Issue: Indirect function call(s) present

Indirect function call(s) in the loop body are preventing the compiler from vectorizing the loop. Indirect calls, sometimes called indirect jumps, get the callee address from a register or memory; direct calls get the callee address from an argument. Even if you force loop vectorization, indirect calls remain serialized.

Recommendation: Remove indirect call(s) inside loop

Indirect function or subroutine calls cannot be vectorized. To fix: Avoid using indirect calls in loops.

Recommendation: Improve branch prediction

For 64-bit applications, branch prediction performance can be negatively impacted when the branch target is more than 4 GB away from the branch. This is more likely to happen when the application is split into shared libraries. To fix: Do the following:

• Upgrade the Glibc library to version 2.23 or higher.
• Set environment variable export LD_PREFER_MAP_32BIT_EXEC=1.

Read More:

• Glibc 2.23 release notes and libc bug report 19367: Improve branch prediction
• Vectorization Resources for Intel® Advisor Users