From: Michal Schmidt <mschmidt@redhat.com>
Date: Wed, 22 Jul 2015 15:50:44 +0000 (+0200)
Subject: basic: more optimizable IN_SET macro
X-Git-Tag: v223~71^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=77247cba3e8f94a3f58d16ec338ae030eb9145af;p=thirdparty%2Fsystemd.git

basic: more optimizable IN_SET macro

Making the array static allows gcc -O2 to generate smaller code:

"size systemd" before:
   text    data     bss     dec     hex filename
1377286  128608    2632 1508526  1704ae systemd

After:
   text    data     bss     dec     hex filename
1374326  128572    2664 1505562  16f91a systemd

(IN_SET still results in worse generated code than using
 "x == FOO || x == BAR || ...". I don't think we'll be able to match
 that with the C preprocessor.)

This change limits the use of IN_SET to sets with constant elements. All
present callers use constants. The compiler would report an "initializer
element is not constant" error otherwise.
---

diff --git a/src/basic/macro.h b/src/basic/macro.h
index 8fae4d0eded..ea01d701d29 100644
--- a/src/basic/macro.h
+++ b/src/basic/macro.h
@@ -406,7 +406,7 @@ do {                                                                    \
 
 #define IN_SET(x, y, ...)                                               \
         ({                                                              \
-                const typeof(y) _array[] = { (y), __VA_ARGS__ };        \
+                static const typeof(y) _array[] = { (y), __VA_ARGS__ }; \
                 const typeof(y) _x = (x);                               \
                 unsigned _i;                                            \
                 bool _found = false;                                    \