move 'MergeBlocksIntoPredecessor' call earlier. Use
getSinglePredecessor to simplify code.
llvm-svn: 121683
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 4e58e492..52ad1ee 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1957,6 +1957,13 @@
// Check for and eliminate duplicate PHI nodes in this block.
Changed |= EliminateDuplicatePHINodes(BB);
+ // Merge basic blocks into their predecessor if there is only one distinct
+ // pred, and if there is only one distinct successor of the predecessor, and
+ // if there are no PHI nodes.
+ //
+ if (MergeBlockIntoPredecessor(BB))
+ return true;
+
// If there is a trivial two-entry PHI node in this basic block, and we can
// eliminate it, do so now.
if (PHINode *PN = dyn_cast<PHINode>(BB->begin()))
@@ -2309,33 +2316,15 @@
}
}
- // Merge basic blocks into their predecessor if there is only one distinct
- // pred, and if there is only one distinct successor of the predecessor, and
- // if there are no PHI nodes.
- //
- if (MergeBlockIntoPredecessor(BB))
- return true;
-
// Otherwise, if this block only has a single predecessor, and if that block
// is a conditional branch, see if we can hoist any code from this block up
// into our predecessor.
- pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
- BasicBlock *OnlyPred = 0;
- for (; PI != PE; ++PI) { // Search all predecessors, see if they are all same
- if (!OnlyPred)
- OnlyPred = *PI;
- else if (*PI != OnlyPred) {
- OnlyPred = 0; // There are multiple different predecessors...
- break;
- }
- }
-
- if (OnlyPred) {
+ if (BasicBlock *OnlyPred = BB->getSinglePredecessor()) {
BranchInst *BI = dyn_cast<BranchInst>(OnlyPred->getTerminator());
if (BI && BI->isConditional()) {
// Get the other block.
BasicBlock *OtherBB = BI->getSuccessor(BI->getSuccessor(0) == BB);
- PI = pred_begin(OtherBB);
+ pred_iterator PI = pred_begin(OtherBB);
++PI;
if (PI == pred_end(OtherBB)) {