Performance impact: MSVC + PGO vs. Clang / Intel ICX + PGO

Development Programming & Scripting
,
1

Hi everyone,

We are working on a performance-heavy project and are currently evaluating our toolchain choices for the Windows production build. Currently, we use MSVC, but we are looking into Clang and Intel ICX (LLVM-based) as potential alternatives.

I would appreciate some insights on the following:

  1. Performance Delta: Has anyone measured a significant difference in CPU performance when comparing MSVC + PGO vs. Clang + PGO or ICX + PGO? How substantial is the performance gain after applying Profile-Guided Optimization across these compilers?
  2. Epic’s Choice: We know Fortnite uses Clang for its Windows builds. Was this decision driven primarily by measurable performance gains over MSVC? Did you also evaluate Intel ICX during this process?
  3. Stability & Integration: Are there any known issues or “gotchas” when switching a large-scale UE project on Windows from MSVC to Clang or ICX as the primary compiler?

Thanks!

Max Bond | Engine Programmer | GSC Game World