Chapter 5. Changes in LLVM Toolset

LLVM Toolset has been updated from version 11.0.0 to 12.0.1 on RHEL 7 and RHEL 8. RHEL 9 Beta is distributed with LLVM Toolset 12.0.1. Notable changes include:

  • The new compiler flag -march=x86-64-v[234] has been added.
  • The compiler flag -fasynchronous-unwind-tables of the clang compiler is now the default on Linux AArch64/PowerPC.
  • The clang compiler now supports the C++20 likelihood attributes [[likely]] and [[unlikely]].
  • The new function attribute tune-cpu has been added. It allows microarchitectural optimizations to be applied independently from the target-cpu attribute or TargetMachine CPU.
  • The new sanitizer -fsanitize=unsigned-shift-base has been added to the integer sanitizer -fsanitize=integer to improve security.
  • Code generation on PowerPC targets has been optimized.
  • The WebAssembly backend is now enabled in LLVM. With this enhancement, you can generate WebAssembly binaries with LLVM and Clang.

For detailed information regarding the updates, see the upstream LLVM 12.0.0 Release Notes.