Add Wasm support (in progress)

examples/wasm_example/BUILD.bazel

@@ -0,0 +1,9 @@
+load("@rules_ll//ll:defs.bzl", "ll_binary")
+
+ll_binary(
+    name = "wasm_example",
+    srcs = ["wasm_example.cpp"],
+    compilation_mode = "wasm",
+    compile_flags = ["-std=c++20"],
+    visibility = ["@//:__pkg__"],
+)

examples/wasm_example/wasm_example.cpp

@@ -0,0 +1,3 @@
+extern "C" int add(int a, int b) {
+  return a + b;
+}

ll/args.bzl

@@ -257,6 +257,10 @@ def compile_object_args(
             format = "--rocm-device-lib-path=%s",
         )
 
+    if ctx.attr.compilation_mode == "wasm":
+        args.add("--target=wasm32-unknown-unknown")
+        # args.add("-emit-llvm-bc")
+
     # Write compilation database.
     args.add("-Xarch_host")
     args.add(cdf, format = "-MJ%s")
@@ -520,6 +524,11 @@ def link_executable_args(ctx, in_files, out_file, mode):
             format = "-rpath=$ORIGIN/%s",
         )
 
+    if ctx.attr.compilation_mode == "wasm":
+        pass
+        # args.add("--no-entry")
+        # args.add("--export-all")  # This must be changed (similar to cppm)
+
     # Additional system libraries.
     args.add("-lm")  # Math.
     args.add("-ldl")  # Dynamic linking.

ll/attributes.bzl

@@ -40,6 +40,7 @@ DEFAULT_ATTRS = {
             "cuda_nvptx",
             "hip_amdgpu",
             "hip_nvptx",
+            "wasm",
             "bootstrap",
         ],
     ),
@@ -309,6 +310,13 @@ LL_TOOLCHAIN_ATTRS = {
         cfg = transition_to_bootstrap,
         default = "@llvm-project//llvm:llvm-link",
     ),
+    "wasm_linker": attr.label(
+        doc = "The linker for WebAssembly",
+        executable = True,
+        allow_single_file = True,
+        cfg = transition_to_bootstrap,
+        default = "@llvm-project//lld:wasm-ld",
+    ),
     "builtin_includes": attr.label(
         doc = "Clang's built-in header files.",
         cfg = "target",

ll/environment.bzl

@@ -30,6 +30,16 @@ def compile_object_environment(ctx):
                 toolchain.linker_executable.dirname,
             ]),
         }
+    elif config in ["wasm"]:
+        return {
+            "LINK": toolchain.bitcode_linker.path,
+            "LLD": toolchain.wasm_linker.path,
+            "LLVM_SYMBOLIZER_PATH": toolchain.symbolizer.path,
+            "PATH": ":".join([
+                toolchain.linker.dirname,
+                toolchain.linker_executable.dirname,
+            ]),
+        }
     elif config in ["cuda_nvptx", "hip_amdgpu", "hip_nvptx"]:
         return {
             "CLANG_OFFLOAD_BUNDLER": toolchain.offload_bundler.path,

ll/inputs.bzl

@@ -71,7 +71,7 @@ def compile_object_inputs(
         toolchain.compiler_runtime
     )
 
-    if config == "cpp":
+    if config in ["cpp", "wasm"]:
         pass
     elif config == "omp_cpu":
         direct += toolchain.omp_header
@@ -135,7 +135,7 @@ def link_executable_inputs(ctx, in_files):
     if ctx.attr.depends_on_llvm:
         direct += toolchain.llvm_project_artifacts
 
-    if config == "cpp":
+    if config in ["cpp", "wasm"]:
         pass
     elif config == "omp_cpu":
         direct += toolchain.libomp
@@ -185,7 +185,7 @@ def link_shared_object_inputs(ctx, in_files):
         toolchain.compiler_runtime
     )
 
-    if config == "cpp":
+    if config == ["cpp", "wasm"]:
         pass
     elif config == "cuda_nvptx":
         pass

ll/toolchain.bzl

@@ -30,6 +30,7 @@ def _ll_toolchain_impl(ctx):
             linker = lld_alias,
             linker_executable = ctx.executable.linker,
             linker_wrapper = ctx.executable.linker_wrapper,
+            wasm_linker = ctx.executable.wasm_linker,
             address_sanitizer = ctx.files.address_sanitizer,
             leak_sanitizer = ctx.files.leak_sanitizer,
             memory_sanitizer = ctx.files.memory_sanitizer,

ll/tools.bzl

@@ -33,7 +33,7 @@ def compile_object_tools(ctx):
         toolchain.opt,
     ]
 
-    if config in ["cpp", "omp_cpu"]:
+    if config in ["cpp", "omp_cpu", "wasm"]:
         return tools
 
     if config in ["cuda_nvptx", "hip_nvptx", "hip_amdgpu"]:

ll/transitions.bzl

@@ -10,6 +10,7 @@ COMPILATION_MODES = [
     "cuda_nvptx",
     "hip_amdgpu",
     "hip_nvptx",
+    "wasm",
 ]
 
 def _ll_transition_impl(