Add some switches helpful for debugging:

-print-before=<Pass Name>

Dump IR before running pass <Pass Name>.

-print-before-all

Dump IR before running each pass.

-print-after-all

Dump IR after running each pass.

These are helpful when tracking down a miscompilation.  It is easy to
get IR dumps and do diffs on them, etc.

To make this work well, add a new getPrinterPass API to Pass so that
each kind of pass (ModulePass, FunctionPass, etc.) can create a Pass
suitable for dumping out the kind of object the Pass works on.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100143 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/IPA/CallGraphSCCPass.cpp

@@ -87,10 +87,40 @@ private:
                         bool IsCheckingMode);
 };
 
+/// PrintCallGraphPass - Print a Module corresponding to a call graph.
+///
+class PrintCallGraphPass : public CallGraphSCCPass {
+private:
+  std::string Banner;
+  raw_ostream &Out;       // raw_ostream to print on.
+
+public:
+  static char ID;
+  PrintCallGraphPass() : CallGraphSCCPass(&ID), Out(dbgs()) {}
+  PrintCallGraphPass(const std::string &B, raw_ostream &o)
+      : CallGraphSCCPass(&ID), Banner(B), Out(o) {}
+
+  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    AU.setPreservesAll();
+  }
+
+  bool runOnSCC(std::vector<CallGraphNode *> &SCC) {
+    Out << Banner;
+    for (std::vector<CallGraphNode *>::iterator n = SCC.begin(), ne = SCC.end();
+         n != ne;
+         ++n) {
+      (*n)->getFunction()->print(Out);
+    }
+    return false;
+  }
+};
+
 } // end anonymous namespace.
 
 char CGPassManager::ID = 0;
 
+char PrintCallGraphPass::ID = 0;
+
 bool CGPassManager::RunPassOnSCC(Pass *P, std::vector<CallGraphNode*> &CurSCC,
                                  CallGraph &CG, bool &CallGraphUpToDate) {
   bool Changed = false;
@@ -396,6 +426,11 @@ bool CGPassManager::doFinalization(CallGraph &CG) {
   return Changed;
 }
 
+Pass *CallGraphSCCPass::createPrinterPass(raw_ostream &O,
+                                          const std::string &Banner) const {
+  return new PrintCallGraphPass(Banner, O);
+}
+
 /// Assign pass manager to manage this pass.
 void CallGraphSCCPass::assignPassManager(PMStack &PMS,
                                          PassManagerType PreferredType) {