[PATCH v2 1/3] autoconf: prefer an unrolled loop for trivial AC_CHECK_FUNCS

[Paolo Bonzini]

An unrolled loop avoids the cost of spawning sed in AS_TR_SH and
AS_TR_CPP.  Prefer it if there is nothing in the second and third
argument of AC_CHECK_FUNCS and the first argument is a literal.
Modify AC_CHECK_FUNCS_ONCE to avoid the variable indirection too.

* lib/autoconf/functions.m4 (AC_CHECK_FUNCS): Unroll loop if safe.
(_AC_CHECK_FUNCS): Move basic implementation here.
(_AC_CHECK_FUNC_ONCE): Expand AC_CHECK_FUNCS here...
(_AC_FUNCS_EXPANSION): ... and not here, so remove.

Signed-off-by: Paolo Bonzini <address@hidden>
---
 lib/autoconf/functions.m4 | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/lib/autoconf/functions.m4 b/lib/autoconf/functions.m4
index 66abe29..ccfb053 100644
--- a/lib/autoconf/functions.m4
+++ b/lib/autoconf/functions.m4
@@ -85,20 +85,24 @@ m4_define([_AH_CHECK_FUNC],
 # `break' to stop the search.
 AC_DEFUN([AC_CHECK_FUNCS],
 [m4_map_args_w([$1], [_AH_CHECK_FUNC(], [)])]dnl
-[AS_FOR([AC_func], [ac_func], [$1],
-[AC_CHECK_FUNC(AC_func,
-              [AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_]AC_func)) $2],
-              [$3])dnl])
+[m4_if([$2$3]AS_LITERAL_IF([$1], [[yes]], [[no]]), [yes],
+       [m4_map_args_w([$1], [_$0(], [)])],
+       [AS_FOR([AC_func], [ac_func], [$1], [_$0(AC_func, [$2], [$3])])])
 ])# AC_CHECK_FUNCS
 
+m4_define([_AC_CHECK_FUNCS],
+[AC_CHECK_FUNC([$1],
+              [AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_]$1)) $2],
+              [$3])
+])
+
 
 # _AC_CHECK_FUNC_ONCE(FUNCTION)
 # -----------------------------
 # Check for a single FUNCTION once.
 m4_define([_AC_CHECK_FUNC_ONCE],
-[_AH_CHECK_FUNC([$1])AC_DEFUN([_AC_Func_$1],
-  [m4_divert_text([INIT_PREPARE], [AS_VAR_APPEND([ac_func_list], [" $1"])])
-_AC_FUNCS_EXPANSION])AC_REQUIRE([_AC_Func_$1])])
+[AC_DEFUN([_AC_Func_$1], [AC_CHECK_FUNCS([$1])])
+AC_REQUIRE([_AC_Func_$1])])
 
 # AC_CHECK_FUNCS_ONCE(FUNCTION...)
 # --------------------------------
@@ -107,13 +111,6 @@ _AC_FUNCS_EXPANSION])AC_REQUIRE([_AC_Func_$1])])
 AC_DEFUN([AC_CHECK_FUNCS_ONCE],
 [m4_map_args_w([$1], [_AC_CHECK_FUNC_ONCE(], [)])])
 
-m4_define([_AC_FUNCS_EXPANSION],
-[
-  m4_divert_text([DEFAULTS], [ac_func_list=])
-  AC_CHECK_FUNCS([$ac_func_list])
-  m4_define([_AC_FUNCS_EXPANSION], [])
-])
-
 
 # _AC_REPLACE_FUNC(FUNCTION)
 # --------------------------
-- 
2.7.4