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Differential D109428 Diff 373537 llvm/lib/Transforms/Utils/SimplifyCFG.cpp

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llvm/lib/Transforms/Utils/SimplifyCFG.cpp

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Show First 20 Lines • Show All 6,605 Lines • ▼ Show 20 Lines	for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i)
Builder.CreateAssumption(Cond);		Builder.CreateAssumption(Cond);
Builder.CreateBr(BI->getSuccessor(0) == BB ? BI->getSuccessor(1)		Builder.CreateBr(BI->getSuccessor(0) == BB ? BI->getSuccessor(1)
: BI->getSuccessor(0));		: BI->getSuccessor(0));
}		}
BI->eraseFromParent();		BI->eraseFromParent();
if (DTU)		if (DTU)
DTU->applyUpdates({{DominatorTree::Delete, Predecessor, BB}});		DTU->applyUpdates({{DominatorTree::Delete, Predecessor, BB}});
return true;		return true;
		} else if (SwitchInst *SI = dyn_cast<SwitchInst>(T)) {
		// Redirect all branches leading to UB into
		// a newly created unreachable block.
		mkazantsevUnsubmitted Done Reply Inline Actions Better Redirect all branches leading to UB into a newly created unreachable block. mkazantsev: Better ``` Redirect all branches leading to UB into a newly created unreachable block. ```
		BasicBlock *Unreachable = BasicBlock::Create(
		Predecessor->getContext(), "unreachable", BB->getParent(), BB);
		Builder.SetInsertPoint(Unreachable);
		// The new block contains only one instruction: Unreachable
		Builder.CreateUnreachable();
		for (auto &Case : SI->cases())
		if (Case.getCaseSuccessor() == BB) {
		BB->removePredecessor(Predecessor);
		Case.setSuccessor(Unreachable);
		}
		if (SI->getDefaultDest() == BB) {
		BB->removePredecessor(Predecessor);
		SI->setDefaultDest(Unreachable);
		}

		if (DTU)
		DTU->applyUpdates(
		{{DominatorTree::Insert, Predecessor, Unreachable},
		{DominatorTree::Delete, Predecessor, BB}});
		lebedev.riUnsubmitted Not Done Reply Inline Actions Is the code clang-formatted? Let's for consistency always do `Insert` first. lebedev.ri: Is the code clang-formatted? Let's for consistency always do `Insert` first.
		return true;
}		}
// TODO: SwitchInst.
}		}
		mkazantsevUnsubmitted Not Done Reply Inline Actions "Create an unreachable block and redirect all edges going to BB into this block". mkazantsev: "Create an unreachable block and redirect all edges going to BB into this block".

return false;		return false;
}		}

bool SimplifyCFGOpt::simplifyOnceImpl(BasicBlock *BB) {		bool SimplifyCFGOpt::simplifyOnceImpl(BasicBlock *BB) {
bool Changed = false;		bool Changed = false;

assert(BB && BB->getParent() && "Block not embedded in function!");		assert(BB && BB->getParent() && "Block not embedded in function!");
assert(BB->getTerminator() && "Degenerate basic block encountered!");		assert(BB->getTerminator() && "Degenerate basic block encountered!");
		mkazantsevUnsubmitted Not Done Reply Inline Actions Interesting follow-up can be done here. Imagine that after this is done, only one edge that doesn't go to `unreachable` remains. In this case, we can remove this switch and insert `assume(switched_value == remained_case_value)`. Totally fine if it's a separate patch. mkazantsev: Interesting follow-up can be done here. Imagine that after this is done, only one edge that…

// Remove basic blocks that have no predecessors (except the entry block)...		// Remove basic blocks that have no predecessors (except the entry block)...
// or that just have themself as a predecessor. These are unreachable.		// or that just have themself as a predecessor. These are unreachable.
if ((pred_empty(BB) && BB != &BB->getParent()->getEntryBlock()) \|\|		if ((pred_empty(BB) && BB != &BB->getParent()->getEntryBlock()) \|\|
BB->getSinglePredecessor() == BB) {		BB->getSinglePredecessor() == BB) {
LLVM_DEBUG(dbgs() << "Removing BB: \n" << *BB);		LLVM_DEBUG(dbgs() << "Removing BB: \n" << *BB);
DeleteDeadBlock(BB, DTU);		DeleteDeadBlock(BB, DTU);
return true;		return true;
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