[PATCH] x86/string: Use compiler builtins whenever possible

From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xen.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	Jan Beulich <JBeulich@suse.com>
Subject: [PATCH] x86/string: Use compiler builtins whenever possible
Date: Tue, 9 Aug 2016 13:41:01 +0100	[thread overview]
Message-ID: <1470746461-26827-1-git-send-email-andrew.cooper3@citrix.com> (raw)

The use of -fno-builtin inhibits this automatic transformation.  Manually
tranform the callsites.  This causes constructs such as strlen("literal") to
be evaluated at compile time, and certain simple operations to be replaced
with repeated string operations.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
---
 xen/include/asm-x86/string.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/xen/include/asm-x86/string.h b/xen/include/asm-x86/string.h
index 34c5561..e194cc1 100644
--- a/xen/include/asm-x86/string.h
+++ b/xen/include/asm-x86/string.h
@@ -13,4 +13,12 @@ extern void *memmove(void *dest, const void *src, size_t n);
 #define __HAVE_ARCH_MEMSET
 #define memset(s,c,n) (__builtin_memset((s),(c),(n)))
 
+#define strcmp(s1, s2)     __builtin_strcmp(s1, s2)
+#define strncmp(s1, s2, n) __builtin_strncmp(s1, s2, n)
+#define strcasecmp(s1, s2) __builtin_strcasecmp(s1, s2)
+#define strchr(s1, c)      __builtin_strchr(s1, c)
+#define strrchr(s1, c)     __builtin_strrchr(s1, c)
+#define strstr(s1, s2)     __builtin_strstr(s1, s2)
+#define strlen(s1)         __builtin_strlen(s1)
+
 #endif /* __X86_STRING_H__ */
-- 
2.1.4


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