Use f2c translations of LAPACK when no Fortran compiler is available (#3539)

* Add C equivalents of the Fortran routines from Reference-LAPACK as fallbacks, and C_LAPACK variable to trigger their use

Author: martin-frbg

CMakeLists.txt

@@ -22,6 +22,8 @@ option(BUILD_WITHOUT_LAPACK "Do not build LAPACK and LAPACKE (Only BLAS or CBLAS
 
 option(BUILD_TESTING "Build LAPACK testsuite when building LAPACK" ON)
 
+option(C_LAPACK "Build LAPACK from C sources instead of the original Fortran" OFF)
+
 option(BUILD_WITHOUT_CBLAS "Do not build the C interface (CBLAS) to the BLAS functions" OFF)
 
 option(DYNAMIC_ARCH "Include support for multiple CPU targets, with automatic selection at runtime (x86/x86_64, aarch64 or ppc only)" OFF)
@@ -175,7 +177,7 @@ endforeach ()
 
 # Can't just use lapack-netlib's CMake files, since they are set up to search for BLAS, build and install a binary. We just want to build a couple of lib files out of lapack and lapacke.
 # Not using add_subdirectory here because lapack-netlib already has its own CMakeLists.txt. Instead include a cmake script with the sources we want.
-if (NOT NOFORTRAN AND NOT NO_LAPACK)
+if (NOT NO_LAPACK)
   include("${PROJECT_SOURCE_DIR}/cmake/lapack.cmake")
   if (NOT NO_LAPACKE)
     include("${PROJECT_SOURCE_DIR}/cmake/lapacke.cmake")

Makefile

@@ -25,11 +25,14 @@ ifeq ($(NO_FORTRAN), 1)
 define NOFORTRAN
 1
 endef
-define NO_LAPACK
+ifneq ($(NO_LAPACK), 1)
+define C_LAPACK
 1
 endef
+endif
 export NOFORTRAN
 export NO_LAPACK
+export C_LAPACK
 endif
 
 LAPACK_NOOPT := $(filter-out -O0 -O1 -O2 -O3 -Ofast -O -Og -Os,$(LAPACK_FFLAGS))
@@ -241,19 +244,14 @@ hpl_p :
 	fi; \
 	done
 
-ifeq ($(NO_LAPACK), 1)
-netlib :
-
-else
 netlib : lapack_prebuild
-ifeq ($(NOFORTRAN), $(filter 0,$(NOFORTRAN)))
+ifneq ($(NO_LAPACK), 1)
 	@$(MAKE) -C $(NETLIB_LAPACK_DIR) lapacklib
 	@$(MAKE) -C $(NETLIB_LAPACK_DIR) tmglib
 endif
 ifneq ($(NO_LAPACKE), 1)
 	@$(MAKE) -C $(NETLIB_LAPACK_DIR) lapackelib
 endif
-endif
 
 ifeq ($(NO_LAPACK), 1)
 re_lapack :
@@ -267,7 +265,7 @@ prof_lapack : lapack_prebuild
 	@$(MAKE) -C $(NETLIB_LAPACK_DIR) lapack_prof
 
 lapack_prebuild :
-ifeq ($(NOFORTRAN), $(filter 0,$(NOFORTRAN)))
+ifeq ($(NO_LAPACK), $(filter 0,$(NO_LAPACK)))
 	-@echo "FC          = $(FC)" > $(NETLIB_LAPACK_DIR)/make.inc
 	-@echo "override FFLAGS      = $(LAPACK_FFLAGS)" >> $(NETLIB_LAPACK_DIR)/make.inc
 	-@echo "FFLAGS_DRV  = $(LAPACK_FFLAGS)" >> $(NETLIB_LAPACK_DIR)/make.inc

Makefile.system

@@ -352,7 +352,7 @@ OBJCONV = $(CROSS_SUFFIX)objconv
 
 # When fortran support was either not detected or actively deselected, only build BLAS.
 ifeq ($(NOFORTRAN), 1)
-NO_LAPACK = 1
+C_LAPACK = 1
 override FEXTRALIB = 
 endif
 
@@ -1303,6 +1303,10 @@ ifeq ($(DYNAMIC_OLDER), 1)
 CCOMMON_OPT	+= -DDYNAMIC_OLDER
 endif
 
+ifeq ($(C_LAPACK), 1)
+CCOMMON_OPT	+= -DC_LAPACK
+endif
+
 ifeq ($(NO_LAPACK), 1)
 CCOMMON_OPT	+= -DNO_LAPACK
 #Disable LAPACK C interface
@@ -1661,6 +1665,7 @@ export USE_OPENMP
 export CROSS
 export CROSS_SUFFIX
 export NOFORTRAN
+export C_LAPACK
 export NO_FBLAS
 export EXTRALIB
 export CEXTRALIB

cmake/f_check.cmake

@@ -25,11 +25,19 @@ check_language(Fortran)
 if(CMAKE_Fortran_COMPILER)
   enable_language(Fortran)
 else()
+  set (NOFORTRAN 1)
   if (NOT NO_LAPACK)
-    message(STATUS "No Fortran compiler found, can build only BLAS but not LAPACK")
+     if (NOT MSVC)
+	message(STATUS "No Fortran compiler found, can build only BLAS and f2c-converted LAPACK")
+	set(C_LAPACK 1)
+	if (INTERFACE64)
+	  set (CCOMMON_OPT "${CCOMMON_OPT} -DLAPACK_ILP64")
+  	endif ()
+	set(TIMER "NONE")
+     else ()
+       message(STATUS "No Fortran compiler found, can build only BLAS")
+     endif()  
   endif()
-  set (NOFORTRAN 1)
-  set (NO_LAPACK 1)
 endif()
 
 if (NOT ONLY_CBLAS)