--- /usr/portage/eclass/toolchain.eclass	2017-05-10 17:13:07.000000000 +0100
+++ toolchain.eclass	2017-06-21 17:32:41.389222791 +0100
@@ -151,7 +151,7 @@
 	# versions which we dropped.  Since graphite was also experimental in
 	# the older versions, we don't want to bother supporting it.  #448024
 	tc_version_is_at_least 4.8 && IUSE+=" graphite" IUSE_DEF+=( sanitize )
-	tc_version_is_at_least 4.9 && IUSE+=" cilk +vtv"
+	tc_version_is_at_least 4.9 && IUSE+=" ada cilk +vtv"
 	tc_version_is_at_least 5.0 && IUSE+=" jit mpx"
 	tc_version_is_at_least 6.0 && IUSE+=" +pie +ssp +pch"
 fi
@@ -160,6 +160,15 @@
 
 SLOT="${GCC_CONFIG_VER}"
 
+# When using Ada, use this bootstrap compiler to build, only when there is no pre-existing Ada compiler.
+if in_iuse ada; then
+	# First time build, so need to bootstrap this.
+	# A newer version of GNAT should build an older version, just not vice-versa. 4.9 can definitely build 5.1.0.
+	#
+	# TODO: Add support for bootstraps for 5.4.0 and 6.3.0
+	GNAT_BOOTSTRAP_VERSION="4.9"
+fi
+
 #---->> DEPEND <<----
 
 RDEPEND="sys-libs/zlib
@@ -361,6 +370,13 @@
 		fi
 	fi
 
+	# TODO: Add support for bootstraps for 5.4.0 and 6.3.0
+	if in_iuse ada; then
+		GCC_SRC_URI+=" amd64? ( https://dev.gentoo.org/~nerdboy/files/gnatboot-${GNAT_BOOTSTRAP_VERSION}-amd64.tar.xz )
+				x86?   ( https://dev.gentoo.org/~nerdboy/files/gnatboot-${GNAT_BOOTSTRAP_VERSION}-i686.tar.xz )
+				arm?   ( https://dev.gentoo.org/~nerdboy/files/gnatboot-${GNAT_BOOTSTRAP_VERSION}-arm.tar.xz )"
+	fi
+
 	echo "${GCC_SRC_URI}"
 }
 
@@ -407,6 +423,26 @@
 	else
 		gcc_quick_unpack
 	fi
+
+	# Unpack the Ada bootstrap if we're using it.
+	if in_iuse ada && ! type -P gnatbind > /dev/null; then
+		mkdir -p "${WORKDIR}/gnat_bootstrap" || die "Couldn't make GNAT bootstrap directory"
+		pushd "${WORKDIR}/gnat_bootstrap" > /dev/null || die
+
+		case $(tc-arch) in
+			amd64)
+				unpack gnatboot-${GNAT_BOOTSTRAP_VERSION}-amd64.tar.xz || die "Failed to unpack AMD64 GNAT bootstrap compiler"
+				;;
+			x86)
+				unpack gnatboot-${GNAT_BOOTSTRAP_VERSION}-i686.tar.xz || die "Failed to unpack x86 GNAT bootstrap compiler"
+				;;
+			arm)
+				unpack gnatboot-${GNAT_BOOTSTRAP_VERSION}-arm.tar.xz || die "Failed to unpack ARM GNAT bootstrap compiler"
+				;;
+		esac
+
+		popd > /dev/null || die
+	fi
 }
 
 gcc_quick_unpack() {
@@ -827,6 +863,27 @@
 	fi
 	[[ -n ${CBUILD} ]] && confgcc+=( --build=${CBUILD} )
 
+	# Add variables we need to make the build find the bootstrap compiler.
+	# We only want to use the bootstrap compiler for stage 1 of bootstrap, this will build the necessary compilers,
+	# then stage 2 uses these compilers.
+	#
+	# We only want to use the bootstrap when we don't have an already installed GNAT compiler.
+	if in_iuse ada && [[ -d ${WORKDIR}/gnat_bootstrap ]] ; then
+		# We need to tell the system about our cross compiler!
+		export GNATBOOT="${WORKDIR}/gnat_bootstrap/usr"
+		export PATH="${GNATBOOT}/bin:${PATH}"
+
+		confgcc+=(
+			CC=${GNATBOOT}/bin/gnatgcc
+			CXX=${GNATBOOT}/bin/gnatg++
+			AR=${GNATBOOT}/bin/gcc-ar
+			AS=as
+			LD=ld
+			NM=${GNATBOOT}/bin/gcc-nm
+			RANLIB=${GNATBOOT}/bin/gcc-ranlib
+		)
+	fi
+
 	confgcc+=(
 		--prefix="${PREFIX}"
 		--bindir="${BINPATH}"
@@ -873,8 +930,8 @@
 	is_f77 && GCC_LANG+=",f77"
 	is_f95 && GCC_LANG+=",f95"
 
-	# We do NOT want 'ADA support' in here!
-	# is_ada && GCC_LANG+=",ada"
+	# We DO want 'Ada support' in here!
+	is_ada && GCC_LANG+=",ada"
 
 	confgcc+=( --enable-languages=${GCC_LANG} )
 
@@ -1696,7 +1753,11 @@
 	cd "${D}"${BINPATH}
 	# Ugh: we really need to auto-detect this list.
 	#      It's constantly out of date.
-	for x in cpp gcc g++ c++ gcov g77 gcj gcjh gfortran gccgo ; do
+	if in_iuse ada ; then
+		local gnat_extra_bins="gnat gnatbind gnatchop gnatclean gnatfind gnatkr gnatlink gnatls gnatmake gnatname gnatprep gnatxref"
+	fi
+
+	for x in cpp gcc g++ c++ gcov g77 gcj gcjh gfortran gccgo ${gnat_extra_bins} ; do
 		# For some reason, g77 gets made instead of ${CTARGET}-g77...
 		# this should take care of that
 		if [[ -f ${x} ]] ; then