Addr{}
+				p.To = args[0]
+			} else {
+				p.From = args[0]
+				p.To = obj.Addr{}
+			}
+		case 2:
+			p.From = args[0]
+			p.To = args[1]
+		default:
+			panic("bad args")
+		}
+		return p
+	}
+
+	framesize := s.Func.Text.To.Offset
+	if framesize < 0 {
+		panic("bad framesize")
+	}
+	s.Func.Args = s.Func.Text.To.Val.(int32)
+	s.Func.Locals = int32(framesize)
+
+	if s.Func.Text.From.Sym.Wrapper() {
+		// if g._panic != nil && g._panic.argp == FP {
+		//   g._panic.argp = bottom-of-frame
+		// }
+		//
+		// MOVD g_panic(g), R0
+		// Get R0
+		// I64Eqz
+		// Not
+		// If
+		//   Get SP
+		//   I64ExtendUI32
+		//   I64Const $framesize+8
+		//   I64Add
+		//   I64Load panic_argp(R0)
+		//   I64Eq
+		//   If
+		//     MOVD SP, panic_argp(R0)
+		//   End
+		// End
+
+		gpanic := obj.Addr{
+			Type:   obj.TYPE_MEM,
+			Reg:    REGG,
+			Offset: 4 * 8, // g_panic
+		}
+
+		panicargp := obj.Addr{
+			Type:   obj.TYPE_MEM,
+			Reg:    REG_R0,
+			Offset: 0, // panic.argp
+		}
+
+		p := s.Func.Text
+		p = appendp(p, AMOVD, gpanic, regAddr(REG_R0))
+
+		p = appendp(p, AGet, regAddr(REG_R0))
+		p = appendp(p, AI64Eqz)
+		p = appendp(p, ANot)
+		p = appendp(p, AIf)
+
+		p = appendp(p, AGet, regAddr(REG_SP))
+		p = appendp(p, AI64ExtendUI32)
+		p = appendp(p, AI64Const, constAddr(framesize+8))
+		p = appendp(p, AI64Add)
+		p = appendp(p, AI64Load, panicargp)
+
+		p = appendp(p, AI64Eq)
+		p = appendp(p, AIf)
+		p = appendp(p, AMOVD, regAddr(REG_SP), panicargp)
+		p = appendp(p, AEnd)
+
+		p = appendp(p, AEnd)
+	}
+
+	if framesize > 0 {
+		p := s.Func.Text
+		p = appendp(p, AGet, regAddr(REG_SP))
+		p = appendp(p, AI32Const, constAddr(framesize))
+		p = appendp(p, AI32Sub)
+		p = appendp(p, ASet, regAddr(REG_SP))
+		p.Spadj = int32(framesize)
+	}
+
+	// Introduce resume points for CALL instructions
+	// and collect other explicit resume points.
+	numResumePoints := 0
+	explicitBlockDepth := 0
+	pc := int64(0) // pc is only incremented when necessary, this avoids bloat of the BrTable instruction
+	var tableIdxs []uint64
+	tablePC := int64(0)
+	base := ctxt.PosTable.Pos(s.Func.Text.Pos).Base()
+	for p := s.Func.Text; p != nil; p = p.Link {
+		prevBase := base
+		base = ctxt.PosTable.Pos(p.Pos).Base()
+
+		switch p.As {
+		case ABlock, ALoop, AIf:
+			explicitBlockDepth++
+
+		case AEnd:
+			if explicitBlockDepth == 0 {
+				panic("End without block")
+			}
+			explicitBlockDepth--
+
+		case ARESUMEPOINT:
+			if explicitBlockDepth != 0 {
+				panic("RESUME can only be used on toplevel")
+			}
+			p.As = AEnd
+			for tablePC <= pc {
+				tableIdxs = append(tableIdxs, uint64(numResumePoints))
+				tablePC++
+			}
+			numResumePoints++
+			pc++
+
+		case obj.ACALL:
+			if explicitBlockDepth != 0 {
+				panic("CALL can only be used on toplevel, try CALLNORESUME instead")
+			}
+			appendp(p, ARESUMEPOINT)
+		}
+
+		p.Pc = pc
+
+		// Increase pc whenever some pc-value table needs a new entry. Don't increase it
+		// more often to avoid bloat of the BrTable instruction.
+		// The "base != prevBase" condition detects inlined instructions. They are an
+		// implicit call, so entering and leaving this section affects the stack trace.
+		if p.As == ACALLNORESUME || p.As == obj.ANOP || p.Spadj != 0 || base != prevBase {
+			pc++
+		}
+	}
+	tableIdxs = append(tableIdxs, uint64(numResumePoints))
+	s.Size = pc + 1
+
+	if !s.Func.Text.From.Sym.NoSplit() {
+		p := s.Func.Text
+
+		if framesize <= objabi.StackSmall {
+			// small stack: SP <= stackguard
+			// Get SP
+			// Get g
+			// I32WrapI64
+			// I32Load $stackguard0
+			// I32GtU
+
+			p = appendp(p, AGet, regAddr(REG_SP))
+			p = appendp(p, AGet, regAddr(REGG))
+			p = appendp(p, AI32WrapI64)
+			p = appendp(p, AI32Load, constAddr(2*int64(ctxt.Arch.PtrSize))) // G.stackguard0
+			p = appendp(p, AI32LeU)
+		} else {
+			// large stack: SP-framesize <= stackguard-StackSmall
+			//              SP <= stackguard+(framesize-StackSmall)
+			// Get SP
+			// Get g
+			// I32WrapI64
+			// I32Load $stackguard0
+			// I32Const $(framesize-StackSmall)
+			// I32Add
+			// I32GtU
+
+			p = appendp(p, AGet, regAddr(REG_SP))
+			p = appendp(p, AGet, regAddr(REGG))
+			p = appendp(p, AI32WrapI64)
+			p = appendp(p, AI32Load, constAddr(2*int64(ctxt.Arch.PtrSize))) // G.stackguard0
+			p = appendp(p, AI32Const, constAddr(int64(framesize)-objabi.StackSmall))
+			p = appendp(p, AI32Add)
+			p = appendp(p, AI32LeU)
+		}
+		// TODO(neelance): handle wraparound case
+
+		p = appendp(p, AIf)
+		p = appendp(p, obj.ACALL, constAddr(0))
+		if s.Func.Text.From.Sym.NeedCtxt() {
+			p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: morestack}
+		} else {
+			p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: morestackNoCtxt}
+		}
+		p = appendp(p, AEnd)
+	}
+
+	// Add Block instructions for resume points and BrTable to jump to selected resume point.
+	if numResumePoints > 0 {
+		p := s.Func.Text
+		p = appendp(p, ALoop) // entryPointLoop, used to jump between basic blocks
+
+		for i := 0; i < numResumePoints+1; i++ {
+			p = appendp(p, ABlock)
+		}
+		p = appendp(p, AGet, regAddr(REG_PC_B)) // read next basic block from PC_B
+		p = appendp(p, ABrTable, obj.Addr{Val: tableIdxs})
+		p = appendp(p, AEnd) // end of Block
+
+		for p.Link != nil {
+			p = p.Link
+		}
+
+		p = appendp(p, AEnd) // end of entryPointLoop
+		p = appendp(p, obj.AUNDEF)
+	}
+
+	p := s.Func.Text
+	currentDepth := 0
+	blockDepths := make(map[*obj.Prog]int)
+	for p != nil {
+		switch p.As {
+		case ABlock, ALoop, AIf:
+			currentDepth++
+			blockDepths[p] = currentDepth
+		case AEnd:
+			currentDepth--
+		}
+
+		switch p.As {
+		case ABr, ABrIf:
+			if p.To.Type == obj.TYPE_BRANCH {
+				blockDepth, ok := blockDepths[p.To.Val.(*obj.Prog)]
+				if !ok {
+					panic("label not at block")
+				}
+				p.To = constAddr(int64(currentDepth - blockDepth))
+			}
+		case obj.AJMP:
+			jmp := *p
+			p.As = obj.ANOP
+
+			if jmp.To.Type == obj.TYPE_BRANCH {
+				// jump to basic block
+				p = appendp(p, AI32Const, constAddr(jmp.To.Val.(*obj.Prog).Pc))
+				p = appendp(p, ASet, regAddr(REG_PC_B))               // write next basic block to PC_B
+				p = appendp(p, ABr, constAddr(int64(currentDepth-1))) // jump to beginning of entryPointLoop
+				break
+			}
+
+			// reset PC_B to function entry
+			p = appendp(p, AI32Const, constAddr(0))
+			p = appendp(p, ASet, regAddr(REG_PC_B))
+
+			// low-level WebAssembly call to function
+			switch jmp.To.Type {
+			case obj.TYPE_MEM:
+				p = appendp(p, ACall, jmp.To)
+			case obj.TYPE_NONE:
+				// (target PC is on stack)
+				p = appendp(p, AI32WrapI64)
+				p = appendp(p, AI32Const, constAddr(16)) // only needs PC_F bits (16-31), PC_B bits (0-15) are zero
+				p = appendp(p, AI32ShrU)
+				p = appendp(p, ACallIndirect)
+			default:
+				panic("bad target for JMP")
+			}
+
+			p = appendp(p, AReturn)
+
+		case obj.ACALL, ACALLNORESUME:
+			call := *p
+			p.As = obj.ANOP
+
+			pcAfterCall := call.Link.Pc
+			if call.To.Sym == sigpanic {
+				pcAfterCall-- // sigpanic expects to be called without advancing the pc
+			}
+
+			// jmpdefer manipulates the return address on the stack so deferreturn gets called repeatedly.
+			// Model this in WebAssembly with a loop.
+			if call.To.Sym == deferreturn {
+				p = appendp(p, ALoop)
+			}
+
+			// SP -= 8
+			p = appendp(p, AGet, regAddr(REG_SP))
+			p = appendp(p, AI32Const, constAddr(8))
+			p = appendp(p, AI32Sub)
+			p = appendp(p, ASet, regAddr(REG_SP))
+
+			// write return address to Go stack
+			p = appendp(p, AGet, regAddr(REG_SP))
+			p = appendp(p, AI64Const, obj.Addr{
+				Type:   obj.TYPE_ADDR,
+				Name:   obj.NAME_EXTERN,
+				Sym:    s,           // PC_F
+				Offset: pcAfterCall, // PC_B
+			})
+			p = appendp(p, AI64Store, constAddr(0))
+
+			// reset PC_B to function entry
+			p = appendp(p, AI32Const, constAddr(0))
+			p = appendp(p, ASet, regAddr(REG_PC_B))
+
+			// low-level WebAssembly call to function
+			switch call.To.Type {
+			case obj.TYPE_MEM:
+				p = appendp(p, ACall, call.To)
+			case obj.TYPE_NONE:
+				// (target PC is on stack)
+				p = appendp(p, AI32WrapI64)
+				p = appendp(p, AI32Const, constAddr(16)) // only needs PC_F bits (16-31), PC_B bits (0-15) are zero
+				p = appendp(p, AI32ShrU)
+				p = appendp(p, ACallIndirect)
+			default:
+				panic("bad target for CALL")
+			}
+
+			// gcWriteBarrier has no return value, it never unwinds the stack
+			if call.To.Sym == gcWriteBarrier {
+				break
+			}
+
+			// jmpdefer removes the frame of deferreturn from the Go stack.
+			// However, its WebAssembly function still returns normally,
+			// so we need to return from deferreturn without removing its
+			// stack frame (no RET), because the frame is already gone.
+			if call.To.Sym == jmpdefer {
+				p = appendp(p, AReturn)
+				break
+			}
+
+			// return value of call is on the top of the stack, indicating whether to unwind the WebAssembly stack
+			p = appendp(p, AIf)
+			if call.As == ACALLNORESUME && call.To.Sym != sigpanic { // sigpanic unwinds the stack, but it never resumes
+				// trying to unwind WebAssembly stack but call has no resume point, terminate with error
+				p = appendp(p, obj.AUNDEF)
+			} else {
+				// unwinding WebAssembly stack to switch goroutine, return 1
+				p = appendp(p, AI32Const, constAddr(1))
+				p = appendp(p, AReturn)
+			}
+			p = appendp(p, AEnd)
+
+			// jump to before the call if jmpdefer has reset the return address to the call's PC
+			if call.To.Sym == deferreturn {
+				p = appendp(p, AGet, regAddr(REG_PC_B))
+				p = appendp(p, AI32Const, constAddr(call.Pc))
+				p = appendp(p, AI32Eq)
+				p = appendp(p, ABrIf, constAddr(0))
+				p = appendp(p, AEnd) // end of Loop
+			}
+
+		case obj.ARET:
+			ret := *p
+			p.As = obj.ANOP
+
+			if framesize > 0 {
+				// SP += framesize
+				p = appendp(p, AGet, regAddr(REG_SP))
+				p = appendp(p, AI32Const, constAddr(framesize))
+				p = appendp(p, AI32Add)
+				p = appendp(p, ASet, regAddr(REG_SP))
+				// TODO(neelance): This should theoretically set Spadj, but it only works without.
+				// p.Spadj = int32(-framesize)
+			}
+
+			if ret.To.Type == obj.TYPE_MEM {
+				// reset PC_B to function entry
+				p = appendp(p, AI32Const, constAddr(0))
+				p = appendp(p, ASet, regAddr(REG_PC_B))
+
+				// low-level WebAssembly call to function
+				p = appendp(p, ACall, ret.To)
+				p = appendp(p, AReturn)
+				break
+			}
+
+			// read return PC_F from Go stack
+			p = appendp(p, AGet, regAddr(REG_SP))
+			p = appendp(p, AI32Load16U, constAddr(2))
+			p = appendp(p, ASet, regAddr(REG_PC_F))
+
+			// read return PC_B from Go stack
+			p = appendp(p, AGet, regAddr(REG_SP))
+			p = appendp(p, AI32Load16U, constAddr(0))
+			p = appendp(p, ASet, regAddr(REG_PC_B))
+
+			// SP += 8
+			p = appendp(p, AGet, regAddr(REG_SP))
+			p = appendp(p, AI32Const, constAddr(8))
+			p = appendp(p, AI32Add)
+			p = appendp(p, ASet, regAddr(REG_SP))
+
+			// not switching goroutine, return 0
+			p = appendp(p, AI32Const, constAddr(0))
+			p = appendp(p, AReturn)
+		}
+
+		p = p.Link
+	}
+
+	p = s.Func.Text
+	for p != nil {
+		switch p.From.Name {
+		case obj.NAME_AUTO:
+			p.From.Offset += int64(framesize)
+		case obj.NAME_PARAM:
+			p.From.Reg = REG_SP
+			p.From.Offset += int64(framesize) + 8 // parameters are after the frame and the 8-byte return address
+		}
+
+		switch p.To.Name {
+		case obj.NAME_AUTO:
+			p.To.Offset += int64(framesize)
+		case obj.NAME_PARAM:
+			p.To.Reg = REG_SP
+			p.To.Offset += int64(framesize) + 8 // parameters are after the frame and the 8-byte return address
+		}
+
+		switch p.As {
+		case AGet:
+			if p.From.Type == obj.TYPE_ADDR {
+				get := *p
+				p.As = obj.ANOP
+
+				switch get.From.Name {
+				case obj.NAME_EXTERN:
+					p = appendp(p, AI64Const, get.From)
+				case obj.NAME_AUTO, obj.NAME_PARAM:
+					p = appendp(p, AGet, regAddr(get.From.Reg))
+					if get.From.Reg == REG_SP {
+						p = appendp(p, AI64ExtendUI32)
+					}
+					if get.From.Offset != 0 {
+						p = appendp(p, AI64Const, constAddr(get.From.Offset))
+						p = appendp(p, AI64Add)
+					}
+				default:
+					panic("bad Get: invalid name")
+				}
+			}
+
+		case AI32Load, AI64Load, AF32Load, AF64Load, AI32Load8S, AI32Load8U, AI32Load16S, AI32Load16U, AI64Load8S, AI64Load8U, AI64Load16S, AI64Load16U, AI64Load32S, AI64Load32U:
+			if p.From.Type == obj.TYPE_MEM {
+				as := p.As
+				from := p.From
+
+				p.As = AGet
+				p.From = regAddr(from.Reg)
+
+				if from.Reg != REG_SP {
+					p = appendp(p, AI32WrapI64)
+				}
+
+				p = appendp(p, as, constAddr(from.Offset))
+			}
+
+		case AMOVB, AMOVH, AMOVW, AMOVD:
+			mov := *p
+			p.As = obj.ANOP
+
+			var loadAs obj.As
+			var storeAs obj.As
+			switch mov.As {
+			case AMOVB:
+				loadAs = AI64Load8U
+				storeAs = AI64Store8
+			case AMOVH:
+				loadAs = AI64Load16U
+				storeAs = AI64Store16
+			case AMOVW:
+				loadAs = AI64Load32U
+				storeAs = AI64Store32
+			case AMOVD:
+				loadAs = AI64Load
+				storeAs = AI64Store
+			}
+
+			appendValue := func() {
+				switch mov.From.Type {
+				case obj.TYPE_CONST:
+					p = appendp(p, AI64Const, constAddr(mov.From.Offset))
+
+				case obj.TYPE_ADDR:
+					switch mov.From.Name {
+					case obj.NAME_NONE, obj.NAME_PARAM, obj.NAME_AUTO:
+						p = appendp(p, AGet, regAddr(mov.From.Reg))
+						if mov.From.Reg == REG_SP {
+							p = appendp(p, AI64ExtendUI32)
+						}
+						p = appendp(p, AI64Const, constAddr(mov.From.Offset))
+						p = appendp(p, AI64Add)
+					case obj.NAME_EXTERN:
+						p = appendp(p, AI64Const, mov.From)
+					default:
+						panic("bad name for MOV")
+					}
+
+				case obj.TYPE_REG:
+					p = appendp(p, AGet, mov.From)
+					if mov.From.Reg == REG_SP {
+						p = appendp(p, AI64ExtendUI32)
+					}
+
+				case obj.TYPE_MEM:
+					p = appendp(p, AGet, regAddr(mov.From.Reg))
+					if mov.From.Reg != REG_SP {
+						p = appendp(p, AI32WrapI64)
+					}
+					p = appendp(p, loadAs, constAddr(mov.From.Offset))
+
+				default:
+					panic("bad MOV type")
+				}
+			}
+
+			switch mov.To.Type {
+			case obj.TYPE_REG:
+				appendValue()
+				if mov.To.Reg == REG_SP {
+					p = appendp(p, AI32WrapI64)
+				}
+				p = appendp(p, ASet, mov.To)
+
+			case obj.TYPE_MEM:
+				switch mov.To.Name {
+				case obj.NAME_NONE, obj.NAME_PARAM:
+					p = appendp(p, AGet, regAddr(mov.To.Reg))
+					if mov.To.Reg != REG_SP {
+						p = appendp(p, AI32WrapI64)
+					}
+				case obj.NAME_EXTERN:
+					p = appendp(p, AI32Const, obj.Addr{Type: obj.TYPE_ADDR, Name: obj.NAME_EXTERN, Sym: mov.To.Sym})
+				default:
+					panic("bad MOV name")
+				}
+				appendValue()
+				p = appendp(p, storeAs, constAddr(mov.To.Offset))
+
+			default:
+				panic("bad MOV type")
+			}
+
+		case ACallImport:
+			p.As = obj.ANOP
+			p = appendp(p, AGet, regAddr(REG_SP))
+			p = appendp(p, ACall, obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: s})
+			p.Mark = WasmImport
+		}
+
+		p = p.Link
+	}
+}
+
+func constAddr(value int64) obj.Addr {
+	return obj.Addr{Type: obj.TYPE_CONST, Offset: value}
+}
+
+func regAddr(reg int16) obj.Addr {
+	return obj.Addr{Type: obj.TYPE_REG, Reg: reg}
+}
+
+func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
+	w := new(bytes.Buffer)
+
+	// Function starts with declaration of locals: numbers and types.
+	switch s.Name {
+	case "memchr":
+		writeUleb128(w, 1) // number of sets of locals
+		writeUleb128(w, 3) // number of locals
+		w.WriteByte(0x7F)  // i32
+	case "memcmp":
+		writeUleb128(w, 1) // number of sets of locals
+		writeUleb128(w, 2) // number of locals
+		w.WriteByte(0x7F)  // i32
+	default:
+		writeUleb128(w, 2)  // number of sets of locals
+		writeUleb128(w, 16) // number of locals
+		w.WriteByte(0x7E)   // i64
+		writeUleb128(w, 16) // number of locals
+		w.WriteByte(0x7C)   // f64
+	}
+
+	for p := s.Func.Text; p != nil; p = p.Link {
+		switch p.As {
+		case AGet:
+			if p.From.Type != obj.TYPE_REG {
+				panic("bad Get: argument is not a register")
+			}
+			reg := p.From.Reg
+			switch {
+			case reg >= REG_PC_F && reg <= REG_RET3:
+				w.WriteByte(0x23) // get_global
+				writeUleb128(w, uint64(reg-REG_PC_F))
+			case reg >= REG_R0 && reg <= REG_F15:
+				w.WriteByte(0x20) // get_local
+				writeUleb128(w, uint64(reg-REG_R0))
+			default:
+				panic("bad Get: invalid register")
+			}
+			continue
+
+		case ASet:
+			if p.To.Type != obj.TYPE_REG {
+				panic("bad Set: argument is not a register")
+			}
+			reg := p.To.Reg
+			switch {
+			case reg >= REG_PC_F && reg <= REG_RET3:
+				w.WriteByte(0x24) // set_global
+				writeUleb128(w, uint64(reg-REG_PC_F))
+			case reg >= REG_R0 && reg <= REG_F15:
+				if p.Link.As == AGet && p.Link.From.Reg == reg {
+					w.WriteByte(0x22) // tee_local
+					p = p.Link
+				} else {
+					w.WriteByte(0x21) // set_local
+				}
+				writeUleb128(w, uint64(reg-REG_R0))
+			default:
+				panic("bad Set: invalid register")
+			}
+			continue
+
+		case ATee:
+			if p.To.Type != obj.TYPE_REG {
+				panic("bad Tee: argument is not a register")
+			}
+			reg := p.To.Reg
+			switch {
+			case reg >= REG_R0 && reg <= REG_F15:
+				w.WriteByte(0x22) // tee_local
+				writeUleb128(w, uint64(reg-REG_R0))
+			default:
+				panic("bad Tee: invalid register")
+			}
+			continue
+
+		case ANot:
+			w.WriteByte(0x45) // i32.eqz
+			continue
+
+		case obj.AUNDEF:
+			w.WriteByte(0x00) // unreachable
+			continue
+
+		case obj.ANOP, obj.ATEXT, obj.AFUNCDATA, obj.APCDATA:
+			// ignore
+			continue
+		}
+
+		switch {
+		case p.As < AUnreachable || p.As > AF64ReinterpretI64:
+			panic(fmt.Sprintf("unexpected assembler op: %s", p.As))
+		case p.As < AEnd:
+			w.WriteByte(byte(p.As - AUnreachable + 0x00))
+		case p.As < ADrop:
+			w.WriteByte(byte(p.As - AEnd + 0x0B))
+		case p.As < AI32Load:
+			w.WriteByte(byte(p.As - ADrop + 0x1A))
+		default:
+			w.WriteByte(byte(p.As - AI32Load + 0x28))
+		}
+
+		switch p.As {
+		case ABlock, ALoop, AIf:
+			if p.From.Offset != 0 {
+				// block type, rarely used, e.g. for code compiled with emscripten
+				w.WriteByte(0x80 - byte(p.From.Offset))
+				continue
+			}
+			w.WriteByte(0x40)
+
+		case ABr, ABrIf:
+			if p.To.Type != obj.TYPE_CONST {
+				panic("bad Br/BrIf")
+			}
+			writeUleb128(w, uint64(p.To.Offset))
+
+		case ABrTable:
+			idxs := p.To.Val.([]uint64)
+			writeUleb128(w, uint64(len(idxs)-1))
+			for _, idx := range idxs {
+				writeUleb128(w, idx)
+			}
+
+		case ACall:
+			switch p.To.Type {
+			case obj.TYPE_CONST:
+				writeUleb128(w, uint64(p.To.Offset))
+
+			case obj.TYPE_MEM:
+				if p.To.Name != obj.NAME_EXTERN && p.To.Name != obj.NAME_STATIC {
+					fmt.Println(p.To)
+					panic("bad name for Call")
+				}
+				r := obj.Addrel(s)
+				r.Off = int32(w.Len())
+				r.Type = objabi.R_CALL
+				if p.Mark&WasmImport != 0 {
+					r.Type = objabi.R_WASMIMPORT
+				}
+				r.Sym = p.To.Sym
+
+			default:
+				panic("bad type for Call")
+			}
+
+		case ACallIndirect:
+			writeUleb128(w, uint64(p.To.Offset))
+			w.WriteByte(0x00) // reserved value
+
+		case AI32Const, AI64Const:
+			if p.From.Name == obj.NAME_EXTERN {
+				r := obj.Addrel(s)
+				r.Off = int32(w.Len())
+				r.Type = objabi.R_ADDR
+				r.Sym = p.From.Sym
+				r.Add = p.From.Offset
+				break
+			}
+			writeSleb128(w, p.From.Offset)
+
+		case AF64Const:
+			b := make([]byte, 8)
+			binary.LittleEndian.PutUint64(b, math.Float64bits(p.From.Val.(float64)))
+			w.Write(b)
+
+		case AI32Load, AI64Load, AF32Load, AF64Load, AI32Load8S, AI32Load8U, AI32Load16S, AI32Load16U, AI64Load8S, AI64Load8U, AI64Load16S, AI64Load16U, AI64Load32S, AI64Load32U:
+			if p.From.Offset < 0 {
+				panic("negative offset for *Load")
+			}
+			if p.From.Type != obj.TYPE_CONST {
+				panic("bad type for *Load")
+			}
+			writeUleb128(w, align(p.As))
+			writeUleb128(w, uint64(p.From.Offset))
+
+		case AI32Store, AI64Store, AF32Store, AF64Store, AI32Store8, AI32Store16, AI64Store8, AI64Store16, AI64Store32:
+			if p.To.Offset < 0 {
+				panic("negative offset")
+			}
+			writeUleb128(w, align(p.As))
+			writeUleb128(w, uint64(p.To.Offset))
+
+		case ACurrentMemory, AGrowMemory:
+			w.WriteByte(0x00)
+
+		}
+	}
+
+	w.WriteByte(0x0b) // end
+
+	s.P = w.Bytes()
+}
+
+func align(as obj.As) uint64 {
+	switch as {
+	case AI32Load8S, AI32Load8U, AI64Load8S, AI64Load8U, AI32Store8, AI64Store8:
+		return 0
+	case AI32Load16S, AI32Load16U, AI64Load16S, AI64Load16U, AI32Store16, AI64Store16:
+		return 1
+	case AI32Load, AF32Load, AI64Load32S, AI64Load32U, AI32Store, AF32Store, AI64Store32:
+		return 2
+	case AI64Load, AF64Load, AI64Store, AF64Store:
+		return 3
+	default:
+		panic("align: bad op")
+	}
+}
+
+func writeUleb128(w io.ByteWriter, v uint64) {
+	more := true
+	for more {
+		c := uint8(v & 0x7f)
+		v >>= 7
+		more = v != 0
+		if more {
+			c |= 0x80
+		}
+		w.WriteByte(c)
+	}
+}
+
+func writeSleb128(w io.ByteWriter, v int64) {
+	more := true
+	for more {
+		c := uint8(v & 0x7f)
+		s := uint8(v & 0x40)
+		v >>= 7
+		more = !((v == 0 && s == 0) || (v == -1 && s != 0))
+		if more {
+			c |= 0x80
+		}
+		w.WriteByte(c)
+	}
+}
diff --git a/src/cmd/internal/objabi/head.go b/src/cmd/internal/objabi/head.go
index ff19606cd2..23c7b62daf 100644
--- a/src/cmd/internal/objabi/head.go
+++ b/src/cmd/internal/objabi/head.go
@@ -40,6 +40,7 @@ const (
 	Hdarwin
 	Hdragonfly
 	Hfreebsd
+	Hjs
 	Hlinux
 	Hnacl
 	Hnetbsd
@@ -57,6 +58,8 @@ func (h *HeadType) Set(s string) error {
 		*h = Hdragonfly
 	case "freebsd":
 		*h = Hfreebsd
+	case "js":
+		*h = Hjs
 	case "linux", "android":
 		*h = Hlinux
 	case "nacl":
@@ -85,6 +88,8 @@ func (h *HeadType) String() string {
 		return "dragonfly"
 	case Hfreebsd:
 		return "freebsd"
+	case Hjs:
+		return "js"
 	case Hlinux:
 		return "linux"
 	case Hnacl:
diff --git a/src/cmd/internal/objabi/reloctype.go b/src/cmd/internal/objabi/reloctype.go
index ac96b3a71b..a3e2868a1b 100644
--- a/src/cmd/internal/objabi/reloctype.go
+++ b/src/cmd/internal/objabi/reloctype.go
@@ -193,6 +193,9 @@ const (
 	// R_ADDRCUOFF resolves to a pointer-sized offset from the start of the
 	// symbol's DWARF compile unit.
 	R_ADDRCUOFF
+
+	// R_WASMIMPORT resolves to the index of the WebAssembly function import.
+	R_WASMIMPORT
 )
 
 // IsDirectJump returns whether r is a relocation for a direct jump.
diff --git a/src/cmd/internal/sys/arch.go b/src/cmd/internal/sys/arch.go
index c761a834b3..487c9260e8 100644
--- a/src/cmd/internal/sys/arch.go
+++ b/src/cmd/internal/sys/arch.go
@@ -21,6 +21,7 @@ const (
 	MIPS64
 	PPC64
 	S390X
+	Wasm
 )
 
 // Arch represents an individual architecture.
@@ -160,6 +161,15 @@ var ArchS390X = &Arch{
 	MinLC:     2,
 }
 
+var ArchWasm = &Arch{
+	Name:      "wasm",
+	Family:    Wasm,
+	ByteOrder: binary.LittleEndian,
+	PtrSize:   8,
+	RegSize:   8,
+	MinLC:     1,
+}
+
 var Archs = [...]*Arch{
 	Arch386,
 	ArchAMD64,
@@ -173,4 +183,5 @@ var Archs = [...]*Arch{
 	ArchPPC64,
 	ArchPPC64LE,
 	ArchS390X,
+	ArchWasm,
 }