Make bugpoint *much* more powerful, giving it the capability to delete instructions

out of a large function to reduce it.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5408 91177308-0d34-0410-b5e6-96231b3b80d8

tools/bugpoint/ExtractFunction.cpp

@@ -9,7 +9,10 @@
 #include "llvm/Module.h"
 #include "llvm/PassManager.h"
 #include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Type.h"
+#include "llvm/Constant.h"
 
 /// extractFunctionFromModule - This method is used to extract the specified
 /// (non-external) function from the current program, slim down the module, and
@@ -19,16 +22,62 @@ Module *BugDriver::extractFunctionFromModule(Function *F) const {
   Module *Result = CloneModule(Program);
 
   // Translate from the old module to the new copied module...
-  F = Result->getFunction(F->getName(), F->getFunctionType());
+  Module::iterator RFI = Result->begin(); // Get iterator to corresponding fn
+  std::advance(RFI, std::distance(Program->begin(), Module::iterator(F)));
 
   // In addition to just parsing the input from GCC, we also want to spiff it up
   // a little bit.  Do this now.
   //
   PassManager Passes;
-  Passes.add(createFunctionExtractionPass(F));    // Extract the function
+  Passes.add(createFunctionExtractionPass(RFI));  // Extract the function
   Passes.add(createGlobalDCEPass());              // Delete unreachable globals
   Passes.add(createFunctionResolvingPass());      // Delete prototypes
   Passes.add(createDeadTypeEliminationPass());    // Remove dead types...
   Passes.run(*Result);
   return Result;
 }
+
+
+/// deleteInstructionFromProgram - This method clones the current Program and
+/// deletes the specified instruction from the cloned module.  It then runs a
+/// series of cleanup passes (ADCE and SimplifyCFG) to eliminate any code which
+/// depends on the value.  The modified module is then returned.
+///
+Module *BugDriver::deleteInstructionFromProgram(Instruction *I,
+                                                unsigned Simplification) const {
+  Module *Result = CloneModule(Program);
+
+  BasicBlock *PBB = I->getParent();
+  Function *PF = PBB->getParent();
+
+  Module::iterator RFI = Result->begin(); // Get iterator to corresponding fn
+  std::advance(RFI, std::distance(Program->begin(), Module::iterator(PF)));
+
+  Function::iterator RBI = RFI->begin();  // Get iterator to corresponding BB
+  std::advance(RBI, std::distance(PF->begin(), Function::iterator(PBB)));
+
+  BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
+  std::advance(RI, std::distance(PBB->begin(), BasicBlock::iterator(I)));
+  I = RI;                                 // Got the corresponding instruction!
+
+  // If this instruction produces a value, replace any users with null values
+  if (I->getType() != Type::VoidTy)
+    I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
+
+  // Remove the instruction from the program.
+  I->getParent()->getInstList().erase(I);
+
+  // In addition to just parsing the input from GCC, we also want to spiff it up
+  // a little bit.  Do this now.
+  //
+  PassManager Passes;
+  if (Simplification > 2)
+    Passes.add(createAggressiveDCEPass());          // Remove dead code...
+  //Passes.add(createInstructionCombiningPass());
+  if (Simplification > 1)
+    Passes.add(createDeadCodeEliminationPass());
+  if (Simplification)
+    Passes.add(createCFGSimplificationPass());      // Delete dead control flow
+  Passes.run(*Result);
+  return Result;
+}