Separate OpenMP handling and allow compilation of Power9 code with older gcc

Makefile.power

@@ -10,54 +10,36 @@ USE_OPENMP = 1
 endif
 
 ifeq ($(CORE), POWER10)
-ifeq ($(USE_OPENMP), 1)
-COMMON_OPT += -Ofast -mcpu=power10 -mtune=power10 -mvsx  -DUSE_OPENMP -fno-fast-math -fopenmp
-FCOMMON_OPT += -O2 -frecursive -mcpu=power10 -mtune=power10  -DUSE_OPENMP -fno-fast-math -fopenmp
-else
 COMMON_OPT += -Ofast -mcpu=power10 -mtune=power10 -mvsx  -fno-fast-math
 FCOMMON_OPT += -O2 -frecursive -mcpu=power10 -mtune=power10  -fno-fast-math
 endif
-endif
 
 ifeq ($(CORE), POWER9)
-ifeq ($(USE_OPENMP), 1)
 ifneq ($(C_COMPILER), PGI)
-CCOMMON_OPT += -Ofast -mcpu=power9 -mtune=power9 -mvsx  -DUSE_OPENMP -fno-fast-math -fopenmp
-else
-CCOMMON_OPT += -fast -Mvect=simd -Mcache_align -DUSE_OPENMP -mp
-endif
-ifneq ($(F_COMPILER), PGI)
-FCOMMON_OPT += -O2 -frecursive -mcpu=power9 -mtune=power9  -DUSE_OPENMP -fno-fast-math -fopenmp
+CCOMMON_OPT += -Ofast -mvsx -fno-fast-math
+ifneq ($(GCCVERSIONGT4), 1)
+$(warning your compiler is too old to fully support POWER9, getting a newer version of gcc is recommended)
+CCOMMON_OPT += -mcpu=power8 -mtune=power8 
 else
-FCOMMON_OPT += -O2 -Mrecursive -DUSE_OPENMP -mp
+CCOMMON_OPT += -mcpu=power9 -mtune=power9 
 endif
 else
-ifneq ($(C_COMPILER), PGI)
-CCOMMON_OPT += -Ofast -mcpu=power9 -mtune=power9 -mvsx  -fno-fast-math
-else
 CCOMMON_OPT += -fast -Mvect=simd -Mcache_align
 endif
 ifneq ($(F_COMPILER), PGI)
-FCOMMON_OPT += -O2 -frecursive -mcpu=power9 -mtune=power9  -fno-fast-math
+FCOMMON_OPT += -O2 -frecursive -fno-fast-math
+ifneq ($(GCCVERSIONGT4), 1)
+$(warning your compiler is too old to fully support POWER9, getting a newer version of gcc is recommended)
+FCOMMON_OPT += -mcpu=power8 -mtune=power8 
 else
-FCOMMON_OPT += -O2 -Mrecursive
+FCOMMON_OPT += -mcpu=power9 -mtune=power9 
 endif
+else
+FCOMMON_OPT += -O2 -Mrecursive
 endif
 endif
 
 ifeq ($(CORE), POWER8)
-ifeq ($(USE_OPENMP), 1)
-ifneq ($(C_COMPILER), PGI)
-CCOMMON_OPT += -Ofast -mcpu=power8 -mtune=power8 -mvsx  -DUSE_OPENMP -fno-fast-math -fopenmp
-else
-CCOMMON_OPT += -fast -Mvect=simd -Mcache_align -DUSE_OPENMP -mp
-endif
-ifneq ($(F_COMPILER), PGI)
-FCOMMON_OPT += -O2 -frecursive -mcpu=power8 -mtune=power8  -DUSE_OPENMP -fno-fast-math -fopenmp
-else
-FCOMMON_OPT += -O2 -Mrecursive -DUSE_OPENMP -mp
-endif
-else
 ifneq ($(C_COMPILER), PGI)
 CCOMMON_OPT += -Ofast -mcpu=power8 -mtune=power8 -mvsx  -fno-fast-math
 else
@@ -73,6 +55,18 @@ else
 FCOMMON_OPT += -O2 -Mrecursive
 endif
 endif
+
+ifeq ($(USE_OPENMP), 1)
+ifneq ($(C_COMPILER), PGI)
+CCOMMON_OPT += -DUSE_OPENMP -fopenmp
+else
+CCOMMON_OPT += -DUSE_OPENMP -mp
+endif
+ifneq ($(F_COMPILER), PGI)
+FCOMMON_OPT += -DUSE_OPENMP -fopenmp
+else
+FCOMMON_OPT += -DUSE_OPENMP -mp
+endif
 endif
 
 # workaround for C->FORTRAN ABI violation in LAPACKE