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/CodeGen/MachineFunctionPass.h

@@ -34,6 +34,9 @@ protected:
   explicit MachineFunctionPass(intptr_t ID) : FunctionPass(ID) {}
   explicit MachineFunctionPass(void *ID) : FunctionPass(ID) {}
 
+  /// createPrinterPass - Get a machine function printer pass.
+  Pass *createPrinterPass(raw_ostream &O, const std::string &Banner) const;
+
   /// runOnMachineFunction - This method must be overloaded to perform the
   /// desired machine code transformation or analysis.
   ///