[PATCH, PR 44133] Preserve sane warnings when deleting loads in SRA

[Martin Jambor <mjambor at suse dot cz>]

Hi,

this is a fix for PR 44133.  We emit a sane warning for uninitialized
loads by replacing the uses of the load by a default definition of a
SRA replacement rather than of the (usually temporary) variable that
we load into.  

As it happens, in these situations there would not normally be a
replacement created so we create one late and since it does not have
to be marked for renaming so we don't.  There is also a new access
function to assert these two approaches to replacement creation do not
mix.

If you look at the testcase you will find out tat the warning is
issued for a wrong line.  This also happens in 4.4 and so is a
diferent bug that I did not attempt to address.

Bootstrapped and tested on x86_64-linux, OK for trunk?

Thanks,

Martin


2010-05-15  Martin Jambor  <mjambor@suse.cz>

	PR middle-end/44133
	* tree-sra.c (create_access_replacement): New parameter rename, mark
	the replaement for renaming only when it is true.
	(get_access_replacement): Pass true in the rename parameter of
	create_access_replacement.
	(get_unrenamed_access_replacement): New function.
	(replace_uses_with_default_def_ssa_name): New parameter racc, get the
	replacement declaration from it.

	* testsuite/gcc.dg/tree-ssa/pr44133.c: New test.
	* testsuite/gcc.dg/tree-ssa/sra-9.c: Make the scan regular
	expression more precise.


Index: mine/gcc/tree-sra.c
===================================================================
*** mine.orig/gcc/tree-sra.c
--- mine/gcc/tree-sra.c
*************** sort_and_splice_var_accesses (tree var)
*** 1586,1599 ****
     ACCESS->replacement.  */
  
  static tree
! create_access_replacement (struct access *access)
  {
    tree repl;
  
    repl = create_tmp_var (access->type, "SR");
    get_var_ann (repl);
    add_referenced_var (repl);
!   mark_sym_for_renaming (repl);
  
    if (!access->grp_partial_lhs
        && (TREE_CODE (access->type) == COMPLEX_TYPE
--- 1586,1600 ----
     ACCESS->replacement.  */
  
  static tree
! create_access_replacement (struct access *access, bool rename)
  {
    tree repl;
  
    repl = create_tmp_var (access->type, "SR");
    get_var_ann (repl);
    add_referenced_var (repl);
!   if (rename)
!     mark_sym_for_renaming (repl);
  
    if (!access->grp_partial_lhs
        && (TREE_CODE (access->type) == COMPLEX_TYPE
*************** get_access_replacement (struct access *a
*** 1669,1678 ****
    gcc_assert (access->grp_to_be_replaced);
  
    if (!access->replacement_decl)
!     access->replacement_decl = create_access_replacement (access);
    return access->replacement_decl;
  }
  
  /* Build a subtree of accesses rooted in *ACCESS, and move the pointer in the
     linked list along the way.  Stop when *ACCESS is NULL or the access pointed
     to it is not "within" the root.  */
--- 1670,1693 ----
    gcc_assert (access->grp_to_be_replaced);
  
    if (!access->replacement_decl)
!     access->replacement_decl = create_access_replacement (access, true);
    return access->replacement_decl;
  }
  
+ /* Return ACCESS scalar replacement, create it if it does not exist yet but do
+    not mark it for renaming.  */
+ 
+ static inline tree
+ get_unrenamed_access_replacement (struct access *access)
+ {
+   gcc_assert (!access->grp_to_be_replaced);
+ 
+   if (!access->replacement_decl)
+     access->replacement_decl = create_access_replacement (access, false);
+   return access->replacement_decl;
+ }
+ 
+ 
  /* Build a subtree of accesses rooted in *ACCESS, and move the pointer in the
     linked list along the way.  Stop when *ACCESS is NULL or the access pointed
     to it is not "within" the root.  */
*************** sra_modify_constructor_assign (gimple *s
*** 2507,2535 ****
  }
  
  /* Create a new suitable default definition SSA_NAME and replace all uses of
!    SSA with it.  */
  
  static void
! replace_uses_with_default_def_ssa_name (tree ssa)
  {
!   tree repl, decl = SSA_NAME_VAR (ssa);
!   if (TREE_CODE (decl) == PARM_DECL)
!     {
!       tree tmp = create_tmp_reg (TREE_TYPE (decl), "SR");
  
!       get_var_ann (tmp);
!       add_referenced_var (tmp);
!       repl = make_ssa_name (tmp, gimple_build_nop ());
!       set_default_def (tmp, repl);
!     }
!   else
      {
!       repl = gimple_default_def (cfun, decl);
!       if (!repl)
! 	{
! 	  repl = make_ssa_name (decl, gimple_build_nop ());
! 	  set_default_def (decl, repl);
! 	}
      }
  
    replace_uses_by (ssa, repl);
--- 2522,2542 ----
  }
  
  /* Create a new suitable default definition SSA_NAME and replace all uses of
!    SSA with it, RACC is access describing the uninitialized part of an
!    aggregate that is being loaded.  */
  
  static void
! replace_uses_with_default_def_ssa_name (tree ssa, struct access *racc)
  {
!   tree repl, decl;
  
!   decl = get_unrenamed_access_replacement (racc);
! 
!   repl = gimple_default_def (cfun, decl);
!   if (!repl)
      {
!       repl = make_ssa_name (decl, gimple_build_nop ());
!       set_default_def (decl, repl);
      }
  
    replace_uses_by (ssa, repl);
*************** sra_modify_assign (gimple *stmt, gimple_
*** 2717,2723 ****
  					     false, false);
  		  gcc_assert (*stmt == gsi_stmt (*gsi));
  		  if (TREE_CODE (lhs) == SSA_NAME)
! 		    replace_uses_with_default_def_ssa_name (lhs);
  
  		  unlink_stmt_vdef (*stmt);
  		  gsi_remove (gsi, true);
--- 2724,2730 ----
  					     false, false);
  		  gcc_assert (*stmt == gsi_stmt (*gsi));
  		  if (TREE_CODE (lhs) == SSA_NAME)
! 		    replace_uses_with_default_def_ssa_name (lhs, racc);
  
  		  unlink_stmt_vdef (*stmt);
  		  gsi_remove (gsi, true);
Index: mine/gcc/testsuite/gcc.dg/tree-ssa/pr44133.c
===================================================================
*** /dev/null
--- mine/gcc/testsuite/gcc.dg/tree-ssa/pr44133.c
***************
*** 0 ****
--- 1,11 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O2 -Wall" } */
+ 
+ struct S { int i, j; };
+ 
+ int foo (int l)
+ {
+   struct S s;
+   s.j = l - 22;   /* { dg-warning ".s\.i. is used uninitialized" } */
+   return s.i + s.j;
+ }
Index: mine/gcc/testsuite/gcc.dg/tree-ssa/sra-9.c
===================================================================
*** mine.orig/gcc/testsuite/gcc.dg/tree-ssa/sra-9.c
--- mine/gcc/testsuite/gcc.dg/tree-ssa/sra-9.c
*************** int foo (int d)
*** 16,20 ****
  }
  
  /* There should be no reference to s.b.  */
! /* { dg-final { scan-tree-dump-times "s\.b" 0 "optimized"} } */
  /* { dg-final { cleanup-tree-dump "optimized" } } */
--- 16,20 ----
  }
  
  /* There should be no reference to s.b.  */
! /* { dg-final { scan-tree-dump-times "= s\.b" 0 "optimized"} } */
  /* { dg-final { cleanup-tree-dump "optimized" } } */