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.
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.
>
