7 files changed, 1247 insertions, 2 deletions

diff --git a/llvm-core/clang-common/Manifest b/llvm-core/clang-common/Manifest
index 508a179f4fc9..04bfb25ffdfc 100644
--- a/llvm-core/clang-common/Manifest
+++ b/llvm-core/clang-common/Manifest
@@ -11,3 +11,8 @@ DIST llvm-project-19.1.4.src.tar.xz.sig 438 BLAKE2B b0925bdb761046d69779e0b035e2
 DIST llvm-project-19.1.7.src.tar.xz 141249332 BLAKE2B 1259ed7f9aca7b35e89d818befdee20fd8bed4d2dc2c2c6f6f56451fd43d35ac03a0a5a406e142d22b25137999dc5b17471c196f8fcf79f20a8296832d900f6d SHA512 c7d63286d662707a9cd54758c9e3aaf52794a91900c484c4a6efa62d90bc719d5e7a345e4192feeb0c9fd11c82570d64677c781e5be1d645556b6aa018e47ec8
 DIST llvm-project-19.1.7.src.tar.xz.sig 438 BLAKE2B 4015140f4ba77de45039bdbdfbaf6f30e75705123d067ea97175d91d7a5b6a75008df01d99ae7aa16aaa3b101f3f41e38d01f04158f95a261d617b3ede0254cd SHA512 195797b06ac80a742e0ccbc03a50dc06dd2e04377d783d5474e3e72c5a75203b60292b047929312a411d22b137a239943fba414a4d136a2be14cbff978eb6bda
 DIST llvm-project-1f26ac10ca1bef40a80be8f81a6f109713bc586f.tar.gz 226424755 BLAKE2B 642befb8d6923f335d1d68129ebb7357f8ba22e110df494dd956c8097e4e5db4b2a88fcc069ab67184b03558f072c68e002bdaf90eba865e38b1473a0ef29eed SHA512 e9bb4fd31bbad5ec864c662515b5ec2e5511cce975040f9f3cd8f009c92f76077928feae0467fd9519a001a379c857f7539c506953d8d5a9209a9f358f414aac
+DIST llvm-project-20.1.0-rc1.src.tar.xz 147144668 BLAKE2B ea4733962f38ea5897c73e91840818921739909c3671749bc8a0b1d2798e5a0815bbe750ade3a2a7414836ab7158754818b2f9370a4ee1bbbd52c96b1e95ef9b SHA512 c23c4b1227b6b0b7c3059358e64a00ee98893236bb1a0a41d7e821bdf2aa8353aea8f9f7b9498899c6807b9b8e2ceb06c3cd62e32fd07a786a319135055541b4
+DIST llvm-project-20.1.0-rc1.src.tar.xz.sig 566 BLAKE2B 32eb278ec4ff1bb9d258b584922b0d227f4126a957ba75af44dcaa63b6a12ef73db56d6a86f24244af47803ddf6a243149d784f08137cbea60b49700be537705 SHA512 d7a334326201f8ca78284b33c325f180538667a0401bc30931e790aacc96dd78f6559c45929b6c335d40ef1dbe772738c0ce55d881ae3d7401733778b485408c
+DIST llvm-project-2cd8207b26ea4269630feba661f68554d7ae3c15.tar.gz 227261597 BLAKE2B 51ce992b651fcf08b7fd520420040803b59f1260947953325400c50bec576c418b162d8ae2d2307e70b885b1185c302a97409bcfe48cdb14b8e1384f4e2dfa9e SHA512 a41749943508ea4a18b47c4e947917b5268544e64372c0c3347f9ab8172a2c229d8b1d813d1e842be1b98aedd624524857ed3bb23fe98ad5f36e7a71581abb4b
+DIST llvm-project-6f241e36831927e3aea113cfc017c34fdeda340a.tar.gz 227203285 BLAKE2B 8d5e424c1836acc82ea766cd2cef104593c44d197ebeb64f18dbe74b1b5baeb4bc84084f5b68bd87ac36f7df25689dd2522cb6674a97da4f96f4f10f7bae5b06 SHA512 2b6e4bd6445eabfa3ace9b45d20797c7afc23f4553a8938399aeba227e3b8ca6a53a7d7762925a845bfed031c37af692b9c08180fbab80db2f3166940e560077
+DIST llvm-project-bfa7edcc6652bdb37d53e0cec64926aab3f280eb.tar.gz 226735989 BLAKE2B 165837dc526e618b44c49d5fa3dceda373452e010a09746bff248903fe77874637d05ab9f5d2f63de7ebce5c14e3b19a131313a4a557adfd20fe9cb93ab60476 SHA512 e9e19176fcf1302727ee34d69eaa820b94959d64ceaf754d8a93ebd5e262cec7fe35e87b08f705b09e42c3ea26b671318eecf10e9137c635b12f481f80fbac23
diff --git a/llvm-core/clang-common/clang-common-19.1.7.ebuild b/llvm-core/clang-common/clang-common-19.1.7.ebuild
index 1c56480336f7..73c6ae9644a5 100644
--- a/llvm-core/clang-common/clang-common-19.1.7.ebuild
+++ b/llvm-core/clang-common/clang-common-19.1.7.ebuild
@@ -10,7 +10,7 @@ HOMEPAGE="https://llvm.org/"
 
 LICENSE="Apache-2.0-with-LLVM-exceptions UoI-NCSA"
 SLOT="0"
-KEYWORDS="~amd64 ~arm ~arm64 ~loong ~mips ~ppc ~ppc64 ~riscv ~sparc ~x86 ~amd64-linux ~arm64-macos ~ppc-macos ~x64-macos"
+KEYWORDS="amd64 ~arm arm64 ~loong ~mips ~ppc ~ppc64 ~riscv ~sparc x86 ~amd64-linux ~arm64-macos ~ppc-macos ~x64-macos"
 IUSE="
 	default-compiler-rt default-libcxx default-lld
 	bootstrap-prefix cet hardened llvm-libunwind
diff --git a/llvm-core/clang-common/clang-common-20.0.0.9999.ebuild b/llvm-core/clang-common/clang-common-20.1.0_rc1.ebuild
index 8e66cf2865d9..1fde60b6b6de 100644
--- a/llvm-core/clang-common/clang-common-20.0.0.9999.ebuild
+++ b/llvm-core/clang-common/clang-common-20.1.0_rc1.ebuild
@@ -1,4 +1,4 @@
-# Copyright 1999-2024 Gentoo Authors
+# Copyright 1999-2025 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=8
diff --git a/llvm-core/clang-common/clang-common-21.0.0.9999.ebuild b/llvm-core/clang-common/clang-common-21.0.0.9999.ebuild
new file mode 100644
index 000000000000..1fde60b6b6de
--- /dev/null
+++ b/llvm-core/clang-common/clang-common-21.0.0.9999.ebuild
@@ -0,0 +1,310 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit bash-completion-r1 llvm.org multilib
+
+DESCRIPTION="Common files shared between multiple slots of clang"
+HOMEPAGE="https://llvm.org/"
+
+LICENSE="Apache-2.0-with-LLVM-exceptions UoI-NCSA"
+SLOT="0"
+IUSE="
+	default-compiler-rt default-libcxx default-lld
+	bootstrap-prefix cet hardened llvm-libunwind
+"
+
+PDEPEND="
+	default-compiler-rt? (
+		llvm-core/clang-runtime:${LLVM_MAJOR}[compiler-rt]
+		llvm-libunwind? ( llvm-runtimes/libunwind[static-libs] )
+		!llvm-libunwind? ( sys-libs/libunwind[static-libs] )
+	)
+	!default-compiler-rt? ( sys-devel/gcc )
+	default-libcxx? ( >=llvm-runtimes/libcxx-${PV}[static-libs] )
+	!default-libcxx? ( sys-devel/gcc )
+	default-lld? ( >=llvm-core/lld-${PV} )
+	!default-lld? ( sys-devel/binutils )
+"
+IDEPEND="
+	!default-compiler-rt? ( sys-devel/gcc-config )
+	!default-libcxx? ( sys-devel/gcc-config )
+"
+
+LLVM_COMPONENTS=( clang/utils )
+llvm.org_set_globals
+
+pkg_pretend() {
+	[[ ${CLANG_IGNORE_DEFAULT_RUNTIMES} ]] && return
+
+	local flag missing_flags=()
+	for flag in default-{compiler-rt,libcxx,lld}; do
+		if ! use "${flag}" && has_version "llvm-core/clang[${flag}]"; then
+			missing_flags+=( "${flag}" )
+		fi
+	done
+
+	if [[ ${missing_flags[@]} ]]; then
+		eerror "It seems that you have the following flags set on llvm-core/clang:"
+		eerror
+		eerror "  ${missing_flags[*]}"
+		eerror
+		eerror "The default runtimes are now set via flags on llvm-core/clang-common."
+		eerror "The build is being aborted to prevent breakage.  Please either set"
+		eerror "the respective flags on this ebuild, e.g.:"
+		eerror
+		eerror "  llvm-core/clang-common ${missing_flags[*]}"
+		eerror
+		eerror "or build with CLANG_IGNORE_DEFAULT_RUNTIMES=1."
+		die "Mismatched defaults detected between llvm-core/clang and llvm-core/clang-common"
+	fi
+}
+
+_doclang_cfg() {
+	local triple="${1}"
+
+	local tool
+	for tool in ${triple}-clang{,++}; do
+		newins - "${tool}.cfg" <<-EOF
+			# This configuration file is used by ${tool} driver.
+			@gentoo-common.cfg
+			@gentoo-common-ld.cfg
+		EOF
+		if [[ ${triple} == x86_64* ]]; then
+			cat >> "${ED}/etc/clang/${tool}.cfg" <<-EOF || die
+				@gentoo-cet.cfg
+			EOF
+		fi
+	done
+
+	if use kernel_Darwin; then
+		cat >> "${ED}/etc/clang/${triple}-clang++.cfg" <<-EOF || die
+			-lc++abi
+		EOF
+	fi
+
+	newins - "${triple}-clang-cpp.cfg" <<-EOF
+		# This configuration file is used by the ${triple}-clang-cpp driver.
+		@gentoo-common.cfg
+	EOF
+	if [[ ${triple} == x86_64* ]]; then
+		cat >> "${ED}/etc/clang/${triple}-clang-cpp.cfg" <<-EOF || die
+			@gentoo-cet.cfg
+		EOF
+	fi
+
+	# Install symlinks for triples with other vendor strings since some
+	# programs insist on mangling the triple.
+	local vendor
+	for vendor in gentoo pc unknown; do
+		local vendor_triple="${triple%%-*}-${vendor}-${triple#*-*-}"
+		for tool in clang{,++,-cpp}; do
+			if [[ ! -f "${ED}/etc/clang/${vendor_triple}-${tool}.cfg" ]]; then
+				dosym "${triple}-${tool}.cfg" "/etc/clang/${vendor_triple}-${tool}.cfg"
+			fi
+		done
+	done
+}
+
+doclang_cfg() {
+	local triple="${1}"
+
+	_doclang_cfg ${triple}
+
+	# LLVM may have different arch names in some cases. For example in x86
+	# profiles the triple uses i686, but llvm will prefer i386 if invoked
+	# with "clang" on x86 or "clang -m32" on x86_64. The gentoo triple will
+	# be used if invoked through ${CHOST}-clang{,++,-cpp} though.
+	#
+	# To make sure the correct triples are installed,
+	# see Triple::getArchTypeName() in llvm/lib/TargetParser/Triple.cpp
+	# and compare with CHOST values in profiles.
+
+	local abi=${triple%%-*}
+	case ${abi} in
+		armv4l|armv4t|armv5tel|armv6j|armv7a)
+			_doclang_cfg ${triple/${abi}/arm}
+			;;
+		i686)
+			_doclang_cfg ${triple/${abi}/i386}
+			;;
+		sparc)
+			_doclang_cfg ${triple/${abi}/sparcel}
+			;;
+		sparc64)
+			_doclang_cfg ${triple/${abi}/sparcv9}
+			;;
+	esac
+}
+
+src_install() {
+	newbashcomp bash-autocomplete.sh clang
+
+	insinto /etc/clang
+	newins - gentoo-runtimes.cfg <<-EOF
+		# This file is initially generated by llvm-core/clang-runtime.
+		# It is used to control the default runtimes using by clang.
+
+		--rtlib=$(usex default-compiler-rt compiler-rt libgcc)
+		--unwindlib=$(usex default-compiler-rt libunwind libgcc)
+		--stdlib=$(usex default-libcxx libc++ libstdc++)
+		-fuse-ld=$(usex default-lld lld bfd)
+	EOF
+
+	newins - gentoo-gcc-install.cfg <<-EOF
+		# This file is maintained by gcc-config.
+		# It is used to specify the selected GCC installation.
+	EOF
+
+	newins - gentoo-common.cfg <<-EOF
+		# This file contains flags common to clang, clang++ and clang-cpp.
+		@gentoo-runtimes.cfg
+		@gentoo-gcc-install.cfg
+		@gentoo-hardened.cfg
+		# bug #870001
+		-include "${EPREFIX}/usr/include/gentoo/maybe-stddefs.h"
+	EOF
+
+	# clang-cpp does not like link args being passed to it when directly
+	# invoked, so use a separate configuration file.
+	newins - gentoo-common-ld.cfg <<-EOF
+		# This file contains flags common to clang and clang++
+		@gentoo-hardened-ld.cfg
+	EOF
+
+	# Baseline hardening (bug #851111)
+	newins - gentoo-hardened.cfg <<-EOF
+		# Some of these options are added unconditionally, regardless of
+		# USE=hardened, for parity with sys-devel/gcc.
+		-Xarch_host -fstack-clash-protection
+		-Xarch_host -fstack-protector-strong
+		-fPIE
+		-include "${EPREFIX}/usr/include/gentoo/fortify.h"
+	EOF
+
+	newins - gentoo-cet.cfg <<-EOF
+		-Xarch_host -fcf-protection=$(usex cet full none)
+	EOF
+
+	if use kernel_Darwin; then
+		newins - gentoo-hardened-ld.cfg <<-EOF
+			# There was -Wl,-z,relro here, but it's not supported on Mac
+			# TODO: investigate whether -bind_at_load or -read_only_stubs will do the job
+		EOF
+	else
+		newins - gentoo-hardened-ld.cfg <<-EOF
+			# Some of these options are added unconditionally, regardless of
+			# USE=hardened, for parity with sys-devel/gcc.
+			-Wl,-z,relro
+			-Wl,-z,now
+		EOF
+	fi
+
+	dodir /usr/include/gentoo
+
+	cat >> "${ED}/usr/include/gentoo/maybe-stddefs.h" <<-EOF || die
+	/* __has_include is an extension, but it's fine, because this is only
+	for Clang anyway. */
+	#if defined __has_include && __has_include (<stdc-predef.h>) && !defined(__GLIBC__)
+	# include <stdc-predef.h>
+	#endif
+	EOF
+
+	local fortify_level=$(usex hardened 3 2)
+	# We have to do this because glibc's headers warn if F_S is set
+	# without optimization and that would at the very least be very noisy
+	# during builds and at worst trigger many -Werror builds.
+	cat >> "${ED}/usr/include/gentoo/fortify.h" <<- EOF || die
+	#ifdef __clang__
+	# pragma clang system_header
+	#endif
+	#ifndef _FORTIFY_SOURCE
+	# if defined(__has_feature)
+	#  define __GENTOO_HAS_FEATURE(x) __has_feature(x)
+	# else
+	#  define __GENTOO_HAS_FEATURE(x) 0
+	# endif
+	#
+	# if !defined(__OPTIMIZE__) || __OPTIMIZE__ == 0
+	# elif !defined(__STDC_HOSTED__) || __STDC_HOSTED__ != 1
+	# elif defined(__SANITIZE_ADDRESS__)
+	# elif __GENTOO_HAS_FEATURE(address_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(hwaddress_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(memory_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(numerical_stability_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(realtime_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(thread_sanitizer)
+	# else
+	#  define _FORTIFY_SOURCE ${fortify_level}
+	# endif
+	#
+	# undef __GENTOO_HAS_FEATURE
+	#endif
+	EOF
+
+	# TODO: Maybe -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_FAST for
+	# non-hardened?
+	if use hardened ; then
+		cat >> "${ED}/etc/clang/gentoo-hardened.cfg" <<-EOF || die
+			# Options below are conditional on USE=hardened.
+			-Xarch_host -D_GLIBCXX_ASSERTIONS
+
+			# Analogue to GLIBCXX_ASSERTIONS
+			# https://libcxx.llvm.org/UsingLibcxx.html#assertions-mode
+			# https://libcxx.llvm.org/Hardening.html#using-hardened-mode
+			-Xarch_host -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE
+		EOF
+
+		cat >> "${ED}/etc/clang/gentoo-hardened-ld.cfg" <<-EOF || die
+			# Options below are conditional on USE=hardened.
+		EOF
+	fi
+
+	# We only install config files for supported ABIs because unprefixed tools
+	# might be used for crosscompilation where e.g. PIE may not be supported.
+	# See bug #912237 and bug #901247. Just ${CHOST} won't do due to bug #912685.
+	local abi
+	for abi in $(get_all_abis); do
+		local abi_chost=$(get_abi_CHOST "${abi}")
+		doclang_cfg "${abi_chost}"
+	done
+
+	if use kernel_Darwin; then
+		cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+			# Gentoo Prefix on Darwin
+			-Wl,-search_paths_first
+		EOF
+		if use bootstrap-prefix ; then
+			# bootstrap-prefix is only set during stage2 of bootstrapping
+			# Prefix, where EPREFIX is set to EPREFIX/tmp.
+			# Here we need to point it at the future lib dir of the stage3's
+			# EPREFIX.
+			cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+				-Wl,-rpath,${EPREFIX}/../usr/lib
+				-Wl,-L,${EPREFIX}/../usr/lib
+				-isystem ${EPREFIX}/../usr/include
+			EOF
+		fi
+		# Using -Wl,-L instead of -L to trick compiler driver to put it
+		# after -isysroot's internal -L
+		cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+			-Wl,-rpath,${EPREFIX}/usr/lib
+			-Wl,-L,${EPREFIX}/usr/lib
+			-isystem ${EPREFIX}/usr/include
+			-isysroot ${EPREFIX}/MacOSX.sdk
+		EOF
+	fi
+}
+
+pkg_preinst() {
+	if has_version -b sys-devel/gcc-config && has_version sys-devel/gcc
+	then
+		local gcc_path=$(gcc-config --get-lib-path 2>/dev/null)
+		if [[ -n ${gcc_path} ]]; then
+			cat >> "${ED}/etc/clang/gentoo-gcc-install.cfg" <<-EOF
+				--gcc-install-dir="${gcc_path%%:*}"
+			EOF
+		fi
+	fi
+}
diff --git a/llvm-core/clang-common/clang-common-21.0.0_pre20250201.ebuild b/llvm-core/clang-common/clang-common-21.0.0_pre20250201.ebuild
new file mode 100644
index 000000000000..1fde60b6b6de
--- /dev/null
+++ b/llvm-core/clang-common/clang-common-21.0.0_pre20250201.ebuild
@@ -0,0 +1,310 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit bash-completion-r1 llvm.org multilib
+
+DESCRIPTION="Common files shared between multiple slots of clang"
+HOMEPAGE="https://llvm.org/"
+
+LICENSE="Apache-2.0-with-LLVM-exceptions UoI-NCSA"
+SLOT="0"
+IUSE="
+	default-compiler-rt default-libcxx default-lld
+	bootstrap-prefix cet hardened llvm-libunwind
+"
+
+PDEPEND="
+	default-compiler-rt? (
+		llvm-core/clang-runtime:${LLVM_MAJOR}[compiler-rt]
+		llvm-libunwind? ( llvm-runtimes/libunwind[static-libs] )
+		!llvm-libunwind? ( sys-libs/libunwind[static-libs] )
+	)
+	!default-compiler-rt? ( sys-devel/gcc )
+	default-libcxx? ( >=llvm-runtimes/libcxx-${PV}[static-libs] )
+	!default-libcxx? ( sys-devel/gcc )
+	default-lld? ( >=llvm-core/lld-${PV} )
+	!default-lld? ( sys-devel/binutils )
+"
+IDEPEND="
+	!default-compiler-rt? ( sys-devel/gcc-config )
+	!default-libcxx? ( sys-devel/gcc-config )
+"
+
+LLVM_COMPONENTS=( clang/utils )
+llvm.org_set_globals
+
+pkg_pretend() {
+	[[ ${CLANG_IGNORE_DEFAULT_RUNTIMES} ]] && return
+
+	local flag missing_flags=()
+	for flag in default-{compiler-rt,libcxx,lld}; do
+		if ! use "${flag}" && has_version "llvm-core/clang[${flag}]"; then
+			missing_flags+=( "${flag}" )
+		fi
+	done
+
+	if [[ ${missing_flags[@]} ]]; then
+		eerror "It seems that you have the following flags set on llvm-core/clang:"
+		eerror
+		eerror "  ${missing_flags[*]}"
+		eerror
+		eerror "The default runtimes are now set via flags on llvm-core/clang-common."
+		eerror "The build is being aborted to prevent breakage.  Please either set"
+		eerror "the respective flags on this ebuild, e.g.:"
+		eerror
+		eerror "  llvm-core/clang-common ${missing_flags[*]}"
+		eerror
+		eerror "or build with CLANG_IGNORE_DEFAULT_RUNTIMES=1."
+		die "Mismatched defaults detected between llvm-core/clang and llvm-core/clang-common"
+	fi
+}
+
+_doclang_cfg() {
+	local triple="${1}"
+
+	local tool
+	for tool in ${triple}-clang{,++}; do
+		newins - "${tool}.cfg" <<-EOF
+			# This configuration file is used by ${tool} driver.
+			@gentoo-common.cfg
+			@gentoo-common-ld.cfg
+		EOF
+		if [[ ${triple} == x86_64* ]]; then
+			cat >> "${ED}/etc/clang/${tool}.cfg" <<-EOF || die
+				@gentoo-cet.cfg
+			EOF
+		fi
+	done
+
+	if use kernel_Darwin; then
+		cat >> "${ED}/etc/clang/${triple}-clang++.cfg" <<-EOF || die
+			-lc++abi
+		EOF
+	fi
+
+	newins - "${triple}-clang-cpp.cfg" <<-EOF
+		# This configuration file is used by the ${triple}-clang-cpp driver.
+		@gentoo-common.cfg
+	EOF
+	if [[ ${triple} == x86_64* ]]; then
+		cat >> "${ED}/etc/clang/${triple}-clang-cpp.cfg" <<-EOF || die
+			@gentoo-cet.cfg
+		EOF
+	fi
+
+	# Install symlinks for triples with other vendor strings since some
+	# programs insist on mangling the triple.
+	local vendor
+	for vendor in gentoo pc unknown; do
+		local vendor_triple="${triple%%-*}-${vendor}-${triple#*-*-}"
+		for tool in clang{,++,-cpp}; do
+			if [[ ! -f "${ED}/etc/clang/${vendor_triple}-${tool}.cfg" ]]; then
+				dosym "${triple}-${tool}.cfg" "/etc/clang/${vendor_triple}-${tool}.cfg"
+			fi
+		done
+	done
+}
+
+doclang_cfg() {
+	local triple="${1}"
+
+	_doclang_cfg ${triple}
+
+	# LLVM may have different arch names in some cases. For example in x86
+	# profiles the triple uses i686, but llvm will prefer i386 if invoked
+	# with "clang" on x86 or "clang -m32" on x86_64. The gentoo triple will
+	# be used if invoked through ${CHOST}-clang{,++,-cpp} though.
+	#
+	# To make sure the correct triples are installed,
+	# see Triple::getArchTypeName() in llvm/lib/TargetParser/Triple.cpp
+	# and compare with CHOST values in profiles.
+
+	local abi=${triple%%-*}
+	case ${abi} in
+		armv4l|armv4t|armv5tel|armv6j|armv7a)
+			_doclang_cfg ${triple/${abi}/arm}
+			;;
+		i686)
+			_doclang_cfg ${triple/${abi}/i386}
+			;;
+		sparc)
+			_doclang_cfg ${triple/${abi}/sparcel}
+			;;
+		sparc64)
+			_doclang_cfg ${triple/${abi}/sparcv9}
+			;;
+	esac
+}
+
+src_install() {
+	newbashcomp bash-autocomplete.sh clang
+
+	insinto /etc/clang
+	newins - gentoo-runtimes.cfg <<-EOF
+		# This file is initially generated by llvm-core/clang-runtime.
+		# It is used to control the default runtimes using by clang.
+
+		--rtlib=$(usex default-compiler-rt compiler-rt libgcc)
+		--unwindlib=$(usex default-compiler-rt libunwind libgcc)
+		--stdlib=$(usex default-libcxx libc++ libstdc++)
+		-fuse-ld=$(usex default-lld lld bfd)
+	EOF
+
+	newins - gentoo-gcc-install.cfg <<-EOF
+		# This file is maintained by gcc-config.
+		# It is used to specify the selected GCC installation.
+	EOF
+
+	newins - gentoo-common.cfg <<-EOF
+		# This file contains flags common to clang, clang++ and clang-cpp.
+		@gentoo-runtimes.cfg
+		@gentoo-gcc-install.cfg
+		@gentoo-hardened.cfg
+		# bug #870001
+		-include "${EPREFIX}/usr/include/gentoo/maybe-stddefs.h"
+	EOF
+
+	# clang-cpp does not like link args being passed to it when directly
+	# invoked, so use a separate configuration file.
+	newins - gentoo-common-ld.cfg <<-EOF
+		# This file contains flags common to clang and clang++
+		@gentoo-hardened-ld.cfg
+	EOF
+
+	# Baseline hardening (bug #851111)
+	newins - gentoo-hardened.cfg <<-EOF
+		# Some of these options are added unconditionally, regardless of
+		# USE=hardened, for parity with sys-devel/gcc.
+		-Xarch_host -fstack-clash-protection
+		-Xarch_host -fstack-protector-strong
+		-fPIE
+		-include "${EPREFIX}/usr/include/gentoo/fortify.h"
+	EOF
+
+	newins - gentoo-cet.cfg <<-EOF
+		-Xarch_host -fcf-protection=$(usex cet full none)
+	EOF
+
+	if use kernel_Darwin; then
+		newins - gentoo-hardened-ld.cfg <<-EOF
+			# There was -Wl,-z,relro here, but it's not supported on Mac
+			# TODO: investigate whether -bind_at_load or -read_only_stubs will do the job
+		EOF
+	else
+		newins - gentoo-hardened-ld.cfg <<-EOF
+			# Some of these options are added unconditionally, regardless of
+			# USE=hardened, for parity with sys-devel/gcc.
+			-Wl,-z,relro
+			-Wl,-z,now
+		EOF
+	fi
+
+	dodir /usr/include/gentoo
+
+	cat >> "${ED}/usr/include/gentoo/maybe-stddefs.h" <<-EOF || die
+	/* __has_include is an extension, but it's fine, because this is only
+	for Clang anyway. */
+	#if defined __has_include && __has_include (<stdc-predef.h>) && !defined(__GLIBC__)
+	# include <stdc-predef.h>
+	#endif
+	EOF
+
+	local fortify_level=$(usex hardened 3 2)
+	# We have to do this because glibc's headers warn if F_S is set
+	# without optimization and that would at the very least be very noisy
+	# during builds and at worst trigger many -Werror builds.
+	cat >> "${ED}/usr/include/gentoo/fortify.h" <<- EOF || die
+	#ifdef __clang__
+	# pragma clang system_header
+	#endif
+	#ifndef _FORTIFY_SOURCE
+	# if defined(__has_feature)
+	#  define __GENTOO_HAS_FEATURE(x) __has_feature(x)
+	# else
+	#  define __GENTOO_HAS_FEATURE(x) 0
+	# endif
+	#
+	# if !defined(__OPTIMIZE__) || __OPTIMIZE__ == 0
+	# elif !defined(__STDC_HOSTED__) || __STDC_HOSTED__ != 1
+	# elif defined(__SANITIZE_ADDRESS__)
+	# elif __GENTOO_HAS_FEATURE(address_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(hwaddress_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(memory_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(numerical_stability_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(realtime_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(thread_sanitizer)
+	# else
+	#  define _FORTIFY_SOURCE ${fortify_level}
+	# endif
+	#
+	# undef __GENTOO_HAS_FEATURE
+	#endif
+	EOF
+
+	# TODO: Maybe -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_FAST for
+	# non-hardened?
+	if use hardened ; then
+		cat >> "${ED}/etc/clang/gentoo-hardened.cfg" <<-EOF || die
+			# Options below are conditional on USE=hardened.
+			-Xarch_host -D_GLIBCXX_ASSERTIONS
+
+			# Analogue to GLIBCXX_ASSERTIONS
+			# https://libcxx.llvm.org/UsingLibcxx.html#assertions-mode
+			# https://libcxx.llvm.org/Hardening.html#using-hardened-mode
+			-Xarch_host -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE
+		EOF
+
+		cat >> "${ED}/etc/clang/gentoo-hardened-ld.cfg" <<-EOF || die
+			# Options below are conditional on USE=hardened.
+		EOF
+	fi
+
+	# We only install config files for supported ABIs because unprefixed tools
+	# might be used for crosscompilation where e.g. PIE may not be supported.
+	# See bug #912237 and bug #901247. Just ${CHOST} won't do due to bug #912685.
+	local abi
+	for abi in $(get_all_abis); do
+		local abi_chost=$(get_abi_CHOST "${abi}")
+		doclang_cfg "${abi_chost}"
+	done
+
+	if use kernel_Darwin; then
+		cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+			# Gentoo Prefix on Darwin
+			-Wl,-search_paths_first
+		EOF
+		if use bootstrap-prefix ; then
+			# bootstrap-prefix is only set during stage2 of bootstrapping
+			# Prefix, where EPREFIX is set to EPREFIX/tmp.
+			# Here we need to point it at the future lib dir of the stage3's
+			# EPREFIX.
+			cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+				-Wl,-rpath,${EPREFIX}/../usr/lib
+				-Wl,-L,${EPREFIX}/../usr/lib
+				-isystem ${EPREFIX}/../usr/include
+			EOF
+		fi
+		# Using -Wl,-L instead of -L to trick compiler driver to put it
+		# after -isysroot's internal -L
+		cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+			-Wl,-rpath,${EPREFIX}/usr/lib
+			-Wl,-L,${EPREFIX}/usr/lib
+			-isystem ${EPREFIX}/usr/include
+			-isysroot ${EPREFIX}/MacOSX.sdk
+		EOF
+	fi
+}
+
+pkg_preinst() {
+	if has_version -b sys-devel/gcc-config && has_version sys-devel/gcc
+	then
+		local gcc_path=$(gcc-config --get-lib-path 2>/dev/null)
+		if [[ -n ${gcc_path} ]]; then
+			cat >> "${ED}/etc/clang/gentoo-gcc-install.cfg" <<-EOF
+				--gcc-install-dir="${gcc_path%%:*}"
+			EOF
+		fi
+	fi
+}
diff --git a/llvm-core/clang-common/clang-common-21.0.0_pre20250208.ebuild b/llvm-core/clang-common/clang-common-21.0.0_pre20250208.ebuild
new file mode 100644
index 000000000000..1fde60b6b6de
--- /dev/null
+++ b/llvm-core/clang-common/clang-common-21.0.0_pre20250208.ebuild
@@ -0,0 +1,310 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit bash-completion-r1 llvm.org multilib
+
+DESCRIPTION="Common files shared between multiple slots of clang"
+HOMEPAGE="https://llvm.org/"
+
+LICENSE="Apache-2.0-with-LLVM-exceptions UoI-NCSA"
+SLOT="0"
+IUSE="
+	default-compiler-rt default-libcxx default-lld
+	bootstrap-prefix cet hardened llvm-libunwind
+"
+
+PDEPEND="
+	default-compiler-rt? (
+		llvm-core/clang-runtime:${LLVM_MAJOR}[compiler-rt]
+		llvm-libunwind? ( llvm-runtimes/libunwind[static-libs] )
+		!llvm-libunwind? ( sys-libs/libunwind[static-libs] )
+	)
+	!default-compiler-rt? ( sys-devel/gcc )
+	default-libcxx? ( >=llvm-runtimes/libcxx-${PV}[static-libs] )
+	!default-libcxx? ( sys-devel/gcc )
+	default-lld? ( >=llvm-core/lld-${PV} )
+	!default-lld? ( sys-devel/binutils )
+"
+IDEPEND="
+	!default-compiler-rt? ( sys-devel/gcc-config )
+	!default-libcxx? ( sys-devel/gcc-config )
+"
+
+LLVM_COMPONENTS=( clang/utils )
+llvm.org_set_globals
+
+pkg_pretend() {
+	[[ ${CLANG_IGNORE_DEFAULT_RUNTIMES} ]] && return
+
+	local flag missing_flags=()
+	for flag in default-{compiler-rt,libcxx,lld}; do
+		if ! use "${flag}" && has_version "llvm-core/clang[${flag}]"; then
+			missing_flags+=( "${flag}" )
+		fi
+	done
+
+	if [[ ${missing_flags[@]} ]]; then
+		eerror "It seems that you have the following flags set on llvm-core/clang:"
+		eerror
+		eerror "  ${missing_flags[*]}"
+		eerror
+		eerror "The default runtimes are now set via flags on llvm-core/clang-common."
+		eerror "The build is being aborted to prevent breakage.  Please either set"
+		eerror "the respective flags on this ebuild, e.g.:"
+		eerror
+		eerror "  llvm-core/clang-common ${missing_flags[*]}"
+		eerror
+		eerror "or build with CLANG_IGNORE_DEFAULT_RUNTIMES=1."
+		die "Mismatched defaults detected between llvm-core/clang and llvm-core/clang-common"
+	fi
+}
+
+_doclang_cfg() {
+	local triple="${1}"
+
+	local tool
+	for tool in ${triple}-clang{,++}; do
+		newins - "${tool}.cfg" <<-EOF
+			# This configuration file is used by ${tool} driver.
+			@gentoo-common.cfg
+			@gentoo-common-ld.cfg
+		EOF
+		if [[ ${triple} == x86_64* ]]; then
+			cat >> "${ED}/etc/clang/${tool}.cfg" <<-EOF || die
+				@gentoo-cet.cfg
+			EOF
+		fi
+	done
+
+	if use kernel_Darwin; then
+		cat >> "${ED}/etc/clang/${triple}-clang++.cfg" <<-EOF || die
+			-lc++abi
+		EOF
+	fi
+
+	newins - "${triple}-clang-cpp.cfg" <<-EOF
+		# This configuration file is used by the ${triple}-clang-cpp driver.
+		@gentoo-common.cfg
+	EOF
+	if [[ ${triple} == x86_64* ]]; then
+		cat >> "${ED}/etc/clang/${triple}-clang-cpp.cfg" <<-EOF || die
+			@gentoo-cet.cfg
+		EOF
+	fi
+
+	# Install symlinks for triples with other vendor strings since some
+	# programs insist on mangling the triple.
+	local vendor
+	for vendor in gentoo pc unknown; do
+		local vendor_triple="${triple%%-*}-${vendor}-${triple#*-*-}"
+		for tool in clang{,++,-cpp}; do
+			if [[ ! -f "${ED}/etc/clang/${vendor_triple}-${tool}.cfg" ]]; then
+				dosym "${triple}-${tool}.cfg" "/etc/clang/${vendor_triple}-${tool}.cfg"
+			fi
+		done
+	done
+}
+
+doclang_cfg() {
+	local triple="${1}"
+
+	_doclang_cfg ${triple}
+
+	# LLVM may have different arch names in some cases. For example in x86
+	# profiles the triple uses i686, but llvm will prefer i386 if invoked
+	# with "clang" on x86 or "clang -m32" on x86_64. The gentoo triple will
+	# be used if invoked through ${CHOST}-clang{,++,-cpp} though.
+	#
+	# To make sure the correct triples are installed,
+	# see Triple::getArchTypeName() in llvm/lib/TargetParser/Triple.cpp
+	# and compare with CHOST values in profiles.
+
+	local abi=${triple%%-*}
+	case ${abi} in
+		armv4l|armv4t|armv5tel|armv6j|armv7a)
+			_doclang_cfg ${triple/${abi}/arm}
+			;;
+		i686)
+			_doclang_cfg ${triple/${abi}/i386}
+			;;
+		sparc)
+			_doclang_cfg ${triple/${abi}/sparcel}
+			;;
+		sparc64)
+			_doclang_cfg ${triple/${abi}/sparcv9}
+			;;
+	esac
+}
+
+src_install() {
+	newbashcomp bash-autocomplete.sh clang
+
+	insinto /etc/clang
+	newins - gentoo-runtimes.cfg <<-EOF
+		# This file is initially generated by llvm-core/clang-runtime.
+		# It is used to control the default runtimes using by clang.
+
+		--rtlib=$(usex default-compiler-rt compiler-rt libgcc)
+		--unwindlib=$(usex default-compiler-rt libunwind libgcc)
+		--stdlib=$(usex default-libcxx libc++ libstdc++)
+		-fuse-ld=$(usex default-lld lld bfd)
+	EOF
+
+	newins - gentoo-gcc-install.cfg <<-EOF
+		# This file is maintained by gcc-config.
+		# It is used to specify the selected GCC installation.
+	EOF
+
+	newins - gentoo-common.cfg <<-EOF
+		# This file contains flags common to clang, clang++ and clang-cpp.
+		@gentoo-runtimes.cfg
+		@gentoo-gcc-install.cfg
+		@gentoo-hardened.cfg
+		# bug #870001
+		-include "${EPREFIX}/usr/include/gentoo/maybe-stddefs.h"
+	EOF
+
+	# clang-cpp does not like link args being passed to it when directly
+	# invoked, so use a separate configuration file.
+	newins - gentoo-common-ld.cfg <<-EOF
+		# This file contains flags common to clang and clang++
+		@gentoo-hardened-ld.cfg
+	EOF
+
+	# Baseline hardening (bug #851111)
+	newins - gentoo-hardened.cfg <<-EOF
+		# Some of these options are added unconditionally, regardless of
+		# USE=hardened, for parity with sys-devel/gcc.
+		-Xarch_host -fstack-clash-protection
+		-Xarch_host -fstack-protector-strong
+		-fPIE
+		-include "${EPREFIX}/usr/include/gentoo/fortify.h"
+	EOF
+
+	newins - gentoo-cet.cfg <<-EOF
+		-Xarch_host -fcf-protection=$(usex cet full none)
+	EOF
+
+	if use kernel_Darwin; then
+		newins - gentoo-hardened-ld.cfg <<-EOF
+			# There was -Wl,-z,relro here, but it's not supported on Mac
+			# TODO: investigate whether -bind_at_load or -read_only_stubs will do the job
+		EOF
+	else
+		newins - gentoo-hardened-ld.cfg <<-EOF
+			# Some of these options are added unconditionally, regardless of
+			# USE=hardened, for parity with sys-devel/gcc.
+			-Wl,-z,relro
+			-Wl,-z,now
+		EOF
+	fi
+
+	dodir /usr/include/gentoo
+
+	cat >> "${ED}/usr/include/gentoo/maybe-stddefs.h" <<-EOF || die
+	/* __has_include is an extension, but it's fine, because this is only
+	for Clang anyway. */
+	#if defined __has_include && __has_include (<stdc-predef.h>) && !defined(__GLIBC__)
+	# include <stdc-predef.h>
+	#endif
+	EOF
+
+	local fortify_level=$(usex hardened 3 2)
+	# We have to do this because glibc's headers warn if F_S is set
+	# without optimization and that would at the very least be very noisy
+	# during builds and at worst trigger many -Werror builds.
+	cat >> "${ED}/usr/include/gentoo/fortify.h" <<- EOF || die
+	#ifdef __clang__
+	# pragma clang system_header
+	#endif
+	#ifndef _FORTIFY_SOURCE
+	# if defined(__has_feature)
+	#  define __GENTOO_HAS_FEATURE(x) __has_feature(x)
+	# else
+	#  define __GENTOO_HAS_FEATURE(x) 0
+	# endif
+	#
+	# if !defined(__OPTIMIZE__) || __OPTIMIZE__ == 0
+	# elif !defined(__STDC_HOSTED__) || __STDC_HOSTED__ != 1
+	# elif defined(__SANITIZE_ADDRESS__)
+	# elif __GENTOO_HAS_FEATURE(address_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(hwaddress_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(memory_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(numerical_stability_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(realtime_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(thread_sanitizer)
+	# else
+	#  define _FORTIFY_SOURCE ${fortify_level}
+	# endif
+	#
+	# undef __GENTOO_HAS_FEATURE
+	#endif
+	EOF
+
+	# TODO: Maybe -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_FAST for
+	# non-hardened?
+	if use hardened ; then
+		cat >> "${ED}/etc/clang/gentoo-hardened.cfg" <<-EOF || die
+			# Options below are conditional on USE=hardened.
+			-Xarch_host -D_GLIBCXX_ASSERTIONS
+
+			# Analogue to GLIBCXX_ASSERTIONS
+			# https://libcxx.llvm.org/UsingLibcxx.html#assertions-mode
+			# https://libcxx.llvm.org/Hardening.html#using-hardened-mode
+			-Xarch_host -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE
+		EOF
+
+		cat >> "${ED}/etc/clang/gentoo-hardened-ld.cfg" <<-EOF || die
+			# Options below are conditional on USE=hardened.
+		EOF
+	fi
+
+	# We only install config files for supported ABIs because unprefixed tools
+	# might be used for crosscompilation where e.g. PIE may not be supported.
+	# See bug #912237 and bug #901247. Just ${CHOST} won't do due to bug #912685.
+	local abi
+	for abi in $(get_all_abis); do
+		local abi_chost=$(get_abi_CHOST "${abi}")
+		doclang_cfg "${abi_chost}"
+	done
+
+	if use kernel_Darwin; then
+		cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+			# Gentoo Prefix on Darwin
+			-Wl,-search_paths_first
+		EOF
+		if use bootstrap-prefix ; then
+			# bootstrap-prefix is only set during stage2 of bootstrapping
+			# Prefix, where EPREFIX is set to EPREFIX/tmp.
+			# Here we need to point it at the future lib dir of the stage3's
+			# EPREFIX.
+			cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+				-Wl,-rpath,${EPREFIX}/../usr/lib
+				-Wl,-L,${EPREFIX}/../usr/lib
+				-isystem ${EPREFIX}/../usr/include
+			EOF
+		fi
+		# Using -Wl,-L instead of -L to trick compiler driver to put it
+		# after -isysroot's internal -L
+		cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+			-Wl,-rpath,${EPREFIX}/usr/lib
+			-Wl,-L,${EPREFIX}/usr/lib
+			-isystem ${EPREFIX}/usr/include
+			-isysroot ${EPREFIX}/MacOSX.sdk
+		EOF
+	fi
+}
+
+pkg_preinst() {
+	if has_version -b sys-devel/gcc-config && has_version sys-devel/gcc
+	then
+		local gcc_path=$(gcc-config --get-lib-path 2>/dev/null)
+		if [[ -n ${gcc_path} ]]; then
+			cat >> "${ED}/etc/clang/gentoo-gcc-install.cfg" <<-EOF
+				--gcc-install-dir="${gcc_path%%:*}"
+			EOF
+		fi
+	fi
+}
diff --git a/llvm-core/clang-common/clang-common-21.0.0_pre20250211.ebuild b/llvm-core/clang-common/clang-common-21.0.0_pre20250211.ebuild
new file mode 100644
index 000000000000..1fde60b6b6de
--- /dev/null
+++ b/llvm-core/clang-common/clang-common-21.0.0_pre20250211.ebuild
@@ -0,0 +1,310 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit bash-completion-r1 llvm.org multilib
+
+DESCRIPTION="Common files shared between multiple slots of clang"
+HOMEPAGE="https://llvm.org/"
+
+LICENSE="Apache-2.0-with-LLVM-exceptions UoI-NCSA"
+SLOT="0"
+IUSE="
+	default-compiler-rt default-libcxx default-lld
+	bootstrap-prefix cet hardened llvm-libunwind
+"
+
+PDEPEND="
+	default-compiler-rt? (
+		llvm-core/clang-runtime:${LLVM_MAJOR}[compiler-rt]
+		llvm-libunwind? ( llvm-runtimes/libunwind[static-libs] )
+		!llvm-libunwind? ( sys-libs/libunwind[static-libs] )
+	)
+	!default-compiler-rt? ( sys-devel/gcc )
+	default-libcxx? ( >=llvm-runtimes/libcxx-${PV}[static-libs] )
+	!default-libcxx? ( sys-devel/gcc )
+	default-lld? ( >=llvm-core/lld-${PV} )
+	!default-lld? ( sys-devel/binutils )
+"
+IDEPEND="
+	!default-compiler-rt? ( sys-devel/gcc-config )
+	!default-libcxx? ( sys-devel/gcc-config )
+"
+
+LLVM_COMPONENTS=( clang/utils )
+llvm.org_set_globals
+
+pkg_pretend() {
+	[[ ${CLANG_IGNORE_DEFAULT_RUNTIMES} ]] && return
+
+	local flag missing_flags=()
+	for flag in default-{compiler-rt,libcxx,lld}; do
+		if ! use "${flag}" && has_version "llvm-core/clang[${flag}]"; then
+			missing_flags+=( "${flag}" )
+		fi
+	done
+
+	if [[ ${missing_flags[@]} ]]; then
+		eerror "It seems that you have the following flags set on llvm-core/clang:"
+		eerror
+		eerror "  ${missing_flags[*]}"
+		eerror
+		eerror "The default runtimes are now set via flags on llvm-core/clang-common."
+		eerror "The build is being aborted to prevent breakage.  Please either set"
+		eerror "the respective flags on this ebuild, e.g.:"
+		eerror
+		eerror "  llvm-core/clang-common ${missing_flags[*]}"
+		eerror
+		eerror "or build with CLANG_IGNORE_DEFAULT_RUNTIMES=1."
+		die "Mismatched defaults detected between llvm-core/clang and llvm-core/clang-common"
+	fi
+}
+
+_doclang_cfg() {
+	local triple="${1}"
+
+	local tool
+	for tool in ${triple}-clang{,++}; do
+		newins - "${tool}.cfg" <<-EOF
+			# This configuration file is used by ${tool} driver.
+			@gentoo-common.cfg
+			@gentoo-common-ld.cfg
+		EOF
+		if [[ ${triple} == x86_64* ]]; then
+			cat >> "${ED}/etc/clang/${tool}.cfg" <<-EOF || die
+				@gentoo-cet.cfg
+			EOF
+		fi
+	done
+
+	if use kernel_Darwin; then
+		cat >> "${ED}/etc/clang/${triple}-clang++.cfg" <<-EOF || die
+			-lc++abi
+		EOF
+	fi
+
+	newins - "${triple}-clang-cpp.cfg" <<-EOF
+		# This configuration file is used by the ${triple}-clang-cpp driver.
+		@gentoo-common.cfg
+	EOF
+	if [[ ${triple} == x86_64* ]]; then
+		cat >> "${ED}/etc/clang/${triple}-clang-cpp.cfg" <<-EOF || die
+			@gentoo-cet.cfg
+		EOF
+	fi
+
+	# Install symlinks for triples with other vendor strings since some
+	# programs insist on mangling the triple.
+	local vendor
+	for vendor in gentoo pc unknown; do
+		local vendor_triple="${triple%%-*}-${vendor}-${triple#*-*-}"
+		for tool in clang{,++,-cpp}; do
+			if [[ ! -f "${ED}/etc/clang/${vendor_triple}-${tool}.cfg" ]]; then
+				dosym "${triple}-${tool}.cfg" "/etc/clang/${vendor_triple}-${tool}.cfg"
+			fi
+		done
+	done
+}
+
+doclang_cfg() {
+	local triple="${1}"
+
+	_doclang_cfg ${triple}
+
+	# LLVM may have different arch names in some cases. For example in x86
+	# profiles the triple uses i686, but llvm will prefer i386 if invoked
+	# with "clang" on x86 or "clang -m32" on x86_64. The gentoo triple will
+	# be used if invoked through ${CHOST}-clang{,++,-cpp} though.
+	#
+	# To make sure the correct triples are installed,
+	# see Triple::getArchTypeName() in llvm/lib/TargetParser/Triple.cpp
+	# and compare with CHOST values in profiles.
+
+	local abi=${triple%%-*}
+	case ${abi} in
+		armv4l|armv4t|armv5tel|armv6j|armv7a)
+			_doclang_cfg ${triple/${abi}/arm}
+			;;
+		i686)
+			_doclang_cfg ${triple/${abi}/i386}
+			;;
+		sparc)
+			_doclang_cfg ${triple/${abi}/sparcel}
+			;;
+		sparc64)
+			_doclang_cfg ${triple/${abi}/sparcv9}
+			;;
+	esac
+}
+
+src_install() {
+	newbashcomp bash-autocomplete.sh clang
+
+	insinto /etc/clang
+	newins - gentoo-runtimes.cfg <<-EOF
+		# This file is initially generated by llvm-core/clang-runtime.
+		# It is used to control the default runtimes using by clang.
+
+		--rtlib=$(usex default-compiler-rt compiler-rt libgcc)
+		--unwindlib=$(usex default-compiler-rt libunwind libgcc)
+		--stdlib=$(usex default-libcxx libc++ libstdc++)
+		-fuse-ld=$(usex default-lld lld bfd)
+	EOF
+
+	newins - gentoo-gcc-install.cfg <<-EOF
+		# This file is maintained by gcc-config.
+		# It is used to specify the selected GCC installation.
+	EOF
+
+	newins - gentoo-common.cfg <<-EOF
+		# This file contains flags common to clang, clang++ and clang-cpp.
+		@gentoo-runtimes.cfg
+		@gentoo-gcc-install.cfg
+		@gentoo-hardened.cfg
+		# bug #870001
+		-include "${EPREFIX}/usr/include/gentoo/maybe-stddefs.h"
+	EOF
+
+	# clang-cpp does not like link args being passed to it when directly
+	# invoked, so use a separate configuration file.
+	newins - gentoo-common-ld.cfg <<-EOF
+		# This file contains flags common to clang and clang++
+		@gentoo-hardened-ld.cfg
+	EOF
+
+	# Baseline hardening (bug #851111)
+	newins - gentoo-hardened.cfg <<-EOF
+		# Some of these options are added unconditionally, regardless of
+		# USE=hardened, for parity with sys-devel/gcc.
+		-Xarch_host -fstack-clash-protection
+		-Xarch_host -fstack-protector-strong
+		-fPIE
+		-include "${EPREFIX}/usr/include/gentoo/fortify.h"
+	EOF
+
+	newins - gentoo-cet.cfg <<-EOF
+		-Xarch_host -fcf-protection=$(usex cet full none)
+	EOF
+
+	if use kernel_Darwin; then
+		newins - gentoo-hardened-ld.cfg <<-EOF
+			# There was -Wl,-z,relro here, but it's not supported on Mac
+			# TODO: investigate whether -bind_at_load or -read_only_stubs will do the job
+		EOF
+	else
+		newins - gentoo-hardened-ld.cfg <<-EOF
+			# Some of these options are added unconditionally, regardless of
+			# USE=hardened, for parity with sys-devel/gcc.
+			-Wl,-z,relro
+			-Wl,-z,now
+		EOF
+	fi
+
+	dodir /usr/include/gentoo
+
+	cat >> "${ED}/usr/include/gentoo/maybe-stddefs.h" <<-EOF || die
+	/* __has_include is an extension, but it's fine, because this is only
+	for Clang anyway. */
+	#if defined __has_include && __has_include (<stdc-predef.h>) && !defined(__GLIBC__)
+	# include <stdc-predef.h>
+	#endif
+	EOF
+
+	local fortify_level=$(usex hardened 3 2)
+	# We have to do this because glibc's headers warn if F_S is set
+	# without optimization and that would at the very least be very noisy
+	# during builds and at worst trigger many -Werror builds.
+	cat >> "${ED}/usr/include/gentoo/fortify.h" <<- EOF || die
+	#ifdef __clang__
+	# pragma clang system_header
+	#endif
+	#ifndef _FORTIFY_SOURCE
+	# if defined(__has_feature)
+	#  define __GENTOO_HAS_FEATURE(x) __has_feature(x)
+	# else
+	#  define __GENTOO_HAS_FEATURE(x) 0
+	# endif
+	#
+	# if !defined(__OPTIMIZE__) || __OPTIMIZE__ == 0
+	# elif !defined(__STDC_HOSTED__) || __STDC_HOSTED__ != 1
+	# elif defined(__SANITIZE_ADDRESS__)
+	# elif __GENTOO_HAS_FEATURE(address_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(hwaddress_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(memory_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(numerical_stability_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(realtime_sanitizer)
+	# elif __GENTOO_HAS_FEATURE(thread_sanitizer)
+	# else
+	#  define _FORTIFY_SOURCE ${fortify_level}
+	# endif
+	#
+	# undef __GENTOO_HAS_FEATURE
+	#endif
+	EOF
+
+	# TODO: Maybe -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_FAST for
+	# non-hardened?
+	if use hardened ; then
+		cat >> "${ED}/etc/clang/gentoo-hardened.cfg" <<-EOF || die
+			# Options below are conditional on USE=hardened.
+			-Xarch_host -D_GLIBCXX_ASSERTIONS
+
+			# Analogue to GLIBCXX_ASSERTIONS
+			# https://libcxx.llvm.org/UsingLibcxx.html#assertions-mode
+			# https://libcxx.llvm.org/Hardening.html#using-hardened-mode
+			-Xarch_host -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE
+		EOF
+
+		cat >> "${ED}/etc/clang/gentoo-hardened-ld.cfg" <<-EOF || die
+			# Options below are conditional on USE=hardened.
+		EOF
+	fi
+
+	# We only install config files for supported ABIs because unprefixed tools
+	# might be used for crosscompilation where e.g. PIE may not be supported.
+	# See bug #912237 and bug #901247. Just ${CHOST} won't do due to bug #912685.
+	local abi
+	for abi in $(get_all_abis); do
+		local abi_chost=$(get_abi_CHOST "${abi}")
+		doclang_cfg "${abi_chost}"
+	done
+
+	if use kernel_Darwin; then
+		cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+			# Gentoo Prefix on Darwin
+			-Wl,-search_paths_first
+		EOF
+		if use bootstrap-prefix ; then
+			# bootstrap-prefix is only set during stage2 of bootstrapping
+			# Prefix, where EPREFIX is set to EPREFIX/tmp.
+			# Here we need to point it at the future lib dir of the stage3's
+			# EPREFIX.
+			cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+				-Wl,-rpath,${EPREFIX}/../usr/lib
+				-Wl,-L,${EPREFIX}/../usr/lib
+				-isystem ${EPREFIX}/../usr/include
+			EOF
+		fi
+		# Using -Wl,-L instead of -L to trick compiler driver to put it
+		# after -isysroot's internal -L
+		cat >> "${ED}/etc/clang/gentoo-common.cfg" <<-EOF || die
+			-Wl,-rpath,${EPREFIX}/usr/lib
+			-Wl,-L,${EPREFIX}/usr/lib
+			-isystem ${EPREFIX}/usr/include
+			-isysroot ${EPREFIX}/MacOSX.sdk
+		EOF
+	fi
+}
+
+pkg_preinst() {
+	if has_version -b sys-devel/gcc-config && has_version sys-devel/gcc
+	then
+		local gcc_path=$(gcc-config --get-lib-path 2>/dev/null)
+		if [[ -n ${gcc_path} ]]; then
+			cat >> "${ED}/etc/clang/gentoo-gcc-install.cfg" <<-EOF
+				--gcc-install-dir="${gcc_path%%:*}"
+			EOF
+		fi
+	fi
+}