diff --git a/dev-ml/llvm/Manifest b/dev-ml/llvm/Manifest
index 392493c200e0c..d173631df2d39 100644
--- a/dev-ml/llvm/Manifest
+++ b/dev-ml/llvm/Manifest
@@ -15,3 +15,4 @@ DIST llvm-project-20.1.4.src.tar.xz.sig 566 BLAKE2B 1f0f057dedf938190554ca1a51d9
 DIST llvm-project-ac8fc09688e10e983b99224b5dc5cbbeeedb1879.tar.gz 231567089 BLAKE2B f7878f114c908b21d179854bc693716b34b963612c6b5172789a37cd21fa316720d4e9498bc7679058db3e822ed240bfdafd85bfd00154914d747d0c0ed1cb48 SHA512 4c39db8b22fa087ca96c3b4541ec77ba8a826a126b4e93b0650e59b3622b22b329f60fa3780dd4572fdece409fd5833eda473046d7547f6ee3ac8aadb8f2fc34
 DIST llvm-project-b9e32749d273a957e60170d6e7ef205fd1fb1834.tar.gz 232146799 BLAKE2B f7c02bf1e6b9958114f07827ff00264774a7ad54b51c6867d7e66d7c9a94a36fb84f371d7d30c2f094a0d539b565fb651786ed9e0641f2bea8d982073f1a8ac0 SHA512 2d81ead79c606e00549d5205584f1bd272e4d7adf4b376fdba19e7fb719710e80b00b22ee3500ab2b990178fa044ca9fcf45bd2063e62e6a217b11775bb3b163
 DIST llvm-project-d1e38eab95b07b422194427474521623916bbf29.tar.gz 232705423 BLAKE2B bf5200c2223d8cdf7c34c84876d8cfeb9429cb6535ced226b1bf9ab468b6401fe3da8759f0fc1ab3112927304c5f74db29b18be60fa961ce99471caa2c6a1f33 SHA512 8fae137725ad4eb0f5bab73895c65b34d1e36ea039c9fb3978c908ecc6023094d84919b97dc405b86e2dd32f585d87b29cee02293c8156d10a8371b516ca5e7a
+DIST llvm-project-fcb4bda9dcfcdb64d8b069e8416c75d7a1a62e52.tar.gz 233149231 BLAKE2B 95a7a012a1e747afcf83ace3785c8ef6a3e10f6075e59eb1c5b077cc9edae244b648f341bc0ac6a45b2afc8f7ffe130a90a741a04465523f30f8322566386703 SHA512 b46f0c90a1c56750cada24183ca382b267a2d2faa0db7d77a8bdd4e94e6303e57d565cf85447b3c0e0efdd3750efef1e10e8ce6f1fe8f1ae10ee31d25ddf3fb7
diff --git a/dev-ml/llvm/llvm-21.0.0_pre20250510.ebuild b/dev-ml/llvm/llvm-21.0.0_pre20250510.ebuild
new file mode 100644
index 0000000000000..bacc5c89fa797
--- /dev/null
+++ b/dev-ml/llvm/llvm-21.0.0_pre20250510.ebuild
@@ -0,0 +1,107 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+PYTHON_COMPAT=( python3_{10..13} )
+inherit cmake llvm.org llvm-utils python-any-r1
+
+DESCRIPTION="OCaml bindings for LLVM"
+HOMEPAGE="https://llvm.org/"
+
+LICENSE="Apache-2.0-with-LLVM-exceptions UoI-NCSA"
+SLOT="0/${PV}"
+IUSE="+debug test"
+RESTRICT="!test? ( test )"
+
+RDEPEND="
+	>=dev-lang/ocaml-4.00.0:0=
+	dev-ml/ocaml-ctypes:=
+	~llvm-core/llvm-${PV}:=[debug?]
+	!llvm-core/llvm[ocaml(-)]
+"
+
+DEPEND="
+	${RDEPEND}
+"
+BDEPEND="
+	${PYTHON_DEPS}
+	dev-lang/perl
+	dev-ml/findlib
+"
+
+LLVM_COMPONENTS=( llvm cmake third-party )
+LLVM_USE_TARGETS=llvm
+llvm.org_set_globals
+
+src_configure() {
+	llvm_prepend_path "${LLVM_MAJOR}"
+
+	local libdir=$(get_libdir)
+	local mycmakeargs=(
+		-DLLVM_LIBDIR_SUFFIX=${libdir#lib}
+
+		-DBUILD_SHARED_LIBS=OFF
+		-DLLVM_BUILD_LLVM_DYLIB=ON
+		-DLLVM_LINK_LLVM_DYLIB=ON
+		-DLLVM_OCAML_OUT_OF_TREE=ON
+
+		# cheap hack: LLVM combines both anyway, and the only difference
+		# is that the former list is explicitly verified at cmake time
+		-DLLVM_TARGETS_TO_BUILD=""
+		-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD="${LLVM_TARGETS// /;}"
+		-DLLVM_BUILD_TESTS=$(usex test)
+
+		# disable various irrelevant deps and settings
+		-DLLVM_ENABLE_FFI=OFF
+		-DLLVM_ENABLE_TERMINFO=OFF
+		-DHAVE_HISTEDIT_H=NO
+		-DLLVM_ENABLE_ASSERTIONS=$(usex debug)
+		-DLLVM_ENABLE_EH=ON
+		-DLLVM_ENABLE_RTTI=ON
+
+		-DLLVM_HOST_TRIPLE="${CHOST}"
+
+		-DPython3_EXECUTABLE="${PYTHON}"
+
+		# TODO: ocamldoc
+	)
+
+	use test && mycmakeargs+=(
+		-DLLVM_LIT_ARGS="$(get_lit_flags)"
+	)
+
+	# LLVM_ENABLE_ASSERTIONS=NO does not guarantee this for us, #614844
+	# also: custom rules for OCaml do not work for CPPFLAGS
+	use debug || local -x CFLAGS="${CFLAGS} -DNDEBUG"
+	cmake_src_configure
+
+	local llvm_libdir=$(llvm-config --libdir)
+	# an ugly hack; TODO: figure out a way to pass -L to ocaml...
+	cd "${BUILD_DIR}/${libdir}" || die
+	ln -s "${llvm_libdir}"/*.so . || die
+
+	if use test; then
+		local llvm_bindir=$(llvm-config --bindir)
+		# Force using system-installed tools.
+		sed -i -e "/llvm_tools_dir/s@\".*\"@\"${llvm_bindir}\"@" \
+			"${BUILD_DIR}"/test/lit.site.cfg.py || die
+	fi
+}
+
+src_compile() {
+	cmake_build ocaml_all
+}
+
+src_test() {
+	# respect TMPDIR!
+	local -x LIT_PRESERVES_TMP=1
+	cmake_build check-llvm-bindings-ocaml
+}
+
+src_install() {
+	DESTDIR="${D}" \
+	cmake -P "${BUILD_DIR}"/bindings/ocaml/cmake_install.cmake || die
+
+	dodoc bindings/ocaml/README.txt
+}