linux-kernel - [PATCH] Makefile: reuse CC_VERSION

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Date:   Fri,  5 Feb 2021 14:01:25 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nathan Chancellor <nathan@...nel.org>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH] Makefile: reuse CC_VERSION_TEXT

I noticed we're invoking $(CC) via $(shell) more than once to check the
version.  Let's reuse the first string captured in $CC_VERSION_TEXT.

Fixes: 315bab4e972d ("kbuild: fix endless syncconfig in case arch Makefile sets CROSS_COMPILE")
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 Makefile | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/Makefile b/Makefile
index a85535eb6a7d..70034d7c1051 100644
--- a/Makefile
+++ b/Makefile
@@ -557,7 +557,13 @@ ifdef building_out_of_srctree
 	{ echo "# this is build directory, ignore it"; echo "*"; } > .gitignore
 endif
 
-ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
+# The expansion should be delayed until arch/$(SRCARCH)/Makefile is included.
+# Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
+# CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
+# and from include/config/auto.conf.cmd to detect the compiler upgrade.
+CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1)
+
+ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
 ifneq ($(CROSS_COMPILE),)
 CLANG_FLAGS	+= --target=$(notdir $(CROSS_COMPILE:%-=%))
 GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
@@ -576,12 +582,6 @@ KBUILD_AFLAGS	+= $(CLANG_FLAGS)
 export CLANG_FLAGS
 endif
 
-# The expansion should be delayed until arch/$(SRCARCH)/Makefile is included.
-# Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
-# CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
-# and from include/config/auto.conf.cmd to detect the compiler upgrade.
-CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1)
-
 ifdef config-build
 # ===========================================================================
 # *config targets only - make sure prerequisites are updated, and descend
-- 
2.30.0.478.g8a0d178c01-goog