Initial checkin of the CallGraphSCCPass class

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8247 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/IPA/CallGraphSCCPass.cpp

@@ -0,0 +1,30 @@
+//===- CallGraphSCCPass.cpp - Pass that operates BU on call graph ---------===//
+//
+// This file implements the CallGraphSCCPass class, which is used for passes
+// which are implemented as bottom-up traversals on the call graph.  Because
+// there may be cycles in the call graph, passes of this type operate on the
+// call-graph in SCC order: that is, they process function bottom-up, except for
+// recursive functions, which they process all at once.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CallGraphSCCPass.h"
+#include "llvm/Analysis/CallGraph.h"
+#include "Support/TarjanSCCIterator.h"
+
+/// getAnalysisUsage - For this class, we declare that we require and preserve
+/// the call graph.  If the derived class implements this method, it should
+/// always explicitly call the implementation here.
+void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.addRequired<CallGraph>();
+  AU.addPreserved<CallGraph>();
+}
+
+bool CallGraphSCCPass::run(Module &M) {
+  CallGraph &CG = getAnalysis<CallGraph>();
+  bool Changed = false;
+  for (TarjanSCC_iterator<CallGraph*> I = tarj_begin(&CG), E = tarj_end(&CG);
+       I != E; ++I)
+    Changed = runOnSCC(**I);
+  return Changed;
+}