diff --git a/js/src/builtin/Intl.cpp b/js/src/builtin/Intl.cpp
index 1879594651..296d0cf25d 100644
--- a/js/src/builtin/Intl.cpp
+++ b/js/src/builtin/Intl.cpp
@@ -41,6 +41,9 @@
 
 #include "vm/NativeObject-inl.h"
 
+#include "mozilla-config.h"
+#include "plvmx.h"
+
 using namespace js;
 
 using mozilla::IsFinite;
@@ -452,7 +455,7 @@ intl_availableLocales(JSContext* cx, CountAvailable countAvailable,
         if (!lang)
             return false;
         char* p;
-        while ((p = strchr(lang, '_')))
+        while ((p = VMX_STRCHR(lang, '_')))
             *p = '-';
         RootedAtom a(cx, Atomize(cx, lang, strlen(lang)));
         if (!a)
diff --git a/js/src/jsstr.cpp b/js/src/jsstr.cpp
index 1df251898c..7cd08dfd23 100644
--- a/js/src/jsstr.cpp
+++ b/js/src/jsstr.cpp
@@ -4722,11 +4722,25 @@ js_strchr_limit(const CharT* s, char16_t c, const CharT* limit)
     return nullptr;
 }
 
+template const char16_t*
+js_strchr_limit(const char16_t* s, char16_t c, const char16_t* limit);
+
+#ifdef TENFOURFOX_VMX
+#warning using VMX latin-1 js_strchr_limit
+
+template <> const Latin1Char *
+js_strchr_limit(const Latin1Char* s, char16_t c, const Latin1Char* limit)
+{
+    return (const Latin1Char *)VMX_MEMCHR((const void *)s, c,
+        (1 + (uint32_t)limit - (uint32_t)s));
+}
+
+#else
+#warning using template latin-1 js_strchr_limit
 template const Latin1Char*
 js_strchr_limit(const Latin1Char* s, char16_t c, const Latin1Char* limit);
+#endif
 
-template const char16_t*
-js_strchr_limit(const char16_t* s, char16_t c, const char16_t* limit);
 
 char16_t*
 js::InflateString(ExclusiveContext* cx, const char* bytes, size_t* lengthp)
diff --git a/nsprpub/lib/libc/include/plvmx.h b/nsprpub/lib/libc/include/plvmx.h
index b4a651c8a2..4c9903b0f2 100644
--- a/nsprpub/lib/libc/include/plvmx.h
+++ b/nsprpub/lib/libc/include/plvmx.h
@@ -15,6 +15,7 @@ extern "C" {
 
 int   vmx_haschr(const void *b, int c, size_t len);
 void *vmx_memchr(const void *b, int c, size_t len);
+char *vmx_strchr(const char *p, int ch);
 
 #if defined (__cplusplus)
 }
@@ -22,6 +23,7 @@ void *vmx_memchr(const void *b, int c, size_t len);
 
 #define VMX_HASCHR vmx_haschr
 #define VMX_MEMCHR vmx_memchr
+#define VMX_STRCHR vmx_strchr
 #else
 #if defined (__cplusplus)
 #define VMX_HASCHR(a,b,c) (memchr(a,b,c) != nullptr)
@@ -29,6 +31,7 @@ void *vmx_memchr(const void *b, int c, size_t len);
 #define VMX_HASCHR(a,b,c) (!!memchr(a,b,c))
 #endif
 #define VMX_MEMCHR memchr
+#define VMX_STRCHR strchr
 #endif
 
 #endif
diff --git a/nsprpub/lib/libc/src/plvmx.c b/nsprpub/lib/libc/src/plvmx.c
index dd80351b3b..4018d74a8c 100644
--- a/nsprpub/lib/libc/src/plvmx.c
+++ b/nsprpub/lib/libc/src/plvmx.c
@@ -117,3 +117,58 @@ void *vmx_memchr(const void *b, int c, size_t length) {
     fprintf(stderr, "failed vmx_memchr()\n");
     return NULL;
 }
+
+char *vmx_strchr(const char *p, int ch) {
+	unsigned char c = (unsigned char)ch;
+	unsigned int val;
+	if ((uint32_t)p & 15) {
+		for (;((uint32_t)p & 15);++p) {
+			if (*p == c)    return ((char *)p);
+			if (*p == '\0') return NULL;
+		}
+	}
+	
+	unsigned int mashedByte =	(c << 24) |
+					(c << 16) |
+					(c << 8)  | c;
+	const vector unsigned char searchVector = (vector unsigned int){
+		mashedByte, mashedByte, mashedByte, mashedByte};
+	const vector unsigned char nullVector = vec_splat_u8(0);
+
+	for(; ; p+=16) {
+		const vector unsigned char *w = (const vector unsigned char*)p;
+		if (vec_any_eq(*w, searchVector)) break;
+		if (vec_any_eq(*w, nullVector))   return NULL;
+	}
+
+	// Some byte has the result; look in groups of 4 to find which one.
+	// Unroll the loop.
+	val = *(unsigned int*)p;
+	if (((val >> 24) & 0xFF) == c) return (void *)p;
+	if (((val >> 16) & 0xFF) == c) return (void *)(1 + p);
+	if (((val >> 8) & 0xFF)  == c) return (void *)(2 + p);
+	if ((val & 0xFF)         == c) return (void *)(3 + p);
+	p += 4;
+	val = *(unsigned int*)p;
+	if (((val >> 24) & 0xFF) == c) return (void *)p;
+	if (((val >> 16) & 0xFF) == c) return (void *)(1 + p);
+	if (((val >> 8) & 0xFF)  == c) return (void *)(2 + p);
+	if ((val & 0xFF)         == c) return (void *)(3 + p);
+	p += 4;
+	val = *(unsigned int*)p;
+	if (((val >> 24) & 0xFF) == c) return (void *)p;
+	if (((val >> 16) & 0xFF) == c) return (void *)(1 + p);
+	if (((val >> 8) & 0xFF)  == c) return (void *)(2 + p);
+	if ((val & 0xFF)         == c) return (void *)(3 + p);
+	p += 4;
+	val = *(unsigned int*)p;
+	if (((val >> 24) & 0xFF) == c) return (void *)p;
+	if (((val >> 16) & 0xFF) == c) return (void *)(1 + p);
+	if (((val >> 8) & 0xFF)  == c) return (void *)(2 + p);
+	if ((val & 0xFF)         == c) return (void *)(3 + p);
+
+	// unreachable
+	fprintf(stderr, "failed vmx_strchr()\n");
+	return NULL;
+}
+