kbuild: optimize object directory creation for incremental build

The previous commit largely optimized the object directory creation. We can optimize it more for incremental build. There are already *.cmd files in the output directory. The existing *.cmd files have been picked up by $(wildcard ...). Obviously, directories containing them exist too, so we can skip "mkdir -p". With this, Kbuild runs almost zero "mkdir -p" in incremental building. Signed-off-by: Masahiro Yamada <[email protected]>
chewitt · Nov 16, 2017 · c4da7ed · c4da7ed
1 parent 8a78756
commit c4da7ed
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
@@ -583,8 +583,13 @@ endif
 ifneq ($(KBUILD_SRC),)
 # Create directories for object files if they do not exist
 obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
+# If cmd_files exist, their directories apparently exist.  Skip mkdir.
+exist-dirs := $(sort $(patsubst %/,%, $(dir $(cmd_files))))
+obj-dirs := $(strip $(filter-out $(exist-dirs), $(obj-dirs)))
+ifneq ($(obj-dirs),)
 $(shell mkdir -p $(obj-dirs))
 endif
+endif
 
 # Declare the contents of the .PHONY variable as phony.  We keep that
 # information in a variable se we can use it in if_changed and friends.