On Wed, Oct 30, 2013 at 1:09 AM, Marc Glisse <[email protected]> wrote:
> On Tue, 29 Oct 2013, Richard Biener wrote:
>
>> For the POINTER_PLUS_EXPR offset argument you should use
>> int_cst_value () to access it (it will unconditionally sign-extend)
>> and use host_integerp (..., 0). That leaves the overflow possibility
>> in place (and you should multiply by BITS_PER_UNIT) which we
>> ignore in enough other places similar to this to ignore ...
>
>
> Like this? (passes bootstrap+testsuite on x86_64-linux-gnu)
>
> 2013-10-30 Marc Glisse <[email protected]>
>
>
> gcc/
> * tree-ssa-alias.c (ao_ref_init_from_ptr_and_size): Look for a
> POINTER_PLUS_EXPR in the defining statement.
>
> gcc/testsuite/
> * gcc.dg/tree-ssa/alias-24.c: New file.
>
>
> --
> Marc Glisse
>
> Index: gcc/testsuite/gcc.dg/tree-ssa/alias-24.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/alias-24.c (revision 0)
> +++ gcc/testsuite/gcc.dg/tree-ssa/alias-24.c (working copy)
> @@ -0,0 +1,22 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +void f (const char *c, int *i)
> +{
> + *i = 42;
> + __builtin_memcpy (i + 1, c, sizeof (int));
> + if (*i != 42) __builtin_abort();
> +}
> +
> +extern void keepit ();
> +void g (const char *c, int *i)
> +{
> + *i = 33;
> + __builtin_memcpy (i - 1, c, 3 * sizeof (int));
> + if (*i != 33) keepit();
> +}
> +
> +/* { dg-final { scan-tree-dump-not "abort" "optimized" } } */
> +/* { dg-final { scan-tree-dump "keepit" "optimized" } } */
> +/* { dg-final { cleanup-tree-dump "optimized" } } */
> +
>
> Property changes on: gcc/testsuite/gcc.dg/tree-ssa/alias-24.c
> ___________________________________________________________________
> Added: svn:keywords
> ## -0,0 +1 ##
> +Author Date Id Revision URL
> \ No newline at end of property
> Added: svn:eol-style
> ## -0,0 +1 ##
> +native
> \ No newline at end of property
> Index: gcc/tree-ssa-alias.c
> ===================================================================
> --- gcc/tree-ssa-alias.c (revision 204188)
> +++ gcc/tree-ssa-alias.c (working copy)
> @@ -567,20 +567,29 @@ void
> ao_ref_init_from_ptr_and_size (ao_ref *ref, tree ptr, tree size)
> {
> HOST_WIDE_INT t1, t2;
> ref->ref = NULL_TREE;
> if (TREE_CODE (ptr) == SSA_NAME)
> {
> gimple stmt = SSA_NAME_DEF_STMT (ptr);
> if (gimple_assign_single_p (stmt)
> && gimple_assign_rhs_code (stmt) == ADDR_EXPR)
> ptr = gimple_assign_rhs1 (stmt);
> + else if (is_gimple_assign (stmt)
> + && gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR
> + && host_integerp (gimple_assign_rhs2 (stmt), 0)
> + && (t1 = int_cst_value (gimple_assign_rhs2 (stmt))) >= 0)
No need to restrict this to positive offsets I think.
> + {
> + ao_ref_init_from_ptr_and_size (ref, gimple_assign_rhs1 (stmt),
> size);
Please don't recurse - forwprop combines series of POINTER_PLUS_EXPRs
and &MEM[ptr, offset] so it shouldn't be necessary.
> + ref->offset += 8 * t1;
BITS_PER_UNIT instead of 8. I'd say just have a 0-initialized
additional_offset var that you unconditionally add ...
> + return;
> + }
> }
>
> if (TREE_CODE (ptr) == ADDR_EXPR)
> ref->base = get_ref_base_and_extent (TREE_OPERAND (ptr, 0),
> &ref->offset, &t1, &t2);
> else
> {
> ref->base = build2 (MEM_REF, char_type_node,
> ptr, null_pointer_node);
> ref->offset = 0;
... here at the end.
Thanks,
Richard.
