[Bug target/85323] New: SSE/AVX/AVX512 shift by 0 not optimized away

[kretz at kde dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85323

            Bug ID: 85323
           Summary: SSE/AVX/AVX512 shift by 0 not optimized away
           Product: gcc
           Version: 8.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kretz at kde dot org
  Target Milestone: ---

In the following test case, all three functions should compile to just `ret`:

#include <x86intrin.h>

__m128i f(__m128i x) {
    x = _mm_sll_epi64(x, __m128i());
    x = _mm_sll_epi32(x, __m128i());
    x = _mm_sll_epi16(x, __m128i());
    x = _mm_srl_epi64(x, __m128i());
    x = _mm_srl_epi32(x, __m128i());
    x = _mm_srl_epi16(x, __m128i());
    x = _mm_sra_epi64(x, __m128i());
    x = _mm_sra_epi32(x, __m128i());
    x = _mm_sra_epi16(x, __m128i());
    x = _mm_slli_epi64(x, 0);
    x = _mm_slli_epi32(x, 0);
    x = _mm_slli_epi16(x, 0);
    x = _mm_srli_epi64(x, 0);
    x = _mm_srli_epi32(x, 0);
    x = _mm_srli_epi16(x, 0);
    x = _mm_srai_epi64(x, 0);
    x = _mm_srai_epi32(x, 0);
    x = _mm_srai_epi16(x, 0);
    return x;
}

__m256i f(__m256i x) {
    x = _mm256_sll_epi64(x, __m128i());
    x = _mm256_sll_epi32(x, __m128i());
    x = _mm256_sll_epi16(x, __m128i());
    x = _mm256_srl_epi64(x, __m128i());
    x = _mm256_srl_epi32(x, __m128i());
    x = _mm256_srl_epi16(x, __m128i());
    x = _mm256_sra_epi64(x, __m128i());
    x = _mm256_sra_epi32(x, __m128i());
    x = _mm256_sra_epi16(x, __m128i());
    x = _mm256_slli_epi64(x, 0);
    x = _mm256_slli_epi32(x, 0);
    x = _mm256_slli_epi16(x, 0);
    x = _mm256_srli_epi64(x, 0);
    x = _mm256_srli_epi32(x, 0);
    x = _mm256_srli_epi16(x, 0);
    x = _mm256_srai_epi64(x, 0);
    x = _mm256_srai_epi32(x, 0);
    x = _mm256_srai_epi16(x, 0);
    return x;
}

__m512i f(__m512i x) {
    x = _mm512_sll_epi64(x, __m128i());
    x = _mm512_sll_epi32(x, __m128i());
    x = _mm512_sll_epi16(x, __m128i());
    x = _mm512_srl_epi64(x, __m128i());
    x = _mm512_srl_epi32(x, __m128i());
    x = _mm512_srl_epi16(x, __m128i());
    x = _mm512_sra_epi64(x, __m128i());
    x = _mm512_sra_epi32(x, __m128i());
    x = _mm512_sra_epi16(x, __m128i());
    x = _mm512_slli_epi64(x, 0);
    x = _mm512_slli_epi32(x, 0);
    x = _mm512_slli_epi16(x, 0);
    x = _mm512_srli_epi64(x, 0);
    x = _mm512_srli_epi32(x, 0);
    x = _mm512_srli_epi16(x, 0);
    x = _mm512_srai_epi64(x, 0);
    x = _mm512_srai_epi32(x, 0);
    x = _mm512_srai_epi16(x, 0);
    return x;
}