Start moving some of the logic for the unreachable code analysis out of libSema

and into libAnalysis.

llvm-svn: 96872

clang/lib/Analysis/ReachableCode.cpp

@@ -0,0 +1,52 @@
+//=- ReachableCodePathInsensitive.cpp ---------------------------*- C++ --*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a flow-sensitive, path-insensitive analysis of
+// determining reachable blocks within a CFG.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/SmallVector.h"
+#include "clang/Analysis/Analyses/ReachableCode.h"
+#include "clang/Analysis/CFG.h"
+
+using namespace clang;
+
+/// ScanReachableFromBlock - Mark all blocks reachable from Start.
+/// Returns the total number of blocks that were marked reachable.
+unsigned clang::ScanReachableFromBlock(const CFGBlock &Start,
+                                       llvm::BitVector &Reachable) {
+  unsigned count = 0;
+  llvm::SmallVector<const CFGBlock*, 12> WL;
+  
+  // Prep work queue
+  Reachable.set(Start.getBlockID());
+  ++count;
+  WL.push_back(&Start);
+  
+  // Find the reachable blocks from 'Start'.
+  while (!WL.empty()) {
+    const CFGBlock *item = WL.back();
+    WL.pop_back();
+    
+    // Look at the successors and mark then reachable.
+    for (CFGBlock::const_succ_iterator I=item->succ_begin(), E=item->succ_end();
+         I != E; ++I)
+      if (const CFGBlock *B = *I) {
+        unsigned blockID = B->getBlockID();
+        if (!Reachable[blockID]) {
+          Reachable.set(blockID);
+          ++count;
+          WL.push_back(B);
+        }
+      }
+  }
+  return count;
+}