Reordered FFTW fatal error; avoids using unset variables

Now variables that are set in FFTW detection are only used when the
variable that reports FFTW has been found is set (i.e. there has not
been a fatal error). Not sure why we haven't seen problems with this
so far, but we do see them on Power7 with cmake 2.8.8 when FFTWF is
not available.

Change-Id: I1a3e84002dda7f29f90eb532ab14ce51dfca6e5c

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4274e2d9cb506c857022e309f66a1ef059da7510..29cb127eb830844f048b488244e8c671bac77098 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -942,15 +942,14 @@ if(${GMX_FFT_LIBRARY} STREQUAL "FFTW3")
     else()
       find_package(FFTW COMPONENTS ${FFTW})
     endif()
+    if(NOT ${FFTW}_FOUND)
+      MESSAGE(FATAL_ERROR "Cannot find FFTW 3 (with correct precision - libfftw3f for single-precision GROMACS or libfftw3 for double-precision GROMACS). Either choose the right precision, choose another FFT(W) library (-DGMX_FFT_LIBRARY), enable the advanced option to let GROMACS build FFTW 3 for you (-DGMX_BUILD_OWN_FFTW=ON) , or use the really slow GROMACS built-in fftpack library (-DGMX_FFT_LIBRARY=fftpack).")
+    endif()
 
     string(TOUPPER "${FFTW}" FFTW)
     set(PKG_FFT "${${FFTW}_PKG}")
     include_directories(${${FFTW}_INCLUDE_DIRS})
     set(FFT_LIBRARIES ${${FFTW}_LIBRARIES})
-    if(NOT ${FFTW}_FOUND)
-      MESSAGE(FATAL_ERROR "Cannot find FFTW 3 (with correct precision - libfftw3f for single-precision GROMACS or libfftw3 for double-precision GROMACS). Either choose the right precision, choose another FFT(W) library (-DGMX_FFT_LIBRARY), enable the advanced option to let GROMACS build FFTW 3 for you (-DGMX_BUILD_OWN_FFTW=ON) , or use the really slow GROMACS built-in fftpack library (-DGMX_FFT_LIBRARY=fftpack).")
-    endif()
-
     set(GMX_FFT_FFTW3 1)
 
     if ((${GMX_CPU_ACCELERATION} MATCHES "SSE" OR ${GMX_CPU_ACCELERATION} MATCHES "AVX") AND NOT ${FFTW}_HAVE_SIMD)