Index: cfe/trunk/docs/ThinLTO.rst =================================================================== --- cfe/trunk/docs/ThinLTO.rst +++ cfe/trunk/docs/ThinLTO.rst @@ -63,7 +63,7 @@ - **ld64**: Starting with `Xcode 8 `_. - **lld**: - Starting with r284050 (ELF only). + Starting with r284050 for ELF, r298942 for COFF. Usage ===== @@ -78,6 +78,13 @@ % clang -flto=thin -O2 file1.c file2.c -c % clang -flto=thin -O2 file1.o file2.o -o a.out +When using lld-link, the -flto option need only be added to the compile step: + +.. code-block:: console + + % clang-cl -flto=thin -O2 -c file1.c file2.c + % lld-link /out:a.exe file1.obj file2.obj + As mentioned earlier, by default the linkers will launch the ThinLTO backend threads in parallel, passing the resulting native object files back to the linker for the final native link. As such, the usage model the same as @@ -111,6 +118,8 @@ ``-Wl,-mllvm,-threads=N`` - lld: ``-Wl,--thinlto-jobs=N`` +- lld-link: + ``/opt:lldltojobs=N`` Incremental ----------- @@ -125,7 +134,7 @@ ``-Wl,-cache_path_lto,/path/to/cache`` - ELF lld (as of LLVM 5.0): ``-Wl,--thinlto-cache-dir=/path/to/cache`` -- COFF lld (as of LLVM 6.0): +- COFF lld-link (as of LLVM 6.0): ``/lldltocache:/path/to/cache`` Cache Pruning @@ -138,7 +147,7 @@ - ELF lld (as of LLVM 5.0): ``-Wl,--thinlto-cache-policy,POLICY`` -- COFF lld (as of LLVM 6.0): +- COFF lld-link (as of LLVM 6.0): ``/lldltocachepolicy:POLICY`` A policy string is a series of key-value pairs separated by ``:`` characters. @@ -187,13 +196,20 @@ when configuring the bootstrap compiler build: * ``-DLLVM_ENABLE_LTO=Thin`` - * ``-DLLVM_PARALLEL_LINK_JOBS=1`` - (since the ThinLTO link invokes parallel backend jobs) * ``-DCMAKE_C_COMPILER=/path/to/host/clang`` * ``-DCMAKE_CXX_COMPILER=/path/to/host/clang++`` * ``-DCMAKE_RANLIB=/path/to/host/llvm-ranlib`` * ``-DCMAKE_AR=/path/to/host/llvm-ar`` + Or, on Windows: + + * ``-DLLVM_ENABLE_LTO=Thin`` + * ``-DCMAKE_C_COMPILER=/path/to/host/clang-cl.exe`` + * ``-DCMAKE_CXX_COMPILER=/path/to/host/clang-cl.exe`` + * ``-DCMAKE_LINKER=/path/to/host/lld-link.exe`` + * ``-DCMAKE_RANLIB=/path/to/host/llvm-ranlib.exe`` + * ``-DCMAKE_AR=/path/to/host/llvm-ar.exe`` + #. To use additional linker arguments for controlling the backend parallelism_ or enabling incremental_ builds of the bootstrap compiler, after configuring the build, modify the resulting CMakeCache.txt file in the