perf(build): don't check the compiler's flags for every target
The TF_FLAGS variable must be recursively expanded as the rules that use
it are defined before it has been fully defined. That has the
unfortunate side effect of spawning a subshell that calls the compiler
for every file that is being built, thrashing multicore build times.
We don't cater to the possibility of the toolchain changing mid build so
precomputing this value would be more sensible. Doing a clean build on
an Intel dual socket Xeon Gold 5218 (i.e. 64 threads) workstation used
to take about 9 seconds. After this patch it takes about 1.5. Single
core performance went from ~45 seconds to about 25.
Change-Id: If56ed0ab3cc42bc482d9dd05a41ffbff4dd7f147
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
diff --git a/Makefile b/Makefile
index 6bbca3b..960befc 100644
--- a/Makefile
+++ b/Makefile
@@ -256,10 +256,12 @@
-Wlogical-op
# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105523
-TF_CFLAGS += $(call cc_option, --param=min-pagesize=0)
+TF_CFLAGS_MIN_PAGE_SIZE := $(call cc_option, --param=min-pagesize=0)
+TF_CFLAGS += $(TF_CFLAGS_MIN_PAGE_SIZE)
ifeq ($(HARDEN_SLS), 1)
- TF_CFLAGS_aarch64 += $(call cc_option, -mharden-sls=all)
+ TF_CFLAGS_MHARDEN_SLS := $(call cc_option, -mharden-sls=all)
+ TF_CFLAGS_aarch64 += $(TF_CFLAGS_MHARDEN_SLS)
endif
else
diff --git a/make_helpers/build_macros.mk b/make_helpers/build_macros.mk
index b6e6421..d454efd 100644
--- a/make_helpers/build_macros.mk
+++ b/make_helpers/build_macros.mk
@@ -96,6 +96,10 @@
# Convenience function to check for a given compiler option. A call to
# $(call cc_option, --no-XYZ) will return --no-XYZ if supported by the compiler
+# NOTE: consider assigning to an immediately expanded temporary variable before
+# assigning. This is because variables like TF_CFLAGS are recursively expanded
+# and assigning this directly will cause it to be expanded every time the
+# variable is used, potentially thrashing multicore performance.
define cc_option
$(shell if $($(ARCH)-cc) $(1) -c -x c /dev/null -o /dev/null >/dev/null 2>&1; then echo $(1); fi )
endef