qsort(3): enhance to handle 32-bit aligned data on 64-bit systems

Implement a small enhancement to the original qsort implementation:
If the data is 32 bit aligned we can side-step the long type
version and use int instead.

The change brings a modest but significant improvement in
32 bit workloads.

Relnotes:	yes

PR:		135718
Taken from:	ache

1 files changed, 21 insertions, 12 deletions

diff --git a/lib/libc/stdlib/qsort.c b/lib/libc/stdlib/qsort.c
index 93e22cd..fa1a0b4 100644
--- a/lib/libc/stdlib/qsort.c
+++ b/lib/libc/stdlib/qsort.c
@@ -41,7 +41,7 @@ typedef int		 cmp_t(void *, const void *, const void *);
 typedef int		 cmp_t(const void *, const void *);
 #endif
 static inline char	*med3(char *, char *, char *, cmp_t *, void *);
-static inline void	 swapfunc(char *, char *, int, int);
+static inline void	 swapfunc(char *, char *, int, int, int);
 
 #define min(a, b)	(a) < (b) ? a : b
 
@@ -59,29 +59,37 @@ static inline void	 swapfunc(char *, char *, int, int);
         } while (--i > 0);				\
 }
 
-#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
-	es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
+#define	SWAPINIT(TYPE, a, es) swaptype_ ## TYPE =	\
+	((char *)a - (char *)0) % sizeof(TYPE) ||	\
+	es % sizeof(TYPE) ? 2 : es == sizeof(TYPE) ? 0 : 1;
 
 static inline void
-swapfunc(a, b, n, swaptype)
+swapfunc(a, b, n, swaptype_long, swaptype_int)
 	char *a, *b;
-	int n, swaptype;
+	int n, swaptype_long, swaptype_int;
 {
-	if(swaptype <= 1)
+	if (swaptype_long <= 1)
 		swapcode(long, a, b, n)
+	else if (swaptype_int <= 1)
+		swapcode(int, a, b, n)
 	else
 		swapcode(char, a, b, n)
 }
 
-#define swap(a, b)					\
-	if (swaptype == 0) {				\
+#define	swap(a, b)					\
+	if (swaptype_long == 0) {			\
 		long t = *(long *)(a);			\
 		*(long *)(a) = *(long *)(b);		\
 		*(long *)(b) = t;			\
+	} else if (swaptype_int == 0) {			\
+		int t = *(int *)(a);			\
+		*(int *)(a) = *(int *)(b);		\
+		*(int *)(b) = t;			\
 	} else						\
-		swapfunc(a, b, es, swaptype)
+		swapfunc(a, b, es, swaptype_long, swaptype_int)
 
-#define vecswap(a, b, n) 	if ((n) > 0) swapfunc(a, b, n, swaptype)
+#define	vecswap(a, b, n)				\
+	if ((n) > 0) swapfunc(a, b, n, swaptype_long, swaptype_int)
 
 #ifdef I_AM_QSORT_R
 #define	CMP(t, x, y) (cmp((t), (x), (y)))
@@ -113,9 +121,10 @@ qsort(void *a, size_t n, size_t es, cmp_t *cmp)
 	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 	size_t d, r;
 	int cmp_result;
-	int swaptype, swap_cnt;
+	int swaptype_long, swaptype_int, swap_cnt;
 
-loop:	SWAPINIT(a, es);
+loop:	SWAPINIT(long, a, es);
+	SWAPINIT(int, a, es);
 	swap_cnt = 0;
 	if (n < 7) {
 		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)