diff --git a/config/cortexa15/make_defs.mk b/config/cortexa15/make_defs.mk
index 0cbf304db..fda2b7589 100644
--- a/config/cortexa15/make_defs.mk
+++ b/config/cortexa15/make_defs.mk
@@ -63,7 +63,7 @@ endif
 # Flags specific to optimized kernels.
 CKOPTFLAGS     := $(COPTFLAGS)
 ifeq ($(CC_VENDOR),gcc)
-CKVECFLAGS     := -march=armv7-a
+CKVECFLAGS     := -mcpu=cortex-a15
 else
 $(error gcc is required for this configuration.)
 endif
diff --git a/config/cortexa53/make_defs.mk b/config/cortexa53/make_defs.mk
index 3e116cd6e..eb9dae08c 100644
--- a/config/cortexa53/make_defs.mk
+++ b/config/cortexa53/make_defs.mk
@@ -57,19 +57,21 @@ endif
 ifeq ($(DEBUG_TYPE),noopt)
 COPTFLAGS      := -O0
 else
-COPTFLAGS      := -O3 -ftree-vectorize -mtune=cortex-a53
+# Use -O2 here to avoid issue #341 -- BLAS check failing, using GCC 8.
+# (It's at least  -ftree-loop-vectorize which causes the trouble.)
+COPTFLAGS      := -O2 -mcpu=cortex-a53
 endif
 
 # Flags specific to optimized kernels.
 CKOPTFLAGS     := $(COPTFLAGS)
 ifeq ($(CC_VENDOR),gcc)
-CKVECFLAGS     := -march=armv8-a+fp+simd -mcpu=cortex-a53
+CKVECFLAGS     := -mcpu=cortex-a53
 else
 $(error gcc is required for this configuration.)
 endif
 
 # Flags specific to reference kernels.
-CROPTFLAGS     := $(CKOPTFLAGS)
+CROPTFLAGS     := $(CKOPTFLAGS) -O3
 ifeq ($(CC_VENDOR),gcc)
 CRVECFLAGS     := $(CKVECFLAGS) -funsafe-math-optimizations -ffp-contract=fast
 else
diff --git a/config/cortexa57/make_defs.mk b/config/cortexa57/make_defs.mk
index 864872bc2..831eb5afb 100644
--- a/config/cortexa57/make_defs.mk
+++ b/config/cortexa57/make_defs.mk
@@ -57,13 +57,13 @@ endif
 ifeq ($(DEBUG_TYPE),noopt)
 COPTFLAGS      := -O0
 else
-COPTFLAGS      := -O3 -ftree-vectorize -mtune=cortex-a57
+COPTFLAGS      := -O3 -mcpu=cortex-a57
 endif
 
 # Flags specific to optimized kernels.
 CKOPTFLAGS     := $(COPTFLAGS)
 ifeq ($(CC_VENDOR),gcc)
-CKVECFLAGS     := -march=armv8-a+fp+simd -mcpu=cortex-a57
+CKVECFLAGS     := -mcpu=cortex-a57
 else
 $(error gcc is required for this configuration.)
 endif
diff --git a/config/cortexa9/make_defs.mk b/config/cortexa9/make_defs.mk
index 310b75b95..3f6b95078 100644
--- a/config/cortexa9/make_defs.mk
+++ b/config/cortexa9/make_defs.mk
@@ -63,7 +63,7 @@ endif
 # Flags specific to optimized kernels.
 CKOPTFLAGS     := $(COPTFLAGS)
 ifeq ($(CC_VENDOR),gcc)
-CKVECFLAGS     := -march=armv7-a
+CKVECFLAGS     := -mcpu=cortex-a9
 else
 $(error gcc is required for this configuration.)
 endif
diff --git a/config/thunderx2/make_defs.mk b/config/thunderx2/make_defs.mk
index 820919d9c..cfe1d3fd9 100644
--- a/config/thunderx2/make_defs.mk
+++ b/config/thunderx2/make_defs.mk
@@ -57,13 +57,13 @@ endif
 ifeq ($(DEBUG_TYPE),noopt)
 COPTFLAGS      := -O0
 else
-COPTFLAGS      := -O3 -ftree-vectorize -mtune=thunderx2t99
+COPTFLAGS      := -O3 -mcpu=thunderx2t99
 endif
 
 # Flags specific to optimized kernels.
 CKOPTFLAGS     := $(COPTFLAGS)
 ifeq ($(CC_VENDOR),gcc)
-CKVECFLAGS     := -march=armv8.1-a+fp+simd -mcpu=thunderx2t99
+CKVECFLAGS     := -mcpu=thunderx2t99
 else
 $(error gcc is required for this configuration.)
 endif