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| H A D | Makefile | 0c22be0712b8771011880972aa30d3412aa3334e Thu Mar 14 23:41:59 UTC 2019 Douglas Anderson <dianders@chromium.org> kbuild: Make NOSTDINC_FLAGS a simply expanded variable
During a simple no-op (nothing changed) build I saw 39 invocations of
the C compiler with the argument "-print-file-name=include". We don't
need to call the C compiler 39 times for this--one time will suffice.
Let's change NOSTDINC_FLAGS to a simply expanded variable to avoid
this since there doesn't appear to be any reason it should be
recursively expanded.
On my build this shaved ~400 ms off my "no-op" build.
Note that the recursive expansion seems to date back to the (really
old) commit e8f5bdb02ce0 ("[PATCH] Makefile include path ordering").
It's a little unclear to me if the point of that patch was to switch
the variable to be recursively expanded (which it did) or to avoid
directly assigning to NOSTDINC_FLAGS (AKA to switch to +=) because
someone else (out of tree?) was setting it. I presume later since if
the only goal was to switch to recursive expansion the patch would
have just removed the ":".
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
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