re PR tree-optimization/42944 (errno misoptimization around malloc call)

2010-02-03  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/42944
	* tree-ssa-alias.c (ref_maybe_used_by_call_p_1): Handle
	calloc.
	(call_may_clobber_ref_p_1): Likewise.  Properly handle
	malloc and calloc clobbering errno.

	* gcc.dg/errno-1.c: New testcase.

From-SVN: r156467

gcc/ChangeLog

+2010-02-03  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/42944
+	* tree-ssa-alias.c (ref_maybe_used_by_call_p_1): Handle
+	calloc.
+	(call_may_clobber_ref_p_1): Likewise.  Properly handle
+	malloc and calloc clobbering errno.
+
 2010-02-03  Steven Bosscher  <steven@gcc.gnu.org>
 
 	* doc/invoke.texi: Fix name of sched1 dump.

gcc/testsuite/ChangeLog

 2010-02-03  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/42944
+	* gcc.dg/errno-1.c: New testcase.
+
+2010-02-03  Richard Guenther  <rguenther@suse.de>
+
 	PR middle-end/42927
 	* gcc.c-torture/compile/pr42927.c: New testcase.
 

gcc/testsuite/gcc.dg/errno-1.c

+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+#include <errno.h>
+#include <stdlib.h>
+
+int main()
+{
+  void *p;
+  errno = 0;
+  p = malloc (-1);
+  if (errno != 0)
+    do_not_optimize_away ();
+  return 0;
+}
+
+/* { dg-final { scan-assembler "do_not_optimize_away" } } */

gcc/tree-ssa-alias.c

@@ -963,6 +963,7 @@ ref_maybe_used_by_call_p_1 (gimple call, ao_ref *ref)
 	/* The following builtins do not read from memory.  */
 	case BUILT_IN_FREE:
 	case BUILT_IN_MALLOC:
+	case BUILT_IN_CALLOC:
 	case BUILT_IN_MEMSET:
 	case BUILT_IN_FREXP:
 	case BUILT_IN_FREXPF:
@@ -1190,6 +1191,21 @@ call_may_clobber_ref_p_1 (gimple call, ao_ref *ref)
 	/* Allocating memory does not have any side-effects apart from
 	   being the definition point for the pointer.  */
 	case BUILT_IN_MALLOC:
+	case BUILT_IN_CALLOC:
+	  /* Unix98 specifies that errno is set on allocation failure.
+	     Until we properly can track the errno location assume it
+	     is not a plain decl but anonymous storage in a different
+	     translation unit.  */
+	  if (flag_errno_math)
+	    {
+	      struct ptr_info_def *pi;
+	      if (DECL_P (base))
+		return false;
+	      if (INDIRECT_REF_P (base)
+		  && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME
+		  && (pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0))))
+		return pi->pt.anything || pi->pt.nonlocal;
+	    }
 	  return false;
 	/* Freeing memory kills the pointed-to memory.  More importantly
 	   the call has to serve as a barrier for moving loads and stores