Restrict now doesn't work for tree-data-ref for non-parm_decl

[Zdenek Dvorak]

Hello,

> your recent rework of tree-data-ref.c broke determining non-dependence
> of src1row and src2row in the following testcase:
> 
> void cvSubInPlace_8bit(short *src1[], short *src2[], int height, int
> num_in_row) {
>    for(int y=0; y<height; y++) {
> 	short* __restrict src1row = src1[y];
> 	short* __restrict src2row = src2[y];
> 
> 	for(int i=num_in_row; i--;) {
> 	    *src1row -= *src2row;
> 	    ++src1row;
> 	    ++src2row;
> 	}
>    }
> }
> 
> The problem is you added
> 
>  if (TYPE_RESTRICT (type_a) && TYPE_RESTRICT (type_b)
>      && (!DR_IS_READ (a) || !DR_IS_READ (b))
>      && decl_a && TREE_CODE (decl_a) == PARM_DECL
>      && decl_b && TREE_CODE (decl_b) == PARM_DECL
>      && TREE_CODE (DECL_CONTEXT (decl_a)) == FUNCTION_DECL
>      && DECL_CONTEXT (decl_a) == DECL_CONTEXT (decl_b))
> ^^^^^^^^^^^^^^^^^^^^^
> The PARM_DECL checks above to our usage of restrict info.
> 
> If I replace them with DECL_P, the dependence is correctly determined again.
> 
> Is there some reason you believe there is a difference between
> restrict on var_decl vs restrict on parm_decl?
> I could understrand if the check was for DECL_P, but i can't see why
> PARM_DECL is special here.

actually, I did not change anything here; the original check was

-   else if (TYPE_RESTRICT (type_a)
-          &&  TYPE_RESTRICT (type_b)
-          && (!DR_IS_READ (drb) || !DR_IS_READ (dra))
-          && TREE_CODE (DR_BASE_ADDRESS (dra)) == SSA_NAME
-          && (decl_a = SSA_NAME_VAR (DR_BASE_ADDRESS (dra)))
-          && TREE_CODE (decl_a) == PARM_DECL
-          && TREE_CODE (DECL_CONTEXT (decl_a)) == FUNCTION_DECL
-          && TREE_CODE (DR_BASE_ADDRESS (drb)) == SSA_NAME
-          && (decl_b = SSA_NAME_VAR (DR_BASE_ADDRESS (drb)))
-          && TREE_CODE (decl_b) == PARM_DECL
-          && TREE_CODE (DECL_CONTEXT (decl_b)) == FUNCTION_DECL
-          && DECL_CONTEXT (decl_a) == DECL_CONTEXT (decl_b))

Which also passes only for PARM_DECLs.  I do not understand things well
enough to say whether restricting this to PARM_DECLs is necessary or not.

> Also, i believe the check should probably additionally be decl_a !=
> decl_b in any case, since otherwise, we will claim things whose base
> object is the same restricted pointer don't alias, even if they have
> the same offset, etc.

Yes, you are right.

Zdenek