diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index c8befa40cdb7d0..95904edd6a063d 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -3327,7 +3327,7 @@ func init() {
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpBitLen32, types.Types[TINT], args[0])
 		},
-		sys.AMD64)
+		sys.AMD64, sys.ARM64)
 	addF("math/bits", "Len32",
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			if s.config.PtrSize == 4 {
@@ -3336,7 +3336,7 @@ func init() {
 			x := s.newValue1(ssa.OpZeroExt32to64, types.Types[TUINT64], args[0])
 			return s.newValue1(ssa.OpBitLen64, types.Types[TINT], x)
 		},
-		sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64)
+		sys.ARM, sys.S390X, sys.MIPS, sys.PPC64)
 	addF("math/bits", "Len16",
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			if s.config.PtrSize == 4 {
diff --git a/src/cmd/compile/internal/ssa/gen/ARM64.rules b/src/cmd/compile/internal/ssa/gen/ARM64.rules
index 1efce66016910b..fc806f75a0ebd4 100644
--- a/src/cmd/compile/internal/ssa/gen/ARM64.rules
+++ b/src/cmd/compile/internal/ssa/gen/ARM64.rules
@@ -123,6 +123,7 @@
 (FMOVSload [off] {sym} ptr (MOVWstore [off] {sym} ptr val _)) -> (FMOVSgpfp val)
 
 (BitLen64 x) -> (SUB (MOVDconst [64]) (CLZ <typ.Int> x))
+(BitLen32 x) -> (SUB (MOVDconst [32]) (CLZW <typ.Int> x))
 
 (Bswap64 x) -> (REV x)
 (Bswap32 x) -> (REVW x)
diff --git a/src/cmd/compile/internal/ssa/rewriteARM64.go b/src/cmd/compile/internal/ssa/rewriteARM64.go
index 2afd0f335ea645..05b8b9c6973337 100644
--- a/src/cmd/compile/internal/ssa/rewriteARM64.go
+++ b/src/cmd/compile/internal/ssa/rewriteARM64.go
@@ -427,6 +427,8 @@ func rewriteValueARM64(v *Value) bool {
 		return rewriteValueARM64_OpAtomicStorePtrNoWB_0(v)
 	case OpAvg64u:
 		return rewriteValueARM64_OpAvg64u_0(v)
+	case OpBitLen32:
+		return rewriteValueARM64_OpBitLen32_0(v)
 	case OpBitLen64:
 		return rewriteValueARM64_OpBitLen64_0(v)
 	case OpBitRev16:
@@ -32715,6 +32717,26 @@ func rewriteValueARM64_OpAvg64u_0(v *Value) bool {
 		return true
 	}
 }
+func rewriteValueARM64_OpBitLen32_0(v *Value) bool {
+	b := v.Block
+	_ = b
+	typ := &b.Func.Config.Types
+	_ = typ
+	// match: (BitLen32 x)
+	// cond:
+	// result: (SUB (MOVDconst [32]) (CLZW <typ.Int> x))
+	for {
+		x := v.Args[0]
+		v.reset(OpARM64SUB)
+		v0 := b.NewValue0(v.Pos, OpARM64MOVDconst, typ.UInt64)
+		v0.AuxInt = 32
+		v.AddArg(v0)
+		v1 := b.NewValue0(v.Pos, OpARM64CLZW, typ.Int)
+		v1.AddArg(x)
+		v.AddArg(v1)
+		return true
+	}
+}
 func rewriteValueARM64_OpBitLen64_0(v *Value) bool {
 	b := v.Block
 	_ = b
diff --git a/test/codegen/mathbits.go b/test/codegen/mathbits.go
index 44ab2c02b75783..d8b1775b0fb019 100644
--- a/test/codegen/mathbits.go
+++ b/test/codegen/mathbits.go
@@ -31,7 +31,7 @@ func LeadingZeros64(n uint64) int {
 func LeadingZeros32(n uint32) int {
 	// amd64:"BSRQ","LEAQ",-"CMOVQEQ"
 	// s390x:"FLOGR"
-	// arm:"CLZ" arm64:"CLZ"
+	// arm:"CLZ" arm64:"CLZW"
 	// mips:"CLZ"
 	return bits.LeadingZeros32(n)
 }