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Some code simplification. It now doesn't generate a prologue if the epilogue

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isn't going to be generated.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58734 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2008-11-05 00:00:21 +00:00
parent 8f027c7fea
commit 613f77439e
1 changed files with 47 additions and 61 deletions
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108
lib/CodeGen/StackProtector.cpp
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@ -43,42 +43,29 @@ namespace {
/// target type sizes.
const TargetLowering *TLI;
/// FailBB - Holds the basic block to jump to when the stack protector check
/// fails.
BasicBlock *FailBB;
/// StackProtFrameSlot - The place on the stack that the stack protector
/// guard is kept.
AllocaInst *StackProtFrameSlot;
/// StackGuardVar - The global variable for the stack guard.
Constant *StackGuardVar;
Function *F;
Module *M;
/// InsertStackProtectorPrologue - Insert code into the entry block that
/// stores the __stack_chk_guard variable onto the stack.
void InsertStackProtectorPrologue();
/// InsertStackProtectorEpilogue - Insert code before the return
/// instructions checking the stack value that was stored in the
/// prologue. If it isn't the same as the original value, then call a
/// "failure" function.
void InsertStackProtectorEpilogue();
/// InsertStackProtectors - Insert code into the prologue and epilogue of
/// the function.
///
/// - The prologue code loads and stores the stack guard onto the stack.
/// - The epilogue checks the value stored in the prologue against the
/// original value. It calls __stack_chk_fail if they differ.
bool InsertStackProtectors();
/// CreateFailBB - Create a basic block to jump to when the stack protector
/// check fails.
void CreateFailBB();
BasicBlock *CreateFailBB();
/// RequiresStackProtector - Check whether or not this function needs a
/// stack protector based upon the stack protector level.
bool RequiresStackProtector() const;
public:
static char ID; // Pass identification, replacement for typeid.
StackProtector() : FunctionPass(&ID), Level(SSP::OFF), TLI(0), FailBB(0) {}
StackProtector() : FunctionPass(&ID), Level(SSP::OFF), TLI(0) {}
StackProtector(SSP::StackProtectorLevel lvl, const TargetLowering *tli)
: FunctionPass(&ID), Level(lvl), TLI(tli), FailBB(0) {}
: FunctionPass(&ID), Level(lvl), TLI(tli) {}
virtual bool runOnFunction(Function &Fn);
};
@ -99,45 +86,42 @@ bool StackProtector::runOnFunction(Function &Fn) {
if (!RequiresStackProtector()) return false;
InsertStackProtectorPrologue();
InsertStackProtectorEpilogue();
// Cleanup.
FailBB = 0;
StackProtFrameSlot = 0;
StackGuardVar = 0;
return true;
return InsertStackProtectors();
}
/// InsertStackProtectorPrologue - Insert code into the entry block that stores
/// the __stack_chk_guard variable onto the stack.
void StackProtector::InsertStackProtectorPrologue() {
BasicBlock &Entry = F->getEntryBlock();
Instruction &InsertPt = Entry.front();
const PointerType *GuardTy = PointerType::getUnqual(Type::Int8Ty);
StackGuardVar = M->getOrInsertGlobal("__stack_chk_guard", GuardTy);
StackProtFrameSlot = new AllocaInst(GuardTy, "StackProt_Frame", &InsertPt);
LoadInst *LI = new LoadInst(StackGuardVar, "StackGuard", false, &InsertPt);
new StoreInst(LI, StackProtFrameSlot, false, &InsertPt);
}
/// InsertStackProtectorEpilogue - Insert code before the return instructions
/// checking the stack value that was stored in the prologue. If it isn't the
/// same as the original value, then call a "failure" function.
void StackProtector::InsertStackProtectorEpilogue() {
// Create the basic block to jump to when the guard check fails.
CreateFailBB();
Function::iterator I = F->begin(), E = F->end();
/// InsertStackProtectors - Insert code into the prologue and epilogue of the
/// function.
///
/// - The prologue code loads and stores the stack guard onto the stack.
/// - The epilogue checks the value stored in the prologue against the original
/// value. It calls __stack_chk_fail if they differ.
bool StackProtector::InsertStackProtectors() {
std::vector<BasicBlock*> ReturnBBs;
ReturnBBs.reserve(F->size());
for (; I != E; ++I)
for (Function::iterator I = F->begin(); I != F->end(); ++I)
if (isa<ReturnInst>(I->getTerminator()))
ReturnBBs.push_back(I);
if (ReturnBBs.empty()) return; // Odd, but could happen. . .
// If this function doesn't return, don't bother with stack protectors.
if (ReturnBBs.empty()) return false;
// Insert code into the entry block that stores the __stack_chk_guard variable
// onto the stack.
BasicBlock &Entry = F->getEntryBlock();
Instruction *InsertPt = &Entry.front();
const PointerType *GuardTy = PointerType::getUnqual(Type::Int8Ty);
// The global variable for the stack guard.
Constant *StackGuardVar = M->getOrInsertGlobal("__stack_chk_guard", GuardTy);
// The place on the stack that the stack protector guard is kept.
AllocaInst *StackProtFrameSlot =
new AllocaInst(GuardTy, "StackProt_Frame", InsertPt);
LoadInst *LI = new LoadInst(StackGuardVar, "StackGuard", false, InsertPt);
new StoreInst(LI, StackProtFrameSlot, false, InsertPt);
// Create the basic block to jump to when the guard check fails.
BasicBlock *FailBB = CreateFailBB();
// Loop through the basic blocks that have return instructions. Convert this:
//
@ -162,8 +146,8 @@ void StackProtector::InsertStackProtectorEpilogue() {
// unreachable
//
for (std::vector<BasicBlock*>::iterator
II = ReturnBBs.begin(), IE = ReturnBBs.end(); II != IE; ++II) {
BasicBlock *BB = *II;
I = ReturnBBs.begin(), E = ReturnBBs.end(); I != E; ++I) {
BasicBlock *BB = *I;
ReturnInst *RI = cast<ReturnInst>(BB->getTerminator());
Function::iterator InsPt = BB; ++InsPt; // Insertion point for new BB.
@ -171,7 +155,7 @@ void StackProtector::InsertStackProtectorEpilogue() {
BasicBlock *NewBB = BB->splitBasicBlock(RI, "SP_return");
// Move the newly created basic block to the point right after the old basic
// block.
// block so that it's in the "fall through" position.
NewBB->removeFromParent();
F->getBasicBlockList().insert(InsPt, NewBB);
@ -181,18 +165,20 @@ void StackProtector::InsertStackProtectorEpilogue() {
ICmpInst *Cmp = new ICmpInst(CmpInst::ICMP_EQ, LI1, LI2, "", BB);
BranchInst::Create(NewBB, FailBB, Cmp, BB);
}
return true;
}
/// CreateFailBB - Create a basic block to jump to when the stack protector
/// check fails.
void StackProtector::CreateFailBB() {
assert(!FailBB && "Failure basic block already created?!");
FailBB = BasicBlock::Create("CallStackCheckFailBlk", F);
BasicBlock *StackProtector::CreateFailBB() {
BasicBlock *FailBB = BasicBlock::Create("CallStackCheckFailBlk", F);
std::vector<const Type*> Params;
Constant *StackChkFail =
M->getOrInsertFunction("__stack_chk_fail", Type::VoidTy, NULL);
CallInst::Create(StackChkFail, "", FailBB);
new UnreachableInst(FailBB);
return FailBB;
}
/// RequiresStackProtector - Check whether or not this function needs a stack