From 5e6940788fb2f8cf3ce4219d3ac0f78317f54696 Mon Sep 17 00:00:00 2001 From: Evan Cheng Date: Sat, 29 Jan 2011 01:29:26 +0000 Subject: Re-commit r124462 with fixes. Tail recursion elim will now dup ret into unconditional predecessor to enable TCE on demand. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124518 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Utils/BasicBlockUtils.cpp | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) (limited to 'lib/Transforms/Utils/BasicBlockUtils.cpp') diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp index 5d3af3759a..acaea195e7 100644 --- a/lib/Transforms/Utils/BasicBlockUtils.cpp +++ b/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(*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(NewRet); } -- cgit v1.2.3-18-g5258