[musl] [PATCH v3] llvm/clang support for musl cross make

[musl] [PATCH v3] llvm/clang support for musl cross make

[Patrick Oppenlander]

[-- Attachment #1: Type: text/plain, Size: 1301 bytes --]

Hi,

attached is a v3 of the musl-cross-make clang build patch.

Changes from v2:

* Update default TARGETS list
* Add some sane default -mfpu options
* Support target specific config by setting TARGET_CONFIG_<target> variable
* Drop spurious musl patch - this was caused by missing -mfpu options
* Switch to ninja

I don't like depending on ninja. Unfortunately there appear to be
numerous parallel make dependency bugs somewhere between cmake and
make which causes parallel "Unix Makefiles" builds to spuriously fail
with the versions of cmake/make on my development machine. cmake+ninja
has never failed for me.

I haven't submitted the three patches included here yet as I'm waiting
for feedback on the overall direction of this work.

I also have some extra patches which make lld & llvm-objcopy usable in
my embedded projects but have not included them here as they're under
upstream review.

Changes from v1:

* Install clang-resource-headers (fixes missing stdatomic.h, etc.)
* Fix installed symlinks (fixes missing cc, c++, cpp)
* Statically link libunwind and libc++abi into libc++.a and libc++.so
* Updated patch for armv7m clang VFP asm crash
* Support setting COMPILER from config.mak
* Support target specific musl config by setting MUSL_CONFIG_<target> variable

Best regards,

Patrick

[-- Attachment #2: 0001-clang-support.patch --]
[-- Type: application/octet-stream, Size: 17984 bytes --]

From db0c4dbe5ff241845655f8b344a72c3134f99cbf Mon Sep 17 00:00:00 2001
From: Patrick Oppenlander <patrick.oppenlander@gmail.com>
Date: Fri, 29 Jan 2021 12:47:59 +1100
Subject: [PATCH] clang support

---
 Makefile                                      |  58 ++++--
 hashes/llvm-project-11.0.0.tar.xz.sha1        |   1 +
 litecross/Makefile.clang                      | 188 ++++++++++++++++++
 litecross/{Makefile => Makefile.gcc}          |   0
 ...add-builtins-to-dynamic-library-link.patch |  30 +++
 ...able-crt-support-on-more-arm-targets.patch |  25 +++
 ...panding-target-triple-in-sysroot-pat.patch |  39 ++++
 7 files changed, 322 insertions(+), 19 deletions(-)
 create mode 100644 hashes/llvm-project-11.0.0.tar.xz.sha1
 create mode 100644 litecross/Makefile.clang
 rename litecross/{Makefile => Makefile.gcc} (100%)
 create mode 100644 patches/llvm-project-11.0.0/0001-libcxxabi-add-builtins-to-dynamic-library-link.patch
 create mode 100644 patches/llvm-project-11.0.0/0002-compiler-rt-enable-crt-support-on-more-arm-targets.patch
 create mode 100644 patches/llvm-project-11.0.0/0003-clang-support-expanding-target-triple-in-sysroot-pat.patch

diff --git a/Makefile b/Makefile
index a412f60..0e29588 100644
--- a/Makefile
+++ b/Makefile
@@ -1,14 +1,7 @@
 
 SOURCES = sources
 
-CONFIG_SUB_REV = 3d5db9ebe860
-BINUTILS_VER = 2.33.1
-GCC_VER = 9.2.0
-MUSL_VER = 1.2.1
-GMP_VER = 6.1.2
-MPC_VER = 1.1.0
-MPFR_VER = 4.0.2
-LINUX_VER = headers-4.19.88
+COMPILER = gcc
 
 GNU_SITE = https://ftp.gnu.org/pub/gnu
 GCC_SITE = $(GNU_SITE)/gcc
@@ -17,6 +10,7 @@ GMP_SITE = $(GNU_SITE)/gmp
 MPC_SITE = $(GNU_SITE)/mpc
 MPFR_SITE = $(GNU_SITE)/mpfr
 ISL_SITE = http://isl.gforge.inria.fr/
+LLVM_SITE = https://github.com/llvm/llvm-project/releases/download
 
 MUSL_SITE = https://www.musl-libc.org/releases
 MUSL_REPO = git://git.musl-libc.org/musl
@@ -30,24 +24,47 @@ SHA1_CMD = sha1sum -c
 COWPATCH = $(CURDIR)/cowpatch.sh
 
 HOST = $(if $(NATIVE),$(TARGET))
-BUILD_DIR = build/$(if $(HOST),$(HOST),local)/$(TARGET)
+BUILD_DIR = build-$(COMPILER)/$(if $(HOST),$(HOST),local)/$(TARGET)
 OUTPUT = $(CURDIR)/output$(if $(HOST),-$(HOST))
 
-REL_TOP = ../../..
+REL_TOP = ../..$(if $(TARGET),/..)
 
 -include config.mak
 
-SRC_DIRS = gcc-$(GCC_VER) binutils-$(BINUTILS_VER) musl-$(MUSL_VER) \
+MUSL_VER ?= 1.2.1
+LINUX_VER ?= headers-4.19.88
+
+ifeq ($(COMPILER),gcc)
+
+CONFIG_SUB_REV ?= 3d5db9ebe860
+BINUTILS_VER ?= 2.33.1
+GCC_VER ?= 9.2.0
+GMP_VER ?= 6.1.2
+MPC_VER ?= 1.1.0
+MPFR_VER ?= 4.0.2
+
+endif
+
+ifeq ($(COMPILER),clang)
+
+LLVM_VER ?= 11.0.0
+
+endif
+
+SRC_DIRS = musl-$(MUSL_VER) \
+	$(if $(GCC_VER),gcc-$(GCC_VER)) \
+	$(if $(BINUTILS_VER),binutils-$(BINUTILS_VER)) \
 	$(if $(GMP_VER),gmp-$(GMP_VER)) \
 	$(if $(MPC_VER),mpc-$(MPC_VER)) \
 	$(if $(MPFR_VER),mpfr-$(MPFR_VER)) \
 	$(if $(ISL_VER),isl-$(ISL_VER)) \
-	$(if $(LINUX_VER),linux-$(LINUX_VER))
+	$(if $(LINUX_VER),linux-$(LINUX_VER)) \
+	$(if $(LLVM_VER),llvm-project-$(LLVM_VER))
 
 all:
 
 clean:
-	rm -rf gcc-* binutils-* musl-* gmp-* mpc-* mpfr-* isl-* build build-* linux-*
+	rm -rf gcc-* binutils-* musl-* gmp-* mpc-* mpfr-* isl-* build build-* linux-* llvm-project-*
 
 distclean: clean
 	rm -rf sources
@@ -70,6 +87,7 @@ $(patsubst hashes/%.sha1,$(SOURCES)/%,$(wildcard hashes/linux-4*)): SITE = $(LIN
 $(patsubst hashes/%.sha1,$(SOURCES)/%,$(wildcard hashes/linux-3*)): SITE = $(LINUX_SITE)/v3.x
 $(patsubst hashes/%.sha1,$(SOURCES)/%,$(wildcard hashes/linux-2.6*)): SITE = $(LINUX_SITE)/v2.6
 $(patsubst hashes/%.sha1,$(SOURCES)/%,$(wildcard hashes/linux-headers-*)): SITE = $(LINUX_HEADERS_SITE)
+$(patsubst hashes/%.sha1,$(SOURCES)/%,$(wildcard hashes/llvm-project-*)): SITE = $(LLVM_SITE)/llvmorg-$(patsubst llvm-project-%,%,$(basename $(basename $(notdir $@))))
 
 $(SOURCES):
 	mkdir -p $@
@@ -150,10 +168,10 @@ extract_all: | $(SRC_DIRS)
 
 # Rules for building.
 
-ifeq ($(TARGET),)
+ifeq ($(COMPILER)$(TARGET),gcc)
 
 all:
-	@echo TARGET must be set via config.mak or command line.
+	@echo TARGET must be set for gcc build via config.mak or command line.
 	@exit 1
 
 else
@@ -162,20 +180,22 @@ $(BUILD_DIR):
 	mkdir -p $@
 
 $(BUILD_DIR)/Makefile: | $(BUILD_DIR)
-	ln -sf $(REL_TOP)/litecross/Makefile $@
+	ln -sf $(REL_TOP)/litecross/Makefile.$(COMPILER) $@
 
 $(BUILD_DIR)/config.mak: | $(BUILD_DIR)
 	printf >$@ '%s\n' \
-	"TARGET = $(TARGET)" \
+	$(if $(TARGET),"TARGET = $(TARGET)") \
 	"HOST = $(HOST)" \
 	"MUSL_SRCDIR = $(REL_TOP)/musl-$(MUSL_VER)" \
-	"GCC_SRCDIR = $(REL_TOP)/gcc-$(GCC_VER)" \
-	"BINUTILS_SRCDIR = $(REL_TOP)/binutils-$(BINUTILS_VER)" \
+	$(if $(GCC_VER),"GCC_SRCDIR = $(REL_TOP)/gcc-$(GCC_VER)") \
+	$(if $(BINUTILS_VER),"BINUTILS_SRCDIR = $(REL_TOP)/binutils-$(BINUTILS_VER)") \
 	$(if $(GMP_VER),"GMP_SRCDIR = $(REL_TOP)/gmp-$(GMP_VER)") \
 	$(if $(MPC_VER),"MPC_SRCDIR = $(REL_TOP)/mpc-$(MPC_VER)") \
 	$(if $(MPFR_VER),"MPFR_SRCDIR = $(REL_TOP)/mpfr-$(MPFR_VER)") \
 	$(if $(ISL_VER),"ISL_SRCDIR = $(REL_TOP)/isl-$(ISL_VER)") \
 	$(if $(LINUX_VER),"LINUX_SRCDIR = $(REL_TOP)/linux-$(LINUX_VER)") \
+	$(if $(LLVM_VER),"LLVM_SRCDIR = $(REL_TOP)/llvm-project-$(LLVM_VER)") \
+	$(if $(LLVM_VER),"LLVM_VER = $(LLVM_VER)") \
 	"-include $(REL_TOP)/config.mak"
 
 all: | $(SRC_DIRS) $(BUILD_DIR) $(BUILD_DIR)/Makefile $(BUILD_DIR)/config.mak
diff --git a/hashes/llvm-project-11.0.0.tar.xz.sha1 b/hashes/llvm-project-11.0.0.tar.xz.sha1
new file mode 100644
index 0000000..ef4b704
--- /dev/null
+++ b/hashes/llvm-project-11.0.0.tar.xz.sha1
@@ -0,0 +1 @@
+3c88390b19ac6779c8d9c89256892d690903412b  llvm-project-11.0.0.tar.xz
diff --git a/litecross/Makefile.clang b/litecross/Makefile.clang
new file mode 100644
index 0000000..d57095c
--- /dev/null
+++ b/litecross/Makefile.clang
@@ -0,0 +1,188 @@
+
+OUTPUT = $(CURDIR)/output
+
+LLVM_SRCDIR = LLVM_SRCDIR_not_set
+MUSL_SRCDIR = MUSL_SRCDIR_not_set
+
+TARGETS = \
+	aarch64-linux-musleabi \
+	armv7-linux-musleabihf \
+	armv7m-linux-musleabi \
+	armv7em-linux-musleabihf \
+	x86_64-linux-musl \
+	# end
+
+TARGET_CONFIG_armv7-linux-musleabihf = -mfpu=vfpv3
+TARGET_CONFIG_armv7em-linux-musleabihf = -mfpu=fpv5-d16
+
+DEFAULT_TARGET = x86_64-linux-musl
+
+TOOLS = \
+	llvm-ar \
+	llvm-nm \
+	llvm-objcopy \
+	llvm-objdump \
+	llvm-ranlib \
+	llvm-size \
+	llvm-strip \
+	# end
+
+-include config.mak
+
+# TODO: determine LLVM_TARGETS_TO_BUILD from TARGETS?
+FULL_LLVM_CONFIG = $(LLVM_CONFIG) \
+	-DCLANG_DEFAULT_CXX_STDLIB=libc++ \
+	-DCLANG_DEFAULT_LINKER=lld \
+	-DCLANG_DEFAULT_OBJCOPY=llvm-objcopy \
+	-DCLANG_DEFAULT_RTLIB=compiler-rt \
+	-DCMAKE_BUILD_TYPE=MinSizeRel \
+	-DCMAKE_INSTALL_PREFIX=/clang \
+	-DDEFAULT_SYSROOT=../../TARGET \
+	-DLLVM_BUILTIN_TARGETS='$(subst $(subst ,, ),;,$(TARGETS))' \
+	-DLLVM_DEFAULT_TARGET_TRIPLE=$(DEFAULT_TARGET) \
+	-DLLVM_DISTRIBUTION_COMPONENTS='clang;clang-resource-headers;lld;LTO;$(subst $(subst ,, ),;,$(TOOLS))' \
+	-DLLVM_ENABLE_PROJECTS='clang;lld' \
+	-DLLVM_ENABLE_RUNTIMES='compiler-rt;libcxx;libcxxabi;libunwind' \
+	-DLLVM_INSTALL_TOOLCHAIN_ONLY=ON \
+	-DLLVM_RUNTIME_TARGETS='$(subst $(subst ,, ),;,$(TARGETS))' \
+	-DLLVM_TARGETS_TO_BUILD='AArch64;ARM;Mips;PowerPC;X86' \
+	$(foreach t,$(TARGETS),-DBUILTINS_$(t)_CMAKE_SYSROOT=$(CURDIR)/obj_sysroot/$(t)) \
+	$(foreach t,$(TARGETS),-DBUILTINS_$(t)_CMAKE_C_FLAGS='$(TARGET_CONFIG_$(t))') \
+	$(foreach t,$(TARGETS),-DBUILTINS_$(t)_CMAKE_ASM_FLAGS='$(TARGET_CONFIG_$(t))') \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_CMAKE_CXX_FLAGS='-L$(CURDIR)/obj_musl/$(t)/lib -B$(CURDIR)/obj_musl/$(t)/lib -Qunused-arguments') \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_CMAKE_C_FLAGS='-L$(CURDIR)/obj_musl/$(t)/lib -B$(CURDIR)/obj_musl/$(t)/lib -Qunused-arguments') \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_CMAKE_SYSROOT=$(CURDIR)/obj_sysroot/$(t)) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_COMPILER_RT_BUILD_LIBFUZZER=OFF) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_COMPILER_RT_BUILD_SANITIZERS=OFF) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_COMPILER_RT_BUILD_XRAY=OFF) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBCXXABI_ENABLE_SHARED=OFF) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBCXXABI_ENABLE_STATIC_UNWINDER=ON) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBCXXABI_INSTALL_LIBRARY=OFF) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBCXXABI_USE_COMPILER_RT=ON) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBCXXABI_USE_LLVM_UNWINDER=ON) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_SHARED_LIBRARY=ON) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBCXX_ENABLE_STATIC_ABI_LIBRARY=ON) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBCXX_HAS_MUSL_LIBC=ON) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBCXX_USE_COMPILER_RT=ON) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBUNWIND_ENABLE_SHARED=OFF) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBUNWIND_INSTALL_LIBRARY=OFF) \
+	$(foreach t,$(TARGETS),-DRUNTIMES_$(t)_LIBUNWIND_USE_COMPILER_RT=ON) \
+	# end
+
+all: llvm musl
+
+install: install-llvm install-musl install-kernel-headers install-configs install-symlinks
+
+llvm: | obj_llvm/.lc_built_3
+musl: | $(foreach t,$(TARGETS),obj_musl/$(t)/.lc_built)
+install-musl: $(foreach t,$(TARGETS),install-musl_$(t))
+install-kernel-headers: $(foreach t,$(TARGETS),install-kernel-headers_$(t))
+install-configs: $(foreach t,$(TARGETS),install-configs_$(t))
+install-symlinks: $(foreach t,$(TARGETS),install-symlinks_$(t))
+
+.PHONY: all llvm musl install-llvm install-musl install-kernel-headers install-configs install-symlinks clean
+
+src_llvm: | $(LLVM_SRCDIR)
+	ln -sf $(LLVM_SRCDIR) $@
+
+src_musl: | $(MUSL_SRCDIR)
+	ln -sf $(MUSL_SRCDIR) $@
+
+src_kernel_headers: | $(LINUX_SRCDIR)
+	ln -sf "$(LINUX_SRCDIR)" $@
+
+%/:
+	mkdir -p $@
+
+obj_llvm/.lc_configured: | obj_llvm/ src_llvm
+	cd obj_llvm && cmake -G "Ninja" $(FULL_LLVM_CONFIG) ../src_llvm/llvm
+	touch $@
+
+obj_llvm/.lc_built_1: | obj_llvm/.lc_configured
+	cd obj_llvm && ninja distribution
+	touch $@
+
+obj_musl/%/.lc_configured: | obj_musl/%/ src_musl obj_llvm/.lc_built_1
+	cd obj_musl/$* && ../../src_musl/configure \
+		--prefix= \
+		--target=$* \
+		--disable-wrapper \
+		LIBCC=../../obj_llvm/lib/clang/$(LLVM_VER)/lib/$*/libclang_rt.builtins.a \
+		CC="../../obj_llvm/bin/clang --target=$* $(TARGET_CONFIG_$*)" \
+		$(MUSL_CONFIG) $(MUSL_CONFIG_$*)
+	touch $@
+
+obj_sysroot/%/.lc_headers: | obj_sysroot/ obj_musl/%/.lc_configured
+	cd obj_musl/$* && $(MAKE) DESTDIR=$(CURDIR)/obj_sysroot/$* install-headers
+	touch $@
+
+obj_llvm/.lc_built_2: | $(foreach t,$(TARGETS),obj_sysroot/$(t)/.lc_headers)
+	cd obj_llvm && ninja builtins
+	touch $@
+
+obj_musl/%/.lc_built: | obj_musl/%/.lc_configured obj_llvm/.lc_built_2
+	cd obj_musl/$* && $(MAKE) AR=../../obj_llvm/bin/llvm-ar \
+				  RANLIB=../../obj_llvm/bin/llvm-ranlib
+	touch $@
+
+obj_sysroot/%/.lc_crt_workaround:
+	# Some configure tests for llvm runtimes fail without crtbegin and
+	# crtend files in the sysroot. The runtimes build generates these files
+	# leading to a chicken-egg problem.
+	mkdir -p obj_sysroot/$*/lib
+	cd obj_sysroot/$*/lib && touch crtbeginT.o crtbeginS.o crtbegin.o crtend.o crtendS.o
+	touch $@
+
+obj_kernel_headers/%/.lc_built: | src_kernel_headers
+	mkdir -p $(CURDIR)/obj_kernel_headers/$*/staged
+	cd src_kernel_headers && $(MAKE) ARCH=$(call fn_linux_arch,$*) O=$(CURDIR)/obj_kernel_headers/$* INSTALL_HDR_PATH=$(CURDIR)/obj_kernel_headers/$*/staged headers_install
+	find obj_kernel_headers/$*/staged/include '(' -name .install -o -name ..install.cmd ')' -exec rm {} +
+	touch $@
+
+obj_sysroot/%/.lc_linux_headers: | obj_kernel_headers/%/.lc_built
+	mkdir -p obj_sysroot/$*/include
+	cp -R obj_kernel_headers/$*/staged/include/* obj_sysroot/$*/include
+
+obj_llvm/.lc_built_3: | $(foreach t,$(TARGETS),obj_musl/$(t)/.lc_built \
+					       obj_sysroot/$(t)/.lc_crt_workaround \
+					       obj_sysroot/$(t)/.lc_linux_headers)
+	cd obj_llvm && ninja runtimes
+	touch $@
+
+install-llvm: | obj_llvm/.lc_built_3
+	cd obj_llvm && DESTDIR=$(DESTDIR)$(OUTPUT) ninja install-distribution install-builtins install-runtimes
+
+install-musl_%: | obj_musl/%/.lc_built
+	cd obj_musl/$* && $(MAKE) $(MUSL_VARS) DESTDIR=$(DESTDIR)$(OUTPUT)/$* install
+
+install-kernel-headers_%: | obj_kernel_headers/%/.lc_built
+	mkdir -p $(DESTDIR)$(OUTPUT)/$*/include
+	cp -R obj_kernel_headers/$*/staged/include/* $(DESTDIR)$(OUTPUT)/$*/include
+
+install-configs_%: | $(DESDIR)$(OUTPUT)/clang/bin/
+	echo "--target=$* $(TARGET_CONFIG_$*)" > $(DESTDIR)$(OUTPUT)/clang/bin/$*-clang.cfg
+	echo "--target=$* $(TARGET_CONFIG_$*)" > $(DESTDIR)$(OUTPUT)/clang/bin/$*-clang++.cfg
+
+install-symlinks_%: | $(DESTDIR)$(OUTPUT)/bin/
+	cd $(DESTDIR)$(OUTPUT)/bin && ln -sf ../clang/bin/clang $*-clang
+	cd $(DESTDIR)$(OUTPUT)/bin && ln -sf ../clang/bin/clang++ $*-clang++
+	cd $(DESTDIR)$(OUTPUT)/bin && ln -sf ../clang/bin/clang-cpp $*-cpp
+	cd $(DESTDIR)$(OUTPUT)/bin && ln -sf ../clang/bin/clang $*-cc
+	cd $(DESTDIR)$(OUTPUT)/bin && ln -sf ../clang/bin/clang++ $*-c++
+	cd $(DESTDIR)$(OUTPUT)/bin && ln -sf ../clang/bin/ld.lld $*-ld
+	$(foreach t,$(TOOLS),cd $(DESTDIR)$(OUTPUT)/bin && ln -sf ../clang/bin/$(t) $*-$(subst llvm-,,$(t);))
+
+clean:
+	rm -rf src_* obj_*
+
+# $(call fn_linux_arch,target-triple)
+#     Determine linux architecture from target triple
+ifeq ($(LINUX_SRCDIR),)
+$(error LINUX_SRCDIR is required for llvm libc++ build)
+endif
+LINUX_ARCH_LIST := $(sort $(notdir $(wildcard $(LINUX_SRCDIR)/arch/*)))
+fn_target_arch = $(firstword $(subst -, ,$(1)))
+fn_target_arch_mangled = $(patsubst i%86,x86,$(patsubst aarch64%,arm64%,$(call fn_target_arch,$(1))))
+fn_linux_arch = $(lastword $(foreach a,$(LINUX_ARCH_LIST),$(if $(filter $(a)%,$(call fn_target_arch_mangled,$(1))),$(a))))
+
+.SECONDARY:
diff --git a/litecross/Makefile b/litecross/Makefile.gcc
similarity index 100%
rename from litecross/Makefile
rename to litecross/Makefile.gcc
diff --git a/patches/llvm-project-11.0.0/0001-libcxxabi-add-builtins-to-dynamic-library-link.patch b/patches/llvm-project-11.0.0/0001-libcxxabi-add-builtins-to-dynamic-library-link.patch
new file mode 100644
index 0000000..d1c3734
--- /dev/null
+++ b/patches/llvm-project-11.0.0/0001-libcxxabi-add-builtins-to-dynamic-library-link.patch
@@ -0,0 +1,30 @@
+From 6f437b42e66c7552c3b92fd1bd46c96ed484dfbf Mon Sep 17 00:00:00 2001
+From: Patrick Oppenlander <patrick.oppenlander@gmail.com>
+Date: Fri, 8 Jan 2021 16:46:37 +1100
+Subject: [PATCH] libcxxabi: add builtins to dynamic library link
+
+Otherwise libc++abi.so fails to link on arm with undefined references to
+some __aeabi_ builtins.
+---
+ libcxxabi/src/CMakeLists.txt | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/libcxxabi/src/CMakeLists.txt b/libcxxabi/src/CMakeLists.txt
+index 42bec421d2be..9dba22ea3d43 100644
+--- a/libcxxabi/src/CMakeLists.txt
++++ b/libcxxabi/src/CMakeLists.txt
+@@ -73,6 +73,11 @@ else()
+   add_library_flags_if(LIBCXXABI_HAS_C_LIB c)
+ endif()
+ 
++if (LIBCXXABI_USE_COMPILER_RT)
++  find_compiler_rt_library(builtins LIBCXXABI_BUILTINS_LIBRARY)
++  list(APPEND LIBCXXABI_SHARED_LIBRARIES "${LIBCXXABI_BUILTINS_LIBRARY}")
++endif ()
++
+ if (LIBCXXABI_USE_LLVM_UNWINDER)
+   # Prefer using the in-tree version of libunwind, either shared or static. If
+   # none are found fall back to using -lunwind.
+-- 
+2.30.0
+
diff --git a/patches/llvm-project-11.0.0/0002-compiler-rt-enable-crt-support-on-more-arm-targets.patch b/patches/llvm-project-11.0.0/0002-compiler-rt-enable-crt-support-on-more-arm-targets.patch
new file mode 100644
index 0000000..efc5092
--- /dev/null
+++ b/patches/llvm-project-11.0.0/0002-compiler-rt-enable-crt-support-on-more-arm-targets.patch
@@ -0,0 +1,25 @@
+From 2425a718046a82e705d05400bd9204b265ca3262 Mon Sep 17 00:00:00 2001
+From: Patrick Oppenlander <patrick.oppenlander@gmail.com>
+Date: Fri, 8 Jan 2021 21:34:39 +1100
+Subject: [PATCH] compiler-rt: enable crt support on more arm targets
+
+---
+ compiler-rt/cmake/config-ix.cmake | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/compiler-rt/cmake/config-ix.cmake b/compiler-rt/cmake/config-ix.cmake
+index 2edc1dabd90d..7d8b95146e9a 100644
+--- a/compiler-rt/cmake/config-ix.cmake
++++ b/compiler-rt/cmake/config-ix.cmake
+@@ -255,7 +255,7 @@ function(is_valid_apple_platform platform is_valid_out)
+ endfunction()
+ 
+ set(ARM64 aarch64)
+-set(ARM32 arm armhf)
++set(ARM32 arm armhf armv7 armv7m armv7em)
+ set(HEXAGON hexagon)
+ set(X86 i386)
+ set(X86_64 x86_64)
+-- 
+2.30.0
+
diff --git a/patches/llvm-project-11.0.0/0003-clang-support-expanding-target-triple-in-sysroot-pat.patch b/patches/llvm-project-11.0.0/0003-clang-support-expanding-target-triple-in-sysroot-pat.patch
new file mode 100644
index 0000000..08a7dec
--- /dev/null
+++ b/patches/llvm-project-11.0.0/0003-clang-support-expanding-target-triple-in-sysroot-pat.patch
@@ -0,0 +1,39 @@
+From f0ecb3850d7825cd967d22c09ed73d990605c70b Mon Sep 17 00:00:00 2001
+From: Patrick Oppenlander <patrick.oppenlander@gmail.com>
+Date: Mon, 11 Jan 2021 10:39:27 +1100
+Subject: [PATCH] clang: support expanding target triple in sysroot path
+
+This allows clang to switch sysroot (or, more usefully, default sysroot)
+based on target triple.
+
+For example, configuring with
+
+-DDEFAULT_SYSROOT=../TARGET
+
+will automatically select a target specific sysroot one level up from
+the clang binary location.
+---
+ clang/lib/Driver/Driver.cpp | 7 +++++++
+ 1 file changed, 7 insertions(+)
+
+diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
+index ece8222dcf24..8a3b068d86b9 100644
+--- a/clang/lib/Driver/Driver.cpp
++++ b/clang/lib/Driver/Driver.cpp
+@@ -1121,6 +1121,13 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
+                     .Default(SaveTempsCwd);
+   }
+ 
++  // expand TARGET in sysroot path
++  if (!SysRoot.empty()) {
++    size_t pos{0};
++    while ((pos = SysRoot.find("TARGET", pos)) != std::string::npos)
++      SysRoot.replace(pos, 6, TargetTriple);
++  }
++
+   setLTOMode(Args);
+ 
+   // Process -fembed-bitcode= flags.
+-- 
+2.30.0
+
-- 
2.30.0