Create a pass to strip dead function declarations (prototypes). This is

for use by llvm-extract and bugpoint.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33916 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/IPO/StripDeadPrototypes.cpp

@@ -0,0 +1,61 @@
+//===-- StripDeadPrototypes.cpp - Removed unused function declarations ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Reid Spencer and is distributed under the 
+// University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass loops over all of the functions in the input module, looking for 
+// dead declarations and removes them.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/IPO.h"
+#include "llvm/Pass.h"
+#include "llvm/Module.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Debug.h"
+#include <vector>
+using namespace llvm;
+
+STATISTIC(NumDeadPrototypes, "Number of dead prototypes removed");
+
+namespace {
+
+/// @brief Pass to remove unused function declarations.
+class StripDeadPrototypesPass : public ModulePass {
+public:
+  StripDeadPrototypesPass() { }
+  virtual bool runOnModule(Module &M);
+};
+RegisterPass<StripDeadPrototypesPass> X("strip-dead-prototypes", 
+                                        "Strip Unused Function Prototypes");
+
+bool StripDeadPrototypesPass::runOnModule(Module &M) {
+  // Collect all the functions we want to erase
+  std::vector<Function*> FuncsToErase;
+  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
+    if (I->isDeclaration() &&         // Function must be only a prototype
+        I->use_empty()) {             // Function must not be used
+      FuncsToErase.push_back(&(*I));
+    }
+
+  // Erase the functions
+  for (std::vector<Function*>::iterator I = FuncsToErase.begin(), 
+       E = FuncsToErase.end(); I != E; ++I )
+    (*I)->eraseFromParent();
+  
+  // Increment the statistic
+  NumDeadPrototypes += FuncsToErase.size();
+
+  // Return an indication of whether we changed anything or not.
+  return !FuncsToErase.empty();
+}
+
+} // end anonymous namespace
+
+ModulePass *llvm::createStripDeadPrototypesPass() {
+  return new StripDeadPrototypesPass();
+}