Re: [PATCH] Remove redundant checking from may_propagate_copy, allow copyprop through (void *) conversion

[Richard Guenther <rguenther at suse dot de>]

On Tue, 4 Sep 2007, Richard Guenther wrote:

> 
> This removes redundant checking done by may_propagate_copy.  First it
> calls useless_type_conversion_p twice, second it does compare alias set
> numbers which useless_type_conversion_p does as well.  As
> useless_type_conversion_p special-cases conversions to (void *) this
> enables us to copypropagate in the testcase added.
> 
> Bootstrapping and testing on x86_64-unknown-linux-gnu in progress.

And the following actually passed bootstrapping and testing.  I'll
install after the usual wait-for-comments.  The new testcase would
ICE in the assert in get_smt_for if we didn't specialize VOID_TYPE
there (I tried to avoid generating a SMT for void, but that was too
tricky).

Richard.


2007-08-04  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-copy.c (may_propagate_copy): Remove redundant
	call to useless_type_conversion_p and alias set comparison.
	(merge_alias_info): Remove redundant alias set comparison.
	* tree-ssa-alias.c (get_smt_for): Ignore differing alias sets
	if one is for VOID.

	* gcc.dg/tree-ssa/ssa-copyprop-2.c: New testcase.
	* gcc.c-torture/compile/20070904-1.c: Likewise.

Index: tree-ssa-copy.c
===================================================================
*** tree-ssa-copy.c	(revision 128067)
--- tree-ssa-copy.c	(working copy)
*************** may_propagate_copy (tree dest, tree orig
*** 129,139 ****
        tree mt_orig = symbol_mem_tag (SSA_NAME_VAR (orig));
        if (mt_dest && mt_orig && mt_dest != mt_orig)
  	return false;
-       else if (!useless_type_conversion_p (type_d, type_o))
- 	return false;
-       else if (get_alias_set (TREE_TYPE (type_d)) != 
- 	       get_alias_set (TREE_TYPE (type_o)))
- 	return false;
  
        /* Also verify flow-sensitive information is compatible.  */
        if (SSA_NAME_PTR_INFO (orig) && SSA_NAME_PTR_INFO (dest))
--- 129,134 ----
*************** merge_alias_info (tree orig_name, tree n
*** 223,234 ****
  #if defined ENABLE_CHECKING
    gcc_assert (useless_type_conversion_p (TREE_TYPE (orig_name),
  					TREE_TYPE (new_name)));
- 
-   /* If the pointed-to alias sets are different, these two pointers
-      would never have the same memory tag.  In this case, NEW should
-      not have been propagated into ORIG.  */
-   gcc_assert (get_alias_set (TREE_TYPE (TREE_TYPE (new_sym)))
- 	      == get_alias_set (TREE_TYPE (TREE_TYPE (orig_sym))));
  #endif
  
    /* Synchronize the symbol tags.  If both pointers had a tag and they
--- 218,223 ----
Index: testsuite/gcc.dg/tree-ssa/ssa-copyprop-2.c
===================================================================
*** testsuite/gcc.dg/tree-ssa/ssa-copyprop-2.c	(revision 0)
--- testsuite/gcc.dg/tree-ssa/ssa-copyprop-2.c	(revision 0)
***************
*** 0 ****
--- 1,21 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -fdump-tree-copyprop1" } */
+ 
+ struct Foo;
+ 
+ void bar(struct Foo *);
+ 
+ void foo(void)
+ {
+   int i[2];
+   char *p1;
+   void *p2;
+   struct Foo *p3;
+   p1 = (char *)&i;
+   p2 = p1;
+   p3 = p2;
+   bar (p3);
+ }
+ 
+ /* { dg-final { scan-tree-dump "\\(struct Foo \\*\\) p1" "copyprop1" } } */
+ /* { dg-final { cleanup-tree-dump "copyprop1" } } */
Index: testsuite/gcc.c-torture/compile/20070904-1.c
===================================================================
*** testsuite/gcc.c-torture/compile/20070904-1.c	(revision 0)
--- testsuite/gcc.c-torture/compile/20070904-1.c	(revision 0)
***************
*** 0 ****
--- 1,11 ----
+ static struct typeinfo *typevec;
+ void ggc_set_mark (struct typeinfo*);
+ void gt_ggc_ma_typevec (void)
+ {
+   if (typevec != ((void *)0))
+     {
+       void *a__ = typevec;
+       ggc_set_mark (a__);
+     }
+ }
+ 
Index: tree-ssa-alias.c
===================================================================
*** tree-ssa-alias.c	(revision 128067)
--- tree-ssa-alias.c	(working copy)
*************** get_smt_for (tree ptr, struct alias_info
*** 3117,3123 ****
  
    /* Make sure that the symbol tag has the same alias set as the
       pointed-to type.  */
!   gcc_assert (tag_set == get_alias_set (tag));
  
    return tag;
  }
--- 3117,3124 ----
  
    /* Make sure that the symbol tag has the same alias set as the
       pointed-to type.  */
!   gcc_assert (VOID_TYPE_P (TREE_TYPE (tag))
! 	      || tag_set == get_alias_set (tag));
  
    return tag;
  }