From b6a467d73d8847e2307e7e95768e3287d51a9fe6 Mon Sep 17 00:00:00 2001
From: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
Date: Mon, 7 Nov 2011 05:26:43 +0000
Subject: config.mk: use memoization in cc-option macro to speed up compilation

Apply memoization to cc-option macro by caching the results of the
gcc calls. This macro is called very often so using cached results
leads to faster compilation times.

The old behaviour can be restored by defining the config option
CONFIG_CC_OPT_CACHE_DISABLE=y.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
---
 config.mk | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

(limited to 'config.mk')

diff --git a/config.mk b/config.mk
index 918cffe3eb..ddaa4775cd 100644
--- a/config.mk
+++ b/config.mk
@@ -107,8 +107,24 @@ HOSTCFLAGS	+= -pedantic
 # Option checker (courtesy linux kernel) to ensure
 # only supported compiler options are used
 #
-cc-option = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null \
-		> /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
+CC_OPTIONS_CACHE_FILE := $(OBJTREE)/include/generated/cc_options.mk
+
+$(if $(wildcard $(CC_OPTIONS_CACHE_FILE)),,\
+	$(shell mkdir -p $(dir $(CC_OPTIONS_CACHE_FILE))))
+
+-include $(CC_OPTIONS_CACHE_FILE)
+
+cc-option-sys = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null \
+		> /dev/null 2>&1; then \
+		echo 'CC_OPTIONS += $(strip $1)' >> $(CC_OPTIONS_CACHE_FILE); \
+		echo "$(1)"; fi)
+
+ifeq ($(CONFIG_CC_OPT_CACHE_DISABLE),y)
+cc-option = $(strip $(if $(call cc-option-sys,$1),$1,$2))
+else
+cc-option = $(strip $(if $(findstring $1,$(CC_OPTIONS)),$1,\
+		$(if $(call cc-option-sys,$1),$1,$2)))
+endif
 
 #
 # Include the make variables (CC, etc...)
-- 
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