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Differential D109428 Diff 371304 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 6,607 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)) {
		// Create the new block in which will redirect the edges that
		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".
		// lead to undefine behavior
		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", SI->getFunction());
		Builder.SetInsertPoint(Unreachable);
		// The new block contains only one instruction: Unreachable
		Builder.CreateUnreachable();
		for (auto &Case : SI->cases())
		if (Case.getCaseSuccessor() == BB)
		Case.setSuccessor(Unreachable);
		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…

		if (DTU)
		DTU->applyUpdates(
		{ { DominatorTree::Delete, Predecessor, BB },
		{ DominatorTree::Insert, Predecessor, Unreachable } });
		return true;
}		}
// TODO: SwitchInst.
}		}

return false;		return false;
}		}

		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.
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!");

// 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.
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