diff options
-rw-r--r-- | lib/Transforms/Utils/SimplifyCFG.cpp | 63 |
1 files changed, 37 insertions, 26 deletions
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index c4fce5e..f6d7d76 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -1728,22 +1728,13 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { return true; } -// SimplifyIndirectBrOnSelect - Replaces -// (indirectbr (select cond, blockaddress(@fn, BlockA), -// blockaddress(@fn, BlockB))) -// with -// (br cond, BlockA, BlockB). -static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) { - // Check that both operands of the select are block addresses. - BlockAddress *TBA = dyn_cast<BlockAddress>(SI->getTrueValue()); - BlockAddress *FBA = dyn_cast<BlockAddress>(SI->getFalseValue()); - if (!TBA || !FBA) - return false; - - // Extract the actual blocks. - BasicBlock *TrueBB = TBA->getBasicBlock(); - BasicBlock *FalseBB = FBA->getBasicBlock(); - +// SimplifyTerminatorOnSelect - Simplifies a terminator by replacing it with a +// branch to TrueBB if Cond is true or to FalseBB if Cond is false. +// Takes care of updating the successors and removing the old terminator. +// Also makes sure not to introduce new successors by assuming that edges to +// non-successor TrueBBs and FalseBBs aren't reachable. +static bool SimplifyTerminatorOnSelect(TerminatorInst *OldTerm, Value *Cond, + BasicBlock *TrueBB, BasicBlock *FalseBB){ // Remove any superfluous successor edges from the CFG. // First, figure out which successors to preserve. // If TrueBB and FalseBB are equal, only try to preserve one copy of that @@ -1752,15 +1743,15 @@ static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) { BasicBlock *KeepEdge2 = TrueBB != FalseBB ? FalseBB : 0; // Then remove the rest. - for (unsigned I = 0, E = IBI->getNumSuccessors(); I != E; ++I) { - BasicBlock *Succ = IBI->getSuccessor(I); + for (unsigned I = 0, E = OldTerm->getNumSuccessors(); I != E; ++I) { + BasicBlock *Succ = OldTerm->getSuccessor(I); // Make sure only to keep exactly one copy of each edge. if (Succ == KeepEdge1) KeepEdge1 = 0; else if (Succ == KeepEdge2) KeepEdge2 = 0; else - Succ->removePredecessor(IBI->getParent()); + Succ->removePredecessor(OldTerm->getParent()); } // Insert an appropriate new terminator. @@ -1768,31 +1759,51 @@ static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) { if (TrueBB == FalseBB) // We were only looking for one successor, and it was present. // Create an unconditional branch to it. - BranchInst::Create(TrueBB, IBI); + BranchInst::Create(TrueBB, OldTerm); else // We found both of the successors we were looking for. // Create a conditional branch sharing the condition of the select. - BranchInst::Create(TrueBB, FalseBB, SI->getCondition(), IBI); + BranchInst::Create(TrueBB, FalseBB, Cond, OldTerm); } else if (KeepEdge1 && (KeepEdge2 || TrueBB == FalseBB)) { // Neither of the selected blocks were successors, so this - // indirectbr must be unreachable. - new UnreachableInst(IBI->getContext(), IBI); + // terminator must be unreachable. + new UnreachableInst(OldTerm->getContext(), OldTerm); } else { // One of the selected values was a successor, but the other wasn't. // Insert an unconditional branch to the one that was found; // the edge to the one that wasn't must be unreachable. if (KeepEdge1 == 0) // Only TrueBB was found. - BranchInst::Create(TrueBB, IBI); + BranchInst::Create(TrueBB, OldTerm); else // Only FalseBB was found. - BranchInst::Create(FalseBB, IBI); + BranchInst::Create(FalseBB, OldTerm); } - EraseTerminatorInstAndDCECond(IBI); + EraseTerminatorInstAndDCECond(OldTerm); return true; } +// SimplifyIndirectBrOnSelect - Replaces +// (indirectbr (select cond, blockaddress(@fn, BlockA), +// blockaddress(@fn, BlockB))) +// with +// (br cond, BlockA, BlockB). +static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) { + // Check that both operands of the select are block addresses. + BlockAddress *TBA = dyn_cast<BlockAddress>(SI->getTrueValue()); + BlockAddress *FBA = dyn_cast<BlockAddress>(SI->getFalseValue()); + if (!TBA || !FBA) + return false; + + // Extract the actual blocks. + BasicBlock *TrueBB = TBA->getBasicBlock(); + BasicBlock *FalseBB = FBA->getBasicBlock(); + + // Perform the actual simplification. + return SimplifyTerminatorOnSelect(IBI, SI->getCondition(), TrueBB, FalseBB); +} + /// TryToSimplifyUncondBranchWithICmpInIt - This is called when we find an icmp /// instruction (a seteq/setne with a constant) as the only instruction in a /// block that ends with an uncond branch. We are looking for a very specific |