duction)
    * libprivatelldb.so goes from 27242 to 18798 symbols (~31% reduction)
    
    Note: to get the full benefit, a clean build is required. Incremental
    builds should still work, but I didn't want to force a full rebuild on
    everybody.
    
    MFC after:      1 week
---
 lib/clang/libllvm/Makefile | 12 ++++++++++++
 lib/clang/llvm.build.mk    |  1 +
 2 files changed, 13 insertions(+)

diff --git a/lib/clang/libllvm/Makefile b/lib/clang/libllvm/Makefile
index 810eac08d8d5..7c45375b8fbf 100644
--- a/lib/clang/libllvm/Makefile
+++ b/lib/clang/libllvm/Makefile
@@ -48,6 +48,8 @@ CFLAGS+=	-DBLAKE3_NO_AVX512 -DBLAKE3_NO_AVX2 -DBLAKE3_NO_SSE41 \
 CFLAGS+=	-DBLAKE3_USE_NEON=0
 .endif
 
+CFLAGS+=	-DLLVM_BUILD_LLVM_DYLIB
+
 SRCDIR=		llvm/lib
 
 # Explanation of different SRCS variants below:
@@ -2050,6 +2052,16 @@ SRCS_ALL+=	${SRCS_COV}
 SRCS+=		${GENSRCS}
 SRCS+=		${SRCS_ALL:O}
 
+# Optimization: for all source files under Target/*/*, use -fvisibility=hidden,
+# which reduces the number of external symbols in the resulting shared library.
+# This is also what upstream does.
+.for src in ${SRCS}
+. if "${src:MTarget/*/*}"
+CFLAGS.${src:T}+=	-fvisibility=hidden
+.info ${src}:	CFLAGS.${src:T}
+. endif
+.endfor
+
 llvm/CodeGen/GenVT.inc: ${LLVM_SRCS}/include/llvm/CodeGen/ValueTypes.td
 	${LLVM_MIN_TBLGEN} -gen-vt \
 	    -I ${LLVM_SRCS}/include -d ${.TARGET}.d -o ${.TARGET} \
diff --git a/lib/clang/llvm.build.mk b/lib/clang/llvm.build.mk
index a26e15679242..b8b4be7dfe28 100644
--- a/lib/clang/llvm.build.mk
+++ b/lib/clang/llvm.build.mk
@@ -122,6 +122,7 @@ LDFLAGS+=	-Wl,-m,elf64lriscv_fbsd
 CXXSTD=		c++17
 CXXFLAGS+=	-fno-exceptions
 CXXFLAGS+=	-fno-rtti
+CXXFLAGS+=	-fvisibility-inlines-hidden
 .if ${.MAKE.OS} == "FreeBSD" || !defined(BOOTSTRAPPING)
 CXXFLAGS.clang+= -stdlib=libc++
 .else