re PR tree-optimization/19831 (Missing DSE/malloc/free optimization)

2011-09-08  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/19831
	* tree-ssa-dce.c (mark_all_reaching_defs_necessary_1): Also
	skip builtins with vdefs that do not really store something.
	(propagate_necessity): For calls to free that we can associate
	with an allocation function do not mark the freed pointer
	definition necessary.
	(eliminate_unnecessary_stmts): Remove a call to free if
	the associated call to an allocation function is not necessary.

	* gcc.dg/tree-ssa/pr19831-1.c: New testcase.
	* gcc.dg/tree-ssa/pr19831-2.c: Likewise.
	* gcc.dg/tree-ssa/pr19831-3.c: Likewise.
	* gcc.dg/errno-1.c: Adjust.

From-SVN: r178687

4 files changed, 87 insertions, 1 deletions

diff --git a/gcc/testsuite/gcc.dg/errno-1.c b/gcc/testsuite/gcc.dg/errno-1.c
index d0365be..295deef 100644
--- a/gcc/testsuite/gcc.dg/errno-1.c
+++ b/gcc/testsuite/gcc.dg/errno-1.c
@@ -6,7 +6,7 @@
 
 int main()
 {
-  void *p;
+  void * volatile p;
   errno = 0;
   p = malloc (-1);
   if (errno != 0)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr19831-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr19831-1.c
new file mode 100644
index 0000000..1c8f972
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr19831-1.c
@@ -0,0 +1,32 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+void test1(void)
+{
+  int *p = __builtin_malloc (sizeof (int) * 4);
+  int *q = p;
+  *q++ = 4;
+  *q++ = 4;
+  __builtin_free (p);
+}
+
+void test3(int b)
+{
+  int *p = __builtin_malloc (sizeof (int) * 4);
+  if (b)
+    __builtin_free (p);
+  *p = 5;
+}
+
+void test4(int b)
+{
+  int *p = __builtin_malloc (sizeof (int) * 4);
+  if (b)
+    __builtin_free (p);
+  *p = 5;
+  __builtin_free (p);
+}
+
+/* { dg-final { scan-tree-dump-times "free" 0 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "malloc" 0 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr19831-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr19831-2.c
new file mode 100644
index 0000000..bc7c4cc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr19831-2.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+void test1(void)
+{
+  int *p = __builtin_malloc (sizeof (int) * 4);
+  *p++ = 4;
+  __builtin_free (p);
+}
+
+/* Undefined.  We can't do anything here.  */
+
+/* { dg-final { scan-tree-dump-times "free" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "malloc" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr19831-3.c b/gcc/testsuite/gcc.dg/tree-ssa/pr19831-3.c
new file mode 100644
index 0000000..02b5572
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr19831-3.c
@@ -0,0 +1,39 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+void test2(void)
+{
+  int *p = __builtin_malloc (sizeof (int) * 4);
+  if (p == (void *)0)
+    __builtin_abort ();
+  __builtin_free (p);
+}
+
+void test5(int b)
+{
+  int *p = __builtin_malloc (sizeof (int) * 4);
+  if (p)
+    __builtin_free (p);
+}
+
+void test6(void)
+{
+  int *p = __builtin_malloc (sizeof (int) * 4);
+  if (p == (void *)0)
+    __builtin_abort ();
+  if (p)
+    __builtin_free (p);
+}
+
+/* We should be able to remove all malloc/free pairs with CDDCE.
+   Assume p was non-NULL for test2.
+   For test5, it doesn't matter if p is NULL or non-NULL.  */
+
+/* { dg-final { scan-tree-dump-times "free" 0 "optimized" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "malloc" 0 "optimized" { xfail *-*-* } } } */
+
+/* But make sure we don't partially optimize for now.  */
+
+/* { dg-final { scan-tree-dump-times "free" 3 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "malloc" 3 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */