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

[Martin Jambor]

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  mjam...@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;
 }

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

[Richard Guenther]

On Fri, 15 Apr 2011, Martin Jambor wrote:

 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?

I think this should be only done for -fstrict-aliasing.

Ok with that change.
Richard.

 Thanks,
 
 Martin
 
 
 
 2011-04-14  Martin Jambor  mjam...@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;
  }
 
 

-- 
Richard Guenther rguent...@suse.de
Novell / SUSE Labs
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