[PATCH 3/4] Simple relaxation of dynamic type change detection routine

[Martin Jambor <mjambor at suse dot cz>]

Hi,

in order to speed up astar, I had to persuade the function that
decides whether a statement potentially modifies the dynamic type of
an object by storing a new value to the VMT pointer to consider the
following statement harmless (all types are integers of some sort):

MEM[(i32 *)b2arp_3(D) + 8B] = 0;

I'd like to experiment with this routine a bit more once I have some
other IPA-CP infrastructure in place but at the moment I opted for a
simple solution:  All scalar non-pointer stores are deemed safe.

VMT pointer is a compiler generated field which is a pointer so legal
user code is not able to store stuff there through some fancy type
casts and compiler generated code should have no reason whatsoever to
that either.  Therefore I believe this change is safe and useful.

I have bootstrapped and tested the patch on x886_64-linux.  OK for
trunk?

Thanks,

Martin



2011-04-14  Martin Jambor  <mjambor@suse.cz>

	* ipa-prop.c (stmt_may_be_vtbl_ptr_store): Return false for scalar
	non-pointer assignments.

Index: src/gcc/ipa-prop.c
===================================================================
--- src.orig/gcc/ipa-prop.c
+++ src/gcc/ipa-prop.c
@@ -405,13 +405,18 @@ stmt_may_be_vtbl_ptr_store (gimple stmt)
     {
       tree lhs = gimple_assign_lhs (stmt);
 
-      if (TREE_CODE (lhs) == COMPONENT_REF
-	  && !DECL_VIRTUAL_P (TREE_OPERAND (lhs, 1))
-	  && !AGGREGATE_TYPE_P (TREE_TYPE (lhs)))
+      if (!AGGREGATE_TYPE_P (TREE_TYPE (lhs)))
+	{
+	  if (!POINTER_TYPE_P (TREE_TYPE (lhs)))
 	    return false;
-      /* In the future we might want to use get_base_ref_and_offset to find
-	 if there is a field corresponding to the offset and if so, proceed
-	 almost like if it was a component ref.  */
+
+	  if (TREE_CODE (lhs) == COMPONENT_REF
+	      && !DECL_VIRTUAL_P (TREE_OPERAND (lhs, 1)))
+	    return false;
+	  /* In the future we might want to use get_base_ref_and_offset to find
+	     if there is a field corresponding to the offset and if so, proceed
+	     almost like if it was a component ref.  */
+	}
     }
   return true;
 }