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.

llvm-svn: 100143

1 files changed, 40 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/LoopPass.cpp b/llvm/lib/Analysis/LoopPass.cpp
index e2d2c2bc9d8..2727d2f9465 100644
--- a/llvm/lib/Analysis/LoopPass.cpp
+++ b/llvm/lib/Analysis/LoopPass.cpp
@@ -14,9 +14,44 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/LoopPass.h"
+#include "llvm/Assembly/PrintModulePass.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/Support/Timer.h"
 using namespace llvm;
 
+namespace {
+
+/// PrintLoopPass - Print a Function corresponding to a Loop.
+///
+class PrintLoopPass : public LoopPass {
+private:
+  std::string Banner;
+  raw_ostream &Out;       // raw_ostream to print on.
+
+public:
+  static char ID;
+  PrintLoopPass() : LoopPass(&ID), Out(dbgs()) {}
+  PrintLoopPass(const std::string &B, raw_ostream &o)
+      : LoopPass(&ID), Banner(B), Out(o) {}
+
+  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    AU.setPreservesAll();
+  }
+
+  bool runOnLoop(Loop *L, LPPassManager &) {
+    Out << Banner;
+    for (Loop::block_iterator b = L->block_begin(), be = L->block_end();
+         b != be;
+         ++b) {
+      (*b)->print(Out);
+    }
+    return false;
+  }
+};
+
+char PrintLoopPass::ID = 0;
+}
+
 //===----------------------------------------------------------------------===//
 // LPPassManager
 //
@@ -306,6 +341,11 @@ void LPPassManager::dumpPassStructure(unsigned Offset) {
 //===----------------------------------------------------------------------===//
 // LoopPass
 
+Pass *LoopPass::createPrinterPass(raw_ostream &O,
+                                  const std::string &Banner) const {
+  return new PrintLoopPass(Banner, O);
+}
+
 // Check if this pass is suitable for the current LPPassManager, if
 // available. This pass P is not suitable for a LPPassManager if P
 // is not preserving higher level analysis info used by other