diff --git a/internal/cmd/generator/Makefile b/internal/cmd/generator/Makefile
index f1e0c86..a634370 100644
--- a/internal/cmd/generator/Makefile
+++ b/internal/cmd/generator/Makefile
@@ -1,6 +1,6 @@
 .PHONY: asm
 asm:
-	clang -S -O2 -mavx2 -masm=intel -mno-red-zone -mstackrealign -mllvm -inline-threshold=1000 -fno-asynchronous-unwind-tables -fno-exceptions -fno-rtti -c ./simd/string.c
+	clang -Wall -S -O2 -mavx2 -masm=intel -mno-red-zone -mstackrealign -mllvm -inline-threshold=1000 -fno-asynchronous-unwind-tables -fno-exceptions -fno-rtti -c ./simd/string.c
 
 .PHONY: generate
 generate:
diff --git a/internal/cmd/generator/simd/string.c b/internal/cmd/generator/simd/string.c
index ebbb10b..0a6314e 100644
--- a/internal/cmd/generator/simd/string.c
+++ b/internal/cmd/generator/simd/string.c
@@ -1,8 +1,29 @@
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
+#include <stdbool.h>
 #include <immintrin.h>
 
+static const bool needEscape[256] = {
+ // 0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
+	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x00-0x0F
+	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x10-0x1F
+	0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x20-0x2F
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x30-0x3F
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x40-0x4F
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, // 0x50-0x5F
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x60-0x6F
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0x70-0x7F
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x80-0x8F
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0x90-0x9F
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0xA0-0xAF
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0xB0-0xBF
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0xC0-0xCF
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0xD0-0xDF
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0xE0-0xEF
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 0xF0-0xFF
+    };
+
 uint64_t findHTMLEscapeIndex64(char *buf, int len) {
   static const uint64_t lsb = 0x0101010101010101;
   static const uint64_t msb = 0x8080808080808080;
@@ -26,7 +47,7 @@ uint64_t findHTMLEscapeIndex64(char *buf, int len) {
     }
     sp += 8;
   }
-  return 8 * chunkLen;
+  return chunkIdx * 8;
 }
 
 uint64_t findHTMLEscapeIndex128(char *buf, int len) {
@@ -40,7 +61,6 @@ uint64_t findHTMLEscapeIndex128(char *buf, int len) {
   static const __m64 gt     = (__m64)(lsb * '>');
   static const __m64 amp    = (__m64)(lsb * '&');
 
-  __m128i zeroV   = _mm_setzero_si128();
   __m128i msbV    = _mm_set_epi64((__m64)(msb), (__m64)(msb));
   __m128i lsbV    = _mm_set_epi64((__m64)(lsb), (__m64)(lsb));
   __m128i spaceV  = _mm_set_epi64(space, space);
@@ -87,7 +107,6 @@ uint64_t findHTMLEscapeIndex256(char *buf, int len) {
   static const __m64 gt     = (__m64)(lsb * '>');
   static const __m64 amp    = (__m64)(lsb * '&');
 
-  __m256i zeroV   = _mm256_setzero_si256();
   __m256i msbV    = _mm256_set1_epi64x(msb);
   __m256i lsbV    = _mm256_set1_epi64x(lsb);
   __m256i spaceV  = _mm256_set1_epi64x(space);
@@ -146,7 +165,14 @@ uint64_t findEscapeIndex64(char *buf, int len) {
     }
     sp += 8;
   }
-  return 8 * chunkLen;
+  int idx = 8 * chunkLen;
+  bool *needEscape = needEscape;
+  for ( ;idx < len; idx++) {
+    if (needEscape[buf[idx]] != 0) {
+      return idx;
+    }
+  }
+  return len;
 }
 
 uint64_t findEscapeIndex128(char *buf, int len) {
@@ -157,7 +183,6 @@ uint64_t findEscapeIndex128(char *buf, int len) {
   static const __m64 quote  = (__m64)(lsb * '"');
   static const __m64 escape = (__m64)(lsb * '\\');
 
-  __m128i zeroV   = _mm_setzero_si128();
   __m128i msbV    = _mm_set_epi64((__m64)(msb), (__m64)(msb));
   __m128i lsbV    = _mm_set_epi64((__m64)(lsb), (__m64)(lsb));
   __m128i spaceV  = _mm_set_epi64(space, space);
@@ -181,10 +206,17 @@ uint64_t findEscapeIndex128(char *buf, int len) {
     sp += 16;
   }
   int idx = 16 * chunkLen;
-  if (len - idx >= 8) {
-    return idx + findEscapeIndex64(sp, len - idx);
+  int remainLen = len - idx;
+  if (remainLen >= 8) {
+    return idx + findEscapeIndex64(sp, remainLen);
   }
-  return idx;
+  bool *needEscape = needEscape;
+  for (; idx < len; idx++) {
+    if (needEscape[buf[idx]] != 0) {
+      return idx;
+    }
+  }
+  return len;
 }
 
 uint64_t findEscapeIndex256(char *buf, int len) {
@@ -195,7 +227,6 @@ uint64_t findEscapeIndex256(char *buf, int len) {
   static const __m64 quote  = (__m64)(lsb * '"');
   static const __m64 escape = (__m64)(lsb * '\\');
 
-  __m256i zeroV   = _mm256_setzero_si256();
   __m256i msbV    = _mm256_set1_epi64x(msb);
   __m256i lsbV    = _mm256_set1_epi64x(lsb);
   __m256i spaceV  = _mm256_set1_epi64x(space);
@@ -214,7 +245,7 @@ uint64_t findEscapeIndex256(char *buf, int len) {
     __m256i mask = _mm256_or_si256(_mm256_or_si256(_mm256_or_si256(n, spaceN), quoteN), escapeN);
     int movemask = _mm256_movemask_epi8(_mm256_and_si256(mask, msbV));
     if (movemask != 0) {
-      return __builtin_ctz(movemask);
+      return __builtin_ctz(movemask) + chunkIdx * 32;
     }
     sp += 32;
   }
@@ -225,5 +256,11 @@ uint64_t findEscapeIndex256(char *buf, int len) {
   } else if (remainLen >= 8) {
     return idx + findEscapeIndex64(sp, remainLen);
   }
-  return idx;
+  bool *needEscape = needEscape;
+  for (; idx < len; idx++) {
+    if (needEscape[buf[idx]] != 0) {
+      return idx;
+    }
+  }
+  return len;
 }
diff --git a/internal/encoder/string.go b/internal/encoder/string.go
index 888d09b..8072a43 100644
--- a/internal/encoder/string.go
+++ b/internal/encoder/string.go
@@ -758,10 +758,6 @@ func appendString(buf []byte, s string) []byte {
 		}
 	ESCAPE:
 		c := s[j]
-		if !needEscape[c] {
-			j++
-			continue
-		}
 		switch c {
 		case '\\', '"':
 			buf = append(buf, s[i:j]...)