}
}
}
-
- return true;
+
+ // Finally, if BB has PHI nodes that are used by things other than the PHIs in
+ // Succ and Succ has predecessors that are not Succ and not Pred, we cannot
+ // fold these blocks, as we don't know whether BB dominates Succ or not to
+ // update the PHI nodes correctly.
+ if (!isa<PHINode>(BB->begin()) || Succ->getSinglePredecessor()) return true;
+
+ // If the predecessors of Succ are only BB and Succ itself, we can handle this.
+ bool IsSafe = true;
+ for (pred_iterator PI = pred_begin(Succ), E = pred_end(Succ); PI != E; ++PI)
+ if (*PI != Succ && *PI != BB) {
+ IsSafe = false;
+ break;
+ }
+ if (IsSafe) return true;
+
+ // If the PHI nodes in BB are only used by instructions in Succ, we are ok.
+ IsSafe = true;
+ for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I) && IsSafe; ++I) {
+ PHINode *PN = cast<PHINode>(I);
+ for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E;
+ ++UI)
+ if (cast<Instruction>(*UI)->getParent() != Succ) {
+ IsSafe = false;
+ break;
+ }
+ }
+
+ return IsSafe;
}
/// TryToSimplifyUncondBranchFromEmptyBlock - BB contains an unconditional