[patch] Discard unreachable nested functions at -O0

[Eric Botcazou <ebotcazou at adacore dot com>]

Hi,

in Ada the front-end generates a lot of nested functions for generic packages 
or composite types and we want them to be discarded if unreachable even at -O0 
to speed things up and save memory.

Some years ago I submitted a patch to that effect:
  http://gcc.gnu.org/ml/gcc-patches/2006-03/msg01201.html
but it was rejected by RTH on technical grounds (we use it internally though).

I'm submitting a revised version, which is trivial since the compiler now 
works in unit-at-a-time mode.  And it's worth noting that this is actually 
supposed to be already implemented, see cgraph_decide_is_function_needed:

     When not optimizing, also output the static functions. (see
     PR24561), but don't do so for always_inline functions, functions
     declared inline and nested functions.  These was optimized out
     in the original implementation and it is unclear whether we want
     to change the behavior here.  */

Tested on x86_64-suse-linux, OK for mainline?


2010-05-31  Eric Botcazou  <ebotcazou@adacore.com>

	* cgraphunit.c (cgraph_decide_is_function_needed): Really return false
	for nested functions in non-optimized compilation.


2010-05-31  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc.dg/nested-func-7.c: New test.
	* gnat.dg/frame_overflow.adb: Adjust directives.


-- 
Eric Botcazou

Index: cgraphunit.c
===================================================================
--- cgraphunit.c	(revision 159937)
+++ cgraphunit.c	(working copy)
@@ -352,13 +352,15 @@ cgraph_decide_is_function_needed (struct
 
      When not optimizing, also output the static functions. (see
      PR24561), but don't do so for always_inline functions, functions
-     declared inline and nested functions.  These was optimized out
+     declared inline and nested functions.  These were optimized out
      in the original implementation and it is unclear whether we want
      to change the behavior here.  */
   if (((TREE_PUBLIC (decl)
-	|| (!optimize && !node->local.disregard_inline_limits
+	|| (!optimize
+	    && !node->local.disregard_inline_limits
 	    && !DECL_DECLARED_INLINE_P (decl)
-	    && !node->origin))
+	    && !(DECL_CONTEXT (decl)
+		 && TREE_CODE (DECL_CONTEXT (decl)) == FUNCTION_DECL)))
        && !flag_whole_program
        && !flag_lto
        && !flag_whopr)
Index: testsuite/gnat.dg/frame_overflow.adb
===================================================================
--- testsuite/gnat.dg/frame_overflow.adb	(revision 159937)
+++ testsuite/gnat.dg/frame_overflow.adb	(working copy)
@@ -1,5 +1,4 @@
 -- { dg-do compile }
--- { dg-xfail-if "missing late warning" { *-*-* } { "-flto" } { "" } }
 
 with System;
 
@@ -11,8 +10,8 @@ procedure frame_overflow is
    type Bitmap_T is record
       Bits : Bitmap_Array_T := (others => False);
    end record;
-   
-   function -- { dg-error "too large" }
+
+   function
      Set_In (Bitmap : Bitmap_T; Bitpos : Bitpos_Range_T)  return Bitmap_T
    is
       Result: Bitmap_T := Bitmap; -- { dg-error "Storage_Error" }

/* { dg-do compile } */
/* { dg-options "-fdump-tree-optimized" } */

void foo (void)
{
  int a;

  void bar (void)
  {
    a = 1;
  }
}

/* { dg-final { scan-tree-dump-not "bar" "optimized" } } */
/* { dg-final { cleanup-tree-dump "optimized" } } */