diff -up Waterfox-ff4597172229f8d71940c3885b74b903b7b1821a/build/unix/mozconfig.linux.pgo Waterfox-ff4597172229f8d71940c3885b74b903b7b1821a/build/unix/mozconfig.linux
--- Waterfox-ff4597172229f8d71940c3885b74b903b7b1821a/build/unix/mozconfig.linux.pgo	2018-12-17 10:39:21.000000000 -0200
+++ Waterfox-ff4597172229f8d71940c3885b74b903b7b1821a/build/unix/mozconfig.linux	2019-01-08 11:26:46.625843204 -0200
@@ -17,6 +17,15 @@ then
   CC="$TOOLTOOL_DIR/gcc/bin/gcc"
   CXX="$TOOLTOOL_DIR/gcc/bin/g++"
 
+  if [ -n "$MOZ_PGO" ]; then
+#      if [ -z "$USE_ARTIFACT" ]; then
+#          ac_add_options --enable-lto
+#      fi
+      export AR="$topsrcdir/gcc/bin/gcc-ar"
+      export NM="$topsrcdir/gcc/bin/gcc-nm"
+      export RANLIB="$topsrcdir/gcc/bin/gcc-ranlib"
+  fi
+
   # We want to make sure we use binutils and other binaries in the tooltool
   # package.
   mk_add_options PATH="$TOOLTOOL_DIR/gcc/bin:$PATH"
diff -up Waterfox-ff4597172229f8d71940c3885b74b903b7b1821a/extensions/spellcheck/src/moz.build.pgo Waterfox-ff4597172229f8d71940c3885b74b903b7b1821a/extensions/spellcheck/src/moz.build
--- Waterfox-ff4597172229f8d71940c3885b74b903b7b1821a/extensions/spellcheck/src/moz.build.pgo	2018-12-17 10:39:21.000000000 -0200
+++ Waterfox-ff4597172229f8d71940c3885b74b903b7b1821a/extensions/spellcheck/src/moz.build	2019-01-08 11:27:26.673823140 -0200
@@ -32,3 +32,5 @@ EXPORTS.mozilla += [
 
 if CONFIG['GNU_CXX']:
     CXXFLAGS += ['-Wno-error=shadow']
+
+CXXFLAGS += ['-fno-devirtualize']