re PR tree-optimization/68680 (On-stack VLA does not cause instrumentation with -fstack-protector)

	PR tree-optimization/68680
	* calls.c (special_function_p): Return ECF_MAY_BE_ALLOCA for
	BUILT_IN_ALLOCA{,_WITH_ALIGN}.  Don't check for __builtin_alloca
	by name.

	* gcc.target/i386/pr68680.c: New test.

From-SVN: r231279

gcc/ChangeLog

 2015-12-04  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/68680
+	* calls.c (special_function_p): Return ECF_MAY_BE_ALLOCA for
+	BUILT_IN_ALLOCA{,_WITH_ALIGN}.  Don't check for __builtin_alloca
+	by name.
+
 	PR tree-optimization/68671
 	* tree-ssa-reassoc.c (maybe_optimize_range_tests): For basic
 	blocks starting with the successor of first bb we've modified

gcc/calls.c

@@ -502,12 +502,9 @@ special_function_p (const_tree fndecl, int flags)
       /* We assume that alloca will always be called by name.  It
 	 makes no sense to pass it as a pointer-to-function to
 	 anything that does not understand its behavior.  */
-      if (((IDENTIFIER_LENGTH (name_decl) == 6
-	    && name[0] == 'a'
-	    && ! strcmp (name, "alloca"))
-	   || (IDENTIFIER_LENGTH (name_decl) == 16
-	       && name[0] == '_'
-	       && ! strcmp (name, "__builtin_alloca"))))
+      if (IDENTIFIER_LENGTH (name_decl) == 6
+	  && name[0] == 'a'
+	  && ! strcmp (name, "alloca"))
 	flags |= ECF_MAY_BE_ALLOCA;
 
       /* Disregard prefix _, __, __x or __builtin_.  */
@@ -553,6 +550,17 @@ special_function_p (const_tree fndecl, int flags)
 	flags |= ECF_NORETURN;
     }
 
+  if (DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL)
+    switch (DECL_FUNCTION_CODE (fndecl))
+      {
+      case BUILT_IN_ALLOCA:
+      case BUILT_IN_ALLOCA_WITH_ALIGN:
+	flags |= ECF_MAY_BE_ALLOCA;
+	break;
+      default:
+	break;
+      }
+
   return flags;
 }
 

gcc/testsuite/ChangeLog

 2015-12-04  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/68680
+	* gcc.target/i386/pr68680.c: New test.
+
 	PR tree-optimization/68671
 	* gcc.dg/pr68671.c: New test.
 

gcc/testsuite/gcc.target/i386/pr68680.c

+/* PR tree-optimization/68680 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-protector-strong" } */
+
+int foo (char *);
+
+int
+bar (unsigned long x)
+{
+  char a[x];
+  return foo (a);
+}
+
+/* Verify that this function is stack protected.  */
+/* { dg-final { scan-assembler "stack_chk_fail" } } */