From b71b2f622a00ab55073214e4e701f902ebeb8dc9 Mon Sep 17 00:00:00 2001 From: Haicheng Wu Date: Sun, 3 Jul 2016 19:14:17 +0000 Subject: [MBB] add a missing corner case in UpdateTerminator() After the block placement, if a block ends with a conditional branch, but the next block is not its successor. The conditional branch should be changed to unconditional branch. This patch fixes PR28307, PR28297, PR28402. Differential Revision: http://reviews.llvm.org/D21811 llvm-svn: 274470 --- llvm/lib/CodeGen/MachineBasicBlock.cpp | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) (limited to 'llvm/lib/CodeGen/MachineBasicBlock.cpp') diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp index e2d0c4b7e85e..d4453c71da29 100644 --- a/llvm/lib/CodeGen/MachineBasicBlock.cpp +++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp @@ -470,17 +470,27 @@ void MachineBasicBlock::updateTerminator() { FallthroughBB = *SI; } - if (!FallthroughBB && canFallThrough()) { - // We fallthrough to the same basic block as the conditional jump targets. - // Remove the conditional jump, leaving unconditional fallthrough. - // FIXME: This does not seem like a reasonable pattern to support, but it - // has been seen in the wild coming out of degenerate ARM test cases. - TII->RemoveBranch(*this); + if (!FallthroughBB) { + if (canFallThrough()) { + // We fallthrough to the same basic block as the conditional jump targets. + // Remove the conditional jump, leaving unconditional fallthrough. + // FIXME: This does not seem like a reasonable pattern to support, but it + // has been seen in the wild coming out of degenerate ARM test cases. + TII->RemoveBranch(*this); + + // Finally update the unconditional successor to be reached via a branch if + // it would not be reached by fallthrough. + if (!isLayoutSuccessor(TBB)) + TII->InsertBranch(*this, TBB, nullptr, Cond, DL); + return; + } - // Finally update the unconditional successor to be reached via a branch if - // it would not be reached by fallthrough. - if (!isLayoutSuccessor(TBB)) - TII->InsertBranch(*this, TBB, nullptr, Cond, DL); + // We enter here iff exactly one successor is TBB which cannot fallthrough + // and the rest successors if any are EHPads. In this case, we need to + // change the conditional branch into unconditional branch. + TII->RemoveBranch(*this); + Cond.clear(); + TII->InsertBranch(*this, TBB, nullptr, Cond, DL); return; } -- cgit v1.2.3