On Tue, May 14, 2013 at 1:34 PM, Marc Glisse <marc.gli...@inria.fr> wrote:
> On Tue, 14 May 2013, Richard Biener wrote:
>
>> On Tue, May 14, 2013 at 1:23 PM, Marc Glisse <marc.gli...@inria.fr> wrote:
>>>
>>> Hello,
>>>
>>> in an earlier patch I apparently introduced a platform dependent signed /
>>> unsigned comparison, so here is a fix. I am taking the chance to fix the
>>> host_integerp second argument nearby: we want non-negative integers.
>>>
>>> Passes bootstrap+testsuite on x86_64-linux-gnu and apparently bootstrap
>>> on
>>> m68k.
>>>
>>> 2013-05-13 Marc Glisse <marc.gli...@inria.fr>
>>>
>>> PR bootstrap/57266
>>> * fold-const.c (fold_binary_loc) <shift>: Use an unsigned
>>> variable for the shift amount. Check that we shift by
>>> non-negative
>>> amounts.
>>>
>>> --
>>> Marc Glisse
>>> Index: gcc/fold-const.c
>>> ===================================================================
>>> --- gcc/fold-const.c (revision 198853)
>>> +++ gcc/fold-const.c (working copy)
>>> @@ -12416,27 +12416,27 @@ fold_binary_loc (location_t loc,
>>> return fold_build2_loc (loc, code, type, op0, tem);
>>>
>>> /* Since negative shift count is not well-defined,
>>> don't try to compute it in the compiler. */
>>> if (TREE_CODE (arg1) == INTEGER_CST && tree_int_cst_sgn (arg1) <
>>> 0)
>>> return NULL_TREE;
>>>
>>> prec = element_precision (type);
>>>
>>> /* Turn (a OP c1) OP c2 into a OP (c1+c2). */
>>> - if (TREE_CODE (op0) == code && host_integerp (arg1, false)
>>> + if (TREE_CODE (op0) == code && host_integerp (arg1, true)
>>> && TREE_INT_CST_LOW (arg1) < prec
>>> - && host_integerp (TREE_OPERAND (arg0, 1), false)
>>> + && host_integerp (TREE_OPERAND (arg0, 1), true)
>>> && TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)) < prec)
>>
>>
>> That looks good, but ...
>>
>>> {
>>> - HOST_WIDE_INT low = (TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1))
>>> - + TREE_INT_CST_LOW (arg1));
>>> + unsigned int low = (TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1))
>>> + + TREE_INT_CST_LOW (arg1));
>>
>>
>> that's wrong. TREE_INT_CST_LOW doesn't fit in an unsigned int.
>> unsigned HOST_WIDE_INT would work though.
>
>
> The checks above show that both TREE_INT_CST_LOW are smaller than prec (for
> which I already used an unsigned int, but an unsigned char might have been
> enough until Kenneth introduces int512_t). Do you still want the change?
Ah, ok. No, fine without the change.
Thanks,
Richard.
>
>> Ok with that change.
>>
>> Thanks,
>> Richard.
>>
>>> /* Deal with a OP (c1 + c2) being undefined but (a OP c1) OP c2
>>> being well defined. */
>>> if (low >= prec)
>>> {
>>> if (code == LROTATE_EXPR || code == RROTATE_EXPR)
>>> low = low % prec;
>>> else if (TYPE_UNSIGNED (type) || code == LSHIFT_EXPR)
>>> return omit_one_operand_loc (loc, type, build_zero_cst
>>> (type),
>>> TREE_OPERAND (arg0, 0));
>
>
> --
> Marc Glisse
