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[libc] Reduce overall code size by externalising strncmp()

Typical saving is 20-30 bytes in each file using strncmp().

Signed-off-by: Michael Brown <mcb30@ipxe.org>
tags/v1.20.1
Michael Brown 11 years ago
parent
commit
06766875ad
2 changed files with 40 additions and 21 deletions
  1. 38
    0
      src/arch/x86/core/x86_string.c
  2. 2
    21
      src/arch/x86/include/bits/string.h

+ 38
- 0
src/arch/x86/core/x86_string.c View File

@@ -104,3 +104,41 @@ void * __memmove ( void *dest, const void *src, size_t len ) {
104 104
 		return __memcpy_reverse ( dest, src, len );
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 	}
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 }
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+
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+/**
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+ * Compare strings (up to a specified length)
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+ *
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+ * @v str1		First string
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+ * @v str2		Second string
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+ * @v len		Maximum length
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+ * @ret diff		Difference
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+ */
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+int strncmp ( const char *str1, const char *str2, size_t len ) {
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+	const void *discard_S;
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+	const void *discard_D;
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+	size_t discard_c;
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+	int diff;
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+
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+	__asm__ __volatile__ ( "\n1:\n\t"
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+			       "dec %2\n\t"
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+			       "js 2f\n\t"
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+			       "lodsb\n\t"
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+			       "scasb\n\t"
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+			       "jne 3f\n\t"
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+			       "testb %b3, %b3\n\t"
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+			       "jnz 1b\n\t"
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+			       /* Equal */
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+			       "\n2:\n\t"
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+			       "xor %3, %3\n\t"
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+			       "jmp 4f\n\t"
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+			       /* Not equal; CF indicates difference */
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+			       "\n3:\n\t"
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+			       "sbb %3, %3\n\t"
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+			       "orb $1, %b3\n\t"
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+			       "\n4:\n\t"
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+			       : "=&S" ( discard_S ), "=&D" ( discard_D ),
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+				 "=&c" ( discard_c ), "=&a" ( diff )
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+			       : "0" ( str1 ), "1" ( str2 ), "2" ( len ) );
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+
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+	return diff;
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+}

+ 2
- 21
src/arch/x86/include/bits/string.h View File

@@ -230,27 +230,8 @@ return dest;
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 }
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 #define __HAVE_ARCH_STRNCMP
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-static inline int strncmp(const char * cs,const char * ct,size_t count)
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-{
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-register int __res;
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-int d0, d1, d2;
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-__asm__ __volatile__(
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-	"1:\tdecl %3\n\t"
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-	"js 2f\n\t"
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-	"lodsb\n\t"
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-	"scasb\n\t"
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-	"jne 3f\n\t"
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-	"testb %%al,%%al\n\t"
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-	"jne 1b\n"
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-	"2:\txorl %%eax,%%eax\n\t"
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-	"jmp 4f\n"
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-	"3:\tsbbl %%eax,%%eax\n\t"
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-	"orb $1,%%al\n"
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-	"4:"
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-		     :"=a" (__res), "=&S" (d0), "=&D" (d1), "=&c" (d2)
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-		     :"1" (cs),"2" (ct),"3" (count));
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-return __res;
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-}
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+
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+extern int strncmp ( const char *str1, const char *str2, size_t len );
254 235
 
255 236
 #define __HAVE_ARCH_STRLEN
256 237
 static inline size_t strlen(const char * s)

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