[helpers] Teach llvm-env to self-host

In addition to debug builds, this teaches llvm-env to create self-hosted
bots that will use the "build" directory of the branch to compile a self-hosted
version of the toolchain. It'll use clang and also lld, if available.

Review changes:

* Check for clang, not just build dir
* Use -x instead of -f
* Always export LLVM_SELFHOST
* Quote strings for good measure
* Using LLVM_CMAKE_FLAGS

Change-Id: I55af0c213ae06cb8b99a33d1a80a05f09fe64c85

2 files changed, 27 insertions, 3 deletions

diff --git a/helpers/llvm-build b/helpers/llvm-build
index 5ef0662..d38cf1d 100755
--- a/helpers/llvm-build
+++ b/helpers/llvm-build
@@ -59,7 +59,7 @@ if [ ! -f build.ninja ] && [ ! -f Makefile ]; then
             -DLLVM_ENABLE_ASSERTIONS=True \
             -DPYTHON_EXECUTABLE=/usr/bin/python2 \
             -DCMAKE_INSTALL_PREFIX=$install_dir \
-            $targets $shared
+            $LLVM_CMAKE_FLAGS $targets $shared
 fi
 
 ## Allow the user to override the number of CPUs used with -jN
diff --git a/helpers/llvm-env b/helpers/llvm-env
index 50c4c81..ba9c98f 100755
--- a/helpers/llvm-env
+++ b/helpers/llvm-env
@@ -75,6 +75,7 @@ elif [ "$1" = "-h" ]; then
   echo "             it will not clean up any branches (you should use"
   echo "             llvm-branch for that)"
   echo "  -d : build the debug version."
+  echo "  -s : build the self-hosted version (CC is set to <branch>/build)."
   eval $clean_exit
 fi
 
@@ -100,10 +101,13 @@ if [ "$1" = "-cleanup" ]; then
 fi
 
 debug_build=false
+selfhost_build=false
 OPTIND=0
-while getopts "d" opt; do
+while getopts "ds" opt; do
   if [ "$opt" = "d" ]; then
     debug_build=true
+  elif [ "$opt" = "s" ]; then
+    selfhost_build=true
   else
     eval $clean_exit
   fi
@@ -121,6 +125,16 @@ llvm_worktree_dir=$LLVM_ROOT/$branch/llvm
 llvm_build_dir=$LLVM_ROOT/$branch/build
 if $debug_build; then
   llvm_build_dir=$LLVM_ROOT/$branch/debug
+elif $selfhost_build; then
+  if [ ! -d "$llvm_build_dir" ] || \
+     [ ! -x "$llvm_build_dir/bin/clang" ] || \
+     [ ! -x "$llvm_build_dir/bin/clang++" ]; then
+    echo "Stage 1 build dir not found at: $llvm_build_dir"
+    echo "Build stage 1 first, then the self-hosted"
+    eval $clean_exit
+  fi
+  llvm_stage1_dir=$llvm_build_dir
+  llvm_build_dir=$LLVM_ROOT/$branch/selfhost
 fi
 
 llvm_install_dir=$LLVM_ROOT/$branch/install
@@ -149,7 +163,17 @@ fi
 export LLVM_SRC=$llvm_worktree_dir
 export LLVM_BLD=$llvm_build_dir
 export LLVM_INSTALL=$llvm_install_dir
-export LLVM_DEBUG=$debug_build # For llvm-build to know
+# For llvm-build to know
+export LLVM_DEBUG=$debug_build
+export LLVM_SELFHOST=$selfhost_build
+
+# Self-hosted builds need to use the previously built clang, maybe LLD.
+if $selfhost_build; then
+  # Clang will automatically pick LLD if available on the same dir
+  LLVM_CMAKE_FLAGS="-DCMAKE_C_COMPILER=$llvm_stage1_dir/bin/clang \
+                    -DCMAKE_CXX_COMPILER=$llvm_stage1_dir/bin/clang++"
+  export LLVM_CMAKE_FLAGS
+fi
 
 # Make it possible to undo changes to the PATH: we export an LLVM_OLD_PATH, and
 # instead of appending the binary dir to $PATH, we append to $LLVM_OLD_PATH (if