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

2 files changed, 12 insertions, 0 deletions

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) \