From f97e5ac4ec8a5ae7ed74829e6c1bf6ce814947f5 Mon Sep 17 00:00:00 2001
From: Jason Evans <jasone@canonware.com>
Date: Sun, 28 Sep 2014 14:43:11 -0700
Subject: [PATCH] Implement compile-time bitmap size computation.

---
 include/jemalloc/internal/bitmap.h | 46 ++++++++++++++++++++++++++++++
 src/bitmap.c                       | 18 ++----------
 test/unit/bitmap.c                 | 16 ++++-------
 3 files changed, 54 insertions(+), 26 deletions(-)

diff --git a/include/jemalloc/internal/bitmap.h b/include/jemalloc/internal/bitmap.h
index 6db4ab70..4ca40ffd 100644
--- a/include/jemalloc/internal/bitmap.h
+++ b/include/jemalloc/internal/bitmap.h
@@ -3,6 +3,7 @@
 
 /* Maximum bitmap bit count is 2^LG_BITMAP_MAXBITS. */
 #define	LG_BITMAP_MAXBITS	LG_RUN_MAXREGS
+#define	BITMAP_MAXBITS		(ZU(1) << LG_BITMAP_MAXBITS)
 
 typedef struct bitmap_level_s bitmap_level_t;
 typedef struct bitmap_info_s bitmap_info_t;
@@ -14,6 +15,51 @@ typedef unsigned long bitmap_t;
 #define	BITMAP_GROUP_NBITS		(ZU(1) << LG_BITMAP_GROUP_NBITS)
 #define	BITMAP_GROUP_NBITS_MASK		(BITMAP_GROUP_NBITS-1)
 
+/* Number of groups required to store a given number of bits. */
+#define	BITMAP_BITS2GROUPS(nbits)					\
+    ((nbits + BITMAP_GROUP_NBITS_MASK) >> LG_BITMAP_GROUP_NBITS)
+
+/*
+ * Number of groups required at a particular level for a given number of bits.
+ */
+#define	BITMAP_GROUPS_L0(nbits)						\
+    BITMAP_BITS2GROUPS(nbits)
+#define	BITMAP_GROUPS_L1(nbits)						\
+    BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS(nbits))
+#define	BITMAP_GROUPS_L2(nbits)						\
+    BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS((nbits))))
+#define	BITMAP_GROUPS_L3(nbits)						\
+    BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS(		\
+	BITMAP_BITS2GROUPS((nbits)))))
+
+/*
+ * Assuming the number of levels, number of groups required for a given number
+ * of bits.
+ */
+#define	BITMAP_GROUPS_1_LEVEL(nbits)					\
+    BITMAP_GROUPS_L0(nbits)
+#define	BITMAP_GROUPS_2_LEVEL(nbits)					\
+    (BITMAP_GROUPS_1_LEVEL(nbits) + BITMAP_GROUPS_L1(nbits))
+#define	BITMAP_GROUPS_3_LEVEL(nbits)					\
+    (BITMAP_GROUPS_2_LEVEL(nbits) + BITMAP_GROUPS_L2(nbits))
+#define	BITMAP_GROUPS_4_LEVEL(nbits)					\
+    (BITMAP_GROUPS_3_LEVEL(nbits) + BITMAP_GROUPS_L3(nbits))
+
+/*
+ * Maximum number of groups required to support LG_BITMAP_MAXBITS.
+ */
+#if LG_BITMAP_MAXBITS <= LG_BITMAP_GROUP_NBITS
+#  define BITMAP_GROUPS_MAX	BITMAP_GROUPS_1_LEVEL(BITMAP_MAXBITS)
+#elif LG_BITMAP_MAXBITS <= LG_BITMAP_GROUP_NBITS * 2
+#  define BITMAP_GROUPS_MAX	BITMAP_GROUPS_2_LEVEL(BITMAP_MAXBITS)
+#elif LG_BITMAP_MAXBITS <= LG_BITMAP_GROUP_NBITS * 3
+#  define BITMAP_GROUPS_MAX	BITMAP_GROUPS_3_LEVEL(BITMAP_MAXBITS)
+#elif LG_BITMAP_MAXBITS <= LG_BITMAP_GROUP_NBITS * 4
+#  define BITMAP_GROUPS_MAX	BITMAP_GROUPS_4_LEVEL(BITMAP_MAXBITS)
+#else
+#  error "Unsupported bitmap size"
+#endif
+
 /* Maximum number of levels possible. */
 #define	BITMAP_MAX_LEVELS						\
     (LG_BITMAP_MAXBITS / LG_SIZEOF_BITMAP)				\
diff --git a/src/bitmap.c b/src/bitmap.c
index e2bd907d..c733372b 100644
--- a/src/bitmap.c
+++ b/src/bitmap.c
@@ -2,19 +2,6 @@
 #include "jemalloc/internal/jemalloc_internal.h"
 
 /******************************************************************************/
-/* Function prototypes for non-inline static functions. */
-
-static size_t	bits2groups(size_t nbits);
-
-/******************************************************************************/
-
-static size_t
-bits2groups(size_t nbits)
-{
-
-	return ((nbits >> LG_BITMAP_GROUP_NBITS) +
-	    !!(nbits & BITMAP_GROUP_NBITS_MASK));
-}
 
 void
 bitmap_info_init(bitmap_info_t *binfo, size_t nbits)
@@ -31,15 +18,16 @@ bitmap_info_init(bitmap_info_t *binfo, size_t nbits)
 	 * that requires only one group.
 	 */
 	binfo->levels[0].group_offset = 0;
-	group_count = bits2groups(nbits);
+	group_count = BITMAP_BITS2GROUPS(nbits);
 	for (i = 1; group_count > 1; i++) {
 		assert(i < BITMAP_MAX_LEVELS);
 		binfo->levels[i].group_offset = binfo->levels[i-1].group_offset
 		    + group_count;
-		group_count = bits2groups(group_count);
+		group_count = BITMAP_BITS2GROUPS(group_count);
 	}
 	binfo->levels[i].group_offset = binfo->levels[i-1].group_offset
 	    + group_count;
+	assert(binfo->levels[i].group_offset <= BITMAP_GROUPS_MAX);
 	binfo->nlevels = i;
 	binfo->nbits = nbits;
 }
diff --git a/test/unit/bitmap.c b/test/unit/bitmap.c
index 8086b888..4ea94f85 100644
--- a/test/unit/bitmap.c
+++ b/test/unit/bitmap.c
@@ -1,17 +1,11 @@
 #include "test/jemalloc_test.h"
 
-#if (LG_BITMAP_MAXBITS > 12)
-#  define MAXBITS	4500
-#else
-#  define MAXBITS	(1U << LG_BITMAP_MAXBITS)
-#endif
-
 TEST_BEGIN(test_bitmap_size)
 {
 	size_t i, prev_size;
 
 	prev_size = 0;
-	for (i = 1; i <= MAXBITS; i++) {
+	for (i = 1; i <= BITMAP_MAXBITS; i++) {
 		size_t size = bitmap_size(i);
 		assert_true(size >= prev_size,
 		    "Bitmap size is smaller than expected");
@@ -24,7 +18,7 @@ TEST_BEGIN(test_bitmap_init)
 {
 	size_t i;
 
-	for (i = 1; i <= MAXBITS; i++) {
+	for (i = 1; i <= BITMAP_MAXBITS; i++) {
 		bitmap_info_t binfo;
 		bitmap_info_init(&binfo, i);
 		{
@@ -47,7 +41,7 @@ TEST_BEGIN(test_bitmap_set)
 {
 	size_t i;
 
-	for (i = 1; i <= MAXBITS; i++) {
+	for (i = 1; i <= BITMAP_MAXBITS; i++) {
 		bitmap_info_t binfo;
 		bitmap_info_init(&binfo, i);
 		{
@@ -70,7 +64,7 @@ TEST_BEGIN(test_bitmap_unset)
 {
 	size_t i;
 
-	for (i = 1; i <= MAXBITS; i++) {
+	for (i = 1; i <= BITMAP_MAXBITS; i++) {
 		bitmap_info_t binfo;
 		bitmap_info_init(&binfo, i);
 		{
@@ -99,7 +93,7 @@ TEST_BEGIN(test_bitmap_sfu)
 {
 	size_t i;
 
-	for (i = 1; i <= MAXBITS; i++) {
+	for (i = 1; i <= BITMAP_MAXBITS; i++) {
 		bitmap_info_t binfo;
 		bitmap_info_init(&binfo, i);
 		{