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[PATCH] Remove bogus PLUS_EXPR -> POINTER_PLUS_EXPR folding
- From: Richard Guenther <rguenther at suse dot de>
- To: gcc-patches at gcc dot gnu dot org
- Date: Fri, 16 Jan 2009 15:31:46 +0100 (CET)
- Subject: [PATCH] Remove bogus PLUS_EXPR -> POINTER_PLUS_EXPR folding
This removes a bogus folding that causes miscompiles of libstdc++
testcases with the ext_pointer class (PR38835) and non-field-sensitive
PTA (field-sensitive PTA is too dumb). I probably anticipated the
problem in PR36227 which should be fixed with that patch as well.
Fold changes
return <retval> = (const struct _Fwd_list_node_base *) ((long unsigned int) this + (long unsigned int) ((const struct _Relative_pointer_impl *) this)->_M_diff);
to
(const struct _Fwd_list_node_base *) this p+ (long unsigned int) ((const struct _Relative_pointer_impl *) this)->_M_diff
which makes PTA correctly conclude that 'this' and the result of the
POINTER_PLUS_EXPR point to the same object. Which they do not - the source
used addition in (long unsigned int) to avoid this issue and the resulting
pointer points somewhere else.
Fixed by removing the folding. This also fixes -Wsystem-header warnings
and miscompiles for the libstdc++ testsuite.
Bootstrap and regtest on x86_64-unknown-linux-gnu ongoing.
Richard.
2009-01-16 Richard Guenther <rguenther@suse.de>
PR tree-optimization/38835
PR middle-end/36227
* fold-const.c (fold_binary): Remove PTR + INT -> (INT)(PTR p+ INT)
and INT + PTR -> (INT)(PTR p+ INT) folding.
* tree-ssa-address.c (create_mem_ref): Properly use POINTER_PLUS_EXPR.
* gcc.dg/tree-ssa/foldaddr-1.c: XFAIL.
Index: gcc/fold-const.c
===================================================================
*** gcc/fold-const.c (revision 143429)
--- gcc/fold-const.c (working copy)
*************** fold_binary (enum tree_code code, tree t
*** 9864,9883 ****
return NULL_TREE;
case PLUS_EXPR:
- /* PTR + INT -> (INT)(PTR p+ INT) */
- if (POINTER_TYPE_P (TREE_TYPE (arg0))
- && INTEGRAL_TYPE_P (TREE_TYPE (arg1)))
- return fold_convert (type, fold_build2 (POINTER_PLUS_EXPR,
- TREE_TYPE (arg0),
- arg0,
- fold_convert (sizetype, arg1)));
- /* INT + PTR -> (INT)(PTR p+ INT) */
- if (POINTER_TYPE_P (TREE_TYPE (arg1))
- && INTEGRAL_TYPE_P (TREE_TYPE (arg0)))
- return fold_convert (type, fold_build2 (POINTER_PLUS_EXPR,
- TREE_TYPE (arg1),
- arg1,
- fold_convert (sizetype, arg0)));
/* A + (-B) -> A - B */
if (TREE_CODE (arg1) == NEGATE_EXPR)
return fold_build2 (MINUS_EXPR, type,
--- 9864,9869 ----
Index: gcc/testsuite/gcc.dg/tree-ssa/foldaddr-1.c
===================================================================
*** gcc/testsuite/gcc.dg/tree-ssa/foldaddr-1.c (revision 143429)
--- gcc/testsuite/gcc.dg/tree-ssa/foldaddr-1.c (working copy)
*************** int foo(char *b)
*** 11,16 ****
/* Folding should have determined that the two addresses were
not identical and thus collapsed the function into a trivial
"return 0". */
! /* { dg-final { scan-tree-dump-times "return 0" 1 "original"} } */
/* { dg-final { cleanup-tree-dump "original" } } */
--- 11,16 ----
/* Folding should have determined that the two addresses were
not identical and thus collapsed the function into a trivial
"return 0". */
! /* { dg-final { scan-tree-dump-times "return 0" 1 "original" { xfail *-*-* } } */
/* { dg-final { cleanup-tree-dump "original" } } */
Index: gcc/tree-ssa-address.c
===================================================================
*** gcc/tree-ssa-address.c (revision 143429)
--- gcc/tree-ssa-address.c (working copy)
*************** create_mem_ref (gimple_stmt_iterator *gs
*** 619,627 ****
{
atype = TREE_TYPE (tmp);
parts.base = force_gimple_operand_gsi (gsi,
! fold_build2 (PLUS_EXPR, atype,
! fold_convert (atype, parts.base),
! tmp),
true, NULL_TREE, true, GSI_SAME_STMT);
}
else
--- 619,627 ----
{
atype = TREE_TYPE (tmp);
parts.base = force_gimple_operand_gsi (gsi,
! fold_build2 (POINTER_PLUS_EXPR, atype,
! tmp,
! fold_convert (sizetype, parts.base)),
true, NULL_TREE, true, GSI_SAME_STMT);
}
else