SIL optimizer: fix two non-deterministic behaviors

The problem was again iterating over pointer sets. This produced non-deterministic use list orderings, which does result in non-deterministic code generation itself.
But somehow debug info generation depends on the use list ordering (which should be investigated why).
And the non-deterministic debug info changes triggered re-running of the llvm pipeline.

Author: eeckstein

lib/SILOptimizer/Transforms/SILMem2Reg.cpp

@@ -54,7 +54,7 @@ typedef llvm::DenseMap<DomTreeNode *, unsigned> DomTreeLevelMap;
 
 /// Promotes a single AllocStackInst into registers..
 class StackAllocationPromoter {
-  typedef llvm::DenseSet<SILBasicBlock *> BlockSet;
+  typedef llvm::SmallSetVector<SILBasicBlock *, 16> BlockSet;
   typedef llvm::DenseMap<SILBasicBlock *, SILInstruction *> BlockToInstMap;
 
   // Use a priority queue keyed on dominator tree level so that inserted nodes
@@ -794,7 +794,7 @@ void StackAllocationPromoter::promoteAllocationToPhi() {
 
         // The successor node is a new PHINode. If this is a new PHI node
         // then it may require additional definitions, so add it to the PQ.
-        if (PhiBlocks.insert(Succ).second)
+        if (PhiBlocks.insert(Succ))
           PQ.push(std::make_pair(SuccNode, SuccLevel));
       }
 

lib/SILOptimizer/Transforms/SimplifyCFG.cpp

@@ -2530,7 +2530,9 @@ static void removeArgument(SILBasicBlock *BB, unsigned i) {
   // Determine the set of predecessors in case any predecessor has
   // two edges to this block (e.g. a conditional branch where both
   // sides reach this block).
-  llvm::SmallPtrSet<SILBasicBlock *, 4> PredBBs;
+  llvm::SetVector<SILBasicBlock *,SmallVector<SILBasicBlock *, 8>,
+                  SmallPtrSet<SILBasicBlock *, 8>> PredBBs;
+
   for (auto *Pred : BB->getPredecessorBlocks())
     PredBBs.insert(Pred);