diff options
| -rw-r--r-- | include/llvm/Analysis/LoopInfo.h | 28 |
1 files changed, 21 insertions, 7 deletions
diff --git a/include/llvm/Analysis/LoopInfo.h b/include/llvm/Analysis/LoopInfo.h index 2babc25cb1..7b38052257 100644 --- a/include/llvm/Analysis/LoopInfo.h +++ b/include/llvm/Analysis/LoopInfo.h @@ -256,6 +256,27 @@ public: /// BlockT *getLoopPreheader() const { // Keep track of nodes outside the loop branching to the header... + BlockT *Out = getLoopPredecessor(); + if (!Out) return 0; + + // Make sure there is only one exit out of the preheader. + typedef GraphTraits<BlockT*> BlockTraits; + typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); + ++SI; + if (SI != BlockTraits::child_end(Out)) + return 0; // Multiple exits from the block, must not be a preheader. + + // The predecessor has exactly one successor, so it is a preheader. + return Out; + } + + /// getLoopPredecessor - If the given loop's header has exactly one unique + /// predecessor outside the loop, return it. Otherwise return null. + /// This is less strict that the loop "preheader" concept, which requires + /// the predecessor to have exactly one successor. + /// + BlockT *getLoopPredecessor() const { + // Keep track of nodes outside the loop branching to the header... BlockT *Out = 0; // Loop over the predecessors of the header node... @@ -273,13 +294,6 @@ public: // Make sure there is only one exit out of the preheader. assert(Out && "Header of loop has no predecessors from outside loop?"); - typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); - ++SI; - if (SI != BlockTraits::child_end(Out)) - return 0; // Multiple exits from the block, must not be a preheader. - - // If there is exactly one preheader, return it. If there was zero, then - // Out is still null. return Out; } |