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

include/llvm/Assembly/PrintModulePass.h

@@ -27,7 +27,9 @@ namespace llvm {
   
   /// createPrintModulePass - Create and return a pass that writes the
   /// module to the specified raw_ostream.
-  ModulePass *createPrintModulePass(raw_ostream *OS, bool DeleteStream=false);
+  ModulePass *createPrintModulePass(raw_ostream *OS,
+                                    bool DeleteStream=false,
+                                    const std::string &Banner = "");
   
   /// createPrintFunctionPass - Create and return a pass that prints
   /// functions to the specified raw_ostream as they are processed.