FindBLAS: Support combination of gfortran and Intel MKL

The module FindBLAS now correctly chooses MKL BLAS libraries to search,
based on the compiler ID. The MKL libraries needed for BLAS functionality
are the following:

  libmkl_{gf|intel}_{lp64|ilp64}.{a|so}
  libmkl_{gnu|intel}_thread.{a|so}       (or libmkl_sequential.{a|so})
  libmkl_core.{a|so}
  libm
  libdl
  lib{gomp|iomp5}.{a|so}                 (only with libmkl_*_thread.*)

To achieve the goal, the following internal variables are defined and used:

  BLAS_mkl_INTFACE   = "gf" or "intel"   (based on compiler ID)
  BLAS_mkl_THREADING = "gnu" or "intel"  (based on compiler ID)
  BLAS_mkl_OMP       = "gomp" or "iomp5" (based on compiler ID)
  BLAS_mkl_LM        = "-lm"             (not set on Windows)
  BLAS_mkl_DL        = "-ldl"            (not set on Windows)

The default values for the first three of them are "intel" and "iomp5",
unless a Fortran compiler is loaded with CMAKE_Fortran_COMPILER_ID
equal to "GNU"; in such case the "gf", "gnu" and "gomp" values are used.

In non-Windows systems, the thread library as well as libm and libdl are
now added to the linker line to allow static linking of libgomp.

Modules/FindBLAS.cmake

@@ -126,6 +126,8 @@ macro(Check_Fortran_Libraries LIBRARIES _prefix _name _flags _list _thread)
     endif ()
   endif ()
 
+  list(APPEND _libdir "${CMAKE_C_IMPLICIT_LINK_DIRECTORIES}")
+
   foreach(_library ${_list})
     set(_combined_name ${_combined_name}_${_library})
 
@@ -170,6 +172,8 @@ macro(Check_Fortran_Libraries LIBRARIES _prefix _name _flags _list _thread)
   if(_libraries_work)
     if("${_list}" STREQUAL "")
       set(${LIBRARIES} "${LIBRARIES}-PLACEHOLDER-FOR-EMPTY-LIBRARIES")
+    else()
+      set(${LIBRARIES} ${${LIBRARIES}} ${_thread})  # for static link
     endif()
   else()
     set(${LIBRARIES} FALSE)
@@ -205,21 +209,34 @@ endif ()
 #BLAS in intel mkl 10+ library? (em64t 64bit)
 if (BLA_VENDOR MATCHES "Intel" OR BLA_VENDOR STREQUAL "All")
   if (NOT BLAS_LIBRARIES)
+
+    # System-specific settings
     if (WIN32)
       if (BLA_STATIC)
         set(BLAS_mkl_DLL_SUFFIX "")
       else()
         set(BLAS_mkl_DLL_SUFFIX "_dll")
       endif()
+    else()
+      if(CMAKE_Fortran_COMPILER_LOADED AND CMAKE_Fortran_COMPILER_ID STREQUAL "GNU")
+          set(BLAS_mkl_INTFACE "gf")
+          set(BLAS_mkl_THREADING "gnu")
+          set(BLAS_mkl_OMP "gomp")
+      else()
+          set(BLAS_mkl_INTFACE "intel")
+          set(BLAS_mkl_THREADING "intel")
+          set(BLAS_mkl_OMP "iomp5")
+      endif()
+      set(BLAS_mkl_LM "-lm")
+      set(BLAS_mkl_LDL "-ldl")
     endif()
+
     if (BLA_VENDOR MATCHES "_64ilp")
       set(BLAS_mkl_ILP_MODE "ilp64")
     else ()
       set(BLAS_mkl_ILP_MODE "lp64")
     endif ()
-    if (NOT WIN32)
-      set(LM "-lm")
-    endif ()
+
     if (CMAKE_C_COMPILER_LOADED OR CMAKE_CXX_COMPILER_LOADED)
       if(BLAS_FIND_QUIETLY OR NOT BLAS_FIND_REQUIRED)
         find_package(Threads)
@@ -269,25 +286,20 @@ if (BLA_VENDOR MATCHES "Intel" OR BLA_VENDOR STREQUAL "All")
         else ()
           if (BLA_VENDOR STREQUAL "Intel10_32" OR BLA_VENDOR STREQUAL "All")
             list(APPEND BLAS_SEARCH_LIBS
-              "mkl_blas95 mkl_intel mkl_intel_thread mkl_core guide")
+              "mkl_blas95 mkl_${BLAS_mkl_INTFACE} mkl_${BLAS_mkl_THREADING}_thread mkl_core guide")
           endif ()
           if (BLA_VENDOR MATCHES "^Intel10_64i?lp$" OR BLA_VENDOR STREQUAL "All")
             # old version
             list(APPEND BLAS_SEARCH_LIBS
-              "mkl_blas95 mkl_intel_${BLAS_mkl_ILP_MODE} mkl_intel_thread mkl_core guide")
+              "mkl_blas95 mkl_${BLAS_mkl_INTFACE}_${BLAS_mkl_ILP_MODE} mkl_${BLAS_mkl_THREADING}_thread mkl_core guide")
 
             # mkl >= 10.3
-            if (CMAKE_C_COMPILER MATCHES ".+gcc")
-              list(APPEND BLAS_SEARCH_LIBS
-                "mkl_blas95_${BLAS_mkl_ILP_MODE} mkl_intel_${BLAS_mkl_ILP_MODE} mkl_gnu_thread mkl_core gomp")
-            else ()
-              list(APPEND BLAS_SEARCH_LIBS
-                "mkl_blas95_${BLAS_mkl_ILP_MODE} mkl_intel_${BLAS_mkl_ILP_MODE} mkl_intel_thread mkl_core iomp5")
-            endif ()
+            list(APPEND BLAS_SEARCH_LIBS
+              "mkl_blas95_${BLAS_mkl_ILP_MODE} mkl_${BLAS_mkl_INTFACE}_${BLAS_mkl_ILP_MODE} mkl_${BLAS_mkl_THREADING}_thread mkl_core ${BLAS_mkl_OMP}")
           endif ()
           if (BLA_VENDOR MATCHES "^Intel10_64i?lp_seq$" OR BLA_VENDOR STREQUAL "All")
             list(APPEND BLAS_SEARCH_LIBS
-              "mkl_blas95_${BLAS_mkl_ILP_MODE} mkl_intel_${BLAS_mkl_ILP_MODE} mkl_sequential mkl_core")
+              "mkl_blas95_${BLAS_mkl_ILP_MODE} mkl_${BLAS_mkl_INTFACE}_${BLAS_mkl_ILP_MODE} mkl_sequential mkl_core")
           endif ()
         endif ()
       else ()
@@ -330,26 +342,21 @@ if (BLA_VENDOR MATCHES "Intel" OR BLA_VENDOR STREQUAL "All")
         else ()
           if (BLA_VENDOR STREQUAL "Intel10_32" OR BLA_VENDOR STREQUAL "All")
             list(APPEND BLAS_SEARCH_LIBS
-              "mkl_intel mkl_intel_thread mkl_core guide")
+              "mkl_${BLAS_mkl_INTFACE} mkl_${BLAS_mkl_THREADING}_thread mkl_core guide")
           endif ()
           if (BLA_VENDOR MATCHES "^Intel10_64i?lp$" OR BLA_VENDOR STREQUAL "All")
 
             # old version
             list(APPEND BLAS_SEARCH_LIBS
-              "mkl_intel_${BLAS_mkl_ILP_MODE} mkl_intel_thread mkl_core guide")
+              "mkl_${BLAS_mkl_INTFACE}_${BLAS_mkl_ILP_MODE} mkl_${BLAS_mkl_THREADING}_thread mkl_core guide")
 
             # mkl >= 10.3
-            if (CMAKE_C_COMPILER MATCHES ".+gcc")
-              list(APPEND BLAS_SEARCH_LIBS
-                "mkl_intel_${BLAS_mkl_ILP_MODE} mkl_gnu_thread mkl_core gomp")
-            else ()
-              list(APPEND BLAS_SEARCH_LIBS
-                "mkl_intel_${BLAS_mkl_ILP_MODE} mkl_intel_thread mkl_core iomp5")
-            endif ()
+            list(APPEND BLAS_SEARCH_LIBS
+              "mkl_${BLAS_mkl_INTFACE}_${BLAS_mkl_ILP_MODE} mkl_${BLAS_mkl_THREADING}_thread mkl_core ${BLAS_mkl_OMP}")
           endif ()
           if (BLA_VENDOR MATCHES "^Intel10_64i?lp_seq$" OR BLA_VENDOR STREQUAL "All")
             list(APPEND BLAS_SEARCH_LIBS
-              "mkl_intel_${BLAS_mkl_ILP_MODE} mkl_sequential mkl_core")
+              "mkl_${BLAS_mkl_INTFACE}_${BLAS_mkl_ILP_MODE} mkl_sequential mkl_core")
           endif ()
 
           #older vesions of intel mkl libs
@@ -373,13 +380,19 @@ if (BLA_VENDOR MATCHES "Intel" OR BLA_VENDOR STREQUAL "All")
             ${BLAS_mkl_SEARCH_SYMBOL}
             ""
             "${SEARCH_LIBS}"
-            "${CMAKE_THREAD_LIBS_INIT};${LM}"
+            "${CMAKE_THREAD_LIBS_INIT};${BLAS_mkl_LM};${BLAS_mkl_LDL}"
             )
         endif ()
       endforeach ()
 
     endif ()
     unset(BLAS_mkl_ILP_MODE)
+    unset(BLAS_mkl_INTFACE)
+    unset(BLAS_mkl_THREADING)
+    unset(BLAS_mkl_OMP)
+    unset(BLAS_mkl_DLL_SUFFIX)
+    unset(BLAS_mkl_LM)
+    unset(BLAS_mkl_LDL)
   endif ()
 endif ()