| Message ID | b8c291828d51f4bebdabbf9679a278533846820a.1457742064.git.pfeiner@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 12/03/2016 01:21, Peter Feiner wrote: > Make was reevaluating the shell commands in CFLAGS for every recipe > because CFLAGS was defined as a recursively-expanded variable. Doing a > simple expansion before putting the command output in CFLAGS prevents > this reevaluation. > > The difference this change makes for the x86 build is stark: > > BEFORE: > make -j 6.17s user 5.74s system 167% cpu 7.117 total > make 6.52s user 5.70s system 89% cpu 13.664 total > > AFTER: > make -j 4.03s user 1.47s system 1036% cpu 0.530 total > make 3.69s user 2.16s system 92% cpu 6.310 total > > Signed-off-by: Peter Feiner <pfeiner@google.com> > --- > Makefile | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/Makefile b/Makefile > index 09999c6..2a2d942 100644 > --- a/Makefile > +++ b/Makefile > @@ -42,9 +42,13 @@ cc-option = $(shell if $(CC) $(1) -S -o /dev/null -xc /dev/null \ > > CFLAGS += -g > CFLAGS += $(autodepend-flags) -Wall -Werror > -CFLAGS += $(call cc-option, -fomit-frame-pointer, "") > -CFLAGS += $(call cc-option, -fno-stack-protector, "") > -CFLAGS += $(call cc-option, -fno-stack-protector-all, "") > + > +fomit_frame_pointer := $(call cc-option, -fomit-frame-pointer, "") > +fnostack_protector := $(call cc-option, -fno-stack-protector, "") > +fnostack_protector_all := $(call cc-option, -fno-stack-protector-all, "") > +CFLAGS += $(fomit_frame_pointer) > +CFLAGS += $(fno_stack_protector) > +CFLAGS += $(fno_stack_protector_all) > > CXXFLAGS += $(CFLAGS) > > Thanks, looks good. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Makefile b/Makefile index 09999c6..2a2d942 100644 --- a/Makefile +++ b/Makefile @@ -42,9 +42,13 @@ cc-option = $(shell if $(CC) $(1) -S -o /dev/null -xc /dev/null \ CFLAGS += -g CFLAGS += $(autodepend-flags) -Wall -Werror -CFLAGS += $(call cc-option, -fomit-frame-pointer, "") -CFLAGS += $(call cc-option, -fno-stack-protector, "") -CFLAGS += $(call cc-option, -fno-stack-protector-all, "") + +fomit_frame_pointer := $(call cc-option, -fomit-frame-pointer, "") +fnostack_protector := $(call cc-option, -fno-stack-protector, "") +fnostack_protector_all := $(call cc-option, -fno-stack-protector-all, "") +CFLAGS += $(fomit_frame_pointer) +CFLAGS += $(fno_stack_protector) +CFLAGS += $(fno_stack_protector_all) CXXFLAGS += $(CFLAGS)
Make was reevaluating the shell commands in CFLAGS for every recipe because CFLAGS was defined as a recursively-expanded variable. Doing a simple expansion before putting the command output in CFLAGS prevents this reevaluation. The difference this change makes for the x86 build is stark: BEFORE: make -j 6.17s user 5.74s system 167% cpu 7.117 total make 6.52s user 5.70s system 89% cpu 13.664 total AFTER: make -j 4.03s user 1.47s system 1036% cpu 0.530 total make 3.69s user 2.16s system 92% cpu 6.310 total Signed-off-by: Peter Feiner <pfeiner@google.com> --- Makefile | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)