path: root/contrib/restricted/wavm/Lib/LLVMJIT/EmitContext.h

#pragma once

#include "LLVMJITPrivate.h"
#include "WAVM/IR/Module.h"
#include "WAVM/IR/Types.h"
#include "WAVM/IR/Value.h"
#include "WAVM/RuntimeABI/RuntimeABI.h"

PUSH_DISABLE_WARNINGS_FOR_LLVM_HEADERS
#include <llvm/IR/Constant.h>
#include <llvm/IR/Constants.h>
#include <llvm/IR/IRBuilder.h>
#include <llvm/IR/Intrinsics.h>
#include <llvm/IR/Value.h>
POP_DISABLE_WARNINGS_FOR_LLVM_HEADERS

#if LLVM_VERSION_MAJOR >= 11
#define LLVM_ALIGNMENT(alignment) llvm::Align(alignment)
#elif LLVM_VERSION_MAJOR >= 10
#define LLVM_ALIGNMENT(alignment) llvm::MaybeAlign(alignment)
#else
#define LLVM_ALIGNMENT(alignment) alignment
#endif

#if LLVM_VERSION_MAJOR >= 12
#define LLVM_ELEMENT_COUNT(numElements) llvm::ElementCount::getFixed(numElements)
#define LLVM_LANE_INDEX_TYPE int
#elif LLVM_VERSION_MAJOR >= 11
#define LLVM_ELEMENT_COUNT(numElements) llvm::ElementCount(numElements, false)
#define LLVM_LANE_INDEX_TYPE int
#else
#define LLVM_ELEMENT_COUNT(numElements) ((unsigned int)(numElements))
#define LLVM_LANE_INDEX_TYPE uint32_t
#endif

#if LLVM_VERSION_MAJOR >= 12
#define LLVM_INTRINSIC_VECTOR_REDUCE_ADD llvm::Intrinsic::vector_reduce_add
#else
#define LLVM_INTRINSIC_VECTOR_REDUCE_ADD llvm::Intrinsic::experimental_vector_reduce_add
#endif

namespace WAVM { namespace LLVMJIT {
	// Code and state that is used for generating IR for both thunks and WASM functions.
	struct EmitContext
	{
		LLVMContext& llvmContext;
		llvm::IRBuilder<> irBuilder;

		llvm::Value* contextPointerVariable;

		struct MemoryInfo
		{
			llvm::Value* basePointerVariable;
			llvm::Value* endAddressVariable;
		};
		std::vector<MemoryInfo> memoryInfos;

		struct TryContext
		{
			llvm::BasicBlock* unwindToBlock;
		};
		std::vector<TryContext> tryStack;

		EmitContext(LLVMContext& inLLVMContext, const std::vector<llvm::Constant*>& inMemoryOffsets)
		: llvmContext(inLLVMContext)
		, irBuilder(inLLVMContext)
		, contextPointerVariable(nullptr)
		, memoryOffsets(inMemoryOffsets)
		{
		}

		llvm::LoadInst* loadFromUntypedPointer(llvm::Value* pointer,
											   llvm::Type* valueType,
											   U32 alignment = 1)
		{
			auto load = irBuilder.CreateLoad(
				valueType,
				irBuilder.CreatePointerCast(pointer, valueType->getPointerTo()));
			load->setAlignment(LLVM_ALIGNMENT(alignment));
			return load;
		}

		void storeToUntypedPointer(llvm::Value* value, llvm::Value* pointer, U32 alignment = 1)
		{
			auto store = irBuilder.CreateStore(
				value, irBuilder.CreatePointerCast(pointer, value->getType()->getPointerTo()));
			store->setAlignment(LLVM_ALIGNMENT(alignment));
		}

		llvm::Value* getCompartmentAddress()
		{
			// Derive the compartment runtime data from the context address by masking off the lower
			// 31 bits.
			return irBuilder.CreateIntToPtr(
				irBuilder.CreateAnd(
					irBuilder.CreatePtrToInt(irBuilder.CreateLoad(llvmContext.i8PtrType, contextPointerVariable),
											 llvmContext.i64Type),
					emitLiteral(llvmContext, ~((U64(1) << 31) - 1))),
				llvmContext.i8PtrType);
		}

		void reloadMemoryBases()
		{
			llvm::Value* compartmentAddress = getCompartmentAddress();

			// Reload the memory base pointer and num reserved bytes values from the
			// CompartmentRuntimeData.
			for(Uptr memoryIndex = 0; memoryIndex < memoryOffsets.size(); ++memoryIndex)
			{
				MemoryInfo& memoryInfo = memoryInfos[memoryIndex];

				llvm::Constant* memoryOffset = memoryOffsets[memoryIndex];
				irBuilder.CreateStore(
					loadFromUntypedPointer(
						irBuilder.CreateInBoundsGEP(llvmContext.i8Type, compartmentAddress, {memoryOffset}),
						llvmContext.i8PtrType,
						sizeof(U8*)),
					memoryInfo.basePointerVariable);

				llvm::Value* memoryNumReservedBytesOffset = llvm::ConstantExpr::getAdd(
					memoryOffset,
					emitLiteralIptr(offsetof(Runtime::MemoryRuntimeData, endAddress),
									memoryOffset->getType()));
				irBuilder.CreateStore(
					loadFromUntypedPointer(irBuilder.CreateInBoundsGEP(
												llvmContext.i8Type, compartmentAddress, {memoryNumReservedBytesOffset}),
										   memoryOffset->getType()),
					memoryInfo.endAddressVariable);
			}
		}

		void initContextVariables(llvm::Value* initialContextPointer, llvm::Type* iptrType)
		{
			memoryInfos.resize(memoryOffsets.size());
			for(Uptr memoryIndex = 0; memoryIndex < memoryOffsets.size(); ++memoryIndex)
			{
				MemoryInfo& memoryInfo = memoryInfos[memoryIndex];

				memoryInfo.basePointerVariable = irBuilder.CreateAlloca(
					llvmContext.i8PtrType, nullptr, "memoryBase" + llvm::Twine(memoryIndex));

				memoryInfo.endAddressVariable = irBuilder.CreateAlloca(
					iptrType,
					nullptr,
					"memoryNumReservedBytesMinusGuardBytes" + llvm::Twine(memoryIndex));
			}
			contextPointerVariable
				= irBuilder.CreateAlloca(llvmContext.i8PtrType, nullptr, "context");
			irBuilder.CreateStore(initialContextPointer, contextPointerVariable);
			reloadMemoryBases();
		}

		// Emits a call to a WAVM intrinsic function.
		ValueVector emitRuntimeIntrinsic(const char* intrinsicName,
										 IR::FunctionType intrinsicType,
										 const std::initializer_list<llvm::Value*>& args)
		{
			WAVM_ASSERT(intrinsicType.callingConvention() == IR::CallingConvention::intrinsic);

			llvm::Module* llvmModule = irBuilder.GetInsertBlock()->getParent()->getParent();
			llvm::Function* intrinsicFunction = llvmModule->getFunction(intrinsicName);
			if(!intrinsicFunction)
			{
				intrinsicFunction = llvm::Function::Create(asLLVMType(llvmContext, intrinsicType),
														   llvm::Function::ExternalLinkage,
														   intrinsicName,
														   llvmModule);
				intrinsicFunction->setCallingConv(
					asLLVMCallingConv(intrinsicType.callingConvention()));
			}

			return emitCallOrInvoke(
				intrinsicFunction, args, intrinsicType, getInnermostUnwindToBlock());
		}

		// Creates either a call or an invoke if the call occurs inside a try.
		ValueVector emitCallOrInvoke(llvm::Value* callee,
									 llvm::ArrayRef<llvm::Value*> args,
									 IR::FunctionType calleeType,
									 llvm::BasicBlock* unwindToBlock = nullptr)
		{
			const IR::CallingConvention callingConvention = calleeType.callingConvention();

			llvm::ArrayRef<llvm::Value*> callArgs = args;

			llvm::Value* resultsArray = nullptr;
			if(callingConvention == IR::CallingConvention::cAPICallback)
			{
				// Pass in pointers to argument and result arrays.
				auto argsArray = irBuilder.CreateAlloca(
					llvmContext.i8Type,
					emitLiteral(llvmContext, Uptr(args.size() * sizeof(IR::UntaggedValue))));
				for(Uptr argIndex = 0; argIndex < args.size(); ++argIndex)
				{
					storeToUntypedPointer(
						args[argIndex],
						irBuilder.CreateInBoundsGEP(
							llvmContext.i8Type,
							argsArray,
							{emitLiteral(llvmContext,
										 Uptr(argIndex * sizeof(IR::UntaggedValue)))}));
				}

				resultsArray = irBuilder.CreateAlloca(
					llvmContext.i8Type,
					emitLiteral(llvmContext,
								Uptr(calleeType.results().size() * sizeof(IR::UntaggedValue))));

				auto callArgsAlloca = (llvm::Value**)alloca(sizeof(llvm::Value*) * 2);
				callArgs = llvm::ArrayRef<llvm::Value*>(callArgsAlloca, 2);
				callArgsAlloca[0] = argsArray;
				callArgsAlloca[1] = resultsArray;
			}
			else if(callingConvention != IR::CallingConvention::c)
			{
				// Augment the argument list with the context pointer.
				auto callArgsAlloca
					= (llvm::Value**)alloca(sizeof(llvm::Value*) * (args.size() + 1));
				callArgs = llvm::ArrayRef<llvm::Value*>(callArgsAlloca, args.size() + 1);
				callArgsAlloca[0] = irBuilder.CreateLoad(llvmContext.i8PtrType, contextPointerVariable);
				for(Uptr argIndex = 0; argIndex < args.size(); ++argIndex)
				{ callArgsAlloca[1 + argIndex] = args[argIndex]; }
			}

			// Call or invoke the callee.
			llvm::Value* returnValue;
			llvm::FunctionType* llvmCalleeType = asLLVMType(llvmContext, calleeType);
			if(!unwindToBlock)
			{
				auto call = irBuilder.CreateCall(llvmCalleeType, callee, callArgs);
				call->setCallingConv(asLLVMCallingConv(callingConvention));
				returnValue = call;
			}
			else
			{
				auto returnBlock = llvm::BasicBlock::Create(
					llvmContext, "invokeReturn", irBuilder.GetInsertBlock()->getParent());
#if LLVM_VERSION_MAJOR >= 8
				auto invoke = irBuilder.CreateInvoke(
					llvmCalleeType, callee, returnBlock, unwindToBlock, callArgs);
#else
				auto invoke = irBuilder.CreateInvoke(callee, returnBlock, unwindToBlock, callArgs);
#endif
				invoke->setCallingConv(asLLVMCallingConv(callingConvention));
				irBuilder.SetInsertPoint(returnBlock);
				returnValue = invoke;
			}

			ValueVector results;
			switch(callingConvention)
			{
			case IR::CallingConvention::wasm: {
				// Update the context variable.
				auto newContextPointer = irBuilder.CreateExtractValue(returnValue, {0});
				irBuilder.CreateStore(newContextPointer, contextPointerVariable);

				// Reload the memory/table base pointers.
				reloadMemoryBases();

				if(areResultsReturnedDirectly(calleeType.results()))
				{
					// If the results are returned directly, extract them from the returned struct.
					for(Uptr resultIndex = 0; resultIndex < calleeType.results().size();
						++resultIndex)
					{
						results.push_back(
							irBuilder.CreateExtractValue(returnValue, {U32(1), U32(resultIndex)}));
					}
				}
				else
				{
					// Otherwise, load them from the context.
					Uptr resultOffset = 0;
					for(IR::ValueType resultType : calleeType.results())
					{
						const U8 resultNumBytes = getTypeByteWidth(resultType);

						resultOffset = (resultOffset + resultNumBytes - 1) & -I8(resultNumBytes);
						WAVM_ASSERT(resultOffset < Runtime::maxThunkArgAndReturnBytes);

						results.push_back(loadFromUntypedPointer(
							irBuilder.CreateInBoundsGEP(llvmContext.i8Type,
														newContextPointer,
														{emitLiteral(llvmContext, resultOffset)}),
							asLLVMType(llvmContext, resultType),
							resultNumBytes));

						resultOffset += resultNumBytes;
					}
				}

				break;
			}
			case IR::CallingConvention::intrinsicWithContextSwitch: {
				auto newContextPointer = returnValue;

				// Update the context variable.
				irBuilder.CreateStore(newContextPointer, contextPointerVariable);

				// Reload the memory/table base pointers.
				reloadMemoryBases();

				// Load the call result from the returned context.
				WAVM_ASSERT(calleeType.results().size() <= 1);
				if(calleeType.results().size() == 1)
				{
					llvm::Type* llvmResultType = asLLVMType(llvmContext, calleeType.results()[0]);
					results.push_back(
						loadFromUntypedPointer(newContextPointer,
											   llvmResultType,
											   IR::getTypeByteWidth(calleeType.results()[0])));
				}

				break;
			}
			case IR::CallingConvention::cAPICallback: {
				// Check whether the call returned an Exception.
				auto exception = returnValue;
				auto function = irBuilder.GetInsertBlock()->getParent();
				auto trapBlock = llvm::BasicBlock::Create(llvmContext, "intrinsicTrap", function);
				auto returnBlock
					= llvm::BasicBlock::Create(llvmContext, "intrinsicReturn", function);
				irBuilder.CreateCondBr(
					irBuilder.CreateICmpEQ(exception,
										   llvm::Constant::getNullValue(llvmContext.i8PtrType)),
					returnBlock,
					trapBlock);

				// If the call returned and Exception, throw it.
				irBuilder.SetInsertPoint(trapBlock);
				llvm::Module* llvmModule = irBuilder.GetInsertBlock()->getParent()->getParent();
				llvm::Type* iptrType
					= llvmModule->getDataLayout().getIntPtrType(exception->getType());
				IR::ValueType iptrValueType = iptrType->getIntegerBitWidth() == 32
												  ? IR::ValueType::i32
												  : IR::ValueType::i64;
				emitRuntimeIntrinsic("throwException",
									 IR::FunctionType(IR::TypeTuple{},
													  IR::TypeTuple{iptrValueType},
													  IR::CallingConvention::intrinsic),
									 {irBuilder.CreatePtrToInt(exception, iptrType)});
				irBuilder.CreateUnreachable();

				// Load the results from the results array.
				irBuilder.SetInsertPoint(returnBlock);
				for(Uptr resultIndex = 0; resultIndex < calleeType.results().size(); ++resultIndex)
				{
					results.push_back(loadFromUntypedPointer(
						irBuilder.CreateInBoundsGEP(
							llvmContext.i8Type,
							resultsArray,
							{emitLiteral(llvmContext, resultIndex * sizeof(IR::UntaggedValue))}),
						asLLVMType(llvmContext, calleeType.results()[resultIndex])));
				}

				break;
			}
			case IR::CallingConvention::intrinsic:
			case IR::CallingConvention::c: {
				WAVM_ASSERT(calleeType.results().size() <= 1);
				if(calleeType.results().size() == 1) { results.push_back(returnValue); }
				break;
			}
			default: WAVM_UNREACHABLE();
			};

			return results;
		}

		void emitReturn(IR::TypeTuple resultTypes, const llvm::ArrayRef<llvm::Value*>& results)
		{
			llvm::Value* returnStruct = getZeroedLLVMReturnStruct(llvmContext, resultTypes);
			returnStruct = irBuilder.CreateInsertValue(
				returnStruct, irBuilder.CreateLoad(llvmContext.i8PtrType, contextPointerVariable), {U32(0)});

			WAVM_ASSERT(resultTypes.size() == results.size());
			if(areResultsReturnedDirectly(resultTypes))
			{
				// If the results are returned directly, insert them into the return struct.
				for(Uptr resultIndex = 0; resultIndex < results.size(); ++resultIndex)
				{
					llvm::Value* result = results[resultIndex];
					returnStruct = irBuilder.CreateInsertValue(
						returnStruct, result, {U32(1), U32(resultIndex)});
				}
			}
			else
			{
				// Otherwise, store them in the context.
				Uptr resultOffset = 0;
				for(Uptr resultIndex = 0; resultIndex < results.size(); ++resultIndex)
				{
					const IR::ValueType resultType = resultTypes[resultIndex];
					const U8 resultNumBytes = IR::getTypeByteWidth(resultType);

					resultOffset = (resultOffset + resultNumBytes - 1) & -I8(resultNumBytes);
					WAVM_ASSERT(resultOffset < Runtime::maxThunkArgAndReturnBytes);

					irBuilder.CreateStore(results[resultIndex],
										  irBuilder.CreatePointerCast(
											  irBuilder.CreateInBoundsGEP(
												  llvmContext.i8Type,
												  irBuilder.CreateLoad(llvmContext.i8PtrType, contextPointerVariable),
												  {emitLiteral(llvmContext, resultOffset)}),
											  asLLVMType(llvmContext, resultType)->getPointerTo()));

					resultOffset += resultNumBytes;
				}
			}

			irBuilder.CreateRet(returnStruct);
		}

		llvm::BasicBlock* getInnermostUnwindToBlock();

	private:
		std::vector<llvm::Constant*> memoryOffsets;
	};
}}