`__llvm_prf_vnodes` and `__llvm_prf_names` are used by runtime but not referenced via relocation in the translation unit. With `-z start-stop-gc` (D96914 https://sourceware.org/bugzilla/show_bug.cgi?id=27451), the linker does not let `__start_/__stop_` references retain them. Place `__llvm_prf_vnodes` and `__llvm_prf_names` in `llvm.used` to make them retained by the linker. This patch changes most existing `UsedVars` cases to `CompilerUsedVars` to reflect the ideal state - if the binary format properly supports section based GC (dead stripping), `llvm.compiler.used` should be sufficient. `__llvm_prf_vnodes` and `__llvm_prf_names` are switched to `UsedVars` since we want them to be unconditionally retained by both compiler and linker. Behaviors on other COFF/Mach-O are not affected.

`__llvm_prf_vnodes` and `__llvm_prf_names` are used by runtime but not referenced via relocation in the translation unit. With `-z start-stop-gc` (D96914 https://sourceware.org/bugzilla/show_bug.cgi?id=27451), the linker does not let `__start_/__stop_` references retain their sections. Place `__llvm_prf_vnodes` and `__llvm_prf_names` in `llvm.used` to make them retained by the linker. This patch changes most existing `UsedVars` cases to `CompilerUsedVars` to reflect the ideal state - if the binary format properly supports section based GC (dead stripping), `llvm.compiler.used` should be sufficient. `__llvm_prf_vnodes` and `__llvm_prf_names` are switched to `UsedVars` since we want them to be unconditionally retained by both compiler and linker. Behaviors on COFF/Mach-O are not affected.

`__llvm_prf_vnodes` and `__llvm_prf_names` are used by runtime but not referenced via relocation in the translation unit. With `-z start-stop-gc` (D96914 https://sourceware.org/bugzilla/show_bug.cgi?id=27451), the linker does not let `__start_/__stop_` references retain themtheir sections. Place `__llvm_prf_vnodes` and `__llvm_prf_names` in `llvm.used` to make them retained by the linker. This patch changes most existing `UsedVars` cases to `CompilerUsedVars` to reflect the ideal state - if the binary format properly supports section based GC (dead stripping), `llvm.compiler.used` should be sufficient. `__llvm_prf_vnodes` and `__llvm_prf_names` are switched to `UsedVars` since we want them to be unconditionally retained by both compiler and linker. Behaviors on other COFF/Mach-O are not affected.