tree.h (struct tree_decl): Add malloc_flag.

* tree.h (struct tree_decl): Add malloc_flag.
	(DECL_IS_MALLOC): Define.
	* c-common.c (attrs): Add A_MALLOC attribute.
	(init_attributes): Add this attribute to the table.
	(decl_attributes): Handle malloc attribute.
	* calls.c (special_function_p): Check for the malloc attribute.
	* extend.texi (Function Attributes): Document malloc attribute.

From-SVN: r30689

gcc/ChangeLog

@@ -1,3 +1,13 @@
+1999-11-28  Anthony Green  <green@cygnus.com>
+
+	* tree.h (struct tree_decl): Add malloc_flag.
+	(DECL_IS_MALLOC): Define.
+	* c-common.c (attrs): Add A_MALLOC attribute.
+	(init_attributes): Add this attribute to the table.
+	(decl_attributes): Handle malloc attribute.
+	* calls.c (special_function_p): Check for the malloc attribute.
+	* extend.texi (Function Attributes): Document malloc attribute.
+
 Sun Nov 28 13:21:00 1999  Jeffrey A Law  (law@cygnus.com)
 
 	* pa.md (reload shift-add patterns): Remove.

gcc/c-common.c

@@ -140,7 +140,7 @@ int skip_evaluation;
 enum attrs {A_PACKED, A_NOCOMMON, A_COMMON, A_NORETURN, A_CONST, A_T_UNION,
 	    A_NO_CHECK_MEMORY_USAGE, A_NO_INSTRUMENT_FUNCTION,
 	    A_CONSTRUCTOR, A_DESTRUCTOR, A_MODE, A_SECTION, A_ALIGNED,
-	    A_UNUSED, A_FORMAT, A_FORMAT_ARG, A_WEAK, A_ALIAS};
+	    A_UNUSED, A_FORMAT, A_FORMAT_ARG, A_WEAK, A_ALIAS, A_MALLOC};
 
 enum format_type { printf_format_type, scanf_format_type,
 		   strftime_format_type };
@@ -481,6 +481,7 @@ init_attributes ()
   add_attribute (A_ALIAS, "alias", 1, 1, 1);
   add_attribute (A_NO_INSTRUMENT_FUNCTION, "no_instrument_function", 0, 0, 1);
   add_attribute (A_NO_CHECK_MEMORY_USAGE, "no_check_memory_usage", 0, 0, 1);
+  add_attribute (A_MALLOC, "malloc", 0, 0, 1);
 }
 
 /* Default implementation of valid_lang_attribute, below.  By default, there
@@ -617,6 +618,13 @@ decl_attributes (node, attributes, prefix_attributes)
 	    warning ("`%s' attribute ignored", IDENTIFIER_POINTER (name));
 	  break;
 
+	case A_MALLOC:
+	  if (TREE_CODE (decl) == FUNCTION_DECL)
+	    DECL_IS_MALLOC (decl) = 1;
+	  else
+	    warning ("`%s' attribute ignored", IDENTIFIER_POINTER (name));
+	  break;
+
 	case A_UNUSED:
 	  if (is_type)
 	    TREE_USED (type) = 1;

gcc/calls.c

@@ -546,10 +546,14 @@ special_function_p (name, fndecl, returns_twice, is_longjmp,
 {
   *returns_twice = 0;
   *is_longjmp = 0;
-  *is_malloc = 0;
   *may_be_alloca = 0;
 
-  if (name != 0 && IDENTIFIER_LENGTH (DECL_NAME (fndecl)) <= 17
+  /* The function decl may have the `malloc' attribute.  */
+  *is_malloc = fndecl && DECL_IS_MALLOC (fndecl);
+
+  if (! is_malloc 
+      && name != 0 
+      && IDENTIFIER_LENGTH (DECL_NAME (fndecl)) <= 17
       /* Exclude functions not at the file scope, or not `extern',
 	 since they are not the magic functions we would otherwise
 	 think they are.  */
@@ -602,8 +606,8 @@ special_function_p (name, fndecl, returns_twice, is_longjmp,
       else if (tname[0] == 'l' && tname[1] == 'o'
 	       && ! strcmp (tname, "longjmp"))
 	*is_longjmp = 1;
-      /* XXX should have "malloc" attribute on functions instead
-	 of recognizing them by name.  */
+      /* Do not add any more malloc-like functions to this list,
+	 instead mark as malloc functions using the malloc attribute.  */
       else if (! strcmp (tname, "malloc")
 	       || ! strcmp (tname, "calloc")
 	       || ! strcmp (tname, "realloc")

gcc/extend.texi

@@ -1310,6 +1310,7 @@ hack ((union foo) x);
 @cindex functions that never return
 @cindex functions that have no side effects
 @cindex functions in arbitrary sections
+@cindex functions that bahave like malloc
 @cindex @code{volatile} applied to function
 @cindex @code{const} applied to function
 @cindex functions with @code{printf}, @code{scanf} or @code{strftime} style arguments
@@ -1323,10 +1324,10 @@ carefully.
 
 The keyword @code{__attribute__} allows you to specify special
 attributes when making a declaration.  This keyword is followed by an
-attribute specification inside double parentheses.  Nine attributes,
+attribute specification inside double parentheses.  Ten attributes,
 @code{noreturn}, @code{const}, @code{format},
-@code{no_instrument_function}, @code{section},
-@code{constructor}, @code{destructor}, @code{unused} and @code{weak} are
+@code{no_instrument_function}, @code{section}, @code{constructor},
+@code{destructor}, @code{unused}, @code{weak} and @code{malloc} are
 currently defined for functions.  Other attributes, including
 @code{section} are supported for variables declarations (@pxref{Variable
 Attributes}) and for types (@pxref{Type Attributes}).
@@ -1540,6 +1541,13 @@ also be used with non-function declarations.  Weak symbols are supported
 for ELF targets, and also for a.out targets when using the GNU assembler
 and linker.
 
+@item malloc
+@cindex @code{malloc} attribute
+The @code{malloc} attribute is used to tell the compiler that a function
+may be treated as if it were the malloc function.  The compiler assumes
+that calls to malloc result in a pointers that cannot alias anything.
+This will often improve optimization.
+
 @item alias ("target")
 @cindex @code{alias} attribute
 The @code{alias} attribute causes the declaration to be emitted as an

gcc/tree.h

@@ -1238,6 +1238,11 @@ struct tree_type
    to redefine for any purpose whatever.  */
 #define DECL_BUILT_IN_NONANSI(NODE) ((NODE)->common.unsigned_flag)
 
+/* Nonzero in a FUNCTION_DECL means this function should be treated
+   as if it were a malloc, meaning it returns a pointer that is
+   not an alias.  */
+#define DECL_IS_MALLOC(NODE) (DECL_CHECK (NODE)->decl.malloc_flag)
+
 /* Nonzero in a FIELD_DECL means it is a bit field, and must be accessed
    specially.  */
 #define DECL_BIT_FIELD(NODE) (DECL_CHECK (NODE)->decl.bit_field_flag)
@@ -1370,6 +1375,7 @@ struct tree_decl
   unsigned no_instrument_function_entry_exit : 1;
   unsigned no_check_memory_usage : 1;
   unsigned comdat_flag : 1;
+  unsigned malloc_flag : 1;
 
   /* For a FUNCTION_DECL, if inline, this is the size of frame needed.
      If built-in, this is the code for which built-in function.