procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

re PR middle-end/11968 (Array reference is incorrectly computed for POINTERS_EXTEND_UNSIGNED)

Browse source 
PR middle-end/11968
	* expr.c (expand_expr <MULT_EXPR>): Remove inappropriate and
	confusing comment; distributivity isn't handled in expand_expr.
	* fold-const.c (extract_muldiv_1 <PLUS_EXPR>):  Allow overflow
	in distributivity, if wrap-around semantics are specified with
	-fwrapv.

From-SVN: r73166
This commit is contained in:
Roger Sayle 2003-11-01 00:59:53 +00:00 • committed by Roger Sayle
parent 3d63de248f
commit 41ba7ed74c
3 changed files with 14 additions and 12 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

9
gcc/ChangeLog
View file

@ -1,3 +1,12 @@
2003-10-31 Roger Sayle <roger@eyesopen.com>
PR middle-end/11968
* expr.c (expand_expr <MULT_EXPR>): Remove inappropriate and
confusing comment; distributivity isn't handled in expand_expr.
* fold-const.c (extract_muldiv_1 <PLUS_EXPR>): Allow overflow
in distributivity, if wrap-around semantics are specified with
-fwrapv.
2003-11-01 Alan Modra <amodra@bigpond.net.au>
PR 12315

10
gcc/expr.c
View file

@ -7854,16 +7854,6 @@ expand_expr (tree exp, rtx target, enum machine_mode tmode,
op0 = expand_expr (TREE_OPERAND (exp, 0), subtarget, VOIDmode,
EXPAND_SUM);
/* If we knew for certain that this is arithmetic for an array
reference, and we knew the bounds of the array, then we could
apply the distributive law across (PLUS X C) for constant C.
Without such knowledge, we risk overflowing the computation
when both X and C are large, but X+C isn't. */
/* ??? Could perhaps special-case EXP being unsigned and C being
positive. In that case we are certain that X+C is no smaller
than X and so the transformed expression will overflow iff the
original would have. */
if (GET_CODE (op0) != REG)
op0 = force_operand (op0, NULL_RTX);
if (GET_CODE (op0) != REG)

7
gcc/fold-const.c
View file

@ -4433,8 +4433,11 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type)
if (code == MULT_EXPR
|| integer_zerop (const_binop (TRUNC_MOD_EXPR, op1, c, 0)))
{
op1 = const_binop (code, convert (ctype, op1), convert (ctype, c), 0);
if (op1 == 0 || TREE_OVERFLOW (op1))
op1 = const_binop (code, convert (ctype, op1),
convert (ctype, c), 0);
/* We allow the constant to overflow with wrapping semantics. */
if (op1 == 0
|| (TREE_OVERFLOW (op1) && ! flag_wrapv))
break;
}
else