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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2015-04-15 16:17:02 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-15 16:35:23 -0700
commit51be17dfff753e72872f096ce1e654734f2fec50 (patch)
treece599aed4449d1357479ae4c07a6100fdc625a40 /lib/vsprintf.c
parent7b1460eccad0621e0c48f52bbedeb7adddc55ac9 (diff)
downloadlinux-51be17dfff753e72872f096ce1e654734f2fec50.tar.bz2
lib/vsprintf.c: eliminate some branches
Since FORMAT_TYPE_INT is simply 1 more than FORMAT_TYPE_UINT, and similarly for BYTE/UBYTE, SHORT/USHORT, LONG/ULONG, we can eliminate a few instructions by making SIGN have the value 1 instead of 2, and then use arithmetic instead of branches for computing the right spec->type. It's a little hacky, but certainly in the same spirit as SMALL needing to have the value 0x20. For example for the spec->qualifier == 'l' case, gcc now generates 75e: 0f b6 53 01 movzbl 0x1(%rbx),%edx 762: 83 e2 01 and $0x1,%edx 765: 83 c2 09 add $0x9,%edx 768: 88 13 mov %dl,(%rbx) instead of 763: 0f b6 53 01 movzbl 0x1(%rbx),%edx 767: 83 e2 02 and $0x2,%edx 76a: 80 fa 01 cmp $0x1,%dl 76d: 19 d2 sbb %edx,%edx 76f: 83 c2 0a add $0xa,%edx 772: 88 13 mov %dl,(%rbx) Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/vsprintf.c')
-rw-r--r--lib/vsprintf.c30
1 files changed, 11 insertions, 19 deletions
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index b235c96167d3..318d583fe862 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -340,8 +340,8 @@ int num_to_str(char *buf, int size, unsigned long long num)
return len;
}
-#define ZEROPAD 1 /* pad with zero */
-#define SIGN 2 /* unsigned/signed long */
+#define SIGN 1 /* unsigned/signed, must be 1 */
+#define ZEROPAD 2 /* pad with zero */
#define PLUS 4 /* show plus */
#define SPACE 8 /* space if plus */
#define LEFT 16 /* left justified */
@@ -447,7 +447,7 @@ char *number(char *buf, char *end, unsigned long long num,
spec.precision = i;
/* leading space padding */
spec.field_width -= spec.precision;
- if (!(spec.flags & (ZEROPAD+LEFT))) {
+ if (!(spec.flags & (ZEROPAD | LEFT))) {
while (--spec.field_width >= 0) {
if (buf < end)
*buf = ' ';
@@ -1738,29 +1738,21 @@ qualifier:
if (spec->qualifier == 'L')
spec->type = FORMAT_TYPE_LONG_LONG;
else if (spec->qualifier == 'l') {
- if (spec->flags & SIGN)
- spec->type = FORMAT_TYPE_LONG;
- else
- spec->type = FORMAT_TYPE_ULONG;
+ BUILD_BUG_ON(FORMAT_TYPE_ULONG + SIGN != FORMAT_TYPE_LONG);
+ spec->type = FORMAT_TYPE_ULONG + (spec->flags & SIGN);
} else if (_tolower(spec->qualifier) == 'z') {
spec->type = FORMAT_TYPE_SIZE_T;
} else if (spec->qualifier == 't') {
spec->type = FORMAT_TYPE_PTRDIFF;
} else if (spec->qualifier == 'H') {
- if (spec->flags & SIGN)
- spec->type = FORMAT_TYPE_BYTE;
- else
- spec->type = FORMAT_TYPE_UBYTE;
+ BUILD_BUG_ON(FORMAT_TYPE_UBYTE + SIGN != FORMAT_TYPE_BYTE);
+ spec->type = FORMAT_TYPE_UBYTE + (spec->flags & SIGN);
} else if (spec->qualifier == 'h') {
- if (spec->flags & SIGN)
- spec->type = FORMAT_TYPE_SHORT;
- else
- spec->type = FORMAT_TYPE_USHORT;
+ BUILD_BUG_ON(FORMAT_TYPE_USHORT + SIGN != FORMAT_TYPE_SHORT);
+ spec->type = FORMAT_TYPE_USHORT + (spec->flags & SIGN);
} else {
- if (spec->flags & SIGN)
- spec->type = FORMAT_TYPE_INT;
- else
- spec->type = FORMAT_TYPE_UINT;
+ BUILD_BUG_ON(FORMAT_TYPE_UINT + SIGN != FORMAT_TYPE_INT);
+ spec->type = FORMAT_TYPE_UINT + (spec->flags & SIGN);
}
return ++fmt - start;