[clang][WebAssembly] Support wasm32-wasi shared libraries
This adds support for Emscripten-style shared libraries [1] to
non-emscripten targets, such as `wasm32-wasi`. 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.dice@fermyon.com>
Reviewed By: sbc100
Differential Revision: https://reviews.llvm.org/D153293
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 8d67ff9..9ceb3c3 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -1103,6 +1103,12 @@
^^^^^^^^^^^^^^^^^^^
- The -mcpu=generic configuration now enables sign-ext and mutable-globals. These
proposals are standardized and available in all major engines.
+- Shared library support (and PIC code generation) for WebAssembly is no longer
+ limited to the Emscripten target OS and now works with other targets such as
+ wasm32-wasi. Note that the `format
+ <https://github.com/WebAssembly/tool-conventions/blob/main/DynamicLinking.md>`_
+ is not yet stable and may change between LLVM versions. Also, WASI does not
+ yet have facilities to load dynamic libraries.
DWARF Support in Clang
----------------------
diff --git a/clang/lib/Driver/ToolChains/WebAssembly.cpp b/clang/lib/Driver/ToolChains/WebAssembly.cpp
index a1c4cd9..4cbc079 100644
--- a/clang/lib/Driver/ToolChains/WebAssembly.cpp
+++ b/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)) {
diff --git a/clang/test/Driver/wasm-toolchain.c b/clang/test/Driver/wasm-toolchain.c
index f391b28..b6d67f0 100644
--- a/clang/test/Driver/wasm-toolchain.c
+++ b/clang/test/Driver/wasm-toolchain.c
@@ -33,6 +33,20 @@
// 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 with a known OS.
+
+// 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"
+
+// -shared should be passed through to `wasm-ld` and not include crt1.o with an unknown OS.
+
+// RUN: %clang -### -shared --target=wasm32-unknown-unknown --sysroot=/foo %s 2>&1 \
+// RUN: | FileCheck -check-prefix=LINK_UNKNOWN_SHARED %s
+// LINK_UNKNOWN_SHARED: "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
+// LINK_UNKNOWN_SHARED: wasm-ld{{.*}}" "-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 +60,18 @@
// RUN: | FileCheck -check-prefix=COMPILE %s
// COMPILE: "-cc1" {{.*}} "-internal-isystem" "/foo/include/wasm32-wasi" "-internal-isystem" "/foo/include"
+// -fPIC should work on a known OS
+
+// RUN: %clang -### -fPIC --target=wasm32-wasi --sysroot=/foo %s 2>&1 \
+// RUN: | FileCheck -check-prefix=COMPILE_KNOWN_PIC %s
+// COMPILE_KNOWN_PIC: "-cc1" {{.*}} "-mrelocation-model" "pic" "-pic-level" "2" {{.*}} "-internal-isystem" "/foo/include/wasm32-wasi" "-internal-isystem" "/foo/include"
+
+// -fPIC should work on an unknown OS
+
+// RUN: %clang -### -fPIC --target=wasm32-unknown-unknown --sysroot=/foo %s 2>&1 \
+// RUN: | FileCheck -check-prefix=COMPILE_UNKNOWN_PIC %s
+// COMPILE_UNKNOWN_PIC: "-cc1" {{.*}} "-mrelocation-model" "pic" "-pic-level" "2"
+
// Thread-related command line tests.
// '-pthread' sets +atomics, +bulk-memory, +mutable-globals, +sign-ext, and --shared-memory
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
index 630c786..788e08e 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
@@ -98,13 +98,6 @@
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;
}
