diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index bed9665cc7e0a9370fc502d2b69ccebda6b66c03..bd49ec61255c7f9d65a18153dfc50e0ad8ed5be1 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -177,14 +177,6 @@ static inline void wrgs32(u32 v, addr_t addr)
 }
 
 /* Note: these only return true/false, not a signed return value! */
-static inline int memcmp(const void *s1, const void *s2, size_t len)
-{
-	u8 diff;
-	asm("repe; cmpsb; setnz %0"
-	    : "=qm" (diff), "+D" (s1), "+S" (s2), "+c" (len));
-	return diff;
-}
-
 static inline int memcmp_fs(const void *s1, addr_t s2, size_t len)
 {
 	u8 diff;
diff --git a/arch/x86/boot/compressed/string.c b/arch/x86/boot/compressed/string.c
index 3b5a82fc6ad7f38d748ff4b8c4562978c1f95f66..920b55e3e241482849ad6bef1fbca65925241ecd 100644
--- a/arch/x86/boot/compressed/string.c
+++ b/arch/x86/boot/compressed/string.c
@@ -1,15 +1,4 @@
 #include "misc.h"
-
-/* Avoid intereference from any defines in string_32.h */
-#undef memcmp
-int memcmp(const void *s1, const void *s2, size_t len)
-{
-	u8 diff;
-	asm("repe; cmpsb; setnz %0"
-	    : "=qm" (diff), "+D" (s1), "+S" (s2), "+c" (len));
-	return diff;
-}
-
 #include "../string.c"
 
 /* misc.h might pull in string_32.h which has a macro for memcpy. undef that */
diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
index 574dedfe28900c0445b24d51b09d168116cb205f..5339040ef86e7aee7b6457ffd50a390597336104 100644
--- a/arch/x86/boot/string.c
+++ b/arch/x86/boot/string.c
@@ -14,6 +14,20 @@
 
 #include "boot.h"
 
+/*
+ * This file gets included in compressed/string.c which might pull in
+ * string_32.h and which in turn maps memcmp to __builtin_memcmp(). Undo
+ * that first.
+ */
+#undef memcmp
+int memcmp(const void *s1, const void *s2, size_t len)
+{
+	u8 diff;
+	asm("repe; cmpsb; setnz %0"
+	    : "=qm" (diff), "+D" (s1), "+S" (s2), "+c" (len));
+	return diff;
+}
+
 int strcmp(const char *str1, const char *str2)
 {
 	const unsigned char *s1 = (const unsigned char *)str1;
diff --git a/arch/x86/boot/string.h b/arch/x86/boot/string.h
index 10939d8da2e06f034313f6c5e688dd65d357bdfc..725e820602b1781308b863a10c105dd3d2734d31 100644
--- a/arch/x86/boot/string.h
+++ b/arch/x86/boot/string.h
@@ -8,6 +8,7 @@
 
 void *memcpy(void *dst, const void *src, size_t len);
 void *memset(void *dst, int c, size_t len);
+int memcmp(const void *s1, const void *s2, size_t len);
 
 /*
  * Access builtin version by default. If one needs to use optimized version,
@@ -15,5 +16,6 @@ void *memset(void *dst, int c, size_t len);
  */
 #define memcpy(d,s,l) __builtin_memcpy(d,s,l)
 #define memset(d,c,l) __builtin_memset(d,c,l)
+#define memcmp	__builtin_memcmp
 
 #endif /* BOOT_STRING_H */