toolchain.eclass: rework bootstrapping logic

* Build stage1 compiler with user's CFLAGS. This consistently ends up
  saving at least 15 minutes for me on a fast amd64 machine and should save
  more on slower machines and architectures.

  There's only any risk here if the host compiler is ancient/very buggy and
  even then, you get a failed bootstrap later on. The GCC developers, per the
  linked bug, end up using STAGE1_CFLAGS="-O2" anyway to speed up the process
  so it's not like this is untested at all.

  mattst88 actually brought this up.. 10 years ago (bug #477548). Let's try
  make that right now.

* Respect LDFLAGS for target libraries for native builds. Not touching this
  for cross builds, at least for now, as it's a bit more delicate.

  (Unfortunately, we have to put a hack in here for now until we can fix
  multilib.eclass - see bug #914881).

Bug: https://gcc.gnu.org/PR111619
Bug: https://bugs.gentoo.org/914881
Closes: https://bugs.gentoo.org/477548
Closes: https://bugs.gentoo.org/831423
Closes: https://bugs.gentoo.org/840392
Apologies-to: Matt Turner <mattst88@gentoo.org>
Signed-off-by: Sam James <sam@gentoo.org>

1 files changed, 35 insertions, 17 deletions

diff --git a/eclass/toolchain.eclass b/eclass/toolchain.eclass
index d93068619cf9..a145e74d5521 100644
--- a/eclass/toolchain.eclass
+++ b/eclass/toolchain.eclass
@@ -1647,19 +1647,48 @@ gcc_do_make() {
 		fi
 	fi
 
-	if [[ ${GCC_MAKE_TARGET} == "all" ]] ; then
-		STAGE1_CFLAGS=${STAGE1_CFLAGS-"${CFLAGS}"}
-	fi
+	local emakeargs=(
+		LDFLAGS="${LDFLAGS}"
+		LIBPATH="${LIBPATH}"
+	)
 
 	if is_crosscompile; then
 		# In 3.4, BOOT_CFLAGS is never used on a crosscompile...
 		# but I'll leave this in anyways as someone might have had
 		# some reason for putting it in here... --eradicator
 		BOOT_CFLAGS=${BOOT_CFLAGS-"-O2"}
+		emakeargs+=( BOOT_CFLAGS="${BOOT_CFLAGS}" )
 	else
-		# we only want to use the system's CFLAGS if not building a
+		# XXX: Hack for bug #914881, clean this up when fixed and go back
+		# to just calling get_abi_LDFLAGS as before.
+		local abi_ldflags="$(get_abi_LDFLAGS ${TARGET_DEFAULT_ABI})"
+		printf -v abi_ldflags -- "-Wl,%s " ${abi_ldflags}
+
+		# If the host compiler is too old, let's use -O0 per the upstream
+		# default to be safe (to avoid a bootstrap comparison failure later).
+		#
+		# The last known issues are with < GCC 4.9 or so, but it's easier
+		# to keep this bound somewhat fresh just to avoid problems. Ultimately,
+		# using not-O0 is just a build-time speed improvement anyway.
+		if tc-is-gcc && ver_test $(gcc-fullversion) -lt 10 ; then
+			STAGE1_CFLAGS="-O0"
+		fi
+
+		# We only want to use the system's CFLAGS if not building a
 		# cross-compiler.
+		STAGE1_CFLAGS=${STAGE1_CFLAGS-"$(get_abi_CFLAGS ${TARGET_DEFAULT_ABI}) ${CFLAGS}"}
+		STAGE1_LDFLAGS=${STAGE1_LDFLAGS-"${abi_ldflags} ${LDFLAGS}"}
 		BOOT_CFLAGS=${BOOT_CFLAGS-"$(get_abi_CFLAGS ${TARGET_DEFAULT_ABI}) ${CFLAGS}"}
+		BOOT_LDFLAGS=${BOOT_LDFLAGS-"${abi_ldflags} ${LDFLAGS}"}
+		LDFLAGS_FOR_TARGET="${LDFLAGS_FOR_TARGET:-${LDFLAGS}}"
+
+		emakeargs+=(
+			STAGE1_CFLAGS="${STAGE1_CFLAGS}"
+			STAGE1_LDFLAGS="${STAGE1_LDFLAGS}"
+			BOOT_CFLAGS="${BOOT_CFLAGS}"
+			BOOT_LDFLAGS="${BOOT_LDFLAGS}"
+			LDFLAGS_FOR_TARGET="${LDFLAGS_FOR_TARGET}"
+		)
 	fi
 
 	if is_jit ; then
@@ -1667,24 +1696,13 @@ gcc_do_make() {
 		pushd "${WORKDIR}"/build-jit > /dev/null || die
 
 		einfo "Building JIT"
-		emake \
-			LDFLAGS="${LDFLAGS}" \
-			STAGE1_CFLAGS="${STAGE1_CFLAGS}" \
-			LIBPATH="${LIBPATH}" \
-			BOOT_CFLAGS="${BOOT_CFLAGS}"
+		emake "${emakeargs[@]}"
 		popd > /dev/null || die
 	fi
 
 	einfo "Compiling ${PN} (${GCC_MAKE_TARGET})..."
-
 	pushd "${WORKDIR}"/build >/dev/null || die
-
-	emake \
-		LDFLAGS="${LDFLAGS}" \
-		STAGE1_CFLAGS="${STAGE1_CFLAGS}" \
-		LIBPATH="${LIBPATH}" \
-		BOOT_CFLAGS="${BOOT_CFLAGS}" \
-		${GCC_MAKE_TARGET}
+	emake "${emakeargs[@]}" ${GCC_MAKE_TARGET}
 
 	if is_ada; then
 		# Without these links, it is not getting the good compiler