On Wed, Apr 20, 2016 at 12:22 PM, Bin.Cheng <amker.ch...@gmail.com> wrote:
> On Wed, Apr 20, 2016 at 9:55 AM, Richard Biener
> <richard.guent...@gmail.com> wrote:
>> On Tue, Apr 19, 2016 at 7:00 PM, Bin Cheng <bin.ch...@arm.com> wrote:
>>> Hi,
>>> Type conversion from integer to smaller unsigned type could be transformed
>>> into BIT_AND_EXPR in compilation. For example,
>>> int i;
>>> for (i = 0; i < n; i++)
>>> {
>>> unsigned char uc = (unsigned char) i; // transformed into X = i &&
>>> 255, in which both X and i are of int type.
>>> b[uc] = 0;
>>> }
>>> X here could a valid SCEV if we can prove that loop doesn't iterate more
>>> than 255 times. In other words, if 'i' is SCEV and its value is in the
>>> range of representable set of type "unsigned char". This information could
>>> be available with -faggressive-loop-optimizations.
>>> This patch adds support for BIT_AND_EXPR in scalar evolution to handle such
>>> cases, as well as two new tests.
>>>
>>> Bootstrap and test on x86_64 & AArch64. Is it OK?
>>
>> Don't use cst_and_fits_in_hwi/int_cst_value - those are odd beasts.
>> Use tree_fits_uhwi_p / tree_to_uhwi.
>> Or just use wi::popcount and verify it against wi::clz.
> Thanks for reviewing, here is the updated patch. Regtest ongoing,
> shouldn't be any surprise though. Is it OK?
Ok.
Thanks,
Richard.
> Thanks,
> bin
>>
>> Richard.
>>
>>> Thanks,
>>> bin
>>>
>>> 2016-03-24 Bin Cheng <bin.ch...@arm.com>
>>>
>>> * tree-scalar-evolution.c (interpret_rhs_expr): Handle BIT_AND_EXPR.
>>>
>>> gcc/testsuite/ChangeLog
>>> 2016-03-24 Bin Cheng <bin.ch...@arm.com>
>>>
>>> * gcc.dg/tree-ssa/scev-11.c: New test.
>>> * gcc.dg/tree-ssa/scev-12.c: New test.
>>>
