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/BugDriver.h

@@ -15,6 +15,7 @@ class PassInfo;
 class Module;
 class Function;
 class AbstractInterpreter;
+class Instruction;
 
 class BugDriver {
   const std::string ToolName;  // Name of bugpoint
@@ -117,6 +118,13 @@ private:
   ///
   Module *extractFunctionFromModule(Function *F) const;
 
+  /// 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 *deleteInstructionFromProgram(Instruction *I, unsigned Simp) const;
+
   /// initializeExecutionEnvironment - This method is used to set up the
   /// environment for executing LLVM programs.
   ///

tools/bugpoint/CrashDebugger.cpp

@@ -114,18 +114,63 @@ bool BugDriver::debugPassCrash(const PassInfo *Pass) {
         delete Program;
         Program = M;
       }
+
+    if (CountFunctions(Program) > 1) {
+      std::cout << "\n*** Couldn't reduce testcase to one function.\n"
+                << "    Attempting to remove individual functions.\n";
+      std::cout << "XXX Individual function removal unimplemented!\n";
+    }
   }
 
-  if (CountFunctions(Program) > 1) {
-    std::cout << "\n*** Couldn't reduce testcase to one function.\n"
-	      << "    Attempting to remove individual functions.\n";
-    std::cout << "XXX Individual function removal unimplemented!\n";
-  }
+  // FIXME: This should attempt to delete entire basic blocks at a time to speed
+  // up convergence...
 
-  // Now that we have deleted the functions that are unneccesary for the
-  // program, try to remove instructions and basic blocks that are not neccesary
-  // to cause the crash.
-  //
+  unsigned Simplification = 4;
+  do {
+    --Simplification;
+    std::cout << "\n*** Attempting to reduce testcase by deleting instruc"
+              << "tions: Simplification Level #" << Simplification << "\n";
+
+    // Now that we have deleted the functions that are unneccesary for the
+    // program, try to remove instructions that are not neccesary to cause the
+    // crash.  To do this, we loop through all of the instructions in the
+    // remaining functions, deleting them (replacing any values produced with
+    // nulls), and then running ADCE and SimplifyCFG.  If the transformed input
+    // still triggers failure, keep deleting until we cannot trigger failure
+    // anymore.
+    //
+  TryAgain:
+    
+    // Loop over all of the (non-terminator) instructions remaining in the
+    // function, attempting to delete them.
+    for (Module::iterator FI = Program->begin(), E = Program->end();
+         FI != E; ++FI)
+      if (!FI->isExternal()) {
+        for (Function::iterator BI = FI->begin(), E = FI->end(); BI != E; ++BI)
+          for (BasicBlock::iterator I = BI->begin(), E = --BI->end();
+               I != E; ++I) {
+            Module *M = deleteInstructionFromProgram(I, Simplification);
+            
+            // Make the function the current program...
+            std::swap(Program, M);
+            
+            // Find out if the pass still crashes on this pass...
+            std::cout << "Checking instruction '" << I->getName() << "': ";
+            if (runPass(Pass)) {
+              // Yup, it does, we delete the old module, and continue trying to
+              // reduce the testcase...
+              EmitProgressBytecode(Pass, "reduced-" + I->getName());
+              delete M;
+              goto TryAgain;  // I wish I had a multi-level break here!
+            }
+            
+            // This pass didn't crash without this instruction, try the next
+            // one.
+            delete Program;
+            Program = M;
+          }
+      }
+  } while (Simplification);
   
   return false;
 }

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;
+}