diff --git a/src/cmd/compile/internal/ssa/_gen/386.rules b/src/cmd/compile/internal/ssa/_gen/386.rules
index db16ab0961..03413b289e 100644
--- a/src/cmd/compile/internal/ssa/_gen/386.rules
+++ b/src/cmd/compile/internal/ssa/_gen/386.rules
@@ -56,8 +56,12 @@
 (Sqrt ...) => (SQRTSD ...)
 (Sqrt32 ...) => (SQRTSS ...)
 
+(Ctz8 x) => (BSFL (ORLconst <typ.UInt32> [0x100] x))
+(Ctz8NonZero ...) => (BSFL ...)
 (Ctz16 x) => (BSFL (ORLconst <typ.UInt32> [0x10000] x))
 (Ctz16NonZero ...) => (BSFL ...)
+(Ctz32 ...) => (LoweredCtz32 ...)
+(Ctz32NonZero ...) => (BSFL ...)
 
 // Lowering extension
 (SignExt8to16  ...) => (MOVBLSX ...)
diff --git a/src/cmd/compile/internal/ssa/_gen/386Ops.go b/src/cmd/compile/internal/ssa/_gen/386Ops.go
index 6f19ea6427..7401ac871c 100644
--- a/src/cmd/compile/internal/ssa/_gen/386Ops.go
+++ b/src/cmd/compile/internal/ssa/_gen/386Ops.go
@@ -302,6 +302,7 @@ func init() {
 
 		{name: "BSFL", argLength: 1, reg: gp11, asm: "BSFL", clobberFlags: true}, // arg0 # of low-order zeroes ; undef if zero
 		{name: "BSFW", argLength: 1, reg: gp11, asm: "BSFW", clobberFlags: true}, // arg0 # of low-order zeroes ; undef if zero
+		{name: "LoweredCtz32", argLength: 1, reg: gp11, clobberFlags: true},      // arg0 # of low-order zeroes
 
 		{name: "BSRL", argLength: 1, reg: gp11, asm: "BSRL", clobberFlags: true}, // arg0 # of high-order zeroes ; undef if zero
 		{name: "BSRW", argLength: 1, reg: gp11, asm: "BSRW", clobberFlags: true}, // arg0 # of high-order zeroes ; undef if zero
diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index 4a24012b1d..b5ca35953c 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -456,6 +456,7 @@ const (
 	Op386NOTL
 	Op386BSFL
 	Op386BSFW
+	Op386LoweredCtz32
 	Op386BSRL
 	Op386BSRW
 	Op386BSWAPL
@@ -5034,6 +5035,20 @@ var opcodeTable = [...]opInfo{
 			},
 		},
 	},
+	{
+		name:         "LoweredCtz32",
+		argLen:       1,
+		clobberFlags: true,
+		asm:          x86.ABSFL,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 239}, // AX CX DX BX BP SI DI
+			},
+			outputs: []outputInfo{
+				{0, 239}, // AX CX DX BX BP SI DI
+			},
+		},
+	},
 	{
 		name:         "BSRL",
 		argLen:       1,
diff --git a/src/cmd/compile/internal/ssa/rewrite386.go b/src/cmd/compile/internal/ssa/rewrite386.go
index f658d9380a..fe5bbe56a3 100644
--- a/src/cmd/compile/internal/ssa/rewrite386.go
+++ b/src/cmd/compile/internal/ssa/rewrite386.go
@@ -315,6 +315,17 @@ func rewriteValue386(v *Value) bool {
 	case OpCtz16NonZero:
 		v.Op = Op386BSFL
 		return true
+	case OpCtz32:
+		v.Op = Op386LoweredCtz32
+		return true
+	case OpCtz32NonZero:
+		v.Op = Op386BSFL
+		return true
+	case OpCtz8:
+		return rewriteValue386_OpCtz8(v)
+	case OpCtz8NonZero:
+		v.Op = Op386BSFL
+		return true
 	case OpCvt32Fto32:
 		v.Op = Op386CVTTSS2SL
 		return true
@@ -8527,6 +8538,22 @@ func rewriteValue386_OpCtz16(v *Value) bool {
 		return true
 	}
 }
+func rewriteValue386_OpCtz8(v *Value) bool {
+	v_0 := v.Args[0]
+	b := v.Block
+	typ := &b.Func.Config.Types
+	// match: (Ctz8 x)
+	// result: (BSFL (ORLconst <typ.UInt32> [0x100] x))
+	for {
+		x := v_0
+		v.reset(Op386BSFL)
+		v0 := b.NewValue0(v.Pos, Op386ORLconst, typ.UInt32)
+		v0.AuxInt = int32ToAuxInt(0x100)
+		v0.AddArg(x)
+		v.AddArg(v0)
+		return true
+	}
+}
 func rewriteValue386_OpDiv8(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index b4a55c00af..e49ba5ee71 100644
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -4492,12 +4492,12 @@ func InitTables() {
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpCtz64, types.Types[types.TINT], args[0])
 		},
-		sys.AMD64, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64, sys.Wasm)
+		sys.AMD64, sys.I386, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64, sys.Wasm)
 	addF("math/bits", "TrailingZeros32",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpCtz32, types.Types[types.TINT], args[0])
 		},
-		sys.AMD64, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64, sys.Wasm)
+		sys.AMD64, sys.I386, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64, sys.Wasm)
 	addF("math/bits", "TrailingZeros16",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			x := s.newValue1(ssa.OpZeroExt16to32, types.Types[types.TUINT32], args[0])
@@ -4531,7 +4531,7 @@ func InitTables() {
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpCtz8, types.Types[types.TINT], args[0])
 		},
-		sys.AMD64, sys.ARM, sys.ARM64, sys.Wasm)
+		sys.AMD64, sys.I386, sys.ARM, sys.ARM64, sys.Wasm)
 	addF("math/bits", "TrailingZeros8",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			x := s.newValue1(ssa.OpZeroExt8to64, types.Types[types.TUINT64], args[0])
diff --git a/src/cmd/compile/internal/x86/ssa.go b/src/cmd/compile/internal/x86/ssa.go
index 6c92ca1f56..811a34cc0b 100644
--- a/src/cmd/compile/internal/x86/ssa.go
+++ b/src/cmd/compile/internal/x86/ssa.go
@@ -831,6 +831,29 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		if base.Debug.Nil != 0 && v.Pos.Line() > 1 { // v.Pos.Line()==1 in generated wrappers
 			base.WarnfAt(v.Pos, "generated nil check")
 		}
+	case ssa.Op386LoweredCtz32:
+		// BSFL in, out
+		p := s.Prog(x86.ABSFL)
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = v.Args[0].Reg()
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = v.Reg()
+
+		// JNZ 2(PC)
+		p1 := s.Prog(x86.AJNE)
+		p1.To.Type = obj.TYPE_BRANCH
+
+		// MOVL $32, out
+		p2 := s.Prog(x86.AMOVL)
+		p2.From.Type = obj.TYPE_CONST
+		p2.From.Offset = 32
+		p2.To.Type = obj.TYPE_REG
+		p2.To.Reg = v.Reg()
+
+		// NOP (so the JNZ has somewhere to land)
+		nop := s.Prog(obj.ANOP)
+		p1.To.SetTarget(nop)
+
 	case ssa.OpClobber:
 		p := s.Prog(x86.AMOVL)
 		p.From.Type = obj.TYPE_CONST
diff --git a/test/codegen/mathbits.go b/test/codegen/mathbits.go
index 86a44d7c93..8c971cf760 100644
--- a/test/codegen/mathbits.go
+++ b/test/codegen/mathbits.go
@@ -293,6 +293,7 @@ func RotateLeftVariable32(n uint32, m int) uint32 {
 func TrailingZeros(n uint) int {
 	// amd64/v1,amd64/v2:"BSFQ","MOVL\t\\$64","CMOVQEQ"
 	// amd64/v3:"TZCNTQ"
+	// 386:"BSFL"
 	// arm:"CLZ"
 	// arm64:"RBIT","CLZ"
 	// s390x:"FLOGR"
@@ -305,6 +306,7 @@ func TrailingZeros(n uint) int {
 func TrailingZeros64(n uint64) int {
 	// amd64/v1,amd64/v2:"BSFQ","MOVL\t\\$64","CMOVQEQ"
 	// amd64/v3:"TZCNTQ"
+	// 386:"BSFL"
 	// arm64:"RBIT","CLZ"
 	// s390x:"FLOGR"
 	// ppc64x/power8:"ANDN","POPCNTD"
@@ -322,6 +324,7 @@ func TrailingZeros64Subtract(n uint64) int {
 func TrailingZeros32(n uint32) int {
 	// amd64/v1,amd64/v2:"BTSQ\\t\\$32","BSFQ"
 	// amd64/v3:"TZCNTL"
+	// 386:"BSFL"
 	// arm:"CLZ"
 	// arm64:"RBITW","CLZW"
 	// s390x:"FLOGR","MOVWZ"
@@ -345,6 +348,7 @@ func TrailingZeros16(n uint16) int {
 
 func TrailingZeros8(n uint8) int {
 	// amd64:"BSFL","BTSL\\t\\$8"
+	// 386:"BSFL"
 	// arm:"ORR\t\\$256","CLZ",-"MOVBU\tR"
 	// arm64:"ORR\t\\$256","RBITW","CLZW",-"MOVBU\tR",-"RBIT\t",-"CLZ\t"
 	// s390x:"FLOGR","OR\t\\$256"