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Subject[PATCH] Makefile: evaluate LDFLAGS_BUILD_ID only once
Date
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>
---
Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 779302695453..c78a266594c1 100644
--- a/Makefile
+++ b/Makefile
@@ -815,7 +815,7 @@ 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)
--
2.11.0
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