Kenneth Zadeck <zad...@naturalbridge.com> writes:
> So what is the big plan here? if you remove it here and then do not
> do it in wide int, then it is not going to be truncated.
Yeah, that is the big plan for trees. Mainline doesn't truncate at the
tree level after:
http://gcc.gnu.org/ml/gcc-patches/2013-11/msg00285.html
and this patch brings wide-int back in line. (The truncations in this patch
were only ever local to wide-int.)
If you're wondering why we don't want to truncate at the tree level,
see the second half of:
http://gcc.gnu.org/ml/gcc-patches/2013-11/msg00174.html
Thanks,
Richard
> On 11/06/2013 05:10 PM, Richard Sandiford wrote:
>> Following the removal of SHIFT_COUNT_TRUNCATED from double-int, this patch
>> reverts the changed I'd made to mimic the old behaviour on wide-int.
>>
>> Tested on powerpc64-linux-gnu and by assembly comparison on a range of
>> targets.
>> OK to install?
>>
>> Thanks,
>> Richard
>>
>>
>> Index: gcc/fold-const.c
>> ===================================================================
>> --- gcc/fold-const.c 2013-11-05 13:06:56.985255941 +0000
>> +++ gcc/fold-const.c 2013-11-05 13:12:28.805655903 +0000
>> @@ -1007,13 +1007,9 @@ int_const_binop_1 (enum tree_code code,
>> /* It's unclear from the C standard whether shifts can overflow.
>> The following code ignores overflow; perhaps a C standard
>> interpretation ruling is needed. */
>> - res = wi::rshift (arg1, arg2, sign,
>> - SHIFT_COUNT_TRUNCATED
>> - ? GET_MODE_BITSIZE (TYPE_MODE (type)) : 0);
>> + res = wi::rshift (arg1, arg2, sign);
>> else
>> - res = wi::lshift (arg1, arg2,
>> - SHIFT_COUNT_TRUNCATED
>> - ? GET_MODE_BITSIZE (TYPE_MODE (type)) : 0);
>> + res = wi::lshift (arg1, arg2);
>> break;
>>
>> case RROTATE_EXPR:
>> Index: gcc/tree-ssa-ccp.c
>> ===================================================================
>> --- gcc/tree-ssa-ccp.c 2013-11-05 13:07:25.659474362 +0000
>> +++ gcc/tree-ssa-ccp.c 2013-11-05 13:12:28.806655910 +0000
>> @@ -1272,20 +1272,15 @@ bit_value_binop_1 (enum tree_code code,
>> else
>> code = RSHIFT_EXPR;
>> }
>> - int shift_precision = SHIFT_COUNT_TRUNCATED ? width : 0;
>> if (code == RSHIFT_EXPR)
>> {
>> - *mask = wi::rshift (wi::ext (r1mask, width, sgn),
>> - shift, sgn, shift_precision);
>> - *val = wi::rshift (wi::ext (r1val, width, sgn),
>> - shift, sgn, shift_precision);
>> + *mask = wi::rshift (wi::ext (r1mask, width, sgn), shift, sgn);
>> + *val = wi::rshift (wi::ext (r1val, width, sgn), shift, sgn);
>> }
>> else
>> {
>> - *mask = wi::ext (wi::lshift (r1mask, shift, shift_precision),
>> - width, sgn);
>> - *val = wi::ext (wi::lshift (r1val, shift, shift_precision),
>> - width, sgn);
>> + *mask = wi::ext (wi::lshift (r1mask, shift), width, sgn);
>> + *val = wi::ext (wi::lshift (r1val, shift), width, sgn);
>> }
>> }
>> }
