feat(zmq): add SIMD sample conversion functions

Add AVX-512 and AVX2 optimized conversion loops between float complex (cf_t)
and int16 complex (c16_t) sample formats in radio/zmq/zmq_simd.h.
Signed-off-by: Bartosz Podrygajlo <bartosz.podrygajlo@openairinterface.org>

radio/zmq/zmq_simd.h

+/*
+ * SPDX-License-Identifier: LicenseRef-CSSL-1.0
+ */
+
+#ifndef ZMQ_SIMD_H
+#define ZMQ_SIMD_H
+
+#include "simde/x86/avx512.h"
+#include "simde/x86/avx2.h"
+
+#include "common/platform_types.h"
+#include <limits>
+#include <algorithm>
+
+constexpr float c16_t_to_cf_t_factor = 32767.0f;
+
+static inline void convert_samples_avx512_tx(float *msg_data, const int16_t *samples, size_t nsamps, float factor)
+{
+  float r_factor = 1.0f / factor;
+  size_t total_elements = nsamps;
+  size_t i = 0;
+  float *output_ptr = msg_data;
+
+#if defined(__AVX512F__)
+  {
+    simde__m512 v_factor = simde_mm512_set1_ps(r_factor);
+    for (; i + 16 <= total_elements; i += 16) {
+      simde__m256i v_in16 = simde_mm256_loadu_si256((const simde__m256i *)&samples[i]);
+      simde__m512i v_in32 = simde_mm512_cvtepi16_epi32(v_in16);
+      simde__m512 v_float = simde_mm512_cvtepi32_ps(v_in32);
+      simde__m512 v_out = simde_mm512_mul_ps(v_float, v_factor);
+      simde_mm512_storeu_ps(&output_ptr[i], v_out);
+    }
+  }
+#endif
+
+#if defined(__AVX2__)
+  {
+    simde__m256 v_factor = simde_mm256_set1_ps(r_factor);
+    for (; i + 16 <= total_elements; i += 16) {
+      simde__m256i v_in16 = simde_mm256_loadu_si256((const simde__m256i *)&samples[i]);
+      simde__m128i v_in16_lo = simde_mm256_castsi256_si128(v_in16);
+      simde__m128i v_in16_hi = simde_mm256_extractf128_si256(v_in16, 1);
+      simde__m256i v_in32_lo = simde_mm256_cvtepi16_epi32(v_in16_lo);
+      simde__m256i v_in32_hi = simde_mm256_cvtepi16_epi32(v_in16_hi);
+      simde__m256 v_float_lo = simde_mm256_cvtepi32_ps(v_in32_lo);
+      simde__m256 v_float_hi = simde_mm256_cvtepi32_ps(v_in32_hi);
+      simde__m256 v_out_lo = simde_mm256_mul_ps(v_float_lo, v_factor);
+      simde__m256 v_out_hi = simde_mm256_mul_ps(v_float_hi, v_factor);
+      simde_mm256_storeu_ps(&output_ptr[i], v_out_lo);
+      simde_mm256_storeu_ps(&output_ptr[i + 8], v_out_hi);
+    }
+  }
+#endif
+
+  // Cleanup loop for remaining elements
+  for (; i < total_elements; i++) {
+    output_ptr[i] = (float)samples[i] * r_factor;
+  }
+}
+
+static inline void convert_samples_avx512_rx(const float *input_floats, int16_t *output_ints, size_t nsamps, float factor)
+{
+  size_t total_elements = nsamps;
+  size_t i = 0;
+
+#if defined(__AVX512F__)
+  {
+    simde__m512 v_factor = simde_mm512_set1_ps(factor);
+    for (; i + 16 <= total_elements; i += 16) {
+      simde__m512 v_float = simde_mm512_loadu_ps(&input_floats[i]);
+      simde__m512 v_mul = simde_mm512_mul_ps(v_float, v_factor);
+      simde__m512i v_int32 = simde_mm512_cvtps_epi32(v_mul);
+      simde__m256i v_int16 = simde_mm512_cvtsepi32_epi16(v_int32);
+      simde_mm256_storeu_si256((simde__m256i *)&output_ints[i], v_int16);
+    }
+  }
+#endif
+
+#if defined(__AVX2__)
+  {
+    simde__m256 v_factor = simde_mm256_set1_ps(factor);
+    for (; i + 16 <= total_elements; i += 16) {
+      simde__m256 v_float1 = simde_mm256_loadu_ps(&input_floats[i]);
+      simde__m256 v_float2 = simde_mm256_loadu_ps(&input_floats[i + 8]);
+      simde__m256 v_mul1 = simde_mm256_mul_ps(v_float1, v_factor);
+      simde__m256 v_mul2 = simde_mm256_mul_ps(v_float2, v_factor);
+      simde__m256i v_int32_1 = simde_mm256_cvtps_epi32(v_mul1);
+      simde__m256i v_int32_2 = simde_mm256_cvtps_epi32(v_mul2);
+      simde__m256i v_packed = simde_mm256_packs_epi32(v_int32_1, v_int32_2);
+      simde__m256i v_permuted = simde_mm256_permute4x64_epi64(v_packed, 0xD8);
+      simde_mm256_storeu_si256((simde__m256i *)&output_ints[i], v_permuted);
+    }
+  }
+#endif
+
+  // Cleanup loop for remaining elements
+  for (; i < total_elements; i++) {
+    output_ints[i] = (int16_t)(input_floats[i] * factor + 0.5f);
+  }
+}
+
+#endif