WebAssemblyFixFunctionBitcasts.cpp File Reference

Fix bitcasted functions. More...

#include "WebAssembly.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"

Go to the source code of this file.

Macros
#define	DEBUG_TYPE   "wasm-fix-function-bitcasts"

Functions
	INITIALIZE_PASS (FixFunctionBitcasts, DEBUG_TYPE, "Fix mismatching bitcasts for WebAssembly", false, false) ModulePass *llvm
static void	findUses (Value *V, Function &F, SmallVectorImpl< std::pair< CallBase *, Function * > > &Uses)
static Function *	createWrapper (Function *F, FunctionType *Ty)
static bool	shouldFixMainFunction (FunctionType *FuncTy, FunctionType *MainTy)

Detailed Description

Fix bitcasted functions.

WebAssembly requires caller and callee signatures to match, however in LLVM, some amount of slop is vaguely permitted. Detect mismatch by looking for bitcasts of functions and rewrite them to use wrapper functions instead.

This doesn't catch all cases, such as when a function's address is taken in one place and casted in another, but it works for many common cases.

Note that LLVM already optimizes away function bitcasts in common cases by dropping arguments as needed, so this pass only ends up getting used in less common cases.

Definition in file WebAssemblyFixFunctionBitcasts.cpp.

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "wasm-fix-function-bitcasts"

Definition at line 35 of file WebAssemblyFixFunctionBitcasts.cpp.

Function Documentation

createWrapper()

static Function * createWrapper ( Function *  F, FunctionType *  Ty  )

static

Definition at line 109 of file WebAssemblyFixFunctionBitcasts.cpp.

References llvm::Function::Create(), llvm::CallInst::Create(), llvm::ReturnInst::Create(), llvm::BasicBlock::Create(), llvm::CastInst::CreateBitOrPointerCast(), llvm::dbgs(), DL, llvm::BasicBlock::end(), F, llvm::UndefValue::get(), llvm::BasicBlock::getDataLayout(), llvm::Value::getType(), llvm::Instruction::insertInto(), llvm::CastInst::isBitOrNoopPointerCastable(), llvm::Type::isStructTy(), llvm::Type::isVoidTy(), LLVM_DEBUG, and Wrapper.

findUses()

static void findUses ( Value *  V, Function &  F, SmallVectorImpl< std::pair< CallBase *, Function * > > &  Uses  )

static

Definition at line 66 of file WebAssemblyFixFunctionBitcasts.cpp.

References A, F, findUses(), and Uses.

Referenced by findUses().

INITIALIZE_PASS()

INITIALIZE_PASS	(	FixFunctionBitcasts	,
		DEBUG_TYPE	,
		"Fix mismatching bitcasts for WebAssembly"	,
		false	,
		false
	)

Definition at line 57 of file WebAssemblyFixFunctionBitcasts.cpp.

shouldFixMainFunction()

static bool shouldFixMainFunction ( FunctionType *  FuncTy, FunctionType *  MainTy  )

static

Definition at line 219 of file WebAssemblyFixFunctionBitcasts.cpp.