lang/rust: resurrect PORT_LLVM as a non-default OPTION

Rust uses LLVM for code generation [0] and bundles their own copy
of a release that they fully support in relation to the rest of
rustc. This however adds to an already intensive build process. For
the benefit of those building from source, resurrect the PORT_LLVM
option, allowing to link with an existing devel/llvm port of the
user's choosing within Rust compatibility ranges. This remains unset
by default.

PORT_LLVM was removed during an era when Rust tracked LLVM trunk,
during the LLVM 7.0 development cycle. Starting with LLVM 8.0, Rust
tracks LLVM releases with upstream cherry-picks, similar to our
base system LLVM process. [1] Additionally, instead of making changes
directly in their bundled LLVM, llvm-wrapper takes care of anything
needed in that area. [2] Issues stemming from this option have since
been resolved or overcome.

[0] https://rustc-dev-guide.rust-lang.org/backend/codegen.html
[1] https://rustc-dev-guide.rust-lang.org/backend/updating-llvm.html
[2] https://github.com/rust-lang/rust/tree/master/compiler/rustc_llvm/llvm-wrapper

Co-authored-by: Evgeniy Khramtsov <2khramtsov_gmail.com>
Approved by: tobik (rust)
Differential Revision: https://reviews.freebsd.org/D32654

lang/rust/Makefile

@@ -48,10 +48,11 @@ CONFLICTS_INSTALL?=	rust-nightly
 # ?= to allow users to still overwrite it in make.conf.
 TMPDIR?=	${WRKDIR}
 
-OPTIONS_DEFINE=		DOCS GDB LTO SOURCES WASM
+OPTIONS_DEFINE=		DOCS GDB LTO PORT_LLVM SOURCES WASM
 OPTIONS_DEFAULT=	SOURCES WASM
 
 GDB_DESC=	Install ports gdb (necessary for debugging rust programs)
+PORT_LLVM_DESC=	Build against devel/llvm instead of bundled copy (experimental)
 SOURCES_DESC=	Install source files
 WASM_DESC=	Build the WebAssembly target (wasm32-unknown-unknown)
 
@@ -60,12 +61,12 @@ DOCS_VARS=		_RUST_BUILD_DOCS=true \
 			_RUST_TOOLS+=rustdoc
 DOCS_VARS_OFF=		_RUST_BUILD_DOCS=false
 GDB_RUN_DEPENDS=	${LOCALBASE}/bin/gdb:devel/gdb
+PORT_LLVM_USES=		llvm:min=14,lib,noexport
+PORT_LLVM_MAKE_ENV=	RUSTFLAGS="-Lnative=${LOCALBASE}/lib"
 SOURCES_VARS=		_COMPONENTS+=rust-src-${_PACKAGE_VERS} \
 			_RUST_TOOLS+=src
 WASM_VARS=		_COMPONENTS+="rust-analysis-${_PACKAGE_VERS}-wasm32-unknown-unknown rust-std-${_PACKAGE_VERS}-wasm32-unknown-unknown" \
-			_RUST_BUILD_WASM=true \
 			_RUST_TARGETS+=wasm32-unknown-unknown
-WASM_VARS_OFF=		_RUST_BUILD_WASM=false
 
 # See WRKSRC/src/stage0.json for the date and version values
 BOOTSTRAPS_DATE?=		2023-07-13
@@ -95,6 +96,13 @@ _COMPONENTS+=		cargo-${_PACKAGE_VERS}-${_RUST_TARGET} \
 
 .include <bsd.port.pre.mk>
 
+.ifndef NIGHTLY_DATE
+PATCH_SITES=	https://github.com/rust-lang/rust/commit/
+# LLVM 17 API compatibility fixes
+PATCHFILES=	71958da4854176c50a8b12470b956d5c7ed11817.patch:-p1 \
+		6ddf9128b2b55f9def80af57f7353d2521527c6a.patch:-p1
+.endif
+
 .if ${OPSYS} != FreeBSD
 IGNORE=		is only for FreeBSD
 .endif
@@ -156,6 +164,11 @@ post-patch:
 	@${REINPLACE_CMD} 's,"files":{[^}]*},"files":{},' \
 		${CARGO_VENDOR_DIR}/*/.cargo-checksum.json
 
+post-patch-PORT_LLVM-on:
+# WASM target hardcodes bundled lld
+	@${REINPLACE_CMD} 's|"rust-lld"|"wasm-ld${LLVM_DEFAULT}"|' \
+		${WRKSRC}/compiler/rustc_target/src/spec/wasm_base.rs
+
 do-configure:
 # Check that the running kernel has COMPAT_FREEBSD11 required by lang/rust post-ino64
 	@${SETENV} CC="${CC}" OPSYS="${OPSYS}" OSVERSION="${OSVERSION}" WRKDIR="${WRKDIR}" \
@@ -190,7 +203,11 @@ do-configure:
 	@${ECHO_CMD} 'default-linker="${CC}"' >> ${WRKSRC}/config.toml
 	@${ECHO_CMD} 'deny-warnings=false' >> ${WRKSRC}/config.toml
 	@${ECHO_CMD} 'verbose-tests=true' >> ${WRKSRC}/config.toml
-	@${ECHO_CMD} 'lld=${_RUST_BUILD_WASM}' >> ${WRKSRC}/config.toml
+.if ${PORT_OPTIONS:MWASM} && !${PORT_OPTIONS:MPORT_LLVM}
+	@${ECHO_CMD} 'lld=true' >> ${WRKSRC}/config.toml
+.else
+	@${ECHO_CMD} 'lld=false' >> ${WRKSRC}/config.toml
+.endif
 .if ${PORT_OPTIONS:MLTO}
 	@${ECHO_CMD} 'lto="thin"' >> ${WRKSRC}/config.toml
 .endif
@@ -230,6 +247,9 @@ do-configure:
 .else
 	@${ECHO_CMD} 'linker="${CC}"' >> ${WRKSRC}/config.toml
 .endif
+.if ${PORT_OPTIONS:MPORT_LLVM}
+	@${ECHO_CMD} 'llvm-config="${LOCALBASE}/bin/${LLVM_CONFIG}"' >> ${WRKSRC}/config.toml
+.endif
 .endfor
 	@${ECHO_CMD} '[dist]' >> ${WRKSRC}/config.toml
 	@${ECHO_CMD} 'src-tarball=false' >> ${WRKSRC}/config.toml

lang/rust/distinfo

@@ -49,3 +49,7 @@ SHA256 (rust/2023-07-13/rust-std-1.71.0-riscv64gc-unknown-freebsd.tar.xz) = 4ca3
 SIZE (rust/2023-07-13/rust-std-1.71.0-riscv64gc-unknown-freebsd.tar.xz) = 24375500
 SHA256 (rust/2023-07-13/cargo-1.71.0-riscv64gc-unknown-freebsd.tar.xz) = b49977e17a42a9175cfa016941a6006f8e188f610f4ed59945f114fcb9f04820
 SIZE (rust/2023-07-13/cargo-1.71.0-riscv64gc-unknown-freebsd.tar.xz) = 10130160
+SHA256 (rust/71958da4854176c50a8b12470b956d5c7ed11817.patch) = 5a6b67dfc1218ea953421816834ffe3aa8ac1fc078dfaea4ebab121460ca5211
+SIZE (rust/71958da4854176c50a8b12470b956d5c7ed11817.patch) = 2007
+SHA256 (rust/6ddf9128b2b55f9def80af57f7353d2521527c6a.patch) = 6eaaaf6714c496b610712aa9ecbe1a1614e042323ec872fbf31a0a74c9020f29
+SIZE (rust/6ddf9128b2b55f9def80af57f7353d2521527c6a.patch) = 1278