build: Experimental LTO support, phase one

 * Only codecs and plugins are enabled
 * Only native builds (so far)
 * Only tested on xDuoo X3 (MIPS, monochrome)
 * opus & speex generate some warnings
 * Significant compile time impact

Change-Id: I519b0d179631a54b2103cd67225bd5ec6ad3bd2f

4 files changed, 31 insertions, 1 deletions

diff --git a/apps/plugins/plugins.make b/apps/plugins/plugins.make
index b430bd2792..4a126f812c 100644
--- a/apps/plugins/plugins.make
+++ b/apps/plugins/plugins.make
@@ -37,6 +37,12 @@ PLUGINLIB_OBJ := $(PLUGINLIB_SRC:.c=.o)
 PLUGINLIB_OBJ := $(PLUGINLIB_OBJ:.S=.o)
 PLUGINLIB_OBJ := $(call full_path_subst,$(ROOTDIR)/%,$(BUILDDIR)/%,$(PLUGINLIB_OBJ))
 
+ifdef USE_LTO
+# We do NOT want LTO on the GCC support file.
+$(BUILDDIR)/apps/plugins/lib/gcc-support.o: PLUGINFLAGS += -fno-lto
+$(BUILDDIR)/apps/plugins/plugin_crt0.o: PLUGINFLAGS += -fno-lto
+endif
+
 ### build data / rules
 ifndef APP_TYPE
 CONFIGFILE := $(FIRMDIR)/export/config/$(MODELNAME).h
@@ -147,6 +153,12 @@ else
 endif
 PLUGINLDFLAGS += $(GLOBAL_LDOPTS)
 
+ifdef USE_LTO
+ PLUGINFLAGS += -flto -fno-builtin -ffreestanding
+ PLUGINLDFLAGS += -flto -fno-builtin -ffreestanding
+ PLUGINLDFLAGS += -e plugin_start
+endif
+
 $(BUILDDIR)/%.rock:
         $(call PRINTS,LD $(@F))$(CC) $(PLUGINFLAGS) -o $(BUILDDIR)/$*.elf \
                 $(filter %.o, $^) \
diff --git a/lib/rbcodec/codecs/codecs.make b/lib/rbcodec/codecs/codecs.make
index 27ba73ab3c..83dc784ee3 100644
--- a/lib/rbcodec/codecs/codecs.make
+++ b/lib/rbcodec/codecs/codecs.make
@@ -33,6 +33,13 @@ else
 endif
 CODECLDFLAGS += $(GLOBAL_LDOPTS)
 
+ifdef USE_LTO
+ CODECLDFLAGS += -flto -fno-builtin -ffreestanding
+ CODECFLAGS += -flto -fno-builtin -ffreestanding
+ CODECLDFLAGS += -e __header
+endif
+
+
 # the codec libraries
 include $(RBCODECLIB_DIR)/codecs/demac/libdemac.make
 include $(RBCODECLIB_DIR)/codecs/liba52/liba52.make
diff --git a/lib/rbcodec/codecs/lib/libcodec.make b/lib/rbcodec/codecs/lib/libcodec.make
index 0788dd6705..b197464528 100644
--- a/lib/rbcodec/codecs/lib/libcodec.make
+++ b/lib/rbcodec/codecs/lib/libcodec.make
@@ -23,6 +23,11 @@ ifneq ($(findstring sdl-sim, $(APP_TYPE)), sdl-sim)
     CODECLIBFLAGS += -ffunction-sections
 endif
 
+ifdef USE_LTO
+# We do NOT want LTO on the GCC support file
+$(CODECDIR)/lib/codeclib.o: CODECLIBFLAGS += -fno-lto
+endif
+
 $(CODECDIR)/lib/%.o: $(RBCODECLIB_DIR)/codecs/lib/%.c
         $(SILENT)mkdir -p $(dir $@)
         $(call PRINTS,CC $(subst $(ROOTDIR)/,,$<))$(CC) \
diff --git a/tools/configure b/tools/configure
index c58ce164ac..bf96bf0058 100755
--- a/tools/configure
+++ b/tools/configure
@@ -945,13 +945,14 @@ whichadvanced () {
     echo ""
     printf "Enter your developer options (press only enter when done)\n\
 (D)EBUG, (L)ogf, Boot(c)hart, (S)imulator, (P)rofiling, (V)oice, (U)SB Serial, (W)in32 crosscompile,\n\
-Win(6)4 crosscompile, (T)est plugins, (O)mit plugins, S(m)all C lib, Logf to Ser(i)al port:"
+Win(6)4 crosscompile, (T)est plugins, (O)mit plugins, S(m)all C lib, Logf to Ser(i)al port, LTO (B)uild "
     if [ "$modelname" = "iaudiom5" ]; then
       printf ", (F)M radio MOD"
     fi
     if [ "$modelname" = "iriverh120" ]; then
       printf ", (R)TC MOD"
     fi
+    printf ":"
     echo ""
   fi
 
@@ -1043,6 +1044,10 @@ Win(6)4 crosscompile, (T)est plugins, (O)mit plugins, S(m)all C lib, Logf to Ser
         win32crosscompile="yes"
         win64="yes"
         ;;
+       [Bb])
+        echo "LTO build enabled"
+        LTO_ARG="export USE_LTO=y"
+        ;;
       "") # Match enter press when finished with advanced options
         cont=0
         ;;
@@ -4806,6 +4811,7 @@ export ANDROID_PLATFORM_VERSION=${ANDROID_PLATFORM_VERSION}
 export TOOLSET=${toolset}
 export PIPER_MODEL_DIR=${PIPER_MODEL_DIR}
 $CCACHE_ARG
+$LTO_ARG
 
 CONFIGURE_OPTIONS=${cmdline}