diff --git a/Makefile b/Makefile
index aba7775..9836831 100644
--- a/Makefile
+++ b/Makefile
@@ -14,6 +14,7 @@ ENABLE_READLINE := 1
 ENABLE_VERIFIC := 0
 ENABLE_COVER := 1
 ENABLE_LIBYOSYS := 0
+ENABLE_GHDL := 0
 
 # other configuration flags
 ENABLE_GPROF := 0
@@ -49,7 +50,7 @@ all: top-all
 YOSYS_SRC := $(dir $(firstword $(MAKEFILE_LIST)))
 VPATH := $(YOSYS_SRC)
 
-CXXFLAGS += -Wall -Wextra -ggdb -I. -I"$(YOSYS_SRC)" -MD -D_YOSYS_ -fPIC -I$(PREFIX)/include
+CXXFLAGS += -Wall -Wextra -g -I. -I"$(YOSYS_SRC)" -MD -D_YOSYS_ -I$(PREFIX)/include
 LDFLAGS += -L$(LIBDIR)
 LDLIBS = -lstdc++ -lm
 
@@ -104,7 +105,7 @@ endif
 ifeq ($(CONFIG),clang)
 CXX = clang
 LD = clang++
-CXXFLAGS += -std=c++11 -Os
+CXXFLAGS += -std=c++11 # -Os
 
 ifneq ($(SANITIZER),)
 $(info [Clang Sanitizer] $(SANITIZER))
@@ -236,6 +237,14 @@ CXXFLAGS += $(patsubst %,-I$(VERIFIC_DIR)/%,$(VERIFIC_COMPONENTS)) -DYOSYS_ENABL
 LDLIBS += $(patsubst %,$(VERIFIC_DIR)/%/*-linux.a,$(VERIFIC_COMPONENTS))
 endif
 
+ifeq ($(ENABLE_GHDL),1)
+GHDL_DIR ?= /usr/local/ghdl
+GHDL_INCLUDE_DIR ?= $(GHDL_DIR)/include
+GHDL_LIB_DIR ?= $(GHDL_DIR)/lib
+CXXFLAGS += -I$(GHDL_INCLUDE_DIR) -DYOSYS_ENABLE_GHDL
+LDLIBS += $(GHDL_LIB_DIR)/libghdlsynth.a $(shell cat $(GHDL_LIB_DIR)/ghdlsynth.link)
+endif
+
 ifeq ($(ENABLE_COVER),1)
 CXXFLAGS += -DYOSYS_ENABLE_COVER
 endif