[PATCH] libosmocore[master]: configure.ac: check for __builtin_cpu_supports call support

[Vadim Yanitskiy]

Review at  https://gerrit.osmocom.org/2519

configure.ac: check for __builtin_cpu_supports call support

The '__builtin_cpu_supports' is a GCC's built-in function which
returns a positive integer if the run-time CPU supports specified
SIMD feature and returns 0 otherwise. It is required for further
SSE optimization of Viterbi decoder.

This change adds a new check, whether compiler supports this call.
See /gcc/X86-Built-in-Functions.html at gcc.gnu.org for reference.

Change-Id: I5d52cfb3e8fab3eedc0293a2842708cbee0f476a
---
M configure.ac
1 file changed, 27 insertions(+), 0 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/libosmocore refs/changes/19/2519/1

diff --git a/configure.ac b/configure.ac
index 672a6df..1dd5930 100644
--- a/configure.ac
+++ b/configure.ac
@@ -242,6 +242,33 @@
 	AM_CONDITIONAL(HAVE_SSE4_1, false)
 fi
 
+dnl Check if the compiler supports specified GCC's built-in function
+AC_DEFUN([CHECK_BUILTIN_SUPPORT], [
+  AC_CACHE_CHECK(
+    [whether ${CC} has $1 built-in],
+    [osmo_cv_cc_has_builtin], [
+      AC_LINK_IFELSE([
+        AC_LANG_PROGRAM([], [
+          __builtin_cpu_supports("sse");
+        ])
+      ],
+      [AS_VAR_SET([osmo_cv_cc_has_builtin], [yes])],
+      [AS_VAR_SET([osmo_cv_cc_has_builtin], [no])])
+    ]
+  )
+
+  AS_IF([test yes = AS_VAR_GET([osmo_cv_cc_has_builtin])], [
+    AC_DEFINE_UNQUOTED(AS_TR_CPP(HAVE_$1), 1,
+      [Define to 1 if compiler has the '$1' built-in function])
+  ], [
+    AC_MSG_WARN($2)
+  ])
+])
+
+dnl Check if the compiler supports runtime SIMD detection
+CHECK_BUILTIN_SUPPORT([__builtin_cpu_supports],
+  [Runtime SIMD detection will be disabled])
+
 AC_OUTPUT(
 	libosmocore.pc
 	libosmocodec.pc

-- 
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I5d52cfb3e8fab3eedc0293a2842708cbee0f476a
Gerrit-PatchSet: 1
Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-Owner: Vadim Yanitskiy <axilirator at gmail.com>