ggml-cpu: add AVX2 optimization for nvfp4 dot product and use UE4M3 LUT (#23961)

ggml/src/ggml-cpu/ggml-cpu.c

@@ -82,6 +82,9 @@ float ggml_table_f32_f16[1 << 16];
 // precomputed f32 table for e8m0 half (1 KB) (simd-mappings.h)
 float ggml_table_f32_e8m0_half[1 << 8];
 
+// precomputed f32 table for ue4m3 (1 KB) (simd-mappings.h)
+float ggml_table_f32_ue4m3[1 << 8];
+
 #if defined(__ARM_ARCH)
 struct ggml_arm_arch_features_type {
     int sve_cnt;
@@ -3798,6 +3801,11 @@ void ggml_cpu_init(void) {
                 ggml_table_f32_e8m0_half[i] = GGML_E8M0_TO_FP32_HALF(i);
             }
 
+            // initialize UE4M3 table (256 entries)
+            for (int i = 0; i < (1 << 8); ++i) {
+                ggml_table_f32_ue4m3[i] = ggml_ue4m3_to_fp32(i);
+            }
+
             const uint64_t t_end = ggml_time_us(); UNUSED(t_end);
 
             GGML_PRINT_DEBUG("%s: GELU, Quick GELU, SILU and EXP tables initialized in %f ms\n", __func__, (t_end - t_start)/1000.0);