From e35c56947f94aefa740412563bfd8760e62d52ca Mon Sep 17 00:00:00 2001
From: Fangrui Song <i@maskray.me>
Date: Wed, 4 Sep 2019 18:49:16 -0700
Subject: [PATCH] llvm monorepo & releases/prereleases

---
 Build.md | 43 ++++++++++++++++++++++++++++---------------
 1 file changed, 28 insertions(+), 15 deletions(-)

diff --git a/Build.md b/Build.md
index a39777e..b81c934 100644
--- a/Build.md
+++ b/Build.md
@@ -237,11 +237,10 @@ these releases.  You must either:
 #### Build clang+llvm by yourself
 
 ```sh
-git clone https://git.llvm.org/git/llvm.git
-git clone https://git.llvm.org/git/clang.git llvm/tools/clang
+git clone https://github.com/llvm/llvm-project.git
+cd llvm-project
 
-cd llvm
-cmake -H. -BRelease -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_COMPILER=cl -DCMAKE_CXX_COMPILER=cl -DLLVM_TARGETS_TO_BUILD=X86
+cmake -Hllvm -BRelease -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_COMPILER=cl -DCMAKE_CXX_COMPILER=cl -DLLVM_TARGETS_TO_BUILD=X86
 ninja -C Release clangFormat clangFrontendTool clangIndex clangTooling clang
 
 # Download ccls
@@ -262,26 +261,27 @@ ninja -C Release
 
 `-D__STDC_FORMAT_MACROS` is because otherwise `mingw-w64-headers/crt/inttypes.h` does not define `PRIu64`.
 
-## Compiling Clang+LLVM from source
-
-MaskRay's config (building trunk LLVM at `~/llvm/Release/`):
+## Build Clang+LLVM from the git monorepo
 
 ```sh
-git clone https://git.llvm.org/git/llvm.git
-git clone https://git.llvm.org/git/clang.git llvm/tools/clang
-cd llvm
-cmake -H. -BRelease -G Ninja -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON -DLLVM_ENABLE_LLD=ON -DLLVM_TARGETS_TO_BUILD=X86
-ninja -C Release clang clangFormat clangFrontendTool clangIndex clangTooling cxx
+git clone https://github.com/llvm/llvm-project.git
+cd llvm-project
+
+cmake -Hllvm -BRelease -G Ninja -DCMAKE_BUILD_TYPE=Release -DLLVM_TARGETS_TO_BUILD=X86
+ninja -C Release clangFormat clangFrontendTool clangIndex clangTooling clang
+# built Release/bin/clang
 ```
 
-* Remove `LLVM_ENABLE_LLD` if you don't have lld (a much faster linker than bfd/gold) installed
-* Remove `BUILD_SHARED_LIBS` if you want to build static libraries (`libclangIndex.a`) instead
+* `LLVM_TARGETS_TO_BUILD` defaults to `ALL`. We just use the frontend, don't generate code, so `X86` should be sufficient. `clang -target powerpc64le-linux -fsyntax-only` still works.
+* Add `-DLLVM_ENABLE_LLD=on` if you have lld (a much faster linker than bfd/gold) installed
+* Add `-DBUILD_SHARED_LIBS=on` if you want to build shared libraries (`libclangIndex.so`)
 
 Then build ccls with `-DCMAKE_PREFIX_PATH`:
 
 ```sh
 cd ~/ccls
-cmake -H. -BRelease -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_EXE_LINKER_FLAGS=-fuse-ld=lld -DCMAKE_PREFIX_PATH="$HOME/llvm/Release;$HOME/llvm/Release/tools/clang;$HOME/llvm;$HOME/llvm/tools/clang"
+LLVM=$HOME/llvm-project
+cmake -H. -BRelease -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_EXE_LINKER_FLAGS=-fuse-ld=lld -DCMAKE_PREFIX_PATH="$LLVM/Release;$LLVM/llvm;$LLVM/clang"
 ninja -C Release
 ```
 
@@ -307,3 +307,16 @@ The cmake build system is expected to find these files:
 ~/llvm/Release/lib/libLLVMSupport.so or libLLVMSupport.a
 ...
 ```
+
+## Build Clang+LLVM from releases.llvm.org or prereleases.llvm.org
+
+Similar to the instructions to build Clang+LLVM from the git monorepo:
+
+```sh
+# Download "LLVM source code" and rename the extracted directory to llvm
+# Download "Clang source code" and rename the extracted directory to llvm/tools/clang
+cd llvm
+cmake -H. -BRelease -G Ninja -DCMAKE_BUILD_TYPE=Release -DLLVM_TARGETS_TO_BUILD=X86
+ninja -C Release clangFormat clangFrontendTool clangIndex clangTooling clang
+# built Release/bin/clang
+```