Initial commit

Author: abrown

.gitignore

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+build
+*.wasm

.gitmodules

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+[submodule "llvm-project"]
+	path = llvm-project
+	url = https://github.com/abrown/llvm-project
+	branch = wasm-openmp
+	shallow = true

Makefile

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+PROJECT_DIR := $(realpath .)
+BUILD_DIR := $(PROJECT_DIR)/build
+
+# Specify a different wasi-sdk with `make WASI_SDK_DIR=...`.
+WASI_SDK_DIR := /opt/wasi-sdk/latest
+WASI_CC := $(WASI_SDK_DIR)/bin/clang
+WASI_SYSROOT := $(WASI_SDK_DIR)/share/wasi-sysroot
+TARGET_FLAGS=--target=wasm32-wasi-threads -pthread
+WASI_LIBC_FLAGS=-D_WASI_EMULATED_SIGNAL -D_WASI_EMULATED_PROCESS_CLOCKS
+SYSROOT_FLAGS=--sysroot=$(WASI_SYSROOT)
+
+# Specify a different location for the OpenMP sources with `make OPENMP_DIR=...`.
+OPENMP_DIR := $(PROJECT_DIR)/llvm-project/openmp
+OPENMP_LIB := $(BUILD_DIR)/runtime/src/libomp.a
+
+# Specify a different Wasm engine to invoke with `make WASM_ENGINE=...`.
+WASM_ENGINE=WASMTIME_LOG=wasmtime_runtime::memory=trace,wasmtime_wasi_threads=trace ../wasmtime/target/release/wasmtime
+
+# The default target--builds and runs everything.
+all: run
+
+# Run the compiled example in a WebAssembly engine.
+run: example.wasm
+	$(WASM_ENGINE) -W threads -S threads $^
+
+# Compile the example; note how we will need the `libomp.a` runtime.
+example.wasm: example.c $(OPENMP_LIB)
+	make check-wasi-sdk
+	$(WASI_CC) -fopenmp=libomp -g --sysroot=$(WASI_SYSROOT) --target=wasm32-wasi-threads \
+	  -I$(BUILD_DIR)/runtime/src -I$(WASI_SYSROOT)/include -pthread \
+	  -Wl,--import-memory,--export-memory,--max-memory=67108864 example.c \
+	  -L$(BUILD_DIR)/runtime/src -lomp \
+	  -lwasi-emulated-getpid \
+	  -o example.wasm
+
+# Compile the `libomp.a` runtime library to WebAssembly. This uses the PR changes from
+# https://github.com/llvm/llvm-project/pull/71297.
+libomp: $(OPENMP_LIB)
+$(OPENMP_LIB): $(OPENMP_DIR)
+	make check-wasi-sdk
+	cmake \
+	  -DCMAKE_BUILD_TYPE=Debug \
+	  -DCMAKE_C_COMPILER="$(WASI_SDK_DIR)/bin/clang" \
+	  -DCMAKE_C_FLAGS="$(TARGET_FLAGS) $(WASI_LIBC_FLAGS) $(SYSROOT_FLAGS)" \
+	  -DCMAKE_CXX_COMPILER="$(WASI_SDK_DIR)/bin/clang++" \
+	  -DCMAKE_CXX_FLAGS="$(TARGET_FLAGS) $(WASI_LIBC_FLAGS) $(SYSROOT_FLAGS)" \
+	  -DCMAKE_LINKER="${WASI_SDK}/bin/ld.lld" \
+	  -B $(BUILD_DIR) \
+	  -S $(OPENMP_DIR)
+	cmake --build $(BUILD_DIR)
+$(OPENMP_DIR):
+	$(error cannot find $@; retrieve the submodule with `git submodule update --init` or rerun with `make OPENMP_DIR=...`)
+
+# Check that the parts of wasi-sdk we need are present; if they're not, fail.
+check-wasi-sdk: $(WASI_CC) $(WASI_SYSROOT)
+$(WASI_CC) $(WASI_SYSROOT):
+	$(error cannot find $@; install wasi-sdk from https://github.com/WebAssembly/wasi-sdk/releases and rerun with `make WASI_SDK_DIR=...`)
+
+clean:
+	rm -f *.wasm
+	rm -rf $(BUILD_DIR)

README.md

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+`wasm-openmp-examples`
+======================
+
+This project contains some sample code demonstrating how to build and run OpenMP code in a
+WebAssembly engine. There are several parts to the [`Makefile`]:
+- `make libomp`: first, we show how to compile `libomp.a`, the OpenMP runtime, to WebAssembly using
+  support for [wasi-threads] in [wasi-sdk]
+- `make examples`: then, we compile our examples, `example*.c`, to WebAssembly and link them with
+  `libomp.a`
+- `make run`: finally, we run the compiled WebAssembly module in the [wasmtime] engine
+- optionally, we show how to patch Clang to avoid a crash with `#pragma omp critical`
+
+[`Makefile`]: ./Makefile
+[wasi-threads]: https://github.com/WebAssembly/wasi-threads
+[wasi-sdk]: https://github.com/WebAssembly/wasi-sdk
+[wasmtime]: https://github.com/bytecodealliance/wasmtime
+
+The work to upstream the "compile-OpenMP-to-WebAssembly" is available at: [llvm-project#71297].
+
+[llvm-project#71297]: https://github.com/llvm/llvm-project/pull/71297
+
+### Build and Run
+
+To execute all Makefile targets in sequence, run:
+
+```
+make
+```

example.c

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+#include <omp.h>
+#include <stdio.h>
+
+int main(int argc, char** argv) {
+#pragma omp parallel num_threads(8)
+  { printf("Hello World... from thread = %d\n", omp_get_thread_num()); }
+}