diff --git a/llvm-runtimes/compiler-rt-sanitizers/Manifest b/llvm-runtimes/compiler-rt-sanitizers/Manifest
index 60bff3dac4a95..276f241a2518e 100644
--- a/llvm-runtimes/compiler-rt-sanitizers/Manifest
+++ b/llvm-runtimes/compiler-rt-sanitizers/Manifest
@@ -15,6 +15,7 @@ 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-1c3a9a853ce68c3c539e7cab21380b9d8b18f426.tar.gz 229448743 BLAKE2B c1eacc2ed05c460f56cf83f16b982e3fa4ac530483d7cf003034239aff3b3dbffbdd3042a3f295a83ec94fcf32f802714e4937fd3761a5e03d4ed1b4093e81bf SHA512 98b7e9fa330a6fce33ca9757caf5d2e41d0b73117cb24b2aed880274c2d6f8a8c1a0028dd0e773fa42deb61dbe3b9dd4fb2f44e50814b966fcdeae8e5b417e6d
+DIST llvm-project-1d133420dc512487e2be0e9d86755f2a7c3497a7.tar.gz 229268288 BLAKE2B aca79bcca631deeab429a03cd2732d78d8ecf0c9615bce181445ed875436806609dc85a57d4f97109492833d620d060ea93fed450a4912c2d94597aeabf84974 SHA512 24ecadfccdf785bfbf27d5007afd2a4d5868493b2c5f48d6cf07c335bfbfef5cba4f12a639971e5f95877ae3b8c7b7fc0c210e404d21036af553de82a5059037
 DIST llvm-project-20.1.0.src.tar.xz 147206476 BLAKE2B 8e8bd8aa995a84d17ac7d634098a6b72a47c30f1752029b620f4541a2de4039edf09117286094ae7bc59c4e84374dcffb8e5ee6ef5feaf4ea7ddb58dd04ea803 SHA512 c90fbc43c40e148357912adc40d799a79cce3d3a929136c137421f6342ed7338659e651f1dedfa8e10b94b9f2897e25b2962e17709add02857f89f10615a2397
 DIST llvm-project-20.1.0.src.tar.xz.sig 566 BLAKE2B 98979ce89f3fe6e95eef6096066cf855245a585608e7d1fddb5bbb2c73077f3ee28204260e18d7e45e3051daae3639520c39bc3d0dc51524873ac213e2511456 SHA512 68da1c2a13aaa48a67bbb9e716f9f030cf372edc651bca2861453378a6a9172a207ff59e29b175001f042888bf1f9c118fbf938f757e1f4c966943baa7e2696a
 DIST llvm-project-20.1.1.src.tar.xz 147215020 BLAKE2B d1774d060036b5340f765d68cc23cbd1e00730874cb3e65b7236303238d7922a7fa191b631c20c3bf17e54c933672a355d4424f2beea17cd25fcf9f5c4c625dd SHA512 b851d3e24a2775f6e789720614a8192d72956f447a39d75e5160a8acf6bd3a3386fab2cca5590b7e020b65e408ccf32432f8dc03519fd4cf60b4b5674fe0547e
diff --git a/llvm-runtimes/compiler-rt-sanitizers/compiler-rt-sanitizers-21.0.0_pre20250322.ebuild b/llvm-runtimes/compiler-rt-sanitizers/compiler-rt-sanitizers-21.0.0_pre20250322.ebuild
new file mode 100644
index 0000000000000..09cf1645bd1a5
--- /dev/null
+++ b/llvm-runtimes/compiler-rt-sanitizers/compiler-rt-sanitizers-21.0.0_pre20250322.ebuild
@@ -0,0 +1,222 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+PYTHON_COMPAT=( python3_{10..13} )
+inherit check-reqs cmake flag-o-matic llvm.org llvm-utils python-any-r1
+
+DESCRIPTION="Compiler runtime libraries for clang (sanitizers & xray)"
+HOMEPAGE="https://llvm.org/"
+
+LICENSE="Apache-2.0-with-LLVM-exceptions || ( UoI-NCSA MIT )"
+SLOT="${LLVM_MAJOR}"
+IUSE="+abi_x86_32 abi_x86_64 +clang +debug test"
+# base targets
+IUSE+=" +ctx-profile +libfuzzer +memprof +orc +profile +xray"
+# sanitizer targets, keep in sync with config-ix.cmake
+# NB: ubsan, scudo deliberately match two entries
+SANITIZER_FLAGS=(
+	asan dfsan lsan msan hwasan tsan ubsan safestack cfi scudo
+	shadowcallstack gwp-asan nsan rtsan
+)
+IUSE+=" ${SANITIZER_FLAGS[@]/#/+}"
+REQUIRED_USE="
+	|| ( ${SANITIZER_FLAGS[*]} libfuzzer orc profile xray )
+	test? (
+		cfi? ( ubsan )
+		gwp-asan? ( scudo )
+	)
+"
+RESTRICT="
+	!clang? ( test )
+	!test? ( test )
+"
+
+DEPEND="
+	llvm-core/llvm:${LLVM_MAJOR}
+	virtual/libcrypt[abi_x86_32(-)?,abi_x86_64(-)?]
+"
+BDEPEND="
+	clang? (
+		llvm-core/clang:${LLVM_MAJOR}
+		llvm-runtimes/compiler-rt:${LLVM_MAJOR}
+	)
+	elibc_glibc? ( net-libs/libtirpc )
+	test? (
+		$(python_gen_any_dep ">=dev-python/lit-15[\${PYTHON_USEDEP}]")
+		=llvm-core/clang-${LLVM_VERSION}*:${LLVM_MAJOR}
+	)
+	!test? (
+		${PYTHON_DEPS}
+	)
+"
+
+LLVM_COMPONENTS=( compiler-rt cmake llvm/cmake )
+LLVM_TEST_COMPONENTS=(
+	llvm/include/llvm/ProfileData llvm/lib/Testing/Support third-party
+)
+llvm.org_set_globals
+
+python_check_deps() {
+	use test || return 0
+	python_has_version ">=dev-python/lit-15[${PYTHON_USEDEP}]"
+}
+
+check_space() {
+	if use test; then
+		local CHECKREQS_DISK_BUILD=11G
+		check-reqs_pkg_pretend
+	fi
+}
+
+pkg_pretend() {
+	check_space
+}
+
+pkg_setup() {
+	check_space
+	python-any-r1_pkg_setup
+}
+
+src_prepare() {
+	sed -i -e 's:-Werror::' lib/tsan/go/buildgo.sh || die
+
+	local flag
+	for flag in "${SANITIZER_FLAGS[@]}"; do
+		if ! use "${flag}"; then
+			local cmake_flag=${flag/-/_}
+			sed -i -e "/COMPILER_RT_HAS_${cmake_flag^^}/s:TRUE:FALSE:" \
+				cmake/config-ix.cmake || die
+		fi
+	done
+
+	# TODO: fix these tests to be skipped upstream
+	if use asan && ! use profile; then
+		rm test/asan/TestCases/asan_and_llvm_coverage_test.cpp || die
+	fi
+	if use ubsan && ! use cfi; then
+		> test/cfi/CMakeLists.txt || die
+	fi
+	# hangs, sigh
+	rm test/tsan/getline_nohang.cpp || die
+
+	llvm.org_src_prepare
+}
+
+src_configure() {
+	llvm_prepend_path "${LLVM_MAJOR}"
+
+	# LLVM_ENABLE_ASSERTIONS=NO does not guarantee this for us, #614844
+	use debug || local -x CPPFLAGS="${CPPFLAGS} -DNDEBUG"
+
+	# pre-set since we need to pass it to cmake
+	BUILD_DIR=${WORKDIR}/compiler-rt_build
+
+	if use clang; then
+		local -x CC=${CHOST}-clang
+		local -x CXX=${CHOST}-clang++
+		strip-unsupported-flags
+	fi
+
+	local flag want_sanitizer=OFF
+	for flag in "${SANITIZER_FLAGS[@]}"; do
+		if use "${flag}"; then
+			want_sanitizer=ON
+			break
+		fi
+	done
+
+	local mycmakeargs=(
+		-DCOMPILER_RT_INSTALL_PATH="${EPREFIX}/usr/lib/clang/${LLVM_MAJOR}"
+		# use a build dir structure consistent with install
+		# this makes it possible to easily deploy test-friendly clang
+		-DCOMPILER_RT_OUTPUT_DIR="${BUILD_DIR}/lib/clang/${LLVM_MAJOR}"
+
+		-DCOMPILER_RT_INCLUDE_TESTS=$(usex test)
+		# builtins & crt installed by llvm-runtimes/compiler-rt
+		-DCOMPILER_RT_BUILD_BUILTINS=OFF
+		-DCOMPILER_RT_BUILD_CRT=OFF
+		-DCOMPILER_RT_BUILD_CTX_PROFILE=$(usex ctx-profile)
+		-DCOMPILER_RT_BUILD_LIBFUZZER=$(usex libfuzzer)
+		-DCOMPILER_RT_BUILD_MEMPROF=$(usex memprof)
+		-DCOMPILER_RT_BUILD_ORC=$(usex orc)
+		-DCOMPILER_RT_BUILD_PROFILE=$(usex profile)
+		-DCOMPILER_RT_BUILD_SANITIZERS="${want_sanitizer}"
+		-DCOMPILER_RT_BUILD_XRAY=$(usex xray)
+
+		-DPython3_EXECUTABLE="${PYTHON}"
+	)
+
+	if use amd64; then
+		mycmakeargs+=(
+			-DCAN_TARGET_i386=$(usex abi_x86_32)
+			-DCAN_TARGET_x86_64=$(usex abi_x86_64)
+		)
+	fi
+
+	if use test; then
+		mycmakeargs+=(
+			-DLLVM_EXTERNAL_LIT="${EPREFIX}/usr/bin/lit"
+			-DLLVM_LIT_ARGS="$(get_lit_flags)"
+
+			# they are created during src_test()
+			-DCOMPILER_RT_TEST_COMPILER="${BUILD_DIR}/lib/llvm/${LLVM_MAJOR}/bin/clang"
+			-DCOMPILER_RT_TEST_CXX_COMPILER="${BUILD_DIR}/lib/llvm/${LLVM_MAJOR}/bin/clang++"
+		)
+
+		# same flags are passed for build & tests, so we need to strip
+		# them down to a subset supported by clang
+		CC=${EPREFIX}/usr/lib/llvm/${LLVM_MAJOR}/bin/clang \
+		CXX=${EPREFIX}/usr/lib/llvm/${LLVM_MAJOR}/bin/clang++ \
+		strip-unsupported-flags
+	fi
+
+	if use prefix && [[ "${CHOST}" == *-darwin* ]] ; then
+		mycmakeargs+=(
+			# setting -isysroot is disabled with compiler-rt-prefix-paths.patch
+			# this allows adding arm64 support using SDK in EPREFIX
+			-DDARWIN_macosx_CACHED_SYSROOT="${EPREFIX}/MacOSX.sdk"
+			# Set version based on the SDK in EPREFIX
+			# This disables i386 for SDK >= 10.15
+			# Will error if has_use tsan and SDK < 10.12
+			-DDARWIN_macosx_OVERRIDE_SDK_VERSION="$(realpath "${EPREFIX}/MacOSX.sdk" | sed -e 's/.*MacOSX\(.*\)\.sdk/\1/')"
+			# Use our libtool instead of looking it up with xcrun
+			-DCMAKE_LIBTOOL="${EPREFIX}/usr/bin/${CHOST}-libtool"
+		)
+	fi
+
+	cmake_src_configure
+
+	if use test; then
+		local sys_dir=( "${EPREFIX}"/usr/lib/clang/${LLVM_MAJOR}/lib/* )
+		[[ -e ${sys_dir} ]] || die "Unable to find ${sys_dir}"
+		[[ ${#sys_dir[@]} -eq 1 ]] || die "Non-deterministic compiler-rt install: ${sys_dir[*]}"
+
+		# copy clang over since resource_dir is located relatively to binary
+		# therefore, we can put our new libraries in it
+		mkdir -p "${BUILD_DIR}"/lib/{llvm/${LLVM_MAJOR}/{bin,$(get_libdir)},clang/${LLVM_MAJOR}/include} || die
+		cp "${EPREFIX}"/usr/lib/llvm/${LLVM_MAJOR}/bin/clang{,++} \
+			"${BUILD_DIR}"/lib/llvm/${LLVM_MAJOR}/bin/ || die
+		cp "${EPREFIX}"/usr/lib/clang/${LLVM_MAJOR}/include/*.h \
+			"${BUILD_DIR}"/lib/clang/${LLVM_MAJOR}/include/ || die
+		cp "${sys_dir}"/*builtins*.a \
+			"${BUILD_DIR}/lib/clang/${LLVM_MAJOR}/lib/${sys_dir##*/}/" || die
+		# we also need LLVMgold.so for gold-based tests
+		if [[ -f ${EPREFIX}/usr/lib/llvm/${LLVM_MAJOR}/$(get_libdir)/LLVMgold.so ]]; then
+			ln -s "${EPREFIX}"/usr/lib/llvm/${LLVM_MAJOR}/$(get_libdir)/LLVMgold.so \
+				"${BUILD_DIR}"/lib/llvm/${LLVM_MAJOR}/$(get_libdir)/ || die
+		fi
+	fi
+}
+
+src_test() {
+	# respect TMPDIR!
+	local -x LIT_PRESERVES_TMP=1
+	# disable sandbox to have it stop clobbering LD_PRELOAD
+	local -x SANDBOX_ON=0
+	# wipe LD_PRELOAD to make ASAN happy
+	local -x LD_PRELOAD=
+
+	cmake_build check-all
+}