Hi Avinash,
On 08/09/25 2:54 pm, Avinash Jayakar wrote:
> Hi,
>
> This is the third version of the patch proposed for master aiming to fix
> PR119702. Requesting review of this patch.
>
> The following sequence of assembly in powerpc64le
> vspltisw 0,1
> vsld 2,2,0
> is replaced by this
> vaddudm 2,2,2
> whenever there is a vector left shift by a constant value 1.
A better commit message is in order here. Something like:
Whenever a vector is left shifted by a constant value 1, gcc generates the
following code:
<code>
Instead the following code can be generated which is more efficient:
<new code>
This patch adds a pattern in altivec.md to recognize a vector left shift by
a constant value, and generate add instructions if constant is 1.
> Added the pattern in altivec.md to recognize a vector left shift by a constant
> value, and generate add instructions if constant is 1.
>
Changelog should be preceded by date, author name and author email id.
Do note that there should be a gap of 2 spaces between date and name, and
between name and email id.
> PR target/119702
> gcc:
> * config/rs6000/altivec.md: Added a define_insn to recognize left shift
> by constant 1 for vector instructions.
> * config/rs6000/predicates.md(shift_constant_1): Added a predicate for
Please change the variable name shift_constant_1. 'shift' can be removed
as this predicate is to check for a vector of 1's and is not related to the
shift operation.
> detecting if all values in a const_vector are 1.
> gcc/testsuite:
> * gcc.target/powerpc/pr119702-1.c: New test for (check generation of
> vadd for different integer types)
>
> Changes made in v3: Incorporated review comments made for patch v2
The "changes" info should come at the beginning of the mail.
> 1. Indentation fixes in the commit message
> 2. define_insn has the name *altivec_vsl<VI_char>_const_1
> 3. Iterate starting from 0 for checking vector constant = 1 and fixed
> source code formatting for the for loop.
> 4. Removed unused macro in pr119702-1.c test file
>
> ---
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr119702-1.c
> b/gcc/testsuite/gcc.target/powerpc/pr119702-1.c
> new file mode 100644
> index 00000000000..2f23ae20084
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr119702-1.c
> @@ -0,0 +1,53 @@
> +/* { dg-do compile } */
> +/* { dg-options "-mdejagnu-cpu=power8 -O2" } */
> +
> +#include <inttypes.h>
> +
> +void lshift1_64(uint64_t *a) {
> + a[0] <<= 1;
> + a[1] <<= 1;
> +}
Version 1 of this patch had more tests, can you please add them too (in
a separate file)?
Regards,
Surya
