From df670a19849c80142069fdf64d01c88ab06964a4 Mon Sep 17 00:00:00 2001 From: Davide Italiano Date: Tue, 6 Dec 2016 02:26:50 +0000 Subject: [PATCH] Revert "[SCCP] Remove manual folding of terminator instructions." This reverts commit r288725 as it broke a bot. llvm-svn: 288759 --- llvm/lib/Transforms/Scalar/SCCP.cpp | 29 +++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-) diff --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Scalar/SCCP.cpp index 6f4a2ae..32f4867 100644 --- a/llvm/lib/Transforms/Scalar/SCCP.cpp +++ b/llvm/lib/Transforms/Scalar/SCCP.cpp @@ -1828,8 +1828,33 @@ static bool runIPSCCP(Module &M, const DataLayout &DL, // Ignore blockaddress users; BasicBlock's dtor will handle them. if (!I) continue; - assert(ConstantFoldTerminator(I->getParent()) && - "Terminator should've been folded"); + bool Folded = ConstantFoldTerminator(I->getParent()); + if (!Folded) { + // The constant folder may not have been able to fold the terminator + // if this is a branch or switch on undef. Fold it manually as a + // branch to the first successor. +#ifndef NDEBUG + if (auto *BI = dyn_cast(I)) { + assert(BI->isConditional() && isa(BI->getCondition()) && + "Branch should be foldable!"); + } else if (auto *SI = dyn_cast(I)) { + assert(isa(SI->getCondition()) && "Switch should fold"); + } else { + llvm_unreachable("Didn't fold away reference to block!"); + } +#endif + + // Make this an uncond branch to the first successor. + TerminatorInst *TI = I->getParent()->getTerminator(); + BranchInst::Create(TI->getSuccessor(0), TI); + + // Remove entries in successor phi nodes to remove edges. + for (unsigned i = 1, e = TI->getNumSuccessors(); i != e; ++i) + TI->getSuccessor(i)->removePredecessor(TI->getParent()); + + // Remove the old terminator. + TI->eraseFromParent(); + } } // Finally, delete the basic block. -- 2.7.4