cc/gcc: enable plugins if needed

Enabling plugins in binutils is not enough, and gcc also
needs to be ./configured with --enable-plugins, although
this is not documented anywhere... :-/

Reported-by: karthik duraisami <kdconstant@hotmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

config/cc/gcc.in

@@ -164,10 +164,32 @@ config CC_GCC_HAS_GRAPHITE
     bool
     default n
 
+# The way LTO works is a bit twisted.
+# See: http://gcc.gnu.org/wiki/LinkTimeOptimization#Requirements
+# Basically:
+#   - if binutils has plugins: LTO is handled by ld/gold by loading
+#     the plugin when linking
+#   - if binutils does not have plugins: LTO is handled by collect2
+# In any case, LTO support does not depend on plugins, but takes
+# advantage of it
 config CC_GCC_HAS_LTO
     bool
     default n
 
+# Only enable gcc's support for plugins if binutils has it as well
+# They are usefull only when doing LTO, but it does no harm enabling
+# them even without LTO.
+config CC_GCC_ENABLE_PLUGINS
+    bool
+    depends on BINUTILS_PLUGINS
+    default y
+
+# If binutils installs gold, enable support for gold in gcc
+config CC_GCC_GOLD
+    bool
+    depends on BINUTILS_GOLD_INSTALLED
+    default y
+
 config CC_GCC_USE_GMP_MPFR
     bool
     default n

config/cc/gcc.in.2

@@ -24,6 +24,14 @@ config CC_GCC_USE_GRAPHITE
       On some systems (eg. Cygwin), PPL and/or CLooG may not
       build properly (yet), so you'll have to say 'N' here.
 
+# The way LTO works is a bit twisted.
+# See: http://gcc.gnu.org/wiki/LinkTimeOptimization#Requirements
+# Basically:
+#   - if binutils has plugins: LTO is handled by ld/gold by loading
+#     the plugin when linking
+#   - if binutils does not have plugins: LTO is handled by collect2
+# In any case, LTO support does not depend on plugins, but takes
+# advantage of it
 config CC_GCC_USE_LTO
     bool
     prompt "Enable LTO"

scripts/build/cc/gcc.sh

@@ -481,13 +481,10 @@ do_cc() {
         "") extra_config+=("--without-long-double-128");;
     esac
 
-    # If LTO is selected and binutils has gold, then enable
-    # building the lto plugin with the --enable-gold option,
-    # but only if gold has support for plugins.
-    if [    "${CT_BINUTILS_GOLD_INSTALLED}" = "y"   \
-         -a "${CT_BINUTILS_GOLD_PLUGINS}" = "y"     \
-         -a "${CT_CC_GCC_USE_LTO}" = "y"            \
-       ]; then
+    if [ "${CT_CC_GCC_ENABLE_PLUGINS}" = "y" ]; then
+        extra_config+=( --enable-plugin )
+    fi
+    if [ "${CT_CC_GCC_GOLD}" = "y" ]; then
         extra_config+=( --enable-gold )
     fi