From e4cc7c58dda80d502e5c66c0c91f7df191d540a8 Mon Sep 17 00:00:00 2001
From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Fri, 23 Mar 2012 11:29:01 +0100
Subject: [PATCH] Simple optimizations

Why open-coding isdigit is a good idea?

Before: call   __ctype_b_loc
        movzbl (%ebx),%edx
        mov    (%eax),%eax
        testb  $0x8,0x1(%eax,%edx,2)
        je     lbl

After:  movzbl (%eax),%edx
        sub    $0x30,%edx
        cmp    $0x9,%dl
        ja     lbl

   text	   data	    bss	    dec	    hex	filename
 236869	    704	  18944	 256517	  3ea05	strace.before
 236719	    700	  18944	 256363	  3e96b	strace

* defs.h: Alias sigemptyset to __sigemptyset on glibc.
* syscall.c (qual_syscall): Open-code isdigit.
(qual_desc): Likewise.
(qual_signal): Open-code isdigit. Remove string copying
which was done for no apparent reason.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---
 defs.h    |  7 +++++++
 syscall.c | 14 +++++---------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/defs.h b/defs.h
index a0445c3f..e46e230a 100644
--- a/defs.h
+++ b/defs.h
@@ -83,6 +83,13 @@ extern char *stpcpy(char *dst, const char *src);
 
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
 
+/* Glibc has an efficient macro for sigemptyset
+ * (it just does one or two assignments of 0 to internal vector of longs).
+ */
+#if defined(__GLIBC__) && defined(__sigemptyset) && !defined(sigemptyset)
+# define sigemptyset __sigemptyset
+#endif
+
 /* Configuration section */
 #ifndef MAX_QUALS
 # if defined(MIPS)
diff --git a/syscall.c b/syscall.c
index 663d678b..c4ac9778 100644
--- a/syscall.c
+++ b/syscall.c
@@ -337,7 +337,7 @@ qual_syscall(const char *s, int bitflag, int not)
 	int i;
 	int rc = -1;
 
-	if (isdigit((unsigned char)*s)) {
+	if (*s >= '0' && *s <= '9') {
 		int i = atoi(s);
 		if (i < 0 || i >= MAX_QUALS)
 			return -1;
@@ -373,26 +373,22 @@ static int
 qual_signal(const char *s, int bitflag, int not)
 {
 	int i;
-	char buf[32];
 
-	if (isdigit((unsigned char)*s)) {
+	if (*s >= '0' && *s <= '9') {
 		int signo = atoi(s);
 		if (signo < 0 || signo >= MAX_QUALS)
 			return -1;
 		qualify_one(signo, bitflag, not, -1);
 		return 0;
 	}
-	if (strlen(s) >= sizeof buf)
-		return -1;
-	strcpy(buf, s);
-	s = buf;
 	if (strncasecmp(s, "SIG", 3) == 0)
 		s += 3;
-	for (i = 0; i <= NSIG; i++)
+	for (i = 0; i <= NSIG; i++) {
 		if (strcasecmp(s, signame(i) + 3) == 0) {
 			qualify_one(i, bitflag, not, -1);
 			return 0;
 		}
+	}
 	return -1;
 }
 
@@ -405,7 +401,7 @@ qual_fault(const char *s, int bitflag, int not)
 static int
 qual_desc(const char *s, int bitflag, int not)
 {
-	if (isdigit((unsigned char)*s)) {
+	if (*s >= '0' && *s <= '9') {
 		int desc = atoi(s);
 		if (desc < 0 || desc >= MAX_QUALS)
 			return -1;