From 0c22be0712b8771011880972aa30d3412aa3334e Mon Sep 17 00:00:00 2001 From: Douglas Anderson Date: Thu, 14 Mar 2019 16:41:59 -0700 Subject: [PATCH] kbuild: Make NOSTDINC_FLAGS a simply expanded variable During a simple no-op (nothing changed) build I saw 39 invocations of the C compiler with the argument "-print-file-name=include". We don't need to call the C compiler 39 times for this--one time will suffice. Let's change NOSTDINC_FLAGS to a simply expanded variable to avoid this since there doesn't appear to be any reason it should be recursively expanded. On my build this shaved ~400 ms off my "no-op" build. Note that the recursive expansion seems to date back to the (really old) commit e8f5bdb02ce0 ("[PATCH] Makefile include path ordering"). It's a little unclear to me if the point of that patch was to switch the variable to be recursively expanded (which it did) or to avoid directly assigning to NOSTDINC_FLAGS (AKA to switch to +=) because someone else (out of tree?) was setting it. I presume later since if the only goal was to switch to recursive expansion the patch would have just removed the ":". Signed-off-by: Douglas Anderson Signed-off-by: Masahiro Yamada --- Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Makefile b/Makefile index 1ef92d705984..08a01add09a6 100644 --- a/Makefile +++ b/Makefile @@ -412,7 +412,7 @@ CHECK = sparse CHECKFLAGS := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \ -Wbitwise -Wno-return-void -Wno-unknown-attribute $(CF) -NOSTDINC_FLAGS = +NOSTDINC_FLAGS := CFLAGS_MODULE = AFLAGS_MODULE = LDFLAGS_MODULE = -- 2.30.2