arm: Auto-vectorization for MVE: vaddv

This patch adds support for the reduc_plus_scal optab with MVE, which
maps to the vaddv instruction.

It moves the reduc_plus_scal_<mode> expander from neon.md to
vec-common.md and adds support for MVE to it.

Since vaddv uses a 32-bits accumulator, we have to truncate it's
result.

For instance:
int32_t test__s8x16 (int8_t *a) {
  int i;
  int8_t result = 0;
  for (i=0; i<16; i++) {
    result += a[i];
  }
  return result;
}
is compiled into:
  vldrb.8 q3, [r0]
  vaddv.s8        r0, q3
  sxtb    r0, r0
  bx      lr

If we used uint8_t instead of int8_t, we still use vaddv.s8        r0, q3,
but truncate with uxtb    r0, r0.

2021-05-25  Christophe Lyon  <christophe.lyon@linaro.org>

	gcc/
	* config/arm/mve.md (mve_vaddvq_<supf><mode>): Prefix with '@'.
	* config/arm/neon.md (reduc_plus_scal_<mode>): Move to ..
	* config/arm/vec-common.md: .. here. Add support for MVE.

	gcc/testsuite/
	* gcc.target/arm/simd/mve-vaddv-1.c: New test.

0 files changed, 0 insertions, 0 deletions