diff --git a/Makefile.system b/Makefile.system
index d5e747824..8d78b420f 100644
--- a/Makefile.system
+++ b/Makefile.system
@@ -783,7 +783,15 @@ endif
 
 ifeq ($(F_COMPILER), FLANG)
 CCOMMON_OPT += -DF_INTERFACE_FLANG
-FCOMMON_OPT += -frecursive
+FCOMMON_OPT += -Mrecursive -Kieee
+ifeq ($(OSNAME), Linux)
+ifeq ($(ARCH), x86_64)
+FLANG_VENDOR := $(shell expr `$(FC) --version|cut -f 1 -d "."|head -1`)
+ifeq ($(FLANG_VENDOR),AOCC)
+FCOMMON_OPT += -fno-unroll-loops
+endif
+endif
+endif
 ifdef BINARY64
 ifdef INTERFACE64
 ifneq ($(INTERFACE64), 0)
@@ -797,11 +805,6 @@ endif
 ifeq ($(USE_OPENMP), 1)
 FCOMMON_OPT += -fopenmp
 endif
-#ifeq ($(OSNAME), Linux)
-#ifeq ($(ARCH), x86_64)
-#FLANG_VENDOR := $(shell expr `$(FC) --version|cut -f 1 -d "."|head -1`)
-#endif
-#endif
 endif
 
 ifeq ($(F_COMPILER), G77)
@@ -1276,12 +1279,7 @@ endif
 
 override CFLAGS     += $(COMMON_OPT) $(CCOMMON_OPT) -I$(TOPDIR)
 override PFLAGS     += $(COMMON_OPT) $(CCOMMON_OPT) -I$(TOPDIR) -DPROFILE $(COMMON_PROF)
-#ifeq ($(FLANG_VENDOR),AOCC)
-ifeq ($(F_COMPILER),FLANG)
-override FFLAGS     += $(filter-out -O2 -O3,$(COMMON_OPT)) -O1 $(FCOMMON_OPT)
-else
 override FFLAGS     += $(COMMON_OPT) $(FCOMMON_OPT)
-endif
 override FPFLAGS    += $(FCOMMON_OPT) $(COMMON_PROF)
 #MAKEOVERRIDES =
 
diff --git a/cmake/fc.cmake b/cmake/fc.cmake
index 9dcedffb2..fc1f9bb22 100644
--- a/cmake/fc.cmake
+++ b/cmake/fc.cmake
@@ -16,7 +16,7 @@ if (${F_COMPILER} STREQUAL "FLANG")
   if (USE_OPENMP)
     set(FCOMMON_OPT "${FCOMMON_OPT} -fopenmp")
   endif ()
-  set(FCOMMON_OPT "${FCOMMON_OPT} -frecursive")
+  set(FCOMMON_OPT "${FCOMMON_OPT} -Mrecursive -Kieee")
 endif ()
 
 if (${F_COMPILER} STREQUAL "G77")
diff --git a/cmake/system.cmake b/cmake/system.cmake
index c2ae471d2..d8dcc3cf3 100644
--- a/cmake/system.cmake
+++ b/cmake/system.cmake
@@ -419,10 +419,9 @@ endif ()
 
 if ("${CMAKE_BUILD_TYPE}" STREQUAL "Release")
 if ("${F_COMPILER}" STREQUAL "FLANG")
-  set(FILTER_FLAGS "-O2;-O3")
-  foreach (FILTER_FLAG ${FILTER_FLAGS})
-    string(REPLACE ${FILTER_FLAG} "-O1" CMAKE_Fortran_FLAGS_RELEASE ${CMAKE_Fortran_FLAGS_RELEASE})
-  endforeach ()
+if (${CMAKE_Fortran_COMPILER_VERSION} VERSION_LESS_EQUAL 3)
+  set(CMAKE_Fortran_FLAGS_RELEASE "${CMAKE_Fortran_FLAGS_RELEASE} -fno-unroll-loops")
+endif ()
 endif ()
 endif ()