[RFC PATCH 1/7] kbuild: remove kbuild cache

From: Masahiro Yamada
Date: Thu Feb 08 2018 - 11:23:21 EST

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With compiler flag tests moved to the configuration phase, the
result of $(call cc-option,...) will be cached in the .config file.
Remove kbuild cache to make it easier to move on.

Revert the following commits:
Commit 9a234a2e384349 ("kbuild: create directory for make cache only when necessary")
Commit e17c400ae194945ee ("kbuild: shrink .cache.mk when it exceeds 1000 lines")
Commit 4e56207130eda9 ("kbuild: Cache a few more calls to the compiler")
Commit 3298b690b21cdb ("kbuild: Add a cache for generated variables")

Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
---

Makefile | 5 +--
scripts/Kbuild.include | 101 +++++++------------------------------------------
2 files changed, 16 insertions(+), 90 deletions(-)

diff --git a/Makefile b/Makefile
index d192dd8..2ee49c9 100644
--- a/Makefile
+++ b/Makefile
@@ -655,7 +655,7 @@ KBUILD_CFLAGS += $(call cc-ifversion, -lt, 0409, \
KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0)

# check for 'asm goto'
-ifeq ($(call shell-cached,$(CONFIG_SHELL) $(srctree)/scripts/gcc-goto.sh $(CC) $(KBUILD_CFLAGS)), y)
+ifeq ($(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-goto.sh $(CC) $(KBUILD_CFLAGS)), y)
KBUILD_CFLAGS += -DCC_HAVE_ASM_GOTO
KBUILD_AFLAGS += -DCC_HAVE_ASM_GOTO
endif
@@ -811,7 +811,7 @@ KBUILD_CFLAGS += $(call cc-option,-fdata-sections,)
endif

# arch Makefile may override CC so keep this after arch Makefile is included
-NOSTDINC_FLAGS += -nostdinc -isystem $(call shell-cached,$(CC) -print-file-name=include)
+NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
CHECKFLAGS += $(NOSTDINC_FLAGS)

# warn about C99 declaration after statement
@@ -1602,7 +1602,6 @@ clean: $(clean-dirs)
-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
-o -name '*.symtypes' -o -name 'modules.order' \
-o -name modules.builtin -o -name '.tmp_*.o.*' \
- -o -name .cache.mk \
-o -name '*.c.[012]*.*' \
-o -name '*.ll' \
-o -name '*.gcno' \) -type f -print | xargs rm -f
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 065324a..9776946 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -8,8 +8,6 @@ squote := '
empty :=
space := $(empty) $(empty)
space_escape := _-_SPACE_-_
-right_paren := )
-left_paren := (

###
# Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
@@ -82,71 +80,6 @@ cc-cross-prefix = \
echo $(c); \
fi)))

-# Tools for caching Makefile variables that are "expensive" to compute.
-#
-# Here we want to help deal with variables that take a long time to compute
-# by making it easy to store these variables in a cache.
-#
-# The canonical example here is testing for compiler flags. On a simple system
-# each call to the compiler takes 10 ms, but on a system with a compiler that's
-# called through various wrappers it can take upwards of 100 ms. If we have
-# 100 calls to the compiler this can take 1 second (on a simple system) or 10
-# seconds (on a complicated system).
-#
-# The "cache" will be in Makefile syntax and can be directly included.
-# Any time we try to reference a variable that's not in the cache we'll
-# calculate it and store it in the cache for next time.
-
-# Include values from last time
-make-cache := $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/,$(if $(obj),$(obj)/)).cache.mk
-$(make-cache): ;
--include $(make-cache)
-
-cached-data := $(filter __cached_%, $(.VARIABLES))
-
-# If cache exceeds 1000 lines, shrink it down to 500.
-ifneq ($(word 1000,$(cached-data)),)
-$(shell tail -n 500 $(make-cache) > $(make-cache).tmp; \
- mv $(make-cache).tmp $(make-cache))
-endif
-
-create-cache-dir := $(if $(KBUILD_SRC),$(if $(cache-data),,1))
-
-# Usage: $(call __sanitize-opt,Hello=Hola$(comma)Goodbye Adios)
-#
-# Convert all '$', ')', '(', '\', '=', ' ', ',', ':' to '_'
-__sanitize-opt = $(subst $$,_,$(subst $(right_paren),_,$(subst $(left_paren),_,$(subst \,_,$(subst =,_,$(subst $(space),_,$(subst $(comma),_,$(subst :,_,$(1)))))))))
-
-# Usage: $(call shell-cached,shell_command)
-# Example: $(call shell-cached,md5sum /usr/bin/gcc)
-#
-# If we've already seen a call to this exact shell command (even in a
-# previous invocation of make!) we'll return the value. If not, we'll
-# compute it and store the result for future runs.
-#
-# This is a bit of voodoo, but basic explanation is that if the variable
-# was undefined then we'll evaluate the shell command and store the result
-# into the variable. We'll then store that value in the cache and finally
-# output the value.
-#
-# NOTE: The $$(2) here isn't actually a parameter to __run-and-store. We
-# happen to know that the caller will have their shell command in $(2) so the
-# result of "call"ing this will produce a reference to that $(2). The reason
-# for this strangeness is to avoid an extra level of eval (and escaping) of
-# $(2).
-define __run-and-store
-ifeq ($(origin $(1)),undefined)
- $$(eval $(1) := $$(shell $$(2)))
-ifeq ($(create-cache-dir),1)
- $$(shell mkdir -p $(dir $(make-cache)))
- $$(eval create-cache-dir :=)
-endif
- $$(shell echo '$(1) := $$($(1))' >> $(make-cache))
-endif
-endef
-__shell-cached = $(eval $(call __run-and-store,$(1)))$($(1))
-shell-cached = $(call __shell-cached,__cached_$(call __sanitize-opt,$(1)),$(1))
-
# output directory for tests below
TMPOUT := $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)

@@ -154,36 +87,30 @@ TMPOUT := $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)
# Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
# Exit code chooses option. "$$TMP" serves as a temporary file and is
# automatically cleaned up.
-__try-run = set -e; \
+try-run = $(shell set -e; \
TMP="$(TMPOUT).$$$$.tmp"; \
TMPO="$(TMPOUT).$$$$.o"; \
if ($(1)) >/dev/null 2>&1; \
then echo "$(2)"; \
else echo "$(3)"; \
fi; \
- rm -f "$$TMP" "$$TMPO"
-
-try-run = $(shell $(__try-run))
-
-# try-run-cached
-# This works like try-run, but the result is cached.
-try-run-cached = $(call shell-cached,$(__try-run))
+ rm -f "$$TMP" "$$TMPO")

# as-option
# Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)

-as-option = $(call try-run-cached,\
+as-option = $(call try-run,\
$(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))

# as-instr
# Usage: cflags-y += $(call as-instr,instr,option1,option2)

-as-instr = $(call try-run-cached,\
+as-instr = $(call try-run,\
printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))

# __cc-option
# Usage: MY_CFLAGS += $(call __cc-option,$(CC),$(MY_CFLAGS),-march=winchip-c6,-march=i586)
-__cc-option = $(call try-run-cached,\
+__cc-option = $(call try-run,\
$(1) -Werror $(2) $(3) -c -x c /dev/null -o "$$TMP",$(3),$(4))

# Do not attempt to build with gcc plugins during cc-option tests.
@@ -203,23 +130,23 @@ hostcc-option = $(call __cc-option, $(HOSTCC),\

# cc-option-yn
# Usage: flag := $(call cc-option-yn,-march=winchip-c6)
-cc-option-yn = $(call try-run-cached,\
+cc-option-yn = $(call try-run,\
$(CC) -Werror $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",y,n)

# cc-disable-warning
# Usage: cflags-y += $(call cc-disable-warning,unused-but-set-variable)
-cc-disable-warning = $(call try-run-cached,\
+cc-disable-warning = $(call try-run,\
$(CC) -Werror $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))

# cc-name
# Expands to either gcc or clang
-cc-name = $(call shell-cached,$(CC) -v 2>&1 | grep -q "clang version" && echo clang || echo gcc)
+cc-name = $(shell $(CC) -v 2>&1 | grep -q "clang version" && echo clang || echo gcc)

# cc-version
-cc-version = $(call shell-cached,$(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh $(CC))
+cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh $(CC))

# cc-fullversion
-cc-fullversion = $(call shell-cached,$(CONFIG_SHELL) \
+cc-fullversion = $(shell $(CONFIG_SHELL) \
$(srctree)/scripts/gcc-version.sh -p $(CC))

# cc-ifversion
@@ -232,23 +159,23 @@ cc-if-fullversion = $(shell [ $(cc-fullversion) $(1) $(2) ] && echo $(3) || echo

# cc-ldoption
# Usage: ldflags += $(call cc-ldoption, -Wl$(comma)--hash-style=both)
-cc-ldoption = $(call try-run-cached,\
+cc-ldoption = $(call try-run,\
$(CC) $(1) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -nostdlib -x c /dev/null -o "$$TMP",$(1),$(2))

# ld-option
# Usage: LDFLAGS += $(call ld-option, -X)
-ld-option = $(call try-run-cached,\
+ld-option = $(call try-run,\
$(CC) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -x c /dev/null -c -o "$$TMPO"; \
$(LD) $(LDFLAGS) $(1) "$$TMPO" -o "$$TMP",$(1),$(2))

# ar-option
# Usage: KBUILD_ARFLAGS := $(call ar-option,D)
# Important: no spaces around options
-ar-option = $(call try-run-cached, $(AR) rc$(1) "$$TMP",$(1),$(2))
+ar-option = $(call try-run, $(AR) rc$(1) "$$TMP",$(1),$(2))

# ld-version
# Note this is mainly for HJ Lu's 3 number binutil versions
-ld-version = $(call shell-cached,$(LD) --version | $(srctree)/scripts/ld-version.sh)
+ld-version = $(shell $(LD) --version | $(srctree)/scripts/ld-version.sh)

# ld-ifversion
# Usage: $(call ld-ifversion, -ge, 22252, y)
--
2.7.4

Next message: Andrey Ryabinin: "Re: INFO: task hung in sync_blockdev"
Previous message: Arnaldo Carvalho de Melo: "Re: [PATCH 11/20 v2] tracing: Add symbol type to function based events"
In reply to: Masahiro Yamada: "[RFC PATCH 2/7] kconfig: add xrealloc() helper"
Next in thread: Masahiro Yamada: "[RFC PATCH 6/7] kconfig: add basic environments to evaluate C flags in Kconfig"
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