[Xen-devel] [XEN PATCH v3 09/23] xen/build: extract clean target from Rules.mk

[Anthony PERARD <anthony.perard@citrix.com>]

From: Anthony PERARD <anthony.perard@gmail.com>

Most of the code executed by Rules.mk isn't necessary for the clean
target, especially not the CFLAGS. This patch makes running make clean
much faster.

The patch extract the clean target into a different Makefile,
Makefile.clean.

Since Makefile.clean, doesn't want to include Config.mk, we need to
define the variables DEPS_INCLUDE and DEPS in a place common to
Rules.mk and Makefile.clean, this is Kbuild.include. DEPS_RM is only
needed in Makefile.clean so can be defined there.

Even so Rules.mk includes Config.mk, it includes Kbuild.include after,
so the effective definition of DEPS_INCLUDE is "xen/" one and the
same one as used by Makefile.clean.

This is inspired by Kbuild, with Makefile.clean partially copied from
Linux v5.4.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---

Notes:
    v3:
    - rewrite of commit message
    - have only subdir-all, without intermediare variable subdir-y and
      subdir-n in Makefile.clean

 xen/Rules.mk               | 12 ------------
 xen/scripts/Kbuild.include |  7 ++++++-
 xen/scripts/Makefile.clean | 30 ++++++++++++++++++++++++++++++
 3 files changed, 36 insertions(+), 13 deletions(-)
 create mode 100644 xen/scripts/Makefile.clean

diff --git a/xen/Rules.mk b/xen/Rules.mk
index e3b19319b1f5..0c1a3ee5905d 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -100,8 +100,6 @@ SPECIAL_DATA_SECTIONS := rodata $(foreach a,1 2 4 8 16, \
 
 include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
 
-DEPS = .*.d
-
 include Makefile
 
 define gendep
@@ -118,10 +116,6 @@ $(foreach o,$(filter-out %/,$(obj-y) $(obj-bin-y) $(extra-y)),$(eval $(call gend
 subdir-y := $(subdir-y) $(filter %/, $(obj-y))
 obj-y    := $(patsubst %/, %/built_in.o, $(obj-y))
 
-subdir-n   := $(subdir-n) $(subdir-) $(filter %/, $(obj-n) $(obj-))
-
-subdir-all := $(subdir-y) $(subdir-n)
-
 $(filter %.init.o,$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS += -DINIT_SECTIONS_ONLY
 
 ifeq ($(CONFIG_COVERAGE),y)
@@ -185,12 +179,6 @@ FORCE:
 %/built_in_bin.o: FORCE
 	$(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in_bin.o
 
-.PHONY: clean
-clean:: $(addprefix _clean_, $(subdir-all))
-	rm -f *.o .*.o.tmp *~ core $(DEPS_RM)
-_clean_%/: FORCE
-	$(MAKE) $(clean) $*
-
 SRCPATH := $(patsubst $(BASEDIR)/%,%,$(CURDIR))
 
 %.o: %.c Makefile
diff --git a/xen/scripts/Kbuild.include b/xen/scripts/Kbuild.include
index 2465cc4060c3..6a9b0c39da53 100644
--- a/xen/scripts/Kbuild.include
+++ b/xen/scripts/Kbuild.include
@@ -2,6 +2,11 @@
 ####
 # kbuild: Generic definitions
 
+###
+# dependencies
+DEPS = .*.d
+DEPS_INCLUDE = $(addsuffix .d2, $(basename $(wildcard $(DEPS))))
+
 # cc-ifversion
 # Usage:  EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1)
 cc-ifversion = $(shell [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000 ] && echo $(3) || echo $(4))
@@ -9,4 +14,4 @@ cc-ifversion = $(shell [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000 ] && echo $(3) || e
 # Shorthand for $(MAKE) clean
 # Usage:
 # $(MAKE) $(clean) dir
-clean := -f $(BASEDIR)/Rules.mk clean -C
+clean := -f $(BASEDIR)/scripts/Makefile.clean clean -C
diff --git a/xen/scripts/Makefile.clean b/xen/scripts/Makefile.clean
new file mode 100644
index 000000000000..53379e6102cc
--- /dev/null
+++ b/xen/scripts/Makefile.clean
@@ -0,0 +1,30 @@
+# SPDX-License-Identifier: GPL-2.0
+# ==========================================================================
+# Cleaning up
+# ==========================================================================
+
+clean::
+
+include $(BASEDIR)/scripts/Kbuild.include
+
+include Makefile
+
+# Figure out what we need to clean from the various variables
+# ==========================================================================
+subdir-all := $(subdir-y) $(subdir-n) $(subdir-) \
+              $(filter %/, $(obj-y) $(obj-n) $(obj-))
+
+DEPS_RM = $(DEPS) $(DEPS_INCLUDE)
+.PHONY: clean
+clean:: $(addprefix _clean_, $(subdir-all))
+	rm -f *.o .*.o.tmp *~ core $(DEPS_RM)
+
+# Descending
+# ---------------------------------------------------------------------------
+
+_clean_%/: FORCE
+	$(MAKE) $(clean) $*
+
+# Force execution of pattern rules (for which PHONY cannot be directly used).
+.PHONY: FORCE
+FORCE:
-- 
Anthony PERARD


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