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-rw-r--r--lib/CodeGen/JumpInstrTables.cpp296
1 files changed, 0 insertions, 296 deletions
diff --git a/lib/CodeGen/JumpInstrTables.cpp b/lib/CodeGen/JumpInstrTables.cpp
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--- a/lib/CodeGen/JumpInstrTables.cpp
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-//===-- JumpInstrTables.cpp: Jump-Instruction Tables ----------------------===//
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-///
-/// \file
-/// \brief An implementation of jump-instruction tables.
-///
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "jt"
-
-#include "llvm/CodeGen/JumpInstrTables.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Analysis/JumpInstrTableInfo.h"
-#include "llvm/CodeGen/Passes.h"
-#include "llvm/IR/Attributes.h"
-#include "llvm/IR/CallSite.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/DerivedTypes.h"
-#include "llvm/IR/Function.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/IR/Module.h"
-#include "llvm/IR/Operator.h"
-#include "llvm/IR/Type.h"
-#include "llvm/IR/Verifier.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
-#include <vector>
-
-using namespace llvm;
-
-char JumpInstrTables::ID = 0;
-
-INITIALIZE_PASS_BEGIN(JumpInstrTables, "jump-instr-tables",
- "Jump-Instruction Tables", true, true)
-INITIALIZE_PASS_DEPENDENCY(JumpInstrTableInfo);
-INITIALIZE_PASS_END(JumpInstrTables, "jump-instr-tables",
- "Jump-Instruction Tables", true, true)
-
-STATISTIC(NumJumpTables, "Number of indirect call tables generated");
-STATISTIC(NumFuncsInJumpTables, "Number of functions in the jump tables");
-
-ModulePass *llvm::createJumpInstrTablesPass() {
- // The default implementation uses a single table for all functions.
- return new JumpInstrTables(JumpTable::Single);
-}
-
-ModulePass *llvm::createJumpInstrTablesPass(JumpTable::JumpTableType JTT) {
- return new JumpInstrTables(JTT);
-}
-
-namespace {
-static const char jump_func_prefix[] = "__llvm_jump_instr_table_";
-static const char jump_section_prefix[] = ".jump.instr.table.text.";
-
-// Checks to see if a given CallSite is making an indirect call, including
-// cases where the indirect call is made through a bitcast.
-bool isIndirectCall(CallSite &CS) {
- if (CS.getCalledFunction())
- return false;
-
- // Check the value to see if it is merely a bitcast of a function. In
- // this case, it will translate to a direct function call in the resulting
- // assembly, so we won't treat it as an indirect call here.
- const Value *V = CS.getCalledValue();
- if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
- return !(CE->isCast() && isa<Function>(CE->getOperand(0)));
- }
-
- // Otherwise, since we know it's a call, it must be an indirect call
- return true;
-}
-
-// Replaces Functions and GlobalAliases with a different Value.
-bool replaceGlobalValueIndirectUse(GlobalValue *GV, Value *V, Use *U) {
- User *Us = U->getUser();
- if (!Us)
- return false;
- if (Instruction *I = dyn_cast<Instruction>(Us)) {
- CallSite CS(I);
-
- // Don't do the replacement if this use is a direct call to this function.
- // If the use is not the called value, then replace it.
- if (CS && (isIndirectCall(CS) || CS.isCallee(U))) {
- return false;
- }
-
- U->set(V);
- } else if (Constant *C = dyn_cast<Constant>(Us)) {
- // Don't replace calls to bitcasts of function symbols, since they get
- // translated to direct calls.
- if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Us)) {
- if (CE->getOpcode() == Instruction::BitCast) {
- // This bitcast must have exactly one user.
- if (CE->user_begin() != CE->user_end()) {
- User *ParentUs = *CE->user_begin();
- if (CallInst *CI = dyn_cast<CallInst>(ParentUs)) {
- CallSite CS(CI);
- Use &CEU = *CE->use_begin();
- if (CS.isCallee(&CEU)) {
- return false;
- }
- }
- }
- }
- }
-
- // GlobalAlias doesn't support replaceUsesOfWithOnConstant. And the verifier
- // requires alias to point to a defined function. So, GlobalAlias is handled
- // as a separate case in runOnModule.
- if (!isa<GlobalAlias>(C))
- C->replaceUsesOfWithOnConstant(GV, V, U);
- } else {
- llvm_unreachable("The Use of a Function symbol is neither an instruction "
- "nor a constant");
- }
-
- return true;
-}
-
-// Replaces all replaceable address-taken uses of GV with a pointer to a
-// jump-instruction table entry.
-void replaceValueWithFunction(GlobalValue *GV, Function *F) {
- // Go through all uses of this function and replace the uses of GV with the
- // jump-table version of the function. Get the uses as a vector before
- // replacing them, since replacing them changes the use list and invalidates
- // the iterator otherwise.
- for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E;) {
- Use &U = *I++;
-
- // Replacement of constants replaces all instances in the constant. So, some
- // uses might have already been handled by the time we reach them here.
- if (U.get() == GV)
- replaceGlobalValueIndirectUse(GV, F, &U);
- }
-
- return;
-}
-} // end anonymous namespace
-
-JumpInstrTables::JumpInstrTables()
- : ModulePass(ID), Metadata(), JITI(nullptr), TableCount(0),
- JTType(JumpTable::Single) {
- initializeJumpInstrTablesPass(*PassRegistry::getPassRegistry());
-}
-
-JumpInstrTables::JumpInstrTables(JumpTable::JumpTableType JTT)
- : ModulePass(ID), Metadata(), JITI(nullptr), TableCount(0), JTType(JTT) {
- initializeJumpInstrTablesPass(*PassRegistry::getPassRegistry());
-}
-
-JumpInstrTables::~JumpInstrTables() {}
-
-void JumpInstrTables::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<JumpInstrTableInfo>();
-}
-
-Function *JumpInstrTables::insertEntry(Module &M, Function *Target) {
- FunctionType *OrigFunTy = Target->getFunctionType();
- FunctionType *FunTy = transformType(JTType, OrigFunTy);
-
- JumpMap::iterator it = Metadata.find(FunTy);
- if (Metadata.end() == it) {
- struct TableMeta Meta;
- Meta.TableNum = TableCount;
- Meta.Count = 0;
- Metadata[FunTy] = Meta;
- it = Metadata.find(FunTy);
- ++NumJumpTables;
- ++TableCount;
- }
-
- it->second.Count++;
-
- std::string NewName(jump_func_prefix);
- NewName += (Twine(it->second.TableNum) + "_" + Twine(it->second.Count)).str();
- Function *JumpFun =
- Function::Create(OrigFunTy, GlobalValue::ExternalLinkage, NewName, &M);
- // The section for this table
- JumpFun->setSection((jump_section_prefix + Twine(it->second.TableNum)).str());
- JITI->insertEntry(FunTy, Target, JumpFun);
-
- ++NumFuncsInJumpTables;
- return JumpFun;
-}
-
-bool JumpInstrTables::hasTable(FunctionType *FunTy) {
- FunctionType *TransTy = transformType(JTType, FunTy);
- return Metadata.end() != Metadata.find(TransTy);
-}
-
-FunctionType *JumpInstrTables::transformType(JumpTable::JumpTableType JTT,
- FunctionType *FunTy) {
- // Returning nullptr forces all types into the same table, since all types map
- // to the same type
- Type *VoidPtrTy = Type::getInt8PtrTy(FunTy->getContext());
-
- // Ignore the return type.
- Type *RetTy = VoidPtrTy;
- bool IsVarArg = FunTy->isVarArg();
- std::vector<Type *> ParamTys(FunTy->getNumParams());
- FunctionType::param_iterator PI, PE;
- int i = 0;
-
- std::vector<Type *> EmptyParams;
- Type *Int32Ty = Type::getInt32Ty(FunTy->getContext());
- FunctionType *VoidFnTy = FunctionType::get(
- Type::getVoidTy(FunTy->getContext()), EmptyParams, false);
- switch (JTT) {
- case JumpTable::Single:
-
- return FunctionType::get(RetTy, EmptyParams, false);
- case JumpTable::Arity:
- // Transform all types to void* so that all functions with the same arity
- // end up in the same table.
- for (PI = FunTy->param_begin(), PE = FunTy->param_end(); PI != PE;
- PI++, i++) {
- ParamTys[i] = VoidPtrTy;
- }
-
- return FunctionType::get(RetTy, ParamTys, IsVarArg);
- case JumpTable::Simplified:
- // Project all parameters types to one of 3 types: composite, integer, and
- // function, matching the three subclasses of Type.
- for (PI = FunTy->param_begin(), PE = FunTy->param_end(); PI != PE;
- ++PI, ++i) {
- assert((isa<IntegerType>(*PI) || isa<FunctionType>(*PI) ||
- isa<CompositeType>(*PI)) &&
- "This type is not an Integer or a Composite or a Function");
- if (isa<CompositeType>(*PI)) {
- ParamTys[i] = VoidPtrTy;
- } else if (isa<FunctionType>(*PI)) {
- ParamTys[i] = VoidFnTy;
- } else if (isa<IntegerType>(*PI)) {
- ParamTys[i] = Int32Ty;
- }
- }
-
- return FunctionType::get(RetTy, ParamTys, IsVarArg);
- case JumpTable::Full:
- // Don't transform this type at all.
- return FunTy;
- }
-
- return nullptr;
-}
-
-bool JumpInstrTables::runOnModule(Module &M) {
- JITI = &getAnalysis<JumpInstrTableInfo>();
-
- // Get the set of jumptable-annotated functions that have their address taken.
- DenseMap<Function *, Function *> Functions;
- for (Function &F : M) {
- if (F.hasFnAttribute(Attribute::JumpTable) && F.hasAddressTaken()) {
- assert(F.hasUnnamedAddr() &&
- "Attribute 'jumptable' requires 'unnamed_addr'");
- Functions[&F] = nullptr;
- }
- }
-
- // Create the jump-table functions.
- for (auto &KV : Functions) {
- Function *F = KV.first;
- KV.second = insertEntry(M, F);
- }
-
- // GlobalAlias is a special case, because the target of an alias statement
- // must be a defined function. So, instead of replacing a given function in
- // the alias, we replace all uses of aliases that target jumptable functions.
- // Note that there's no need to create these functions, since only aliases
- // that target known jumptable functions are replaced, and there's no way to
- // put the jumptable annotation on a global alias.
- DenseMap<GlobalAlias *, Function *> Aliases;
- for (GlobalAlias &GA : M.aliases()) {
- Constant *Aliasee = GA.getAliasee();
- if (Function *F = dyn_cast<Function>(Aliasee)) {
- auto it = Functions.find(F);
- if (it != Functions.end()) {
- Aliases[&GA] = it->second;
- }
- }
- }
-
- // Replace each address taken function with its jump-instruction table entry.
- for (auto &KV : Functions)
- replaceValueWithFunction(KV.first, KV.second);
-
- for (auto &KV : Aliases)
- replaceValueWithFunction(KV.first, KV.second);
-
- return !Functions.empty();
-}
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