WebAssemblyFixFunctionBitcasts.cpp File Reference

Fix bitcasted functions. More...

#include "WebAssembly.h"
#include "llvm/IR/Analysis.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PassManager.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 (WebAssemblyFixFunctionBitcastsLegacy, 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)
static bool	fixFunctionBitcasts (Module &M)

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 38 of file WebAssemblyFixFunctionBitcasts.cpp.

Function Documentation

createWrapper()

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

static

Definition at line 112 of file WebAssemblyFixFunctionBitcasts.cpp.

References Call, llvm::BasicBlock::Create(), llvm::Function::Create(), llvm::dbgs(), DL, F, llvm::PoisonValue::get(), llvm::BasicBlock::getDataLayout(), llvm::Value::getType(), llvm::CastInst::isBitOrNoopPointerCastable(), llvm::Type::isStructTy(), llvm::Type::isVoidTy(), LLVM_DEBUG, llvm::GlobalValue::PrivateLinkage, and Wrapper.

Referenced by fixFunctionBitcasts().

findUses()

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

static

Definition at line 69 of file WebAssemblyFixFunctionBitcasts.cpp.

References A(), llvm::dyn_cast(), F, findUses(), llvm::Value::users(), and Uses.

Referenced by findUses(), and fixFunctionBitcasts().

fixFunctionBitcasts()

bool fixFunctionBitcasts ( Module & M )

static

Definition at line 225 of file WebAssemblyFixFunctionBitcasts.cpp.

References C(), llvm::cast(), llvm::CallInst::Create(), createWrapper(), llvm::dbgs(), F, findUses(), llvm::FunctionType::get(), llvm::PointerType::get(), llvm::PoisonValue::get(), llvm::CallBase::getCalledOperand(), llvm::CallBase::getFunctionType(), llvm::Type::getInt32Ty(), llvm::GlobalValue::getLinkage(), llvm::GlobalValue::getVisibility(), llvm::GlobalValue::isDeclaration(), LLVM_DEBUG, llvm::CallBase::setCalledOperand(), llvm::Value::setName(), shouldFixMainFunction(), llvm::Value::stripPointerCasts(), llvm::CallingConv::Swift, llvm::CallingConv::SwiftTail, llvm::DenseMapBase< DerivedT, KeyT, ValueT, KeyInfoT, BucketT >::try_emplace(), Uses, and Wrapper.

Referenced by llvm::WebAssemblyFixFunctionBitcastsPass::run().

INITIALIZE_PASS()

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

Definition at line 60 of file WebAssemblyFixFunctionBitcasts.cpp.

References llvm::createWebAssemblyFixFunctionBitcastsLegacyPass(), and DEBUG_TYPE.

shouldFixMainFunction()

bool shouldFixMainFunction ( FunctionType * FuncTy, FunctionType * MainTy )

static

Definition at line 216 of file WebAssemblyFixFunctionBitcasts.cpp.

Referenced by fixFunctionBitcasts().