diff --git a/debian/changelog b/debian/changelog
index d642fe46..8b47e430 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,15 @@
+llvm-toolchain-15 (1:15.0.2-2~exp2) UNRELEASED; urgency=medium
+
+  * Add better support for the WebAssembly (wasm32/wasm64) targets:
+    - Ship compiler-rt for the wasm32 and wasm64 targets. (Closes: #1010932)
+    - Add patch wasm-compiler-rt-default.diff to default to compiler-rt for
+      these targets. libgcc does not currently exist for WebAssembly in neither
+      Debian nor upstream, and therefore compiler-rt is the only option.
+    - Add patch wasm-sysroot-usr.diff to support a system-installed (i.e. shipped
+      in /usr) wasi-libc. (Closes: #1020746)
+
+ -- Faidon Liambotis <paravoid@debian.org>  Fri, 07 Oct 2022 16:44:57 +0300
+
 llvm-toolchain-15 (1:15.0.2-2~exp1) experimental; urgency=medium
 
   * Ship bolt
diff --git a/debian/patches/series b/debian/patches/series
index be3883aa..fd314c94 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -138,6 +138,8 @@ llvm-runtimes-builtins-build-check.diff
 compilerrt-builtins-arch-fix-armhf.diff
 compilerrt-build-scudo-standalone-option.diff
 wasm-ld-path.diff
+wasm-compiler-rt-default.diff
+wasm-sysroot-usr.diff
 issue-54242.diff
 revert-update-doc.diff
 unwind-force-pthread-dl.diff
diff --git a/debian/patches/wasm-compiler-rt-default.diff b/debian/patches/wasm-compiler-rt-default.diff
new file mode 100644
index 00000000..351fcc79
--- /dev/null
+++ b/debian/patches/wasm-compiler-rt-default.diff
@@ -0,0 +1,31 @@
+--- a/clang/lib/Driver/ToolChains/WebAssembly.cpp
++++ b/clang/lib/Driver/ToolChains/WebAssembly.cpp
+@@ -369,6 +369,18 @@ ToolChain::RuntimeLibType WebAssembly::G
+   return ToolChain::RLT_CompilerRT;
+ }
+ 
++ToolChain::RuntimeLibType WebAssembly::GetRuntimeLibType(
++    const ArgList &Args) const {
++  if (Arg *A = Args.getLastArg(options::OPT_rtlib_EQ)) {
++    StringRef Value = A->getValue();
++    if (Value != "compiler-rt")
++      getDriver().Diag(clang::diag::err_drv_unsupported_rtlib_for_platform)
++          << Value << "WebAssembly";
++  }
++
++  return ToolChain::RLT_CompilerRT;
++}
++
+ ToolChain::CXXStdlibType
+ WebAssembly::GetCXXStdlibType(const ArgList &Args) const {
+   if (Arg *A = Args.getLastArg(options::OPT_stdlib_EQ)) {
+--- a/clang/lib/Driver/ToolChains/WebAssembly.h
++++ b/clang/lib/Driver/ToolChains/WebAssembly.h
+@@ -61,6 +61,7 @@ private:
+                         llvm::opt::ArgStringList &CC1Args,
+                         Action::OffloadKind DeviceOffloadKind) const override;
+   RuntimeLibType GetDefaultRuntimeLibType() const override;
++  RuntimeLibType GetRuntimeLibType(const llvm::opt::ArgList &Args) const override;
+   CXXStdlibType GetCXXStdlibType(const llvm::opt::ArgList &Args) const override;
+   void
+   AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
diff --git a/debian/patches/wasm-sysroot-usr.diff b/debian/patches/wasm-sysroot-usr.diff
new file mode 100644
index 00000000..ae73057b
--- /dev/null
+++ b/debian/patches/wasm-sysroot-usr.diff
@@ -0,0 +1,62 @@
+--- a/clang/lib/Driver/ToolChains/WebAssembly.cpp
++++ b/clang/lib/Driver/ToolChains/WebAssembly.cpp
+@@ -174,7 +174,7 @@ WebAssembly::WebAssembly(const Driver &D
+ 
+   getProgramPaths().push_back(getDriver().getInstalledDir());
+ 
+-  auto SysRoot = getDriver().SysRoot;
++  std::string SysRoot = computeSysRoot();
+   if (getTriple().getOS() == llvm::Triple::UnknownOS) {
+     // Theoretically an "unknown" OS should mean no standard libraries, however
+     // it could also mean that a custom set of libraries is in use, so just add
+@@ -402,6 +402,7 @@ void WebAssembly::AddClangSystemIncludeA
+     return;
+ 
+   const Driver &D = getDriver();
++  std::string SysRoot = computeSysRoot();
+ 
+   if (!DriverArgs.hasArg(options::OPT_nobuiltininc)) {
+     SmallString<128> P(D.ResourceDir);
+@@ -427,10 +428,10 @@ void WebAssembly::AddClangSystemIncludeA
+ 
+   if (getTriple().getOS() != llvm::Triple::UnknownOS) {
+     const std::string MultiarchTriple =
+-        getMultiarchTriple(D, getTriple(), D.SysRoot);
+-    addSystemInclude(DriverArgs, CC1Args, D.SysRoot + "/include/" + MultiarchTriple);
++        getMultiarchTriple(D, getTriple(), SysRoot);
++    addSystemInclude(DriverArgs, CC1Args, SysRoot + "/include/" + MultiarchTriple);
+   }
+-  addSystemInclude(DriverArgs, CC1Args, D.SysRoot + "/include");
++  addSystemInclude(DriverArgs, CC1Args, SysRoot + "/include");
+ }
+ 
+ void WebAssembly::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
+@@ -478,6 +479,17 @@ Tool *WebAssembly::buildLinker() const {
+   return new tools::wasm::Linker(*this);
+ }
+ 
++std::string WebAssembly::computeSysRoot() const {
++  if (!getDriver().SysRoot.empty())
++    return getDriver().SysRoot;
++
++  std::string Path = "/usr";
++  if (getVFS().exists(Path))
++    return Path;
++
++  return std::string();
++}
++
+ void WebAssembly::addLibCxxIncludePaths(
+     const llvm::opt::ArgList &DriverArgs,
+     llvm::opt::ArgStringList &CC1Args) const {
+--- a/clang/lib/Driver/ToolChains/WebAssembly.h
++++ b/clang/lib/Driver/ToolChains/WebAssembly.h
+@@ -89,6 +89,8 @@ private:
+                              llvm::opt::ArgStringList &CC1Args) const;
+   void addLibStdCXXIncludePaths(const llvm::opt::ArgList &DriverArgs,
+                                 llvm::opt::ArgStringList &CC1Args) const;
++
++  std::string computeSysRoot() const override;
+ };
+ 
+ } // end namespace toolchains
diff --git a/debian/rules b/debian/rules
index 0ccca717..78e0581e 100755
--- a/debian/rules
+++ b/debian/rules
@@ -27,7 +27,7 @@ DEBIAN_REVISION := $(shell dpkg-parsechangelog |  sed -rne "s,^Version: 1:([0-9.
 ifneq (,$(filter parallel=%,$(subst $(COMMA), ,$(DEB_BUILD_OPTIONS))))
   NJOBS := -j $(subst parallel=,,$(filter parallel=%,$(subst $(COMMA), ,$(DEB_BUILD_OPTIONS))))
 else
-  NJOBS := $(shell nproc)
+  NJOBS := -j $(shell nproc)
 endif
 
 VENDOR=$(shell lsb_release -is)
@@ -713,7 +713,38 @@ else
 endif
 	touch $@
 
-override_dh_auto_build: debian-full-build debian-libfuzzer-build debian-libclc-build
+debian-rtlib-wasm-build:
+	echo "Using cmake: $(CMAKE_BIN)"
+	for build in wasm32 wasm64; do \
+		mkdir -p build-compiler-rt-$$build; \
+		$(CMAKE_BIN) -B build-compiler-rt-$$build -S compiler-rt/lib/builtins/ \
+		-G Ninja \
+		-DCMAKE_C_COMPILER_TARGET=$$build-unknown-unknown \
+		-DCMAKE_CXX_COMPILER_TARGET=$$build-unknown-unknown \
+		-DCMAKE_ASM_COMPILER_TARGET=$$build-unknown-unknown \
+		-DCMAKE_C_COMPILER=$(STAGE_2_BIN_DIR)/clang \
+		-DCMAKE_CXX_COMPILER=$(STAGE_2_BIN_DIR)/clang++ \
+		-DCMAKE_C_FLAGS="$(opt_flags) $(STAGE_2_CFLAGS)" \
+		-DCMAKE_CXX_FLAGS="$(opt_flags) $(STAGE_2_CXXFLAGS)" \
+		-DCMAKE_SHARED_LINKER_FLAGS="$(STAGE_2_LDFLAGS) -L$(STAGE_2_LIB_DIR)" \
+		-DCMAKE_MODULE_LINKER_FLAGS="$(STAGE_2_LDFLAGS) -L$(STAGE_2_LIB_DIR)" \
+		-DCMAKE_EXE_LINKER_FLAGS="$(STAGE_2_LDFLAGS) -L$(STAGE_2_LIB_DIR)" \
+		-DCMAKE_INSTALL_PREFIX=/usr/lib/llvm-$(LLVM_VERSION)/lib/clang/$(LLVM_VERSION_FULL) \
+		-DCMAKE_INSTALL_DATADIR=lib \
+		-DCMAKE_INSTALL_INCLUDEDIR=include \
+		-DLLVM_CONFIG_PATH=$(STAGE_2_BIN_DIR)/llvm-config \
+		-DCOMPILER_RT_STANDALONE_BUILD=ON \
+		-DCOMPILER_RT_BAREMETAL_BUILD=ON \
+		-DCOMPILER_RT_INCLUDE_TESTS=OFF \
+		-DCOMPILER_RT_USE_LIBCXX=OFF \
+		-DCOMPILER_RT_USE_BUILTINS_LIBRARY=ON \
+		-DCOMPILER_RT_DEFAULT_TARGET_TRIPLE=$$build-unknown-unknown \
+		-DCOMPILER_RT_OS_DIR=wasi; \
+		ninja -C build-compiler-rt-$$build $(NJOBS) $(VERBOSE); \
+	done
+	touch $@
+
+override_dh_auto_build: debian-full-build debian-libfuzzer-build debian-libclc-build debian-rtlib-wasm-build
 
 override_dh_prep: build_doc
 	dh_prep
@@ -860,6 +891,9 @@ ifeq ($(LLVM_SPIRV_INSTALLED),yes)
 	DESTDIR=$(DEB_INST) ninja $(VERBOSE) -C libclc/build install
 endif
 
+	DESTDIR=$(DEB_INST) ninja $(VERBOSE) -C build-compiler-rt-wasm32 install
+	DESTDIR=$(DEB_INST) ninja $(VERBOSE) -C build-compiler-rt-wasm64 install
+
 # Rename binaries
 	mkdir -p $(DEB_INST)/usr/bin/
 	cd $(DEB_INST)/usr/bin/; \
@@ -1007,7 +1041,9 @@ ifeq ($(shell dpkg --compare-versions $(shell dpkg-query -W -f '$${Version}' bin
 	: # for some reasons, the +x might be removed
 	chmod -f +x $(CURDIR)/debian/*/usr/lib/llvm-$(LLVM_VERSION)/bin/* || true
 else
-	dh_strip -a -v
+	# GNU strip doesn't recognize WebAssembly binaries, and actually corrupts them.
+	# llvm-strip (as of 15.0.2) fails with --strip-debug (but works with --strip-all)
+	dh_strip -a -v -Xlibclang_rt.builtins-wasm32.a -Xlibclang_rt.builtins-wasm64.a
 endif
 
 override_dh_install:
@@ -1143,6 +1179,7 @@ override_dh_auto_clean:
 	rm -f $(CURDIR)/clang/tools/clang-format/clang-format-diff-$(LLVM_VERSION)
 	rm -f $(CURDIR)/clang/tools/clang-format/clang-format-$(LLVM_VERSION).py
 	rm -rf libclc/build
+	rm -rf build-compiler-rt-wasm32 build-compiler-rt-wasm64
 	if test -f lld/docs/ld.lld-$(LLVM_VERSION).1; then \
 		mv lld/docs/ld.lld-$(LLVM_VERSION).1 lld/docs/ld.lld.1; \
 	fi
@@ -1158,4 +1195,4 @@ override_dh_auto_clean:
 	: # remove extra stamps
 	rm -f debian-*-build
 
-.PHONY: override_dh_strip preconfigure debian-full-build debian-libfuzzer-build debian-libclc-build
+.PHONY: override_dh_strip preconfigure debian-full-build debian-libfuzzer-build debian-libclc-build debian-rtlib-wasm-build