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/Makefile b/Makefile
index 721246d..eddd48d 100644
--- a/Makefile
+++ b/Makefile
@@ -204,6 +204,18 @@
AS = $(CC) -c -x assembler-with-cpp $(TF_CFLAGS_$(ARCH))
CPP = $(CC) -E
PP = $(CC) -E
+else ifneq ($(findstring gcc,$(notdir $(CC))),)
+TF_CFLAGS_aarch32 = $(march32-directive)
+TF_CFLAGS_aarch64 = $(march64-directive)
+ifeq ($(ENABLE_LTO),1)
+ # Enable LTO only for aarch64
+ ifeq (${ARCH},aarch64)
+ LTO_CFLAGS = -flto
+ # Use gcc as a wrapper for the ld, recommended for LTO
+ LINKER := ${CROSS_COMPILE}gcc
+ endif
+endif
+LD = $(LINKER)
else
TF_CFLAGS_aarch32 = $(march32-directive)
TF_CFLAGS_aarch64 = $(march64-directive)
@@ -300,11 +312,28 @@
ifneq ($(findstring armlink,$(notdir $(LD))),)
TF_LDFLAGS += --diag_error=warning --lto_level=O1
TF_LDFLAGS += --remove --info=unused,unusedsymbols
+TF_LDFLAGS += $(TF_LDFLAGS_$(ARCH))
+else ifneq ($(findstring gcc,$(notdir $(LD))),)
+# Pass ld options with Wl or Xlinker switches
+TF_LDFLAGS += -Wl,--fatal-warnings -O1
+TF_LDFLAGS += -Wl,--gc-sections
+ifeq ($(ENABLE_LTO),1)
+ ifeq (${ARCH},aarch64)
+ TF_LDFLAGS += -flto -fuse-linker-plugin
+ endif
+endif
+# GCC automatically adds fix-cortex-a53-843419 flag when used to link
+# which breaks some builds, so disable if errata fix is not explicitly enabled
+ifneq (${ERRATA_A53_843419},1)
+ TF_LDFLAGS += -mno-fix-cortex-a53-843419
+endif
+TF_LDFLAGS += -nostdlib
+TF_LDFLAGS += $(subst --,-Xlinker --,$(TF_LDFLAGS_$(ARCH)))
else
TF_LDFLAGS += --fatal-warnings -O1
TF_LDFLAGS += --gc-sections
-endif
TF_LDFLAGS += $(TF_LDFLAGS_$(ARCH))
+endif
DTC_FLAGS += -I dts -O dtb
DTC_CPPFLAGS += -nostdinc -Iinclude -undef -x assembler-with-cpp
@@ -405,7 +434,11 @@
ifeq ($(ENABLE_PIE),1)
TF_CFLAGS += -fpie
- TF_LDFLAGS += -pie --no-dynamic-linker
+ ifneq ($(findstring gcc,$(notdir $(LD))),)
+ TF_LDFLAGS += -Wl,-pie -Wl,--no-dynamic-linker
+ else
+ TF_LDFLAGS += -pie --no-dynamic-linker
+ endif
else
PIE_FOUND := $(findstring --enable-default-pie,${GCC_V_OUTPUT})
ifneq ($(PIE_FOUND),)