Integrating LLVM optimizations with wasm-opt #7634
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| /* | ||
| * Copyright 2024 WebAssembly Community Group participants | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| // | ||
| // Run LLVM to optimize the wasm. | ||
| // | ||
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| #include "pass.h" | ||
| #include "support/utilities.h" | ||
| #include "wasm-builder.h" | ||
| #include "wasm-traversal.h" | ||
| #include "wasm.h" | ||
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| #include "llvm/IR/DerivedTypes.h" | ||
| #include "llvm/IR/GlobalAlias.h" | ||
| #include "llvm/IR/GlobalValue.h" | ||
| #include "llvm/IR/IRBuilder.h" | ||
| #include "llvm/IR/LLVMContext.h" | ||
| #include "llvm/IR/Module.h" | ||
| #include "llvm/IR/Type.h" | ||
| #include "llvm/IR/Value.h" | ||
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| #include <cassert> | ||
| #include <iostream> | ||
| #include <llvm-18/llvm/IR/BasicBlock.h> | ||
| #include <llvm-18/llvm/IR/Constants.h> | ||
| #include <llvm-18/llvm/IR/GlobalVariable.h> | ||
| #include <llvm-18/llvm/IR/Instructions.h> | ||
| #include <llvm-18/llvm/Support/Alignment.h> | ||
| #include <llvm-18/llvm/Support/Casting.h> | ||
| #include <memory> | ||
| #include <string> | ||
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| using namespace llvm; | ||
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| namespace wasm { | ||
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| llvm::Type* convertWasmTypeToLLVMType(Type* wasmType, | ||
| llvm::IRBuilder<>& builder); | ||
| llvm::Type* determineLoadType(Load* wasmLoad, llvm::IRBuilder<>& builder); | ||
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| struct LLVMCodeGen : Visitor<LLVMCodeGen, Value*> { | ||
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| std::unique_ptr<LLVMContext> llvmCtx; | ||
| std::unique_ptr<llvm::Module> llvmMod; | ||
| std::unique_ptr<IRBuilder<>> llvmBuilder; | ||
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| std::unique_ptr<Builder> wasmBuilder; | ||
| Module* module; | ||
| Function* func; | ||
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| int funCounter; | ||
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| LLVMCodeGen() { | ||
| llvmCtx = std::make_unique<LLVMContext>(); | ||
| llvmMod = std::make_unique<llvm::Module>("LLVMOpt", *llvmCtx); | ||
| llvmBuilder = std::make_unique<IRBuilder<>>(*llvmCtx); | ||
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| llvmMod->setTargetTriple("wasm32-unknown-unknown"); | ||
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| funCounter = 0; | ||
| } | ||
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| Value* visitModule(Module* module_) { | ||
| module = module_; | ||
| for (auto& mem : module->memories) { | ||
| // Handle memory | ||
| visitMemory(mem.get()); | ||
| } | ||
| for (auto& func : module->functions) { | ||
| visitFunction(func.get()); | ||
| // if (auto llvmFn = dyn_cast<llvm::Function>(visitFunction(func.get()))) | ||
| // { | ||
| // auto* entryBB = llvm::BasicBlock::Create(*llvmCtx, "entry", llvmFn); | ||
| // llvmBuilder->SetInsertPoint(entryBB); | ||
| // } | ||
| } | ||
| std::cout << "Module generated successfully!" << std::endl; | ||
| llvmMod->dump(); | ||
| return nullptr; | ||
| } | ||
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| Value* visitMemory(Memory* mem) { | ||
| // Given: Memory* mem = ...; | ||
| auto pageSize = Memory::kPageSize; // 64KB | ||
| uint64_t totalSize = mem->initial * pageSize; | ||
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| // Create global memory buffer | ||
| ArrayType* memType = ArrayType::get(llvmBuilder->getInt8Ty(), totalSize); | ||
| GlobalVariable* llvmMem = new GlobalVariable( | ||
| *llvmMod, | ||
| memType, // Type (e.g., [65536 x i8]) | ||
| false, // isConstant = false (mutable) | ||
| GlobalValue::AvailableExternallyLinkage, // TODO: Check this | ||
| ConstantAggregateZero::get(memType), | ||
| "wasm_memory"); | ||
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| // For shared memory (if needed) | ||
| if (mem->shared) { | ||
| llvmMem->setUnnamedAddr(GlobalValue::UnnamedAddr::Global); | ||
| } | ||
| return nullptr; | ||
| } | ||
| Value* visitFunction(Function* func) { | ||
| std::cout << "[visitFunction]" << std::endl; | ||
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| // Create function type | ||
| std::vector<llvm::Type*> llvmParamsTypes; | ||
| std::vector<llvm::Type*> llvmResultTypes; | ||
| for (auto param : func->getParams()) { | ||
| llvmParamsTypes.push_back( | ||
| convertWasmTypeToLLVMType(¶m, *llvmBuilder)); | ||
| } | ||
| for (auto result : func->getResults()) { | ||
| llvmResultTypes.push_back( | ||
| convertWasmTypeToLLVMType(&result, *llvmBuilder)); | ||
| } | ||
| // Currently not support multiple value results. | ||
| assert(llvmResultTypes.size() == 1); | ||
| llvm::FunctionType* funcType = | ||
| llvm::FunctionType::get(llvmResultTypes[0], llvmParamsTypes, false); | ||
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| llvm::Function* llvmFn = llvm::Function::Create( | ||
| funcType, | ||
| GlobalValue::ExternalLinkage, // TODO: be used outside, to prevents LLVM | ||
| // from assuming the function is unused | ||
| "func" + std::to_string(funCounter++), | ||
| llvmMod.get()); | ||
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| // Create a new basic block to start insertion into. | ||
| BasicBlock* BB = BasicBlock::Create(*llvmCtx, "entry", llvmFn); | ||
| llvmBuilder->SetInsertPoint(BB); | ||
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| if (Value* ret = visit(func->body)) { | ||
| // Finish off the function. | ||
| llvmBuilder->CreateRet(ret); | ||
| return llvmFn; | ||
| } | ||
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| // Error reading body, remove function | ||
| llvmFn->eraseFromParent(); | ||
| assert(0 && "Now we just trap"); | ||
| return nullptr; | ||
| } | ||
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| // Visiting. | ||
| Value* visitBlock(Block* block) { | ||
| Value* ret = nullptr; | ||
| for (auto expr : block->list) { | ||
| ret = visit(expr); | ||
| } | ||
| return ret; | ||
| } | ||
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| Value* visitConst(Const* c) { | ||
| assert(c->type.isBasic()); | ||
| switch (c->type.getBasic()) { | ||
|
There was a problem hiding this comment. Note LLVM supports WASM's |
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| case wasm::Type::i32: | ||
| return ConstantInt::get(llvmBuilder->getInt32Ty(), c->value.geti32()); | ||
| case wasm::Type::f32: | ||
| return ConstantInt::get(llvmBuilder->getFloatTy(), c->value.getf32()); | ||
| case wasm::Type::i64: | ||
| return ConstantInt::get(llvmBuilder->getInt64Ty(), c->value.geti64()); | ||
| case wasm::Type::f64: | ||
| return ConstantInt::get(llvmBuilder->getDoubleTy(), c->value.getf64()); | ||
| case wasm::Type::v128: | ||
| case wasm::Type::none: | ||
| case wasm::Type::unreachable: | ||
| break; | ||
| default: | ||
| WASM_UNREACHABLE("Unknown type"); | ||
| } | ||
| return nullptr; | ||
| } | ||
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| Value* visitStore(Store* store) { | ||
| // 1. Get the @wasm_memory global variable. | ||
| GlobalVariable* wasmMemory = | ||
| llvmMod->getGlobalVariable("wasm_memory", true); | ||
|
There was a problem hiding this comment. If multiple memories are supported, this would be unsound. There was a problem hiding this comment. The initial though would be:
So, in my humble view, it's better to satrt with MVP first. |
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| assert(wasmMemory && "wasm_memory global not found"); | ||
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| // 2. Cast the global to i8* (pointer to first byte of memory) | ||
| Value* basePtr = llvmBuilder->CreatePointerCast( | ||
| wasmMemory, llvmBuilder->getInt8Ty()->getPointerTo(), "mem_base"); | ||
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| // 3. Evaluate the pointer (offset from memory base) | ||
| auto* totalOffset = llvmBuilder->CreateAdd( | ||
| visit(store->ptr), | ||
| ConstantInt::get(llvmBuilder->getInt32Ty(), store->offset.addr), | ||
| "mem_offset"); | ||
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| // 4. Compute the final address: basePtr + totalOffSet | ||
| Value* addr = llvmBuilder->CreateGEP( | ||
| llvmBuilder->getInt8Ty(), basePtr, totalOffset, "mem_ptr"); | ||
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| // 5. Determine the type of the value to store | ||
| llvm::Type* storedType = | ||
| convertWasmTypeToLLVMType(&store->valueType, *llvmBuilder); | ||
| Value* typedPtr = | ||
| llvmBuilder->CreateBitCast(addr, storedType->getPointerTo(), "typed_ptr"); | ||
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| // 6. Create the store instruction | ||
| StoreInst* storeInst = | ||
| llvmBuilder->CreateStore(visit(store->value), typedPtr); | ||
| storeInst->setAlignment(llvm::Align(store->align.addr)); | ||
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| // Handle alignment (WebAssembly uses pow2 alignment) | ||
| return storeInst; | ||
| } | ||
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| Value* visitLoad(Load* load) { | ||
| // As above visitStore | ||
| GlobalVariable* wasmMemory = llvmMod->getGlobalVariable("wasm_memory"); | ||
| assert(wasmMemory && "wasm_memory global not found"); | ||
| Value* basePtr = llvmBuilder->CreatePointerCast( | ||
| wasmMemory, llvmBuilder->getPtrTy(), "mem_base"); | ||
| Value* totalOffset = llvmBuilder->CreateAdd( | ||
| visit(load->ptr), | ||
| ConstantInt::get(llvmBuilder->getInt32Ty(), load->offset.addr), | ||
| "mem_offset"); | ||
| Value* finalAddr = llvmBuilder->CreateGEP( | ||
| llvmBuilder->getInt8Ty(), basePtr, totalOffset, "mem_ptr"); | ||
| llvm::Type* loadedType = determineLoadType(load, *llvmBuilder); | ||
| Value* typedPtr = llvmBuilder->CreateBitCast( | ||
| finalAddr, loadedType->getPointerTo(), "typed_ptr"); | ||
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| // Handle alignment (WebAssembly uses pow2 alignment) | ||
| unsigned alignment = load->align != 0 ? (1 << load->align) : load->bytes; | ||
| LoadInst* loadInst = | ||
| llvmBuilder->CreateLoad(loadedType, typedPtr, load->memory.toString()); | ||
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| loadInst->setAlignment(llvm::Align(alignment)); | ||
| loadInst->setVolatile(load->isAtomic); // Atomic implies volatile in LLVM | ||
| return loadInst; | ||
| } | ||
| }; | ||
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| struct LLVMOpt : public Pass { | ||
| std::unique_ptr<Pass> create() override { | ||
| return std::make_unique<LLVMOpt>(); | ||
| } | ||
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| void run(Module* module) override { LLVMCodeGen().visitModule(module); } | ||
| }; | ||
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| Pass* createLLVMOptPass() { return new LLVMOpt(); } | ||
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| llvm::Type* convertWasmTypeToLLVMType(Type* wasmType, | ||
| llvm::IRBuilder<>& llvmBuilder) { | ||
| switch (wasmType->getBasic()) { | ||
| case Type::i32: | ||
| return llvmBuilder.getInt32Ty(); | ||
| case Type::i64: | ||
| return llvmBuilder.getInt64Ty(); | ||
| case Type::f32: | ||
| return llvmBuilder.getFloatTy(); | ||
| case Type::f64: | ||
| return llvmBuilder.getDoubleTy(); | ||
| case Type::v128: /* handle vector type */ | ||
| break; | ||
| default: | ||
| // Handle other cases or throw error | ||
| WASM_UNREACHABLE("Unsupported WASM type"); | ||
| } | ||
| return nullptr; | ||
| } | ||
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| llvm::Type* determineLoadType(Load* wasmLoad, llvm::IRBuilder<>& llvmBuilder) { | ||
| // First check the explicit type if available | ||
| if (wasmLoad->type != Type::none) { | ||
| switch (wasmLoad->type.getBasic()) { | ||
| case Type::i32: | ||
| return llvmBuilder.getInt32Ty(); | ||
| case Type::i64: | ||
| return llvmBuilder.getInt64Ty(); | ||
| case Type::f32: | ||
| return llvmBuilder.getFloatTy(); | ||
| case Type::f64: | ||
| return llvmBuilder.getDoubleTy(); | ||
| case Type::v128: /* SIMD */ | ||
| return llvm::FixedVectorType::get(llvmBuilder.getInt32Ty(), 4); | ||
| default: | ||
| break; | ||
| } | ||
| } | ||
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| // Fall back to byte size and signedness | ||
| switch (wasmLoad->bytes) { | ||
| case 1: | ||
| return wasmLoad->signed_ ? llvmBuilder.getInt8Ty() | ||
| : llvmBuilder.getInt8Ty(); | ||
| case 2: | ||
| return wasmLoad->signed_ ? llvmBuilder.getInt16Ty() | ||
| : llvmBuilder.getInt16Ty(); | ||
| case 4: | ||
| return wasmLoad->signed_ ? llvmBuilder.getInt32Ty() | ||
| : llvmBuilder.getInt32Ty(); | ||
| case 8: | ||
| return llvmBuilder.getInt64Ty(); | ||
| default: | ||
| assert(false && "Invalid load byte size"); | ||
| return llvmBuilder.getInt32Ty(); // fallback | ||
| } | ||
| } | ||
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| } // namespace wasm | ||
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How would this be rewritten back into, presumably, multi-memory WASM? Or should this pass only work on single-memory WASM?
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I'm still relatively new to compilers and WebAssembly (currently studying both), so please forgive any naivety in my code. This was just a small attempt...
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As a newbie, I’m trying to learn compilers and sys like llvm and wasm. However, the docs are huge and not very beginner-friendly. Any advice on where and how to start? Thanks!