From 96d4120ac08db3f2d566e8e5c3bc134a24aa0afc Mon Sep 17 00:00:00 2001
From: Jason Evans <jasone@canonware.com>
Date: Mon, 2 Apr 2012 14:50:03 -0700
Subject: [PATCH] Avoid NULL check in free() and malloc_usable_size().

Generalize isalloc() to handle NULL pointers in such a way that the NULL
checking overhead is only paid when introspecting huge allocations (or
NULL).  This allows free() and malloc_usable_size() to no longer check
for NULL.

Submitted by Igor Bukanov and Mike Hommey.
---
 Makefile.in                                   |  2 +-
 .../jemalloc/internal/jemalloc_internal.h.in  | 10 +++----
 src/jemalloc.c                                | 26 ++++++++-----------
 test/null.c                                   | 19 ++++++++++++++
 test/null.exp                                 |  2 ++
 5 files changed, 37 insertions(+), 22 deletions(-)
 create mode 100644 test/null.c
 create mode 100644 test/null.exp

diff --git a/Makefile.in b/Makefile.in
index 821c0634..d8b671ad 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -65,7 +65,7 @@ DOCS_HTML := $(DOCS_XML:@objroot@%.xml=@srcroot@%.html)
 DOCS_MAN3 := $(DOCS_XML:@objroot@%.xml=@srcroot@%.3)
 DOCS := $(DOCS_HTML) $(DOCS_MAN3)
 CTESTS := @srcroot@test/aligned_alloc.c @srcroot@test/allocated.c \
-	@srcroot@test/bitmap.c @srcroot@test/mremap.c \
+	@srcroot@test/bitmap.c @srcroot@test/mremap.c @srcroot@test/null.c \
 	@srcroot@test/posix_memalign.c @srcroot@test/thread_arena.c \
 	@srcroot@test/thread_tcache_enabled.c
 ifeq (@enable_experimental@, 1)
diff --git a/include/jemalloc/internal/jemalloc_internal.h.in b/include/jemalloc/internal/jemalloc_internal.h.in
index db2deb03..ed21bbe7 100644
--- a/include/jemalloc/internal/jemalloc_internal.h.in
+++ b/include/jemalloc/internal/jemalloc_internal.h.in
@@ -633,8 +633,6 @@ isalloc(const void *ptr)
 	size_t ret;
 	arena_chunk_t *chunk;
 
-	assert(ptr != NULL);
-
 	chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
 	if (chunk != ptr) {
 		/* Region. */
@@ -642,8 +640,10 @@ isalloc(const void *ptr)
 			ret = arena_salloc_demote(ptr);
 		else
 			ret = arena_salloc(ptr);
-	} else
+	} else if (ptr != NULL)
 		ret = huge_salloc(ptr);
+	else
+		ret = 0;
 
 	return (ret);
 }
@@ -664,12 +664,10 @@ idalloc(void *ptr)
 {
 	arena_chunk_t *chunk;
 
-	assert(ptr != NULL);
-
 	chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
 	if (chunk != ptr)
 		arena_dalloc(chunk->arena, chunk, ptr);
-	else
+	else if (ptr != NULL)
 		huge_dalloc(ptr, true);
 }
 
diff --git a/src/jemalloc.c b/src/jemalloc.c
index 1deabcd9..86ce695b 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -1100,22 +1100,18 @@ JEMALLOC_ATTR(visibility("default"))
 void
 je_free(void *ptr)
 {
+	size_t usize;
 
-	if (ptr != NULL) {
-		size_t usize;
+	assert(malloc_initialized || IS_INITIALIZER);
 
-		assert(malloc_initialized || IS_INITIALIZER);
-
-		if (config_prof && opt_prof) {
-			usize = isalloc(ptr);
-			prof_free(ptr, usize);
-		} else if (config_stats) {
-			usize = isalloc(ptr);
-		}
-		if (config_stats)
-			thread_allocated_tsd_get()->deallocated += usize;
-		idalloc(ptr);
-	}
+	if (config_prof && opt_prof) {
+		usize = isalloc(ptr);
+		prof_free(ptr, usize);
+	} else if (config_stats)
+		usize = isalloc(ptr);
+	if (config_stats)
+		thread_allocated_tsd_get()->deallocated += usize;
+	idalloc(ptr);
 }
 
 /*
@@ -1200,7 +1196,7 @@ je_malloc_usable_size(const void *ptr)
 	if (config_ivsalloc)
 		ret = ivsalloc(ptr);
 	else
-		ret = (ptr != NULL) ? isalloc(ptr) : 0;
+		ret = isalloc(ptr);
 
 	return (ret);
 }
diff --git a/test/null.c b/test/null.c
new file mode 100644
index 00000000..ccd7ced3
--- /dev/null
+++ b/test/null.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <assert.h>
+
+#define	JEMALLOC_MANGLE
+#include "jemalloc_test.h"
+
+int
+main(void)
+{
+
+	fprintf(stderr, "Test begin\n");
+
+	free(malloc(1));
+	free(NULL);
+	assert(malloc_usable_size(NULL) == 0);
+
+	fprintf(stderr, "Test end\n");
+	return (0);
+}
diff --git a/test/null.exp b/test/null.exp
new file mode 100644
index 00000000..369a88dd
--- /dev/null
+++ b/test/null.exp
@@ -0,0 +1,2 @@
+Test begin
+Test end