toolchain.eclass: build JIT variant separately to avoid slowdown

It's what GCC upstream recommend to avoid slowing down the main GCC
binaries which need to be built w/ -fPIC for JIT.

We build twice but do an extremely minimal build for the JIT part
which is rather quick. Install the JIT version first, then the main GCC
variant, so the overlapping binaries come from the main build => more featureful,
correct build options/needed ones for a full GCC build, etc.

Closes: https://bugs.gentoo.org/843341
Signed-off-by: Sam James <sam@gentoo.org>

1 files changed, 65 insertions, 14 deletions

diff --git a/eclass/toolchain.eclass b/eclass/toolchain.eclass
index 69d674f46b64..cc601995f1f9 100644
--- a/eclass/toolchain.eclass
+++ b/eclass/toolchain.eclass
@@ -19,7 +19,7 @@ _TOOLCHAIN_ECLASS=1
 DESCRIPTION="The GNU Compiler Collection"
 HOMEPAGE="https://gcc.gnu.org/"
 
-inherit flag-o-matic gnuconfig libtool multilib pax-utils toolchain-funcs prefix
+inherit edo flag-o-matic gnuconfig libtool multilib pax-utils toolchain-funcs prefix
 
 tc_is_live() {
 	[[ ${PV} == *9999* ]]
@@ -851,7 +851,6 @@ toolchain_src_configure() {
 	is_d   && GCC_LANG+=",d"
 	is_gcj && GCC_LANG+=",java"
 	is_go  && GCC_LANG+=",go"
-	is_jit && GCC_LANG+=",jit"
 	if is_objc || is_objcxx ; then
 		GCC_LANG+=",objc"
 		use objc-gc && confgcc+=( --enable-objc-gc )
@@ -922,10 +921,6 @@ toolchain_src_configure() {
 		confgcc+=( --disable-libstdcxx-pch )
 	fi
 
-	# The JIT support requires this.
-	# But see bug #843341.
-	is_jit && confgcc+=( --enable-host-shared )
-
 	# build-id was disabled for file collisions: bug #526144
 	#
 	# # Turn on the -Wl,--build-id flag by default for ELF targets. bug #525942
@@ -1337,17 +1332,35 @@ toolchain_src_configure() {
 	echo
 
 	# Build in a separate build tree
-	mkdir -p "${WORKDIR}"/build
+	mkdir -p "${WORKDIR}"/build || die
 	pushd "${WORKDIR}"/build > /dev/null
 
 	# ...and now to do the actual configuration
 	addwrite /dev/zero
 
-	echo "${S}"/configure "${confgcc[@]}"
+	if is_jit ; then
+		einfo "Configuring JIT gcc"
+
+		mkdir -p "${WORKDIR}"/build-jit || die
+		pushd "${WORKDIR}"/build-jit > /dev/null || die
+		CONFIG_SHELL="${BROOT}"/bin/bash edo "${S}"/configure \
+				"${confgcc[@]}" \
+				--disable-libada \
+				--disable-libsanitizer \
+				--disable-libvtv \
+				--disable-libgomp \
+				--disable-libquadmath \
+				--disable-libatomic \
+				--disable-lto \
+				--disable-bootstrap \
+				--enable-host-shared \
+				--enable-languages=jit
+		popd > /dev/null || die
+	fi
+
 	# Older gcc versions did not detect bash and re-exec itself, so force the
 	# use of bash. Newer ones will auto-detect, but this is not harmful.
-	CONFIG_SHELL="${BROOT}/bin/bash" \
-		"${BROOT}"/bin/bash "${S}"/configure "${confgcc[@]}" || die "failed to run configure"
+	CONFIG_SHELL="${BROOT}"/bin/bash edo "${S}"/configure "${confgcc[@]}"
 
 	# Return to whatever directory we were in before
 	popd > /dev/null
@@ -1640,8 +1653,8 @@ gcc_do_make() {
 
 	# default target
 	if is_crosscompile || tc-is-cross-compiler ; then
-		# 3 stage bootstrapping doesnt quite work when you cant run the
-		# resulting binaries natively ^^;
+		# 3 stage bootstrapping doesn't quite work when you can't run the
+		# resulting binaries natively
 		GCC_MAKE_TARGET=${GCC_MAKE_TARGET-all}
 	else
 		if _tc_use_if_iuse pgo; then
@@ -1719,6 +1732,19 @@ gcc_do_make() {
 		fi
 	fi
 
+	if is_jit ; then
+		# TODO: docs for jit?
+		pushd "${WORKDIR}"/build-jit > /dev/null || die
+
+		einfo "Building JIT"
+		emake \
+			LDFLAGS="${LDFLAGS}" \
+			STAGE1_CFLAGS="${STAGE1_CFLAGS}" \
+			LIBPATH="${LIBPATH}" \
+			BOOT_CFLAGS="${BOOT_CFLAGS}"
+		popd > /dev/null || die
+	fi
+
 	popd >/dev/null
 }
 
@@ -1762,8 +1788,32 @@ toolchain_src_install() {
 			&& rm -f "${x}"
 	done < <(find gcc/include*/ -name '*.h')
 
+	if is_jit ; then
+		# See https://gcc.gnu.org/onlinedocs/gcc-11.3.0/jit/internals/index.html#packaging-notes
+		# and bug #843341.
+		#
+		# Both of the non-JIT and JIT builds  are configured to install to $(DESTDIR)
+		# Install the configuration with --enable-host-shared first
+		# *then* the one without, so that the faster build
+		# of "cc1" et al overwrites the slower build.
+		#
+		# Do the 'make install' from the build directory
+		pushd "${WORKDIR}"/build-jit > /dev/null || die
+		S="${WORKDIR}"/build-jit emake DESTDIR="${D}" install
+
+		# Punt some tools which are really only useful while building gcc
+		find "${ED}" -name install-tools -prune -type d -exec rm -rf "{}" \;
+		# This one comes with binutils
+		find "${ED}" -name libiberty.a -delete
+
+		# Move the libraries to the proper location
+		gcc_movelibs
+
+		popd > /dev/null || die
+	fi
+
 	# Do the 'make install' from the build directory
-	S="${WORKDIR}"/build emake DESTDIR="${D}" install || die
+	S="${WORKDIR}"/build emake DESTDIR="${D}" install
 
 	# Punt some tools which are really only useful while building gcc
 	find "${ED}" -name install-tools -prune -type d -exec rm -rf "{}" \;
@@ -1956,9 +2006,10 @@ gcc_movelibs() {
 		dodir "${HOSTLIBPATH#${EPREFIX}}"
 		mv "${ED}"/usr/$(get_libdir)/libcc1* "${D}${HOSTLIBPATH}" || die
 	fi
+
 	# libgccjit gets installed to /usr/lib, not /usr/$(get_libdir). Probably
 	# due to a bug in gcc build system.
-	if is_jit ; then
+	if [[ ${PWD} == "${WORKDIR}"/build-jit ]] && is_jit ; then
 		dodir "${LIBPATH#${EPREFIX}}"
 		mv "${ED}"/usr/lib/libgccjit* "${D}${LIBPATH}" || die
 	fi