Add LINK_JOBS logic to all three builder scripts

The stress, helper and bisect build scripts needed the LLVM_LINK_JOBS option
to make sure it doesn't run out of memory while linking, especially in SoCs
that have a lot more cores than RAM (ex. HiKey).

This patch calculates the jobs by seeing how much RAM the target has and adding
+1, as link jobs rarely take more than 1GB, but the final ones do use several
hundred. Also making sure we don't exceed the number of cores.

A few other small changes:
 * Replace "else if" by "elif"
 * Build only minimal targets on ARM (even o full build)
 * Fixed a -j$PARALLEL bug introduced by a prvious commit
 * Converted a few backticks into $()

Change-Id: If4f2189623338d2924357ecd3d4ee18feb522c32

1 files changed, 22 insertions, 5 deletions

diff --git a/helpers/llvm-build b/helpers/llvm-build
index 0cef8a0..0556b6e 100755
--- a/helpers/llvm-build
+++ b/helpers/llvm-build
@@ -11,7 +11,8 @@
 safe_run verify_env
 
 ## CMD line options and defaults
-PARALLEL=-j`grep -c proc /proc/cpuinfo`
+CPUS=$(grep -c proc /proc/cpuinfo)
+PARALLEL=-j$CPUS
 build_dir=$LLVM_BLD
 install_dir=$LLVM_INSTALL
 build_type=Release
@@ -23,6 +24,8 @@ update=false
 check=false
 master=false
 inst=false
+minimal_targets="-DLLVM_TARGETS_TO_BUILD='ARM;X86;AArch64'"
+link_jobs=
 
 if [ "$1" = "-h" ]; then
   echo $syntax
@@ -32,7 +35,7 @@ fi
 ## Choose between make and ninja
 make=make
 generator="Unix Makefiles"
-if which ninja 2>&1 > /dev/null; then
+if which ninja > /dev/null 2>&1; then
   make=ninja
   generator="Ninja"
 fi
@@ -41,7 +44,21 @@ fi
 if [ "$LLVM_DEBUG" = true ]; then
   build_type=Debug
   shared=-DBUILD_SHARED_LIBS=True
-  targets=-DLLVM_TARGETS_TO_BUILD="ARM;X86;AArch64"
+  targets=$minimal_targets
+fi
+
+# Building on ARM?
+if grep -q "ARM.* Processor" /proc/cpuinfo; then
+  targets=$minimal_targets
+  if [ "$make" = "ninja" ]; then
+    link=$(free -g | awk '/Mem/ {print $2}')
+    if [ "$link" -gt "$CPUS" ]; then
+      link=$CPUS
+    else
+      link=$((link+1))
+    fi
+    link_jobs="-DLLVM_PARALLEL_LINK_JOBS=$link"
+  fi
 fi
 
 ## Make sure sure build dir is there
@@ -65,8 +82,8 @@ if [ ! -f build.ninja ] && [ ! -f Makefile ]; then
             -DLLVM_ENABLE_ASSERTIONS=True \
             -DPYTHON_EXECUTABLE=/usr/bin/python2 \
             -DCMAKE_INSTALL_PREFIX=$install_dir \
-            -DLLVM_LIT_ARGS="-sv -j$PARALLEL" \
-            $LLVM_CMAKE_FLAGS $targets $shared
+            -DLLVM_LIT_ARGS="-sv $PARALLEL" \
+            $LLVM_CMAKE_FLAGS $targets $shared $link_jobs
 fi
 
 ## Build