Alignment - Alignment - 2026.1 English - UG1603

Applications can load from data memory (DM) into vector registers and store the contents of vector registers into DM. Memory instructions in the AI Engine that operate on vectors have alignment requirements. Therefore, functions are provided for both aligned and unaligned accesses.

The following functions are assumed to operate on pointers that meet the alignment requirements for a vector load or store of the size:

• aie::load_v
• aie::store_v

The following functions are assumed to operate on pointers that only align to the element of the vector:

• aie::load_unaligned_v
• aie::store_unaligned_v

Vector load and store that operate on memory that has met the vector operation alignment requirement use fewer cycles relative to unaligned accesses. Unaligned accesses can incur additional overhead depending on the amount of misalignment.

alignas(aie::vector_decl_align) int32 buffer[16];
int32* pv=buffer;
aie::vector<int32,8> v1=aie::load_v<8>(pv);
aie::vector<int32,8> v2=aie::load_unaligned_v<8>(pv+1);

You can use the alignas standard C specifier to ensure proper alignment of local memory. In the following example, reals aligns to a 16-byte boundary.

alignas(16) const int32 reals[8] = 
       {32767, 23170, 0, -23170, -32768, -23170, 0, 23170};

The API provides a global constant value (aie::vector_decl_align) that you can use to align the buffer to a boundary that works for any vector size.

alignas(aie::vector_decl_align) static cint16 my_buffer[8]={{0,0},{1,-1},{2,-2},{3,-3},{4,-4},{5,-5},{6,-6},{7,-7}};