Enable Link Time Optimization in GCC
This patch enables LTO for TF-A when compiled with GCC.
LTO is disabled by default and is enabled by
ENABLE_LTO=1 build option.
LTO is enabled only for aarch64 as there seem to be
a bug in the aarch32 compiler when LTO is enabled.
The changes in the makefiles include:
- Adding -flto and associated flags to enable LTO.
- Using gcc as a wrapper at link time instead of ld.
This is recommended when using LTO as gcc internally
takes care of invoking the necessary plugins for LTO.
- Adding switches to pass options to ld.
- Adding a flag to disable fix for erratum cortex-a53-843419
unless explicitly enabled. This is needed because GCC
seem to automatically add the erratum fix when used
as a wrapper for LD.
Additionally, this patch updates the TF-A user guide with
the new build option.
Signed-off-by: zelalem-aweke <zelalem.aweke@arm.com>
Change-Id: I1188c11974da98434b7dc9344e058cd1eacf5468
diff --git a/make_helpers/build_macros.mk b/make_helpers/build_macros.mk
index b89d87e..47f3ebd 100644
--- a/make_helpers/build_macros.mk
+++ b/make_helpers/build_macros.mk
@@ -236,7 +236,7 @@
$(OBJ): $(2) $(filter-out %.d,$(MAKEFILE_LIST)) | bl$(3)_dirs
$$(ECHO) " CC $$<"
- $$(Q)$$(CC) $$(TF_CFLAGS) $$(CFLAGS) $(BL_CFLAGS) -D$(IMAGE) $(MAKE_DEP) -c $$< -o $$@
+ $$(Q)$$(CC) $$(LTO_CFLAGS) $$(TF_CFLAGS) $$(CFLAGS) $(BL_CFLAGS) -D$(IMAGE) $(MAKE_DEP) -c $$< -o $$@
-include $(DEP)
@@ -433,6 +433,10 @@
--map --list="$(MAPFILE)" --scatter=${PLAT_DIR}/scat/bl${1}.scat \
$(LDPATHS) $(LIBWRAPPER) $(LDLIBS) $(BL_LIBS) \
$(BUILD_DIR)/build_message.o $(OBJS)
+else ifneq ($(findstring gcc,$(notdir $(LD))),)
+ $$(Q)$$(LD) -o $$@ $$(TF_LDFLAGS) $$(LDFLAGS) -Wl,-Map=$(MAPFILE) \
+ -Wl,-T$(LINKERFILE) $(BUILD_DIR)/build_message.o \
+ $(OBJS) $(LDPATHS) $(LIBWRAPPER) $(LDLIBS) $(BL_LIBS)
else
$$(Q)$$(LD) -o $$@ $$(TF_LDFLAGS) $$(LDFLAGS) -Map=$(MAPFILE) \
--script $(LINKERFILE) $(BUILD_DIR)/build_message.o \