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[PM] Refactor the bounds checking pass to remove a method only called in 

one place.

llvm-svn: 316135
This commit is contained in:
Chandler Carruth 2017-10-18 22:42:36 +00:00
parent da9600e646
commit 3f0e056df4
1 changed files with 25 additions and 28 deletions
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53
llvm/lib/Transforms/Instrumentation/BoundsChecking.cpp
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@ -60,7 +60,6 @@ namespace {
BasicBlock *TrapBB;
BasicBlock *getTrapBB();
void emitBranchToTrap(Value *Cmp = nullptr);
bool instrument(Value *Ptr, Value *Val, const DataLayout &DL);
};
}
@ -92,32 +91,6 @@ BasicBlock *BoundsChecking::getTrapBB() {
}
/// emitBranchToTrap - emit a branch instruction to a trap block.
/// If Cmp is non-null, perform a jump only if its value evaluates to true.
void BoundsChecking::emitBranchToTrap(Value *Cmp) {
// check if the comparison is always false
ConstantInt *C = dyn_cast_or_null<ConstantInt>(Cmp);
if (C) {
++ChecksSkipped;
if (!C->getZExtValue())
return;
else
Cmp = nullptr; // unconditional branch
}
++ChecksAdded;
BasicBlock::iterator Inst = Builder->GetInsertPoint();
BasicBlock *OldBB = Inst->getParent();
BasicBlock *Cont = OldBB->splitBasicBlock(Inst);
OldBB->getTerminator()->eraseFromParent();
if (Cmp)
BranchInst::Create(getTrapBB(), Cont, Cmp, OldBB);
else
BranchInst::Create(getTrapBB(), OldBB);
}
/// instrument - adds run-time bounds checks to memory accessing instructions.
/// Ptr is the pointer that will be read/written, and InstVal is either the
/// result from the load or the value being stored. It is used to determine the
@ -158,8 +131,32 @@ bool BoundsChecking::instrument(Value *Ptr, Value *InstVal,
Value *Cmp1 = Builder->CreateICmpSLT(Offset, ConstantInt::get(IntTy, 0));
Or = Builder->CreateOr(Cmp1, Or);
}
emitBranchToTrap(Or);
// check if the comparison is always false
ConstantInt *C = dyn_cast_or_null<ConstantInt>(Or);
if (C) {
++ChecksSkipped;
// If non-zero, nothing to do.
if (!C->getZExtValue())
return true;
}
++ChecksAdded;
BasicBlock::iterator SplitI = Builder->GetInsertPoint();
BasicBlock *OldBB = SplitI->getParent();
BasicBlock *Cont = OldBB->splitBasicBlock(SplitI);
OldBB->getTerminator()->eraseFromParent();
if (C) {
// If we have a constant zero, unconditionally branch.
// FIXME: We should really handle this differently to bypass the splitting
// the block.
BranchInst::Create(getTrapBB(), OldBB);
return true;
}
// Create the conditional branch.
BranchInst::Create(getTrapBB(), Cont, Or, OldBB);
return true;
}