Richard Biener via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> On Tue, Nov 17, 2020 at 12:24 PM Richard Sandiford via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
>>
>> We're now able to vectorise the set-up loop:
>>
>> int p = power2 (fns[i].po2);
>> for (int j = 0; j < N; j++)
>> a[j] = ((p << 4) * j) / (N - 1) - (p << 5);
>>
>> Rather than adjust the expected output for that, it seemed better
>> to disable optimisation for the testing code.
>>
>> Tested on aarch64-linux-gnu (with and without SVE), arm-linux-gnueabihf
>> and x86_64-linux-gnu. OK to install?
>
> In other places we just add a asm ("" : : : "memory") to the loop body, can
> you
> do it like htat?
I wondered about that, but I don't think it's reliable long-term.
We could (perhaps rightly) decide that it's a win to vectorise the
rhs of a[j] even if the asm prevents us from doing a vector store.
Thanks,
Richard
>
> Thanks,
> RIchard.
>
>> Richard
>>
>>
>> gcc/testsuite/
>> * gcc.dg/vect/vect-sdiv-pow2-1.c (main): Disable optimization.
>> ---
>> gcc/testsuite/gcc.dg/vect/vect-sdiv-pow2-1.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/gcc/testsuite/gcc.dg/vect/vect-sdiv-pow2-1.c
>> b/gcc/testsuite/gcc.dg/vect/vect-sdiv-pow2-1.c
>> index be70bc6c47e..bf387133d01 100644
>> --- a/gcc/testsuite/gcc.dg/vect/vect-sdiv-pow2-1.c
>> +++ b/gcc/testsuite/gcc.dg/vect/vect-sdiv-pow2-1.c
>> @@ -53,7 +53,7 @@ power2 (int x)
>>
>> #define N 50
>>
>> -int
>> +int __attribute__ ((optimize (0)))
>> main (void)
>> {
>> int a[N], b[N], c[N];
