diff --git a/src/cmd/compile/internal/amd64/ssa.go b/src/cmd/compile/internal/amd64/ssa.go
index ebeff445d6..54c0c0fb5a 100644
--- a/src/cmd/compile/internal/amd64/ssa.go
+++ b/src/cmd/compile/internal/amd64/ssa.go
@@ -303,6 +303,20 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 			m.To.Reg = x86.REG_DX
 		}
 
+	case ssa.OpAMD64MULQU2:
+		// Arg[0] is already in AX as it's the only register we allow
+		// results hi in DX, lo in AX
+		p := gc.Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = v.Args[1].Reg()
+
+	case ssa.OpAMD64DIVQU2:
+		// Arg[0], Arg[1] are already in Dx, AX, as they're the only registers we allow
+		// results q in AX, r in DX
+		p := gc.Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = v.Args[2].Reg()
+
 	case ssa.OpAMD64AVGQU:
 		// compute (x+y)/2 unsigned.
 		// Do a 64-bit add, the overflow goes into the carry.
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 8e9e915fd4..1e653fe619 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -545,6 +545,22 @@ func (s *state) stmt(n *Node) {
 		s.assign(n.List.Second(), resok, false, false, n.Lineno, 0, false)
 		return
 
+	case OAS2FUNC:
+		// We come here only when it is an intrinsic call returning two values.
+		if !isIntrinsicCall(n.Rlist.First()) {
+			s.Fatalf("non-intrinsic AS2FUNC not expanded %v", n.Rlist.First())
+		}
+		v := s.intrinsicCall(n.Rlist.First())
+		v1 := s.newValue1(ssa.OpSelect0, n.List.First().Type, v)
+		v2 := s.newValue1(ssa.OpSelect1, n.List.Second().Type, v)
+		// Make a fake node to mimic loading return value, ONLY for write barrier test.
+		// This is future-proofing against non-scalar 2-result intrinsics.
+		// Currently we only have scalar ones, which result in no write barrier.
+		fakeret := &Node{Op: OINDREG, Reg: int16(Thearch.REGSP)}
+		s.assign(n.List.First(), v1, needwritebarrier(n.List.First(), fakeret), false, n.Lineno, 0, false)
+		s.assign(n.List.Second(), v2, needwritebarrier(n.List.Second(), fakeret), false, n.Lineno, 0, false)
+		return
+
 	case ODCL:
 		if n.Left.Class == PAUTOHEAP {
 			Fatalf("DCL %v", n)
@@ -2483,23 +2499,15 @@ type sizedIntrinsicKey struct {
 }
 
 // disableForInstrumenting returns nil when instrumenting, fn otherwise
-func disableForInstrumenting(fn func(*state, *Node) *ssa.Value) func(*state, *Node) *ssa.Value {
+func disableForInstrumenting(fn intrinsicBuilder) intrinsicBuilder {
 	if instrumenting {
 		return nil
 	}
 	return fn
 }
 
-// enableForRuntime returns fn when compiling runtime, nil otherwise
-func enableForRuntime(fn func(*state, *Node) *ssa.Value) func(*state, *Node) *ssa.Value {
-	if compiling_runtime {
-		return fn
-	}
-	return nil
-}
-
 // enableOnArch returns fn on given archs, nil otherwise
-func enableOnArch(fn func(*state, *Node) *ssa.Value, archs ...sys.ArchFamily) func(*state, *Node) *ssa.Value {
+func enableOnArch(fn intrinsicBuilder, archs ...sys.ArchFamily) intrinsicBuilder {
 	if Thearch.LinkArch.InFamily(archs...) {
 		return fn
 	}
@@ -2513,9 +2521,7 @@ func intrinsicInit() {
 	// initial set of intrinsics.
 	i.std = map[intrinsicKey]intrinsicBuilder{
 		/******** runtime ********/
-		intrinsicKey{"", "slicebytetostringtmp"}: enableForRuntime(disableForInstrumenting(func(s *state, n *Node) *ssa.Value {
-			// pkg name left empty because intrinsification only should apply
-			// inside the runtime package when non instrumented.
+		intrinsicKey{"runtime", "slicebytetostringtmp"}: disableForInstrumenting(func(s *state, n *Node) *ssa.Value {
 			// Compiler frontend optimizations emit OARRAYBYTESTRTMP nodes
 			// for the backend instead of slicebytetostringtmp calls
 			// when not instrumenting.
@@ -2523,7 +2529,7 @@ func intrinsicInit() {
 			ptr := s.newValue1(ssa.OpSlicePtr, ptrto(Types[TUINT8]), slice)
 			len := s.newValue1(ssa.OpSliceLen, Types[TINT], slice)
 			return s.newValue2(ssa.OpStringMake, n.Type, ptr, len)
-		})),
+		}),
 		intrinsicKey{"runtime", "KeepAlive"}: func(s *state, n *Node) *ssa.Value {
 			data := s.newValue1(ssa.OpIData, ptrto(Types[TUINT8]), s.intrinsicFirstArg(n))
 			s.vars[&memVar] = s.newValue2(ssa.OpKeepAlive, ssa.TypeMem, data, s.mem())
@@ -2717,6 +2723,16 @@ func intrinsicInit() {
 		i.std[intrinsicKey{"runtime/internal/atomic", "Xadd"}]
 	i.ptrSized[sizedIntrinsicKey{"sync/atomic", "AddUintptr", 8}] =
 		i.std[intrinsicKey{"runtime/internal/atomic", "Xadd64"}]
+
+	/******** math/big ********/
+	i.intSized[sizedIntrinsicKey{"math/big", "mulWW", 8}] =
+		enableOnArch(func(s *state, n *Node) *ssa.Value {
+			return s.newValue2(ssa.OpMul64uhilo, ssa.MakeTuple(Types[TUINT64], Types[TUINT64]), s.intrinsicArg(n, 0), s.intrinsicArg(n, 1))
+		}, sys.AMD64)
+	i.intSized[sizedIntrinsicKey{"math/big", "divWW", 8}] =
+		enableOnArch(func(s *state, n *Node) *ssa.Value {
+			return s.newValue3(ssa.OpDiv128u, ssa.MakeTuple(Types[TUINT64], Types[TUINT64]), s.intrinsicArg(n, 0), s.intrinsicArg(n, 1), s.intrinsicArg(n, 2))
+		}, sys.AMD64)
 }
 
 // findIntrinsic returns a function which builds the SSA equivalent of the
@@ -2732,6 +2748,9 @@ func findIntrinsic(sym *Sym) intrinsicBuilder {
 		intrinsicInit()
 	}
 	pkg := sym.Pkg.Path
+	if sym.Pkg == localpkg {
+		pkg = myimportpath
+	}
 	fn := sym.Name
 	f := intrinsics.std[intrinsicKey{pkg, fn}]
 	if f != nil {
diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index 3d4a49bebe..ddd36e7b18 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -813,7 +813,7 @@ opswitch:
 		}
 		n = liststmt(ll)
 
-		// a,b,... = fn()
+	// a,b,... = fn()
 	case OAS2FUNC:
 		init.AppendNodes(&n.Ninit)
 
@@ -821,6 +821,11 @@ opswitch:
 		walkexprlistsafe(n.List.Slice(), init)
 		r = walkexpr(r, init)
 
+		if isIntrinsicCall(r) {
+			n.Rlist.Set1(r)
+			break
+		}
+
 		ll := ascompatet(n.Op, n.List, r.Type, 0, init)
 		for i, n := range ll {
 			ll[i] = applywritebarrier(n)
diff --git a/src/cmd/compile/internal/ssa/gen/AMD64.rules b/src/cmd/compile/internal/ssa/gen/AMD64.rules
index 175c899ff6..65d85c4231 100644
--- a/src/cmd/compile/internal/ssa/gen/AMD64.rules
+++ b/src/cmd/compile/internal/ssa/gen/AMD64.rules
@@ -49,6 +49,9 @@
 (Hmul8   x y) -> (HMULB  x y)
 (Hmul8u  x y) -> (HMULBU x y)
 
+(Mul64uhilo x y) -> (MULQU2 x y)
+(Div128u xhi xlo y) -> (DIVQU2 xhi xlo y)
+
 (Avg64u x y) -> (AVGQU x y)
 
 (Mod64  x y) -> (Select1 (DIVQ  x y))
diff --git a/src/cmd/compile/internal/ssa/gen/AMD64Ops.go b/src/cmd/compile/internal/ssa/gen/AMD64Ops.go
index f9739e90fc..7dacfe3cf2 100644
--- a/src/cmd/compile/internal/ssa/gen/AMD64Ops.go
+++ b/src/cmd/compile/internal/ssa/gen/AMD64Ops.go
@@ -211,6 +211,9 @@ func init() {
 		{name: "DIVLU", argLength: 2, reg: gp11div, typ: "(UInt32,UInt32)", asm: "DIVL", clobberFlags: true}, // [arg0 / arg1, arg0 % arg1]
 		{name: "DIVWU", argLength: 2, reg: gp11div, typ: "(UInt16,UInt16)", asm: "DIVW", clobberFlags: true}, // [arg0 / arg1, arg0 % arg1]
 
+		{name: "MULQU2", argLength: 2, reg: regInfo{inputs: []regMask{ax, gpsp}, outputs: []regMask{dx, ax}}, asm: "MULQ", clobberFlags: true},     // arg0 * arg1, returns (hi, lo)
+		{name: "DIVQU2", argLength: 3, reg: regInfo{inputs: []regMask{dx, ax, gpsp}, outputs: []regMask{ax, dx}}, asm: "DIVQ", clobberFlags: true}, // arg0:arg1 / arg2 (128-bit divided by 64-bit), returns (q, r)
+
 		{name: "ANDQ", argLength: 2, reg: gp21, asm: "ANDQ", commutative: true, resultInArg0: true, clobberFlags: true}, // arg0 & arg1
 		{name: "ANDL", argLength: 2, reg: gp21, asm: "ANDL", commutative: true, resultInArg0: true, clobberFlags: true}, // arg0 & arg1
 		{name: "ANDQconst", argLength: 1, reg: gp11, asm: "ANDQ", aux: "Int64", resultInArg0: true, clobberFlags: true}, // arg0 & auxint
diff --git a/src/cmd/compile/internal/ssa/gen/genericOps.go b/src/cmd/compile/internal/ssa/gen/genericOps.go
index c1bc38c13f..22ddc8fb82 100644
--- a/src/cmd/compile/internal/ssa/gen/genericOps.go
+++ b/src/cmd/compile/internal/ssa/gen/genericOps.go
@@ -58,6 +58,9 @@ var genericOps = []opData{
 	{name: "Hmul64", argLength: 2},
 	{name: "Hmul64u", argLength: 2},
 
+	{name: "Mul32uhilo", argLength: 2, typ: "(UInt32,UInt32)"}, // arg0 * arg1, returns (hi, lo)
+	{name: "Mul64uhilo", argLength: 2, typ: "(UInt64,UInt64)"}, // arg0 * arg1, returns (hi, lo)
+
 	// Weird special instruction for strength reduction of divides.
 	{name: "Avg64u", argLength: 2}, // (uint64(arg0) + uint64(arg1)) / 2, correct to all 64 bits.
 
@@ -69,6 +72,7 @@ var genericOps = []opData{
 	{name: "Div32u", argLength: 2},
 	{name: "Div64", argLength: 2},
 	{name: "Div64u", argLength: 2},
+	{name: "Div128u", argLength: 3}, // arg0:arg1 / arg2 (128-bit divided by 64-bit), returns (q, r)
 
 	{name: "Mod8", argLength: 2},  // arg0 % arg1, signed
 	{name: "Mod8u", argLength: 2}, // arg0 % arg1, unsigned
@@ -424,8 +428,6 @@ var genericOps = []opData{
 	{name: "Sub32carry", argLength: 2, typ: "(UInt32,Flags)"}, // arg0 - arg1, returns (value, carry)
 	{name: "Sub32withcarry", argLength: 3},                    // arg0 - arg1 - arg2, arg2=carry (0 or 1)
 
-	{name: "Mul32uhilo", argLength: 2, typ: "(UInt32,UInt32)"}, // arg0 * arg1, returns (hi, lo)
-
 	{name: "Signmask", argLength: 1, typ: "Int32"},  // 0 if arg0 >= 0, -1 if arg0 < 0
 	{name: "Zeromask", argLength: 1, typ: "UInt32"}, // 0 if arg0 == 0, 0xffffffff if arg0 != 0
 
diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index cd897198d4..1a0e989c3d 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -442,6 +442,8 @@ const (
 	OpAMD64DIVQU
 	OpAMD64DIVLU
 	OpAMD64DIVWU
+	OpAMD64MULQU2
+	OpAMD64DIVQU2
 	OpAMD64ANDQ
 	OpAMD64ANDL
 	OpAMD64ANDQconst
@@ -1443,6 +1445,8 @@ const (
 	OpHmul32u
 	OpHmul64
 	OpHmul64u
+	OpMul32uhilo
+	OpMul64uhilo
 	OpAvg64u
 	OpDiv8
 	OpDiv8u
@@ -1452,6 +1456,7 @@ const (
 	OpDiv32u
 	OpDiv64
 	OpDiv64u
+	OpDiv128u
 	OpMod8
 	OpMod8u
 	OpMod16
@@ -1702,7 +1707,6 @@ const (
 	OpAdd32withcarry
 	OpSub32carry
 	OpSub32withcarry
-	OpMul32uhilo
 	OpSignmask
 	OpZeromask
 	OpCvt32Uto32F
@@ -4904,6 +4908,39 @@ var opcodeTable = [...]opInfo{
 			},
 		},
 	},
+	{
+		name:         "MULQU2",
+		argLen:       2,
+		clobberFlags: true,
+		asm:          x86.AMULQ,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 1},     // AX
+				{1, 65535}, // AX CX DX BX SP BP SI DI R8 R9 R10 R11 R12 R13 R14 R15
+			},
+			outputs: []outputInfo{
+				{0, 4}, // DX
+				{1, 1}, // AX
+			},
+		},
+	},
+	{
+		name:         "DIVQU2",
+		argLen:       3,
+		clobberFlags: true,
+		asm:          x86.ADIVQ,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 4},     // DX
+				{1, 1},     // AX
+				{2, 65535}, // AX CX DX BX SP BP SI DI R8 R9 R10 R11 R12 R13 R14 R15
+			},
+			outputs: []outputInfo{
+				{0, 1}, // AX
+				{1, 4}, // DX
+			},
+		},
+	},
 	{
 		name:         "ANDQ",
 		argLen:       2,
@@ -17959,6 +17996,16 @@ var opcodeTable = [...]opInfo{
 		argLen:  2,
 		generic: true,
 	},
+	{
+		name:    "Mul32uhilo",
+		argLen:  2,
+		generic: true,
+	},
+	{
+		name:    "Mul64uhilo",
+		argLen:  2,
+		generic: true,
+	},
 	{
 		name:    "Avg64u",
 		argLen:  2,
@@ -18004,6 +18051,11 @@ var opcodeTable = [...]opInfo{
 		argLen:  2,
 		generic: true,
 	},
+	{
+		name:    "Div128u",
+		argLen:  3,
+		generic: true,
+	},
 	{
 		name:    "Mod8",
 		argLen:  2,
@@ -19313,11 +19365,6 @@ var opcodeTable = [...]opInfo{
 		argLen:  3,
 		generic: true,
 	},
-	{
-		name:    "Mul32uhilo",
-		argLen:  2,
-		generic: true,
-	},
 	{
 		name:    "Signmask",
 		argLen:  1,
diff --git a/src/cmd/compile/internal/ssa/rewriteAMD64.go b/src/cmd/compile/internal/ssa/rewriteAMD64.go
index a55b7ff6fb..f36a5aa439 100644
--- a/src/cmd/compile/internal/ssa/rewriteAMD64.go
+++ b/src/cmd/compile/internal/ssa/rewriteAMD64.go
@@ -394,6 +394,8 @@ func rewriteValueAMD64(v *Value, config *Config) bool {
 		return rewriteValueAMD64_OpCvt64to64F(v, config)
 	case OpDeferCall:
 		return rewriteValueAMD64_OpDeferCall(v, config)
+	case OpDiv128u:
+		return rewriteValueAMD64_OpDiv128u(v, config)
 	case OpDiv16:
 		return rewriteValueAMD64_OpDiv16(v, config)
 	case OpDiv16u:
@@ -612,6 +614,8 @@ func rewriteValueAMD64(v *Value, config *Config) bool {
 		return rewriteValueAMD64_OpMul64(v, config)
 	case OpMul64F:
 		return rewriteValueAMD64_OpMul64F(v, config)
+	case OpMul64uhilo:
+		return rewriteValueAMD64_OpMul64uhilo(v, config)
 	case OpMul8:
 		return rewriteValueAMD64_OpMul8(v, config)
 	case OpNeg16:
@@ -14268,6 +14272,23 @@ func rewriteValueAMD64_OpDeferCall(v *Value, config *Config) bool {
 		return true
 	}
 }
+func rewriteValueAMD64_OpDiv128u(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (Div128u xhi xlo y)
+	// cond:
+	// result: (DIVQU2 xhi xlo y)
+	for {
+		xhi := v.Args[0]
+		xlo := v.Args[1]
+		y := v.Args[2]
+		v.reset(OpAMD64DIVQU2)
+		v.AddArg(xhi)
+		v.AddArg(xlo)
+		v.AddArg(y)
+		return true
+	}
+}
 func rewriteValueAMD64_OpDiv16(v *Value, config *Config) bool {
 	b := v.Block
 	_ = b
@@ -16667,6 +16688,21 @@ func rewriteValueAMD64_OpMul64F(v *Value, config *Config) bool {
 		return true
 	}
 }
+func rewriteValueAMD64_OpMul64uhilo(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (Mul64uhilo x y)
+	// cond:
+	// result: (MULQU2 x y)
+	for {
+		x := v.Args[0]
+		y := v.Args[1]
+		v.reset(OpAMD64MULQU2)
+		v.AddArg(x)
+		v.AddArg(y)
+		return true
+	}
+}
 func rewriteValueAMD64_OpMul8(v *Value, config *Config) bool {
 	b := v.Block
 	_ = b