From 2d1166e3fa23d4230b9518b690e4a76aa2a8c3a1 Mon Sep 17 00:00:00 2001
From: Xavier Arteaga <xavier@softwareradiosystems.com>
Date: Thu, 17 Aug 2017 10:13:03 +0200
Subject: [PATCH] Added FMA flag

---
 cmake/modules/FindSSE.cmake | 40 +++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/cmake/modules/FindSSE.cmake b/cmake/modules/FindSSE.cmake
index 30be8a206..3440f01c1 100644
--- a/cmake/modules/FindSSE.cmake
+++ b/cmake/modules/FindSSE.cmake
@@ -7,6 +7,7 @@ include(CheckCSourceRuns)
 option(ENABLE_SSE "Enable compile-time SSE4.1 support." ON)
 option(ENABLE_AVX "Enable compile-time AVX support."  ON)
 option(ENABLE_AVX2 "Enable compile-time AVX2 support."  ON)
+option(ENABLE_FMA "Enable compile-time FMA support."  ON)
 
 if (ENABLE_SSE)
     #
@@ -97,8 +98,43 @@ if (ENABLE_SSE)
       if (HAVE_AVX2)
           message(STATUS "AVX2 is enabled - target CPU must support it")
       endif()
-  endif()
+    endif()
+
+    if (ENABLE_FMA)
+
+        #
+        # Check compiler for AVX intrinsics
+        #
+        if (CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_CLANG )
+            set(CMAKE_REQUIRED_FLAGS "-mfma")
+            check_c_source_runs("
+            #include <immintrin.h>
+            int main()
+            {
+              __m256 a, b, c, r;
+              const float src[8] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f };
+              float dst[8];
+              a = _mm256_loadu_ps( src );
+              b = _mm256_loadu_ps( src );
+              c = _mm256_loadu_ps( src );
+              r = _mm256_fmadd_ps( a, b, c );
+              _mm256_storeu_ps( dst, r );
+              int i = 0;
+              for( i = 0; i < 8; i++ ){
+                if( ( src[i] * src[i] + src[i] ) != dst[i] ){
+                  return -1;
+                }
+              }
+              return 0;
+            }"
+                    HAVE_FMA)
+        endif()
+
+        if (HAVE_FMA)
+            message(STATUS "FMA is enabled - target CPU must support it")
+        endif()
+    endif()
 
 endif()
 
-mark_as_advanced(HAVE_SSE, HAVE_AVX, HAVE_AVX2)
+mark_as_advanced(HAVE_SSE, HAVE_AVX, HAVE_AVX2, HAVE_FMA)