These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 4.67 s (backtrack: 8/20).

[ebuild  N     ] llvm-core/clang-common-21.1.8::gentoo  USE="cet -bootstrap-prefix -default-compiler-rt -default-libcxx -default-lld -emacs -hardened -llvm-libunwind -verify-sig" 155233 KiB
[ebuild  N     ] llvm-runtimes/clang-rtlib-config-21:21::gentoo  USE="-default-compiler-rt" 0 KiB
[ebuild  N     ] llvm-runtimes/clang-stdlib-config-21:21::gentoo  USE="-default-libcxx" 0 KiB
[ebuild  N     ] llvm-runtimes/clang-unwindlib-config-21:21::gentoo  USE="-default-compiler-rt -llvm-libunwind" 0 KiB
[ebuild  N     ] llvm-core/clang-linker-config-21:21::gentoo  USE="-default-lld" 0 KiB
[ebuild  NS    ] llvm-core/llvm-21.1.8:21/21.1::gentoo [22.1.1:22/22.1::gentoo] USE="binutils-plugin libffi zstd -debug (-debuginfod) -doc -exegesis -libedit -test -verify-sig -xml -z3" LLVM_TARGETS="(AArch64) (AMDGPU) (ARM) (AVR) (BPF) (Hexagon) (Lanai) (LoongArch) (MSP430) (Mips) (NVPTX) (PowerPC) (RISCV) (SPIRV) (Sparc) (SystemZ) (VE) (WebAssembly) (X86) (XCore) -ARC -CSKY -DirectX -M68k -Xtensa" 297 KiB
[ebuild  NS    ] llvm-core/llvm-toolchain-symlinks-21:21::gentoo [22:22::gentoo] USE="-multilib-symlinks -native-symlinks" 0 KiB
[ebuild  N     ] llvm-core/clang-21.1.8:21/21.1::gentoo  USE="extra (pie) static-analyzer -debug -doc (-ieee-long-double) -test -verify-sig -xml" LLVM_TARGETS="(AArch64) (AMDGPU) (ARM) (AVR) (BPF) (Hexagon) (Lanai) (LoongArch) (MSP430) (Mips) (NVPTX) (PowerPC) (RISCV) (SPIRV) (Sparc) (SystemZ) (VE) (WebAssembly) (X86) (XCore) -ARC -CSKY -DirectX -M68k -Xtensa" PYTHON_SINGLE_TARGET="python3_14 -python3_12 -python3_13" 0 KiB
[ebuild  N     ] llvm-core/clang-toolchain-symlinks-21:21::gentoo  USE="-gcc-symlinks -multilib-symlinks -native-symlinks" 0 KiB
[ebuild  N     ] llvm-runtimes/compiler-rt-21.1.8:21::gentoo  USE="atomic-builtins (clang) -debug -test -verify-sig" 0 KiB
[ebuild  N     ] llvm-runtimes/compiler-rt-sanitizers-21.1.8:21::gentoo  USE="asan cfi (clang) ctx-profile dfsan gwp-asan hwasan libfuzzer lsan memprof msan nsan orc profile rtsan safestack scudo tsan ubsan xray -debug (-shadowcallstack) -test -verify-sig" 2 KiB
[ebuild  N     ] llvm-runtimes/openmp-23.1.3:0/23.1::gentoo  USE="clang -cuda -debug -fortran -gdb-plugin -hwloc -level-zero -offload -ompt -rocm -test -verify-sig" PYTHON_SINGLE_TARGET="python3_14 -python3_12 -python3_13" 175021 KiB
[ebuild  N     ] llvm-runtimes/clang-runtime-21.1.8-r1:21::gentoo  USE="compiler-rt openmp sanitize -default-compiler-rt -default-libcxx -default-lld -libcxx -llvm-libunwind -polly" 0 KiB

Total: 13 packages (11 new, 2 in new slots), Size of downloads: 330551 KiB

WARNING: One or more updates/rebuilds have been skipped due to a dependency conflict:

llvm-core/clang-common:0

  (llvm-core/clang-common-23.1.3:0/0::gentoo, ebuild scheduled for merge) USE="cet -bootstrap-prefix -default-compiler-rt -default-libcxx -default-lld -emacs -hardened -llvm-libunwind -verify-sig" conflicts with
    =llvm-core/clang-common-21.1.8