diff --git a/Formula/yosys.rb b/Formula/yosys.rb
new file mode 100644
index 0000000000..9e6657e02e
--- /dev/null
+++ b/Formula/yosys.rb
@@ -0,0 +1,112 @@
+class Yosys < Formula
+  desc "Framework for Verilog RTL synthesis"
+  homepage "http://www.clifford.at/yosys/"
+  url "https://github.com/cliffordwolf/yosys/archive/yosys-0.7.tar.gz"
+  sha256 "3df986d0c6bf20b78193456e11c660f2ad935cc126537c2dc5726e78896d6e6e"
+
+  depends_on "python3"
+  depends_on "libffi" => :recommended
+  depends_on "readline" => :recommended
+  depends_on "pkg-config" => :build
+  depends_on "bison" => :build
+
+  # The makefile in Yosys 0.7 adds library search paths from macports, which a homebrew build
+  # should not be using. It also prints warnings about a missing brew command.
+  # See https://github.com/cliffordwolf/yosys/pull/303 for discussion.
+  # The patch is based on the Makefile changes in this upstream commit:
+  # https://github.com/cliffordwolf/yosys/commit/a431f4ee311b9563f546201d255e429e9ce58cfa
+  patch :DATA
+
+  # This ABC revision is specified in the makefile.
+  # The makefile by default checks it out using mercurial,
+  # but this recipe instead downloads a tar.gz archive.
+  resource "abc" do
+    url "https://bitbucket.org/alanmi/abc/get/eb6eca6807cc.tar.gz"
+    sha256 "ae9acddad38a950d48466e2f66de8116f2d21d03c78f5a270fa3bf77c3fd7b5b"
+  end
+
+  def install
+    args = []
+    resource("abc").stage buildpath/"abc"
+    args << "ENABLE_PLUGINS=0" if build.without? "libffi"
+    args << "ENABLE_READLINE=0" if build.without? "readline"
+    system "make", "install", "PREFIX=#{prefix}", "PRETTY=0", "ABCREV=default", *args
+  end
+
+  test do
+    system "#{bin}/yosys", "-p", "hierarchy; proc; opt; techmap; opt;", "-o", "synth.v", "#{pkgshare}/adff2dff.v"
+  end
+end
+
+__END__
+diff --git a/Makefile b/Makefile
+index 0a61fe65..2d973b18 100644
+--- a/Makefile
++++ b/Makefile
+@@ -53,23 +53,31 @@ CXXFLAGS += -Wall -Wextra -ggdb -I. -I"$(YOSYS_SRC)" -MD -D_YOSYS_ -fPIC -I$(PRE
+ LDFLAGS += -L$(LIBDIR)
+ LDLIBS = -lstdc++ -lm
+
+-PKG_CONFIG = pkg-config
+-SED = sed
+-BISON = bison
++PKG_CONFIG ?= pkg-config
++SED ?= sed
++BISON ?= bison
+
+ ifeq (Darwin,$(findstring Darwin,$(shell uname)))
+-	# add macports/homebrew include and library path to search directories, don't use '-rdynamic' and '-lrt':
+-	CXXFLAGS += -I/opt/local/include -I/usr/local/opt/readline/include
+-	LDFLAGS += -L/opt/local/lib -L/usr/local/opt/readline/lib
+-	# add homebrew's libffi include and library path
+-	CXXFLAGS += $(shell PKG_CONFIG_PATH=$$(brew list libffi | grep pkgconfig | xargs dirname) pkg-config --silence-errors --cflags libffi)
+-	LDFLAGS += $(shell PKG_CONFIG_PATH=$$(brew list libffi | grep pkgconfig | xargs dirname) pkg-config --silence-errors --libs libffi)
+-	# use bison installed by homebrew if available
+-	BISON = $(shell (brew list bison | grep -m1 "bin/bison") || echo bison)
+-	SED = sed
++# homebrew search paths
++ifneq ($(shell which brew),)
++BREW_PREFIX := $(shell brew --prefix)/opt
++CXXFLAGS += -I$(BREW_PREFIX)/readline/include
++LDFLAGS += -L$(BREW_PREFIX)/readline/lib
++PKG_CONFIG_PATH := $(BREW_PREFIX)/libffi/lib/pkgconfig:$(PKG_CONFIG_PATH)
++PKG_CONFIG_PATH := $(BREW_PREFIX)/tcl-tk/lib/pkgconfig:$(PKG_CONFIG_PATH)
++export PATH := $(BREW_PREFIX)/bison/bin:$(BREW_PREFIX)/gettext/bin:$(BREW_PREFIX)/flex/bin:$(PATH)
++
++# macports search paths
++else ifneq ($(shell which port),)
++PORT_PREFIX := $(patsubst %/bin/port,%,$(shell which port))
++CXXFLAGS += -I$(PORT_PREFIX)/include
++LDFLAGS += -L$(PORT_PREFIX)/lib
++PKG_CONFIG_PATH := $(PORT_PREFIX)/lib/pkgconfig:$(PKG_CONFIG_PATH)
++export PATH := $(PORT_PREFIX)/bin:$(PATH)
++endif
+ else
+-	LDFLAGS += -rdynamic
+-	LDLIBS += -lrt
++LDFLAGS += -rdynamic
++LDLIBS += -lrt
+ endif
+
+ YOSYS_VER := 0.7
+@@ -202,15 +210,16 @@ endif
+ endif
+
+ ifeq ($(ENABLE_PLUGINS),1)
+-CXXFLAGS += -DYOSYS_ENABLE_PLUGINS $(shell $(PKG_CONFIG) --silence-errors --cflags libffi)
+-LDLIBS += $(shell $(PKG_CONFIG) --silence-errors --libs libffi || echo -lffi) -ldl
++CXXFLAGS += $(shell PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) $(PKG_CONFIG) --silence-errors --cflags libffi) -DYOSYS_ENABLE_PLUGINS
++LDLIBS += $(shell PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) $(PKG_CONFIG) --silence-errors --libs libffi || echo -lffi) -ldl
+ endif
+
+ ifeq ($(ENABLE_TCL),1)
+ TCL_VERSION ?= tcl$(shell bash -c "tclsh <(echo 'puts [info tclversion]')")
+ TCL_INCLUDE ?= /usr/include/$(TCL_VERSION)
+-CXXFLAGS += -I$(TCL_INCLUDE) -DYOSYS_ENABLE_TCL
+-LDLIBS += -l$(TCL_VERSION)
++
++CXXFLAGS += $(shell PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) $(PKG_CONFIG) --silence-errors --cflags tcl || echo -I$(TCL_INCLUDE)) -DYOSYS_ENABLE_TCL
++LDLIBS += $(shell PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) $(PKG_CONFIG) --silence-errors --libs tcl || echo -l$(TCL_VERSION))
+ endif
+
+ ifeq ($(ENABLE_GPROF),1)