From 2c5e9d71aba3b1a85f07c08d2c09d40b8547264b Mon Sep 17 00:00:00 2001
From: dim <dim@FreeBSD.org>
Date: Thu, 3 May 2012 16:50:55 +0000
Subject: Vendor import of llvm release_31 branch r155985:
http://llvm.org/svn/llvm-project/llvm/branches/release_31@155985
---
lib/CodeGen/MachineBasicBlock.cpp | 36 +++++++++++++++++++++++++++++-------
1 file changed, 29 insertions(+), 7 deletions(-)
(limited to 'lib/CodeGen/MachineBasicBlock.cpp')
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index 6c8a107..1abb8f2 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -392,22 +392,44 @@ void MachineBasicBlock::updateTerminator() {
TII->InsertBranch(*this, TBB, 0, Cond, dl);
}
} else {
+ // Walk through the successors and find the successor which is not
+ // a landing pad and is not the conditional branch destination (in TBB)
+ // as the fallthrough successor.
+ MachineBasicBlock *FallthroughBB = 0;
+ for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) {
+ if ((*SI)->isLandingPad() || *SI == TBB)
+ continue;
+ assert(!FallthroughBB && "Found more than one fallthrough successor.");
+ 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);
+
+ // 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, 0, Cond, dl);
+ return;
+ }
+
// The block has a fallthrough conditional branch.
- MachineBasicBlock *MBBA = *succ_begin();
- MachineBasicBlock *MBBB = *llvm::next(succ_begin());
- if (MBBA == TBB) std::swap(MBBB, MBBA);
if (isLayoutSuccessor(TBB)) {
if (TII->ReverseBranchCondition(Cond)) {
// We can't reverse the condition, add an unconditional branch.
Cond.clear();
- TII->InsertBranch(*this, MBBA, 0, Cond, dl);
+ TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl);
return;
}
TII->RemoveBranch(*this);
- TII->InsertBranch(*this, MBBA, 0, Cond, dl);
- } else if (!isLayoutSuccessor(MBBA)) {
+ TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl);
+ } else if (!isLayoutSuccessor(FallthroughBB)) {
TII->RemoveBranch(*this);
- TII->InsertBranch(*this, TBB, MBBA, Cond, dl);
+ TII->InsertBranch(*this, TBB, FallthroughBB, Cond, dl);
}
}
}
--
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