diff --git a/cl/_testdata/print/out.ll b/cl/_testdata/print/out.ll
index 27462d72..800dd205 100644
--- a/cl/_testdata/print/out.ll
+++ b/cl/_testdata/print/out.ll
@@ -847,7 +847,7 @@ _llgo_3:                                          ; preds = %_llgo_0
 
 define void @main.printfloat(double %0) {
 _llgo_0:
-  %1 = fcmp one double %0, %0
+  %1 = fcmp une double %0, %0
   br i1 %1, label %_llgo_1, label %_llgo_3
 
 _llgo_1:                                          ; preds = %_llgo_0
diff --git a/cl/_testrt/builtin/in.go b/cl/_testrt/builtin/in.go
index e16f2465..86780665 100644
--- a/cl/_testrt/builtin/in.go
+++ b/cl/_testrt/builtin/in.go
@@ -40,7 +40,53 @@ func main() {
 		println(n)
 	}
 	println(demo, fn1, fn2, fn3)
+
+	for i, v := range "中abcd" {
+		println(i, v)
+	}
+
+	println(Inf(1), Inf(-1), NaN(), IsNaN(NaN()), IsNaN(1.0))
+
+	data1 := []byte("中abcd")
+	data2 := []rune("中abcd")
+	println(data1, data2)
+	println(string(data1), string(data2), string(data1[3]), string(data2[0]))
+	s1 := "abc"
+	s2 := "abd"
+	println(s1 == "abc", s1 == s2, s1 != s2, s1 < s2, s1 <= s2, s1 > s2, s1 >= s2)
 }
 
 func demo() {
 }
+
+const (
+	uvnan    = 0x7FF8000000000001
+	uvinf    = 0x7FF0000000000000
+	uvneginf = 0xFFF0000000000000
+	uvone    = 0x3FF0000000000000
+	mask     = 0x7FF
+	shift    = 64 - 11 - 1
+	bias     = 1023
+	signMask = 1 << 63
+	fracMask = 1<<shift - 1
+)
+
+// Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
+func Inf(sign int) float64 {
+	var v uint64
+	if sign >= 0 {
+		v = uvinf
+	} else {
+		v = uvneginf
+	}
+	return Float64frombits(v)
+}
+
+// NaN returns an IEEE 754 “not-a-number” value.
+func NaN() float64 { return Float64frombits(uvnan) }
+
+func IsNaN(f float64) (is bool) {
+	return f != f
+}
+
+func Float64frombits(b uint64) float64 { return *(*float64)(unsafe.Pointer(&b)) }
diff --git a/cl/_testrt/builtin/out.ll b/cl/_testrt/builtin/out.ll
index d6c806f3..dfc39090 100644
--- a/cl/_testrt/builtin/out.ll
+++ b/cl/_testrt/builtin/out.ll
@@ -17,7 +17,61 @@ source_filename = "main"
 @3 = private unnamed_addr constant [6 x i8] c"hello\00", align 1
 @4 = private unnamed_addr constant [4 x i8] c"def\00", align 1
 @5 = private unnamed_addr constant [5 x i8] c"ABCD\00", align 1
-@6 = private unnamed_addr constant [3 x i8] c"fn\00", align 1
+@6 = private unnamed_addr constant [8 x i8] c"\E4\B8\ADabcd\00", align 1
+@7 = private unnamed_addr constant [8 x i8] c"\E4\B8\ADabcd\00", align 1
+@8 = private unnamed_addr constant [8 x i8] c"\E4\B8\ADabcd\00", align 1
+@9 = private unnamed_addr constant [4 x i8] c"abc\00", align 1
+@10 = private unnamed_addr constant [4 x i8] c"abc\00", align 1
+@11 = private unnamed_addr constant [4 x i8] c"abc\00", align 1
+@12 = private unnamed_addr constant [4 x i8] c"abd\00", align 1
+@13 = private unnamed_addr constant [4 x i8] c"abc\00", align 1
+@14 = private unnamed_addr constant [4 x i8] c"abd\00", align 1
+@15 = private unnamed_addr constant [4 x i8] c"abc\00", align 1
+@16 = private unnamed_addr constant [4 x i8] c"abd\00", align 1
+@17 = private unnamed_addr constant [4 x i8] c"abc\00", align 1
+@18 = private unnamed_addr constant [4 x i8] c"abd\00", align 1
+@19 = private unnamed_addr constant [4 x i8] c"abc\00", align 1
+@20 = private unnamed_addr constant [4 x i8] c"abd\00", align 1
+@21 = private unnamed_addr constant [4 x i8] c"abc\00", align 1
+@22 = private unnamed_addr constant [4 x i8] c"abd\00", align 1
+@23 = private unnamed_addr constant [3 x i8] c"fn\00", align 1
+
+define double @main.Float64frombits(i64 %0) {
+_llgo_0:
+  %1 = call ptr @"github.com/goplus/llgo/internal/runtime.AllocZ"(i64 8)
+  store i64 %0, ptr %1, align 4
+  %2 = load double, ptr %1, align 8
+  ret double %2
+}
+
+define double @main.Inf(i64 %0) {
+_llgo_0:
+  %1 = icmp sge i64 %0, 0
+  br i1 %1, label %_llgo_1, label %_llgo_3
+
+_llgo_1:                                          ; preds = %_llgo_0
+  br label %_llgo_2
+
+_llgo_2:                                          ; preds = %_llgo_3, %_llgo_1
+  %2 = phi i64 [ 9218868437227405312, %_llgo_1 ], [ -4503599627370496, %_llgo_3 ]
+  %3 = call double @main.Float64frombits(i64 %2)
+  ret double %3
+
+_llgo_3:                                          ; preds = %_llgo_0
+  br label %_llgo_2
+}
+
+define i1 @main.IsNaN(double %0) {
+_llgo_0:
+  %1 = fcmp une double %0, %0
+  ret i1 %1
+}
+
+define double @main.NaN() {
+_llgo_0:
+  %0 = call double @main.Float64frombits(i64 9221120237041090561)
+  ret double %0
+}
 
 define void @main.demo() {
 _llgo_0:
@@ -380,13 +434,199 @@ _llgo_0:
   %175 = extractvalue { ptr, ptr } %174, 0
   call void @"github.com/goplus/llgo/internal/runtime.PrintPointer"(ptr %175)
   call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 10)
+  %176 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %177 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %176, i32 0, i32 0
+  store ptr @6, ptr %177, align 8
+  %178 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %176, i32 0, i32 1
+  store i64 7, ptr %178, align 4
+  %179 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %176, align 8
+  %180 = call ptr @"github.com/goplus/llgo/internal/runtime.NewStringIter"(%"github.com/goplus/llgo/internal/runtime.String" %179)
+  br label %_llgo_1
+
+_llgo_1:                                          ; preds = %_llgo_2, %_llgo_0
+  %181 = call { i1, i64, i32 } @"github.com/goplus/llgo/internal/runtime.StringIterNext"(ptr %180)
+  %182 = extractvalue { i1, i64, i32 } %181, 0
+  br i1 %182, label %_llgo_2, label %_llgo_3
+
+_llgo_2:                                          ; preds = %_llgo_1
+  %183 = extractvalue { i1, i64, i32 } %181, 1
+  %184 = extractvalue { i1, i64, i32 } %181, 2
+  call void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64 %183)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  %185 = sext i32 %184 to i64
+  call void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64 %185)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 10)
+  br label %_llgo_1
+
+_llgo_3:                                          ; preds = %_llgo_1
+  %186 = call double @main.Inf(i64 1)
+  %187 = call double @main.Inf(i64 -1)
+  %188 = call double @main.NaN()
+  %189 = call double @main.NaN()
+  %190 = call i1 @main.IsNaN(double %189)
+  %191 = call i1 @main.IsNaN(double 1.000000e+00)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintFloat"(double %186)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintFloat"(double %187)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintFloat"(double %188)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintBool"(i1 %190)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintBool"(i1 %191)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 10)
+  %192 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %193 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %192, i32 0, i32 0
+  store ptr @7, ptr %193, align 8
+  %194 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %192, i32 0, i32 1
+  store i64 7, ptr %194, align 4
+  %195 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %192, align 8
+  %196 = call %"github.com/goplus/llgo/internal/runtime.Slice" @"github.com/goplus/llgo/internal/runtime.StringToBytes"(%"github.com/goplus/llgo/internal/runtime.String" %195)
+  %197 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %198 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %197, i32 0, i32 0
+  store ptr @8, ptr %198, align 8
+  %199 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %197, i32 0, i32 1
+  store i64 7, ptr %199, align 4
+  %200 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %197, align 8
+  %201 = call %"github.com/goplus/llgo/internal/runtime.Slice" @"github.com/goplus/llgo/internal/runtime.StringToRunes"(%"github.com/goplus/llgo/internal/runtime.String" %200)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintSlice"(%"github.com/goplus/llgo/internal/runtime.Slice" %196)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintSlice"(%"github.com/goplus/llgo/internal/runtime.Slice" %201)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 10)
+  %202 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.StringFromBytes"(%"github.com/goplus/llgo/internal/runtime.Slice" %196)
+  %203 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.StringFromRunes"(%"github.com/goplus/llgo/internal/runtime.Slice" %201)
+  %204 = extractvalue %"github.com/goplus/llgo/internal/runtime.Slice" %196, 0
+  %205 = getelementptr inbounds i8, ptr %204, i64 3
+  %206 = load i8, ptr %205, align 1
+  %207 = sext i8 %206 to i32
+  %208 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.StringFromRune"(i32 %207)
+  %209 = extractvalue %"github.com/goplus/llgo/internal/runtime.Slice" %201, 0
+  %210 = getelementptr inbounds i32, ptr %209, i64 0
+  %211 = load i32, ptr %210, align 4
+  %212 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.StringFromRune"(i32 %211)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %202)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %203)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %208)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %212)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 10)
+  %213 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %214 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %213, i32 0, i32 0
+  store ptr @9, ptr %214, align 8
+  %215 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %213, i32 0, i32 1
+  store i64 3, ptr %215, align 4
+  %216 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %213, align 8
+  %217 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %218 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %217, i32 0, i32 0
+  store ptr @10, ptr %218, align 8
+  %219 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %217, i32 0, i32 1
+  store i64 3, ptr %219, align 4
+  %220 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %217, align 8
+  %221 = call i1 @"github.com/goplus/llgo/internal/runtime.StringEqual"(%"github.com/goplus/llgo/internal/runtime.String" %216, %"github.com/goplus/llgo/internal/runtime.String" %220)
+  %222 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %223 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %222, i32 0, i32 0
+  store ptr @11, ptr %223, align 8
+  %224 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %222, i32 0, i32 1
+  store i64 3, ptr %224, align 4
+  %225 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %222, align 8
+  %226 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %227 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %226, i32 0, i32 0
+  store ptr @12, ptr %227, align 8
+  %228 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %226, i32 0, i32 1
+  store i64 3, ptr %228, align 4
+  %229 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %226, align 8
+  %230 = call i1 @"github.com/goplus/llgo/internal/runtime.StringEqual"(%"github.com/goplus/llgo/internal/runtime.String" %225, %"github.com/goplus/llgo/internal/runtime.String" %229)
+  %231 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %232 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %231, i32 0, i32 0
+  store ptr @13, ptr %232, align 8
+  %233 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %231, i32 0, i32 1
+  store i64 3, ptr %233, align 4
+  %234 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %231, align 8
+  %235 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %236 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %235, i32 0, i32 0
+  store ptr @14, ptr %236, align 8
+  %237 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %235, i32 0, i32 1
+  store i64 3, ptr %237, align 4
+  %238 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %235, align 8
+  %239 = call i1 @"github.com/goplus/llgo/internal/runtime.StringEqual"(%"github.com/goplus/llgo/internal/runtime.String" %234, %"github.com/goplus/llgo/internal/runtime.String" %238)
+  %240 = xor i1 %239, true
+  %241 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %242 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %241, i32 0, i32 0
+  store ptr @15, ptr %242, align 8
+  %243 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %241, i32 0, i32 1
+  store i64 3, ptr %243, align 4
+  %244 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %241, align 8
+  %245 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %246 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %245, i32 0, i32 0
+  store ptr @16, ptr %246, align 8
+  %247 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %245, i32 0, i32 1
+  store i64 3, ptr %247, align 4
+  %248 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %245, align 8
+  %249 = call i1 @"github.com/goplus/llgo/internal/runtime.StringLess"(%"github.com/goplus/llgo/internal/runtime.String" %244, %"github.com/goplus/llgo/internal/runtime.String" %248)
+  %250 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %251 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %250, i32 0, i32 0
+  store ptr @17, ptr %251, align 8
+  %252 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %250, i32 0, i32 1
+  store i64 3, ptr %252, align 4
+  %253 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %250, align 8
+  %254 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %255 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %254, i32 0, i32 0
+  store ptr @18, ptr %255, align 8
+  %256 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %254, i32 0, i32 1
+  store i64 3, ptr %256, align 4
+  %257 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %254, align 8
+  %258 = call i1 @"github.com/goplus/llgo/internal/runtime.StringLess"(%"github.com/goplus/llgo/internal/runtime.String" %257, %"github.com/goplus/llgo/internal/runtime.String" %253)
+  %259 = xor i1 %258, true
+  %260 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %261 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %260, i32 0, i32 0
+  store ptr @19, ptr %261, align 8
+  %262 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %260, i32 0, i32 1
+  store i64 3, ptr %262, align 4
+  %263 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %260, align 8
+  %264 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %265 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %264, i32 0, i32 0
+  store ptr @20, ptr %265, align 8
+  %266 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %264, i32 0, i32 1
+  store i64 3, ptr %266, align 4
+  %267 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %264, align 8
+  %268 = call i1 @"github.com/goplus/llgo/internal/runtime.StringLess"(%"github.com/goplus/llgo/internal/runtime.String" %267, %"github.com/goplus/llgo/internal/runtime.String" %263)
+  %269 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %270 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %269, i32 0, i32 0
+  store ptr @21, ptr %270, align 8
+  %271 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %269, i32 0, i32 1
+  store i64 3, ptr %271, align 4
+  %272 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %269, align 8
+  %273 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
+  %274 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %273, i32 0, i32 0
+  store ptr @22, ptr %274, align 8
+  %275 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %273, i32 0, i32 1
+  store i64 3, ptr %275, align 4
+  %276 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %273, align 8
+  %277 = call i1 @"github.com/goplus/llgo/internal/runtime.StringLess"(%"github.com/goplus/llgo/internal/runtime.String" %272, %"github.com/goplus/llgo/internal/runtime.String" %276)
+  %278 = xor i1 %277, true
+  call void @"github.com/goplus/llgo/internal/runtime.PrintBool"(i1 %221)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintBool"(i1 %230)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintBool"(i1 %240)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintBool"(i1 %249)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintBool"(i1 %259)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintBool"(i1 %268)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 32)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintBool"(i1 %278)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 10)
   ret i32 0
 }
 
-declare void @"github.com/goplus/llgo/internal/runtime.init"()
-
 declare ptr @"github.com/goplus/llgo/internal/runtime.AllocZ"(i64)
 
+declare void @"github.com/goplus/llgo/internal/runtime.init"()
+
 declare %"github.com/goplus/llgo/internal/runtime.Slice" @"github.com/goplus/llgo/internal/runtime.NewSlice3"(ptr, i64, i64, i64, i64, i64)
 
 declare void @"github.com/goplus/llgo/internal/runtime.PrintSlice"(%"github.com/goplus/llgo/internal/runtime.Slice")
@@ -431,7 +671,7 @@ define void @"main.main$1"() {
 _llgo_0:
   %0 = alloca %"github.com/goplus/llgo/internal/runtime.String", align 8
   %1 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %0, i32 0, i32 0
-  store ptr @6, ptr %1, align 8
+  store ptr @23, ptr %1, align 8
   %2 = getelementptr inbounds %"github.com/goplus/llgo/internal/runtime.String", ptr %0, i32 0, i32 1
   store i64 2, ptr %2, align 4
   %3 = load %"github.com/goplus/llgo/internal/runtime.String", ptr %0, align 8
@@ -439,3 +679,21 @@ _llgo_0:
   call void @"github.com/goplus/llgo/internal/runtime.PrintByte"(i8 10)
   ret void
 }
+
+declare ptr @"github.com/goplus/llgo/internal/runtime.NewStringIter"(%"github.com/goplus/llgo/internal/runtime.String")
+
+declare { i1, i64, i32 } @"github.com/goplus/llgo/internal/runtime.StringIterNext"(ptr)
+
+declare %"github.com/goplus/llgo/internal/runtime.Slice" @"github.com/goplus/llgo/internal/runtime.StringToBytes"(%"github.com/goplus/llgo/internal/runtime.String")
+
+declare %"github.com/goplus/llgo/internal/runtime.Slice" @"github.com/goplus/llgo/internal/runtime.StringToRunes"(%"github.com/goplus/llgo/internal/runtime.String")
+
+declare %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.StringFromBytes"(%"github.com/goplus/llgo/internal/runtime.Slice")
+
+declare %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.StringFromRunes"(%"github.com/goplus/llgo/internal/runtime.Slice")
+
+declare %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.StringFromRune"(i32)
+
+declare i1 @"github.com/goplus/llgo/internal/runtime.StringEqual"(%"github.com/goplus/llgo/internal/runtime.String", %"github.com/goplus/llgo/internal/runtime.String")
+
+declare i1 @"github.com/goplus/llgo/internal/runtime.StringLess"(%"github.com/goplus/llgo/internal/runtime.String", %"github.com/goplus/llgo/internal/runtime.String")
diff --git a/cl/_testrt/cast/out.ll b/cl/_testrt/cast/out.ll
index 794eea9e..1f82dabd 100644
--- a/cl/_testrt/cast/out.ll
+++ b/cl/_testrt/cast/out.ll
@@ -82,7 +82,7 @@ _llgo_2:                                          ; preds = %_llgo_0
 define void @main.cvt32Fto64F(float %0, double %1) {
 _llgo_0:
   %2 = fpext float %0 to double
-  %3 = fcmp one double %2, %1
+  %3 = fcmp une double %2, %1
   br i1 %3, label %_llgo_1, label %_llgo_2
 
 _llgo_1:                                          ; preds = %_llgo_0
@@ -198,7 +198,7 @@ _llgo_2:                                          ; preds = %_llgo_0
 define void @main.cvt64Fto32F(double %0, float %1) {
 _llgo_0:
   %2 = fptrunc double %0 to float
-  %3 = fcmp one float %2, %1
+  %3 = fcmp une float %2, %1
   br i1 %3, label %_llgo_1, label %_llgo_2
 
 _llgo_1:                                          ; preds = %_llgo_0
@@ -227,7 +227,7 @@ _llgo_2:                                          ; preds = %_llgo_0
 define void @main.cvt64Uto64F(i64 %0, double %1) {
 _llgo_0:
   %2 = uitofp i64 %0 to double
-  %3 = fcmp one double %2, %1
+  %3 = fcmp une double %2, %1
   br i1 %3, label %_llgo_1, label %_llgo_2
 
 _llgo_1:                                          ; preds = %_llgo_0
@@ -256,7 +256,7 @@ _llgo_2:                                          ; preds = %_llgo_0
 define void @main.cvt64to64F(i64 %0, double %1) {
 _llgo_0:
   %2 = sitofp i64 %0 to double
-  %3 = fcmp one double %2, %1
+  %3 = fcmp une double %2, %1
   br i1 %3, label %_llgo_1, label %_llgo_2
 
 _llgo_1:                                          ; preds = %_llgo_0
diff --git a/cl/compile.go b/cl/compile.go
index 1b23d3b8..991c136e 100644
--- a/cl/compile.go
+++ b/cl/compile.go
@@ -714,6 +714,12 @@ func (p *context) compileInstrOrValue(b llssa.Builder, iv instrOrValue, asValue
 	case *ssa.Extract:
 		x := p.compileValue(b, v.Tuple)
 		ret = b.Extract(x, v.Index)
+	case *ssa.Range:
+		x := p.compileValue(b, v.X)
+		ret = b.Range(x)
+	case *ssa.Next:
+		iter := p.compileValue(b, v.Iter)
+		ret = b.Next(iter, v.IsString)
 	default:
 		panic(fmt.Sprintf("compileInstrAndValue: unknown instr - %T\n", iv))
 	}
diff --git a/internal/runtime/llgo_autogen.lla b/internal/runtime/llgo_autogen.lla
index a5c5b75b..92d400d6 100644
Binary files a/internal/runtime/llgo_autogen.lla and b/internal/runtime/llgo_autogen.lla differ
diff --git a/internal/runtime/utf8.go b/internal/runtime/utf8.go
new file mode 100644
index 00000000..f43ee67e
--- /dev/null
+++ b/internal/runtime/utf8.go
@@ -0,0 +1,132 @@
+// Copyright 2016 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 runtime
+
+// Numbers fundamental to the encoding.
+const (
+	runeError = '\uFFFD'     // the "error" Rune or "Unicode replacement character"
+	runeSelf  = 0x80         // characters below runeSelf are represented as themselves in a single byte.
+	maxRune   = '\U0010FFFF' // Maximum valid Unicode code point.
+)
+
+// Code points in the surrogate range are not valid for UTF-8.
+const (
+	surrogateMin = 0xD800
+	surrogateMax = 0xDFFF
+)
+
+const (
+	t1 = 0x00 // 0000 0000
+	tx = 0x80 // 1000 0000
+	t2 = 0xC0 // 1100 0000
+	t3 = 0xE0 // 1110 0000
+	t4 = 0xF0 // 1111 0000
+	t5 = 0xF8 // 1111 1000
+
+	maskx = 0x3F // 0011 1111
+	mask2 = 0x1F // 0001 1111
+	mask3 = 0x0F // 0000 1111
+	mask4 = 0x07 // 0000 0111
+
+	rune1Max = 1<<7 - 1
+	rune2Max = 1<<11 - 1
+	rune3Max = 1<<16 - 1
+
+	// The default lowest and highest continuation byte.
+	locb = 0x80 // 1000 0000
+	hicb = 0xBF // 1011 1111
+)
+
+// countrunes returns the number of runes in s.
+// func countrunes(s string) int {
+// 	n := 0
+// 	for range s {
+// 		n++
+// 	}
+// 	return n
+// }
+
+// decoderune returns the non-ASCII rune at the start of
+// s[k:] and the index after the rune in s.
+//
+// decoderune assumes that caller has checked that
+// the to be decoded rune is a non-ASCII rune.
+//
+// If the string appears to be incomplete or decoding problems
+// are encountered (runeerror, k + 1) is returned to ensure
+// progress when decoderune is used to iterate over a string.
+func decoderune(s string, k int) (r rune, pos int) {
+	pos = k
+
+	if k >= len(s) {
+		return runeError, k + 1
+	}
+
+	s = s[k:]
+
+	switch {
+	case t2 <= s[0] && s[0] < t3:
+		// 0080-07FF two byte sequence
+		if len(s) > 1 && (locb <= s[1] && s[1] <= hicb) {
+			r = rune(s[0]&mask2)<<6 | rune(s[1]&maskx)
+			pos += 2
+			if rune1Max < r {
+				return
+			}
+		}
+	case t3 <= s[0] && s[0] < t4:
+		// 0800-FFFF three byte sequence
+		if len(s) > 2 && (locb <= s[1] && s[1] <= hicb) && (locb <= s[2] && s[2] <= hicb) {
+			r = rune(s[0]&mask3)<<12 | rune(s[1]&maskx)<<6 | rune(s[2]&maskx)
+			pos += 3
+			if rune2Max < r && !(surrogateMin <= r && r <= surrogateMax) {
+				return
+			}
+		}
+	case t4 <= s[0] && s[0] < t5:
+		// 10000-1FFFFF four byte sequence
+		if len(s) > 3 && (locb <= s[1] && s[1] <= hicb) && (locb <= s[2] && s[2] <= hicb) && (locb <= s[3] && s[3] <= hicb) {
+			r = rune(s[0]&mask4)<<18 | rune(s[1]&maskx)<<12 | rune(s[2]&maskx)<<6 | rune(s[3]&maskx)
+			pos += 4
+			if rune3Max < r && r <= maxRune {
+				return
+			}
+		}
+	}
+
+	return runeError, k + 1
+}
+
+// encoderune writes into p (which must be large enough) the UTF-8 encoding of the rune.
+// It returns the number of bytes written.
+func encoderune(p []byte, r rune) int {
+	// Negative values are erroneous. Making it unsigned addresses the problem.
+	switch i := uint32(r); {
+	case i <= rune1Max:
+		p[0] = byte(r)
+		return 1
+	case i <= rune2Max:
+		_ = p[1] // eliminate bounds checks
+		p[0] = t2 | byte(r>>6)
+		p[1] = tx | byte(r)&maskx
+		return 2
+	case i > maxRune, surrogateMin <= i && i <= surrogateMax:
+		r = runeError
+		fallthrough
+	case i <= rune3Max:
+		_ = p[2] // eliminate bounds checks
+		p[0] = t3 | byte(r>>12)
+		p[1] = tx | byte(r>>6)&maskx
+		p[2] = tx | byte(r)&maskx
+		return 3
+	default:
+		_ = p[3] // eliminate bounds checks
+		p[0] = t4 | byte(r>>18)
+		p[1] = tx | byte(r>>12)&maskx
+		p[2] = tx | byte(r>>6)&maskx
+		p[3] = tx | byte(r)&maskx
+		return 4
+	}
+}
diff --git a/internal/runtime/z_string.go b/internal/runtime/z_string.go
index f4d20906..e34ae730 100644
--- a/internal/runtime/z_string.go
+++ b/internal/runtime/z_string.go
@@ -70,4 +70,119 @@ func NewStringSlice(base String, i, j int) String {
 	return String{nil, 0}
 }
 
+type StringIter struct {
+	s   string
+	pos int
+}
+
+func NewStringIter(s string) *StringIter {
+	return &StringIter{s, 0}
+}
+
+func StringIterNext(it *StringIter) (ok bool, k int, v rune) {
+	if it.pos >= len(it.s) {
+		return false, 0, 0
+	}
+	k = it.pos
+	if c := it.s[it.pos]; c < runeSelf {
+		it.pos++
+		v = rune(c)
+	} else {
+		v, it.pos = decoderune(it.s, it.pos)
+	}
+	ok = true
+	return
+}
+
+func StringToBytes(s String) []byte {
+	if s.len == 0 {
+		return nil
+	}
+	data := make([]byte, s.len)
+	c.Memcpy(unsafe.Pointer(&data[0]), s.data, uintptr(s.len))
+	return data
+}
+
+func StringToRunes(s string) []rune {
+	if len(s) == 0 {
+		return nil
+	}
+	data := make([]rune, len(s))
+	var index uint
+	for i := 0; i < len(s); {
+		if c := s[i]; c < runeSelf {
+			data[index] = rune(c)
+			i++
+		} else {
+			data[index], i = decoderune(s, i)
+		}
+		index++
+	}
+	return data[:index:index]
+}
+
+func StringFromBytes(b Slice) (s String) {
+	if b.len == 0 {
+		return
+	}
+	s.len = b.len
+	s.data = AllocU(uintptr(s.len))
+	c.Memcpy(s.data, b.data, uintptr(b.len))
+	return
+}
+
+func StringFromRunes(rs []rune) (s String) {
+	if len(rs) == 0 {
+		return
+	}
+	data := make([]byte, len(rs)*4)
+	var index int
+	for _, r := range rs {
+		n := encoderune(data[index:], r)
+		index += n
+	}
+	s.len = index
+	s.data = unsafe.Pointer(&data[0])
+	return
+}
+
+func StringFromRune(r rune) (s String) {
+	var buf [4]byte
+	n := encoderune(buf[:], r)
+	s.len = n
+	s.data = unsafe.Pointer(&buf[0])
+	return
+}
+
+func StringEqual(x, y String) bool {
+	if x.len != y.len {
+		return false
+	}
+	if x.data != y.data {
+		for i := 0; i < x.len; i++ {
+			if *(*byte)(c.Advance(x.data, i)) != *(*byte)(c.Advance(y.data, i)) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func StringLess(x, y String) bool {
+	n := x.len
+	if n > y.len {
+		n = y.len
+	}
+	for i := 0; i < n; i++ {
+		ix := *(*byte)(c.Advance(x.data, i))
+		iy := *(*byte)(c.Advance(y.data, i))
+		if ix < iy {
+			return true
+		} else if ix > iy {
+			return false
+		}
+	}
+	return x.len < y.len
+}
+
 // -----------------------------------------------------------------------------
diff --git a/ssa/expr.go b/ssa/expr.go
index 314848a4..0258755c 100644
--- a/ssa/expr.go
+++ b/ssa/expr.go
@@ -315,7 +315,7 @@ var uintPredOpToLLVM = []llvm.IntPredicate{
 
 var floatPredOpToLLVM = []llvm.FloatPredicate{
 	token.EQL - predOpBase: llvm.FloatOEQ,
-	token.NEQ - predOpBase: llvm.FloatONE,
+	token.NEQ - predOpBase: llvm.FloatUNE,
 	token.LSS - predOpBase: llvm.FloatOLT,
 	token.LEQ - predOpBase: llvm.FloatOLE,
 	token.GTR - predOpBase: llvm.FloatOGT,
@@ -405,7 +405,26 @@ func (b Builder) BinOp(op token.Token, x, y Expr) Expr {
 			pred := boolPredOpToLLVM[op-predOpBase]
 			return Expr{llvm.CreateICmp(b.impl, pred, x.impl, y.impl), tret}
 		case vkString, vkComplex:
-			panic("todo")
+			switch op {
+			case token.EQL:
+				return b.InlineCall(b.Pkg.rtFunc("StringEqual"), x, y)
+			case token.NEQ:
+				ret := b.InlineCall(b.Pkg.rtFunc("StringEqual"), x, y)
+				ret.impl = llvm.CreateNot(b.impl, ret.impl)
+				return ret
+			case token.LSS:
+				return b.InlineCall(b.Pkg.rtFunc("StringLess"), x, y)
+			case token.LEQ:
+				ret := b.InlineCall(b.Pkg.rtFunc("StringLess"), y, x)
+				ret.impl = llvm.CreateNot(b.impl, ret.impl)
+				return ret
+			case token.GTR:
+				return b.InlineCall(b.Pkg.rtFunc("StringLess"), y, x)
+			case token.GEQ:
+				ret := b.InlineCall(b.Pkg.rtFunc("StringLess"), x, y)
+				ret.impl = llvm.CreateNot(b.impl, ret.impl)
+				return ret
+			}
 		}
 	}
 	panic("todo")
@@ -833,6 +852,27 @@ func (b Builder) Convert(t Type, x Expr) (ret Expr) {
 		case types.UnsafePointer:
 			ret.impl = castPtr(b.impl, x.impl, t.ll)
 			return
+		case types.String:
+			switch xtyp := x.RawType().Underlying().(type) {
+			case *types.Slice:
+				if etyp, ok := xtyp.Elem().Underlying().(*types.Basic); ok {
+					switch etyp.Kind() {
+					case types.Byte:
+						ret.impl = b.InlineCall(b.Func.Pkg.rtFunc("StringFromBytes"), x).impl
+						return
+					case types.Rune:
+						ret.impl = b.InlineCall(b.Func.Pkg.rtFunc("StringFromRunes"), x).impl
+						return
+					}
+				}
+			case *types.Basic:
+				if x.Type != b.Prog.Int32() {
+					x.Type = b.Prog.Int32()
+					x.impl = castInt(b, x.impl, b.Prog.Int32())
+				}
+				ret.impl = b.InlineCall(b.Func.Pkg.rtFunc("StringFromRune"), x).impl
+				return
+			}
 		}
 		switch xtyp := x.RawType().Underlying().(type) {
 		case *types.Basic:
@@ -867,6 +907,19 @@ func (b Builder) Convert(t Type, x Expr) (ret Expr) {
 	case *types.Pointer:
 		ret.impl = castPtr(b.impl, x.impl, t.ll)
 		return
+	case *types.Slice:
+		if x.kind == vkString {
+			if etyp, ok := typ.Elem().Underlying().(*types.Basic); ok {
+				switch etyp.Kind() {
+				case types.Byte:
+					ret.impl = b.InlineCall(b.Func.Pkg.rtFunc("StringToBytes"), x).impl
+					return
+				case types.Rune:
+					ret.impl = b.InlineCall(b.Func.Pkg.rtFunc("StringToRunes"), x).impl
+					return
+				}
+			}
+		}
 	}
 	panic("todo")
 }
@@ -969,6 +1022,51 @@ func (b Builder) Call(fn Expr, args ...Expr) (ret Expr) {
 	return
 }
 
+// The Range instruction yields an iterator over the domain and range
+// of X, which must be a string or map.
+//
+// Elements are accessed via Next.
+//
+// Type() returns an opaque and degenerate "rangeIter" type.
+//
+// Pos() returns the ast.RangeStmt.For.
+//
+// Example printed form:
+//
+//	t0 = range "hello":string
+func (b Builder) Range(x Expr) Expr {
+	switch x.kind {
+	case vkString:
+		return b.InlineCall(b.Pkg.rtFunc("NewStringIter"), x)
+	}
+	panic("todo")
+}
+
+// The Next instruction reads and advances the (map or string)
+// iterator Iter and returns a 3-tuple value (ok, k, v).  If the
+// iterator is not exhausted, ok is true and k and v are the next
+// elements of the domain and range, respectively.  Otherwise ok is
+// false and k and v are undefined.
+//
+// Components of the tuple are accessed using Extract.
+//
+// The IsString field distinguishes iterators over strings from those
+// over maps, as the Type() alone is insufficient: consider
+// map[int]rune.
+//
+// Type() returns a *types.Tuple for the triple (ok, k, v).
+// The types of k and/or v may be types.Invalid.
+//
+// Example printed form:
+//
+//	t1 = next t0
+func (b Builder) Next(iter Expr, isString bool) (ret Expr) {
+	if isString {
+		return b.InlineCall(b.Pkg.rtFunc("StringIterNext"), iter)
+	}
+	panic("todo")
+}
+
 // A Builtin represents a specific use of a built-in function, e.g. len.
 //
 // Builtins are immutable values.  Builtins do not have addresses.