Developer Guide and Reference

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Handling Floating-point Array Operations in a Loop Body

Following the guidelines below will help auto-vectorization of the loop.
  • Statements within the loop body may contain float or double operations (typically on arrays). The following arithmetic operations are supported: addition, subtraction, multiplication, division, negation, square root,
    MAX
    ,
    MIN
    , and mathematical functions such as
    SIN
    and
    COS
    .
  • Writing to a single-precision scalar/array and a double scalar/array within the same loop decreases the chance of auto-vectorization due to the differences in the vector length (that is, the number of elements in the vector register) between float and double types. If auto-vectorization fails, try to avoid using mixed data types.
The special
__m64
,
__m128
, and
__m256
datatypes are not vectorizable. The loop body cannot contain any function calls. Use of the Intel® Streaming SIMD Extensions (Intel® SSE) and Intel® Advanced Vector Extensions (Intel® AVX) intrinsics (for example,
mm_add_ps
) is not allowed.

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