From bd74370b8657fc6fdab7b0d5024d011985183809 Mon Sep 17 00:00:00 2001
From: Rabin Vincent <rabin@rab.in>
Date: Sun, 30 Apr 2017 18:16:00 +0200
Subject: Makefile: evaluate LDFLAGS_BUILD_ID only once

Evaluate LDFLAGS_BUILD_ID (which involves invoking the compiler) only
once instead of over and over.

This provides a ~20% reduction in null build time with x86 allnoconfig:

$ make allnoconfig && make -j8
$ perf stat -r5 -e sched:sched_process_exec make -j8
-       2 119      sched:sched_process_exec
+       1 878      sched:sched_process_exec

-       1,238817018 seconds time elapsed
+       0,971020553 seconds time elapsed

Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---
 Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'Makefile')

diff --git a/Makefile b/Makefile
index 10d6cd348abb..35497e933995 100644
--- a/Makefile
+++ b/Makefile
@@ -829,7 +829,7 @@ KBUILD_AFLAGS   += $(ARCH_AFLAGS)   $(KAFLAGS)
 KBUILD_CFLAGS   += $(ARCH_CFLAGS)   $(KCFLAGS)
 
 # Use --build-id when available.
-LDFLAGS_BUILD_ID = $(patsubst -Wl$(comma)%,%,\
+LDFLAGS_BUILD_ID := $(patsubst -Wl$(comma)%,%,\
 			      $(call cc-ldoption, -Wl$(comma)--build-id,))
 KBUILD_LDFLAGS_MODULE += $(LDFLAGS_BUILD_ID)
 LDFLAGS_vmlinux += $(LDFLAGS_BUILD_ID)
-- 
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