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This adds support for Emscripten-style shared libraries [1] to the `wasm32-wasi`
target. Previously, only static linking was supported, and the `-shared` and
`-fPIC` flags were simply ignored. Now both flags are honored.
Since WASI runtimes do not necessarily include JavaScript support, we cannot
rely on the JS-based Emscripten linker to link shared libraries. Instead, we
link them using the Component Model proposal [2].
We have prototyped shared library support in `wasi-sdk` [3] and put together a
demo [4] which uses a patched version of `wit-component` [5] to link libraries
using the Component Model. We plan to submit the required changes upstream to
the respective repositories in the next week or two.
[1] https://github.com/WebAssembly/tool-conventions/blob/main/DynamicLinking.md
[2]
https://github.com/WebAssembly/component-model/blob/main/design/mvp/examples/SharedEverythingDynamicLinking.md
[3] https://github.com/dicej/wasi-sdk/tree/dynamic-linking
[4] https://github.com/dicej/component-linking-demo
[5]
https://github.com/bytecodealliance/wasm-tools/tree/main/crates/wit-component
Signed-off-by: Joel Dice <joel.d...@fermyon.com>
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D153293
Files:
clang/docs/ReleaseNotes.rst
clang/lib/Driver/ToolChains/WebAssembly.cpp
clang/test/Driver/wasm-toolchain.c
llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
llvm/utils/lit/lit/llvm/config.py
Index: llvm/utils/lit/lit/llvm/config.py
===================================================================
--- llvm/utils/lit/lit/llvm/config.py
+++ llvm/utils/lit/lit/llvm/config.py
@@ -328,6 +328,9 @@
return False
def make_itanium_abi_triple(self, triple):
+ if triple == "wasm32-wasi":
+ return triple
+
m = re.match(r"(\w+)-(\w+)-(\w+)", triple)
if not m:
self.lit_config.fatal(
@@ -339,6 +342,9 @@
return m.group(1) + "-" + m.group(2) + "-" + m.group(3) + "-gnu"
def make_msabi_triple(self, triple):
+ if triple == "wasm32-wasi":
+ return triple
+
m = re.match(r"(\w+)-(\w+)-(\w+)", triple)
if not m:
self.lit_config.fatal("Could not turn '%s' into MS ABI triple" % triple)
Index: llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
===================================================================
--- llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
+++ llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
@@ -99,13 +99,6 @@
return Reloc::Static;
}
- if (!TT.isOSEmscripten()) {
- // Relocation modes other than static are currently implemented in a way
- // that only works for Emscripten, so disable them if we aren't targeting
- // Emscripten.
- return Reloc::Static;
- }
-
return *RM;
}
Index: clang/test/Driver/wasm-toolchain.c
===================================================================
--- clang/test/Driver/wasm-toolchain.c
+++ clang/test/Driver/wasm-toolchain.c
@@ -33,6 +33,13 @@
// LINK_KNOWN: "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
// LINK_KNOWN: wasm-ld{{.*}}" "-L/foo/lib/wasm32-wasi" "crt1.o" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
+// -shared should be passed through to `wasm-ld` and not include crt1.o
+
+// RUN: %clang -### -shared --target=wasm32-wasi --sysroot=/foo %s 2>&1 \
+// RUN: | FileCheck -check-prefix=LINK_KNOWN_SHARED %s
+// LINK_KNOWN_SHARED: "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
+// LINK_KNOWN_SHARED: wasm-ld{{.*}}" "-L/foo/lib/wasm32-wasi" "-shared" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
+
// A basic C link command-line with optimization with known OS.
// RUN: %clang -### -O2 --target=wasm32-wasi --sysroot=/foo %s 2>&1 \
@@ -46,6 +53,12 @@
// RUN: | FileCheck -check-prefix=COMPILE %s
// COMPILE: "-cc1" {{.*}} "-internal-isystem" "/foo/include/wasm32-wasi" "-internal-isystem" "/foo/include"
+// -fPIC should work for WASI
+
+// RUN: %clang -### -fPIC --target=wasm32-wasi --sysroot=/foo %s 2>&1 \
+// RUN: | FileCheck -check-prefix=COMPILE_PIC %s
+// COMPILE_PIC: "-cc1" {{.*}} "-mrelocation-model" "pic" "-pic-level" "2" {{.*}} "-internal-isystem" "/foo/include/wasm32-wasi" "-internal-isystem" "/foo/include"
+
// Thread-related command line tests.
// '-pthread' sets +atomics, +bulk-memory, +mutable-globals, +sign-ext, and --shared-memory
Index: clang/lib/Driver/ToolChains/WebAssembly.cpp
===================================================================
--- clang/lib/Driver/ToolChains/WebAssembly.cpp
+++ clang/lib/Driver/ToolChains/WebAssembly.cpp
@@ -101,13 +101,16 @@
<< CM << A->getOption().getName();
}
}
- if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles))
+ if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles, options::OPT_shared))
CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath(Crt1)));
if (Entry) {
CmdArgs.push_back(Args.MakeArgString("--entry"));
CmdArgs.push_back(Args.MakeArgString(Entry));
}
+ if (Args.hasArg(options::OPT_shared))
+ CmdArgs.push_back(Args.MakeArgString("-shared"));
+
AddLinkerInputs(ToolChain, Inputs, Args, CmdArgs, JA);
if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -701,6 +701,8 @@
WebAssembly Support
^^^^^^^^^^^^^^^^^^^
+- The `wasm32-wasi` target now supports `Emscripten-style shared libraries
+ <https://github.com/WebAssembly/tool-conventions/blob/main/DynamicLinking.md>`_.
AVR Support
^^^^^^^^^^^
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