I updated source to 349966 on a Pi3b+. I run "make -j4 buildworld" and it kicks out when trying to build "llvm-tblgen". Here is the last messages:
...
--- CodeGenTarget.o ---
c++  -O2 -pipe -I/usr/obj/usr/src/arm64.aarch64/tmp/obj-tools/lib/clang/libllvm -I/usr/src/lib/clang/include -I/usr/src/contrib/llvm/include -DLLVM_BUILD_GLOBAL_ISEL -D__STDC_LIMIT_MACROS -D__STDC_CONSTANT_MACROS -DNDEBUG -DLLVM_DEFAULT_TARGET_TRIPLE=\"aarch64-unknown-freebsd12.0\" -DLLVM_HOST_TRIPLE=\"aarch64-unknown-freebsd12.0\" -DDEFAULT_SYSROOT=\"/usr/obj/usr/src/arm64.aarch64/tmp\" -DLLVM_TARGET_ENABLE_AARCH64 -DLLVM_TARGET_ENABLE_ARM -DLLVM_NATIVE_ASMPARSER=LLVMInitializeAArch64AsmParser -DLLVM_NATIVE_ASMPRINTER=LLVMInitializeAArch64AsmPrinter -DLLVM_NATIVE_DISASSEMBLER=LLVMInitializeAArch64Disassembler -DLLVM_NATIVE_TARGET=LLVMInitializeAArch64Target -DLLVM_NATIVE_TARGETINFO=LLVMInitializeAArch64TargetInfo -DLLVM_NATIVE_TARGETMC=LLVMInitializeAArch64TargetMC -ffunction-sections -fdata-sections -gline-tables-only -MD -MF.depend.CodeGenTarget.o -MTCodeGenTarget.o -Qunused-arguments -I/usr/obj/usr/src/arm64.aarch64/tmp/legacy/usr/include  -fno-exceptions -fno-rtti -std=c++11 -stdlib=libc++ -Wno-c++11-extensions  -c /usr/src/contrib/llvm/utils/TableGen/CodeGenTarget.cpp -o CodeGenTarget.o
--- CodeGenDAGPatterns.o ---
c++: error: unable to execute command: Killed
c++: error: clang frontend command failed due to signal (use -v to see invocation)
FreeBSD clang version 8.0.0 (tags/RELEASE_800/final 356365) (based on LLVM 8.0.0)
Target: aarch64-unknown-freebsd12.0
Thread model: posix
InstalledDir: /usr/bin
c++: note: diagnostic msg: PLEASE submit a bug report to https://bugs.freebsd.org/submit/ and include the crash backtrace, preprocessed source, and associated run script.
c++: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
c++: note: diagnostic msg: /tmp/CodeGenDAGPatterns-3a9721.cpp
c++: note: diagnostic msg: /tmp/CodeGenDAGPatterns-3a9721.sh
c++: note: diagnostic msg: 

********************
*** [CodeGenDAGPatterns.o] Error code 254

make[3]: stopped in /usr/src/usr.bin/clang/llvm-tblgen
1 error

make[3]: stopped in /usr/src/usr.bin/clang/llvm-tblgen
*** [_bootstrap-tools-usr.bin/clang/llvm-tblgen] Error code 2

make[2]: stopped in /usr/src
1 error

make[2]: stopped in /usr/src
*** [_bootstrap-tools] Error code 2

make[1]: stopped in /usr/src
1 error

make[1]: stopped in /usr/src
*** [buildworld] Error code 2

make: stopped in /usr/src
1 error

make: stopped in /usr/src

Attached is:
Preprocessed source(s) and associated run script(s) are located at:
c++: note: diagnostic msg: /tmp/CodeGenDAGPatterns-3a9721.cpp

The following is:
c++: note: diagnostic msg: /tmp/CodeGenDAGPatterns-3a9721.sh

# Crash reproducer for FreeBSD clang version 8.0.0 (tags/RELEASE_800/final 356365) (based on LLVM 8.0.0)
# Driver args: "--driver-mode=g++" "-O2" "-pipe" "-I" "/usr/obj/usr/src/arm64.aarch64/tmp/obj-tools/lib/clang/libllvm" "-I" "/usr/src/lib/clang/include" "-I" "/usr/src/contrib/llvm/include" "-D" "LLVM_BUILD_GLOBAL_ISEL" "-D" "__STDC_LIMIT_MACROS" "-D" "__STDC_CONSTANT_MACROS" "-D" "NDEBUG" "-D" "LLVM_DEFAULT_TARGET_TRIPLE=\"aarch64-unknown-freebsd12.0\"" "-D" "LLVM_HOST_TRIPLE=\"aarch64-unknown-freebsd12.0\"" "-D" "DEFAULT_SYSROOT=\"/usr/obj/usr/src/arm64.aarch64/tmp\"" "-D" "LLVM_TARGET_ENABLE_AARCH64" "-D" "LLVM_TARGET_ENABLE_ARM" "-D" "LLVM_NATIVE_ASMPARSER=LLVMInitializeAArch64AsmParser" "-D" "LLVM_NATIVE_ASMPRINTER=LLVMInitializeAArch64AsmPrinter" "-D" "LLVM_NATIVE_DISASSEMBLER=LLVMInitializeAArch64Disassembler" "-D" "LLVM_NATIVE_TARGET=LLVMInitializeAArch64Target" "-D" "LLVM_NATIVE_TARGETINFO=LLVMInitializeAArch64TargetInfo" "-D" "LLVM_NATIVE_TARGETMC=LLVMInitializeAArch64TargetMC" "-ffunction-sections" "-fdata-sections" "-gline-tables-only" "-MD" "-MF" ".depend.CodeGenDAGPatterns.o" "-MT" "CodeGenDAGPatterns.o" "-Qunused-arguments" "-I" "/usr/obj/usr/src/arm64.aarch64/tmp/legacy/usr/include" "-fno-exceptions" "-fno-rtti" "-std=c++11" "-stdlib=libc++" "-Wno-c++11-extensions" "-c" "/usr/src/contrib/llvm/utils/TableGen/CodeGenDAGPatterns.cpp" "-o" "CodeGenDAGPatterns.o"
# Original command:  "/usr/bin/c++" "-cc1" "-triple" "aarch64-unknown-freebsd12.0" "-emit-obj" "-disable-free" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "CodeGenDAGPatterns.cpp" "-mrelocation-model" "static" "-mthread-model" "posix" "-mdisable-fp-elim" "-masm-verbose" "-mconstructor-aliases" "-fuse-init-array" "-target-cpu" "generic" "-target-feature" "+neon" "-target-abi" "aapcs" "-fallow-half-arguments-and-returns" "-dwarf-column-info" "-debug-info-kind=line-tables-only" "-dwarf-version=2" "-debugger-tuning=gdb" "-ffunction-sections" "-fdata-sections" "-coverage-notes-file" "/usr/obj/usr/src/arm64.aarch64/tmp/obj-tools/usr.bin/clang/llvm-tblgen/CodeGenDAGPatterns.gcno" "-resource-dir" "/usr/lib/clang/8.0.0" "-dependency-file" ".depend.CodeGenDAGPatterns.o" "-sys-header-deps" "-MT" "CodeGenDAGPatterns.o" "-I" "/usr/obj/usr/src/arm64.aarch64/tmp/obj-tools/lib/clang/libllvm" "-I" "/usr/src/lib/clang/include" "-I" "/usr/src/contrib/llvm/include" "-D" "LLVM_BUILD_GLOBAL_ISEL" "-D" "__STDC_LIMIT_MACROS" "-D" "__STDC_CONSTANT_MACROS" "-D" "NDEBUG" "-D" "LLVM_DEFAULT_TARGET_TRIPLE=\"aarch64-unknown-freebsd12.0\"" "-D" "LLVM_HOST_TRIPLE=\"aarch64-unknown-freebsd12.0\"" "-D" "DEFAULT_SYSROOT=\"/usr/obj/usr/src/arm64.aarch64/tmp\"" "-D" "LLVM_TARGET_ENABLE_AARCH64" "-D" "LLVM_TARGET_ENABLE_ARM" "-D" "LLVM_NATIVE_ASMPARSER=LLVMInitializeAArch64AsmParser" "-D" "LLVM_NATIVE_ASMPRINTER=LLVMInitializeAArch64AsmPrinter" "-D" "LLVM_NATIVE_DISASSEMBLER=LLVMInitializeAArch64Disassembler" "-D" "LLVM_NATIVE_TARGET=LLVMInitializeAArch64Target" "-D" "LLVM_NATIVE_TARGETINFO=LLVMInitializeAArch64TargetInfo" "-D" "LLVM_NATIVE_TARGETMC=LLVMInitializeAArch64TargetMC" "-I" "/usr/obj/usr/src/arm64.aarch64/tmp/legacy/usr/include" "-internal-isystem" "/usr/include/c++/v1" "-O2" "-Wno-c++11-extensions" "-std=c++11" "-fdeprecated-macro" "-fdebug-compilation-dir" "/usr/obj/usr/src/arm64.aarch64/tmp/obj-tools/usr.bin/clang/llvm-tblgen" "-ferror-limit" "19" "-fmessage-length" "0" "-fno-rtti" "-fno-signed-char" "-fobjc-runtime=gnustep" "-fdiagnostics-show-option" "-vectorize-loops" "-vectorize-slp" "-o" "CodeGenDAGPatterns.o" "-x" "c++" "/usr/src/contrib/llvm/utils/TableGen/CodeGenDAGPatterns.cpp" "-faddrsig"
 "/usr/bin/c++" "-cc1" "-triple" "aarch64-unknown-freebsd12.0" "-emit-obj" "-disable-free" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "CodeGenDAGPatterns.cpp" "-mrelocation-model" "static" "-mthread-model" "posix" "-mdisable-fp-elim" "-masm-verbose" "-mconstructor-aliases" "-fuse-init-array" "-target-cpu" "generic" "-target-feature" "+neon" "-target-abi" "aapcs" "-fallow-half-arguments-and-returns" "-dwarf-column-info" "-debug-info-kind=line-tables-only" "-dwarf-version=2" "-debugger-tuning=gdb" "-ffunction-sections" "-fdata-sections" "-coverage-notes-file" "/usr/obj/usr/src/arm64.aarch64/tmp/obj-tools/usr.bin/clang/llvm-tblgen/CodeGenDAGPatterns.gcno" "-sys-header-deps" "-D" "LLVM_BUILD_GLOBAL_ISEL" "-D" "__STDC_LIMIT_MACROS" "-D" "__STDC_CONSTANT_MACROS" "-D" "NDEBUG" "-D" "LLVM_DEFAULT_TARGET_TRIPLE=\"aarch64-unknown-freebsd12.0\"" "-D" "LLVM_HOST_TRIPLE=\"aarch64-unknown-freebsd12.0\"" "-D" "DEFAULT_SYSROOT=\"/usr/obj/usr/src/arm64.aarch64/tmp\"" "-D" "LLVM_TARGET_ENABLE_AARCH64" "-D" "LLVM_TARGET_ENABLE_ARM" "-D" "LLVM_NATIVE_ASMPARSER=LLVMInitializeAArch64AsmParser" "-D" "LLVM_NATIVE_ASMPRINTER=LLVMInitializeAArch64AsmPrinter" "-D" "LLVM_NATIVE_DISASSEMBLER=LLVMInitializeAArch64Disassembler" "-D" "LLVM_NATIVE_TARGET=LLVMInitializeAArch64Target" "-D" "LLVM_NATIVE_TARGETINFO=LLVMInitializeAArch64TargetInfo" "-D" "LLVM_NATIVE_TARGETMC=LLVMInitializeAArch64TargetMC" "-O2" "-Wno-c++11-extensions" "-std=c++11" "-fdeprecated-macro" "-ferror-limit" "19" "-fmessage-length" "0" "-fno-rtti" "-fno-signed-char" "-fobjc-runtime=gnustep" "-fdiagnostics-show-option" "-vectorize-loops" "-vectorize-slp" "-x" "c++" "CodeGenDAGPatterns-3a9721.cpp" "-faddrsig"