From d983eba7dc16a56e51a593e333caad9889b44af6 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Sat, 29 Jan 2011 04:46:23 +0000
Subject: Re-apply r124518 with fix. Watch out for invalidated iterator.
llvm-svn: 124526
---
llvm/lib/Transforms/Utils/BasicBlockUtils.cpp | 31 ++++++++++++++++++++++++---
1 file changed, 28 insertions(+), 3 deletions(-)
(limited to 'llvm/lib/Transforms/Utils/BasicBlockUtils.cpp')
diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 5d3af3759a0..acaea195e71 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -509,7 +509,32 @@ void llvm::FindFunctionBackedges(const Function &F,
// Go up one level.
InStack.erase(VisitStack.pop_back_val().first);
}
- } while (!VisitStack.empty());
-
-
+ } while (!VisitStack.empty());
+}
+
+/// FoldReturnIntoUncondBranch - This method duplicates the specified return
+/// instruction into a predecessor which ends in an unconditional branch. If
+/// the return instruction returns a value defined by a PHI, propagate the
+/// right value into the return. It returns the new return instruction in the
+/// predecessor.
+ReturnInst *llvm::FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
+ BasicBlock *Pred) {
+ Instruction *UncondBranch = Pred->getTerminator();
+ // Clone the return and add it to the end of the predecessor.
+ Instruction *NewRet = RI->clone();
+ Pred->getInstList().push_back(NewRet);
+
+ // If the return instruction returns a value, and if the value was a
+ // PHI node in "BB", propagate the right value into the return.
+ for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
+ i != e; ++i)
+ if (PHINode *PN = dyn_cast<PHINode>(*i))
+ if (PN->getParent() == BB)
+ *i = PN->getIncomingValueForBlock(Pred);
+
+ // Update any PHI nodes in the returning block to realize that we no
+ // longer branch to them.
+ BB->removePredecessor(Pred);
+ UncondBranch->eraseFromParent();
+ return cast<ReturnInst>(NewRet);
}
--
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