On 02/08/14 02:03, Kugan wrote:
>>>> if (rhs_uns)
>>>> return wi::ge_p (min, 0); // if min >= 0 then range contains positive
>>>> values
>>>> else
>>>> return wi::le_p (max, wi::max_value (TYPE_PRECISION (TREE_TYPE
>>>> (ssa)), SIGNED); // if max <= signed-max-of-type then range doesn't
>>>> need sign-extension
>>>
>>> I think we will have to check that ssa has necessary sign/zero extension
>>> when assigned to lhs_type. If PROMOTE_MODE tells us that ssa's type will
>>> be interpreted differently, the value range of ssa also will have
>>> corresponding range. In this cases, shouldn’t we have to check for
>>> upper and lower limit for both min and max?
>>
>> Hmm? That's exactly what the check is testing... we know that
>> min <= max thus if min >= 0 then max >= 0.
>>
>> zero_extension will never do anything on [0, INF]
>>
>> If max < MAX-SIGNED then sign-extension will not do anything. Ok,
>> sign-extension will do sth for negative values still. So rather
>>
>> if (rhs_uns)
>> return wi::geu_p (min, 0);
>> else
>> return wi::ges_p (min, 0) && wi::les_p (max, wi::max_value
>> (TYPE_PRECISION (TREE_TYPE (ssa)), SIGNED));
>>
>> ?
Looking at your comments again, I think we have to consider three things
here.
To be able assign to LHS (of lhs_uns and lhs_mode) without conversion of
RHS (tree SSA)
* If we ignore the mode changes (i.e. LHS_mode can be different in terms
of precision) and ignore PROMOTE_MODE and consider only the sign of LHS
and RHS
if (lhs_uns)
return wi::ge_p (min, 0, rhs_signop); // if min >= 0 then range
contains positive values
else
if (rhs_uns)
// if max <= signed-max-of-type then range doesn't need sign-extension
return wi::le_p (max, wi::max_value (TYPE_PRECISION (TREE_TYPE
(ssa)), SIGNED);
else
return true;
* However, if we consider the PROMOTE_MODE might change the RHS sign
if (lhs_uns)
{
return wi::ge_p (min, 0, rhs_signop);
}
else
{
signed_max = wide_int::from (TYPE_MAX_VALUE (lhs_type),
TYPE_PRECISION (TREE_TYPE (ssa)),
rhs_signop);
if (rhs_uns)
/* If PROMOTE_MODE changed an RHS signed to unsigned and
SSA contains negative value range, we still have to do sign-extend.
*/
return wi::ge_p (min, 0, TYPE_SIGN (TREE_TYPE (ssa)))
&& wi::le_p (max, signed_max, rhs_signop);
else
/* If PROMOTE_MODE changed an RHS unsigned to signed and SSA contains
value
range more than signed-max-of-type, we still have to do sign-extend.
*/
return wi::le_p (max, signed_max, TYPE_SIGN (TREE_TYPE (ssa)));
}
* If we also consider that LHS mode and RHS mode precision can be different
if (lhs_uns)
{
unsigned_max = wide_int::from (TYPE_MAX_VALUE (lhs_type),
TYPE_PRECISION (TREE_TYPE (ssa)),
rhs_signop);
/* If min >= 0 then range contains positive values and doesnt need
zero-extension. If max <= unsigned-max-of-type, then value fits type.
*/
return wi::ge_p (min, 0, rhs_signop)
&& wi::le_p (max, unsigned_max, rhs_signop);
}
else
{
signed_max = wide_int::from (TYPE_MAX_VALUE (lhs_type),
TYPE_PRECISION (TREE_TYPE (ssa)),
rhs_signop);
signed_min = wide_int::from (TYPE_MIN_VALUE (lhs_type),
TYPE_PRECISION (TREE_TYPE (ssa)),
rhs_signop);
if (rhs_uns)
/* If PROMOTE_MODE changed an RHS signed to unsigned and
SSA contains negative value range, we still have to do sign-extend.
*/
return wi::ge_p (min, 0, TYPE_SIGN (TREE_TYPE (ssa)))
&& wi::le_p (max, signed_max, rhs_signop);
else
/* If PROMOTE_MODE changed an RHS unsigned to signed and SSA contains
value
range more than signed-max-of-type, we still have to do sign-extend.
*/
return wi::le_p (max, signed_max, TYPE_SIGN (TREE_TYPE (ssa)))
&& wi::ge_p (min, signed_min, rhs_signop);
}
}
Since we can have PROMOTE_MODE changing the sign and LHS mode and RHS
mode precision can be different, the check should be the third one. Does
that make sense or am I still missing it?
Thanks again for your time,
Kugan
