Why doesn't Burst emit AVX even though my CPU supports it?

Burst targets the lowest common denominator by default. Project Settings → Burst AOT Settings → CPU Architecture → AVX2 (or AVX-512). Build for that target and verify in Burst Inspector.

Burst can emit multiple architectures. Pick comma-separated: SSE2, AVX2. Runtime selects best supported. Cost is build size; benefit is broader perf.

Jobs → Burst → Open Inspector. Filter to your job. View Assembly tab. AVX YMM/ZMM registers visible if vectorized.

Fix: Burst Doesn't Emit AVX

Quick answer: Project Settings → Burst AOT → CPU Architecture = AVX2 (or AVX-512). Verify in Burst Inspector Assembly view.

Profile shows scalar SIMD code. Modern desktop CPU supports AVX2 fine. Burst was targeting SSE4 baseline.

The Fix

Project Settings → Burst AOT Settings:
  CPU Architecture (Windows x64):
    [✓] AVX2
    [ ] AVX512        // optional
    [✓] SSE4         // fallback

Build → Build And Run.

// Inspector check
Jobs → Burst → Open Inspector
  Filter: SimulationJob
  Assembly: vmovups ymm0 / vmulps ymm1 / vaddps ymm2 visible

Multiple targets ship multiple binaries; runtime picks best. Cost is build size and slightly longer compile times.

Verifying

Profiler ms reduces 30-50% on AVX2-capable CPU. SSE4 fallback covers older CPUs.

“Right target. AVX emits. Faster.”

Related Issues

For Burst FunctionPointer, see function pointer. For Burst SharedStatic, see SharedStatic.

AVX2 target. Wider lanes.