Rework CFG edges to encode potentially unreachable edges, instead of just making them NULL.

This is to support some analyses, like -Wunreachable-code, that
will need to recover the original unprunned CFG edges in order
to suppress issues that aren't really bugs in practice.

There are two important changes here:

- AdjacentBlock replaces CFGBlock* for CFG successors/predecessors.
  This has the size of 2 pointers, instead of 1.  This is unlikely
  to have a significant memory impact on Sema since a single
  CFG usually exists at one time, but could impact the memory
  usage of the static analyzer.  This could possibly be optimized
  down to a single pointer with some cleverness.

- Predecessors can now contain null predecessors, which means
  some analyses doing a reverse traversal will need to take into
  account.  This already exists for successors, which contain
  successor slots for specific branch kinds (e.g., 'if') that
  expect a fixed number of successors, even if a branch is
  not reachable.

llvm-svn: 202325

1 files changed, 5 insertions, 0 deletions

diff --git a/clang/lib/Analysis/UninitializedValues.cpp b/clang/lib/Analysis/UninitializedValues.cpp
index 332c02c..8e8ccb0 100644
--- a/clang/lib/Analysis/UninitializedValues.cpp
+++ b/clang/lib/Analysis/UninitializedValues.cpp
@@ -535,6 +535,9 @@ public:
       for (CFGBlock::const_pred_iterator I = B->pred_begin(), E = B->pred_end();
            I != E; ++I) {
         const CFGBlock *Pred = *I;
+        if (!Pred)
+          continue;
+        
         Value AtPredExit = vals.getValue(Pred, B, vd);
         if (AtPredExit == Initialized)
           // This block initializes the variable.
@@ -751,6 +754,8 @@ static bool runOnBlock(const CFGBlock *block, const CFG &cfg,
   for (CFGBlock::const_pred_iterator I = block->pred_begin(),
        E = block->pred_end(); I != E; ++I) {
     const CFGBlock *pred = *I;
+    if (!pred)
+      continue;
     if (wasAnalyzed[pred->getBlockID()]) {
       vals.mergeIntoScratch(vals.getValueVector(pred), isFirst);
       isFirst = false;