1 files changed, 117 insertions, 0 deletions
diff --git a/lib/Transforms/IPO/ExtractFunction.cpp b/lib/Transforms/IPO/ExtractFunction.cpp
new file mode 100644
index 0000000000..4cce79be61
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+++ b/lib/Transforms/IPO/ExtractFunction.cpp
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+//===-- ExtractFunction.cpp - Function extraction pass --------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass extracts
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/IPO.h"
+using namespace llvm;
+
+namespace {
+  class FunctionExtractorPass : public ModulePass {
+    Function *Named;
+    bool deleteFunc;
+  public:
+    /// FunctionExtractorPass - If deleteFn is true, this pass deletes as the
+    /// specified function. Otherwise, it deletes as much of the module as
+    /// possible, except for the function specified.
+    ///
+    FunctionExtractorPass(Function *F = 0, bool deleteFn = true)
+      : Named(F), deleteFunc(deleteFn) {}
+
+    bool runOnModule(Module &M) {
+      if (Named == 0) {
+        Named = M.getMainFunction();
+        if (Named == 0) return false;  // No function to extract
+      }
+
+      if (deleteFunc)
+        return deleteFunction();
+      else
+        return isolateFunction(M);
+    }
+
+    bool deleteFunction() {
+      Named->setLinkage(GlobalValue::ExternalLinkage);
+      Named->deleteBody();
+      assert(Named->isExternal() && "This didn't make the function external!");
+      return true;
+    }
+
+    bool isolateFunction(Module &M) {
+      // Make sure our result is globally accessible...
+      Named->setLinkage(GlobalValue::ExternalLinkage);
+
+      // Mark all global variables internal
+      for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
+        if (!I->isExternal()) {
+          I->setInitializer(0);  // Make all variables external
+          I->setLinkage(GlobalValue::ExternalLinkage);
+        }
+
+      // All of the functions may be used by global variables or the named
+      // function.  Loop through them and create a new, external functions that
+      // can be "used", instead of ones with bodies.
+      std::vector<Function*> NewFunctions;
+
+      Function *Last = --M.end();  // Figure out where the last real fn is.
+
+      for (Module::iterator I = M.begin(); ; ++I) {
+        if (&*I != Named) {
+          Function *New = new Function(I->getFunctionType(),
+                                       GlobalValue::ExternalLinkage,
+                                       I->getName());
+          I->setName("");  // Remove Old name
+
+          // If it's not the named function, delete the body of the function
+          I->dropAllReferences();
+
+          M.getFunctionList().push_back(New);
+          NewFunctions.push_back(New);
+        }
+
+        if (&*I == Last) break;  // Stop after processing the last function
+      }
+
+      // Now that we have replacements all set up, loop through the module,
+      // deleting the old functions, replacing them with the newly created
+      // functions.
+      if (!NewFunctions.empty()) {
+        unsigned FuncNum = 0;
+        Module::iterator I = M.begin();
+        do {
+          if (&*I != Named) {
+            // Make everything that uses the old function use the new dummy fn
+            I->replaceAllUsesWith(NewFunctions[FuncNum++]);
+
+            Function *Old = I;
+            ++I;  // Move the iterator to the new function
+
+            // Delete the old function!
+            M.getFunctionList().erase(Old);
+
+          } else {
+            ++I;  // Skip the function we are extracting
+          }
+        } while (&*I != NewFunctions[0]);
+      }
+
+      return true;
+    }
+  };
+
+  RegisterPass<FunctionExtractorPass> X("extract", "Function Extractor");
+}
+
+ModulePass *llvm::createFunctionExtractionPass(Function *F, bool deleteFn) {
+  return new FunctionExtractorPass(F, deleteFn);
+}