Implement a new method, CloneAndPruneFunctionInto, as documented.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28519 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 189 insertions, 3 deletions

diff --git a/lib/Transforms/Utils/CloneFunction.cpp b/lib/Transforms/Utils/CloneFunction.cpp
index f6341fa3cf..623da058db 100644
--- a/lib/Transforms/Utils/CloneFunction.cpp
+++ b/lib/Transforms/Utils/CloneFunction.cpp
@@ -19,6 +19,7 @@
 #include "llvm/Instructions.h"
 #include "llvm/Function.h"
 #include "ValueMapper.h"
+#include "llvm/Transforms/Utils/Local.h"
 using namespace llvm;
 
 // CloneBasicBlock - See comments in Cloning.h
@@ -143,3 +144,190 @@ Function *llvm::CloneFunction(const Function *F,
   return NewF;
 }
 
+
+
+namespace {
+  /// PruningFunctionCloner - This class is a private class used to implement
+  /// the CloneAndPruneFunctionInto method.
+  struct PruningFunctionCloner {
+    Function *NewFunc;
+    const Function *OldFunc;
+    std::map<const Value*, Value*> &ValueMap;
+    std::vector<ReturnInst*> &Returns;
+    const char *NameSuffix;
+    ClonedCodeInfo *CodeInfo;
+
+  public:
+    PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
+                          std::map<const Value*, Value*> &valueMap,
+                          std::vector<ReturnInst*> &returns,
+                          const char *nameSuffix, 
+                          ClonedCodeInfo *codeInfo)
+    : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
+      NameSuffix(nameSuffix), CodeInfo(codeInfo) {
+    }
+
+    /// CloneBlock - The specified block is found to be reachable, clone it and
+    /// anything that it can reach.
+    void CloneBlock(const BasicBlock *BB);
+    
+  public:
+    /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
+    /// mapping its operands through ValueMap if they are available.
+    Constant *ConstantFoldMappedInstruction(const Instruction *I);
+  };
+}
+
+/// CloneBlock - The specified block is found to be reachable, clone it and
+/// anything that it can reach.
+void PruningFunctionCloner::CloneBlock(const BasicBlock *BB) {
+  Value *&BBEntry = ValueMap[BB];
+
+  // Have we already cloned this block?
+  if (BBEntry) return;
+  
+  // Nope, clone it now.
+  BasicBlock *NewBB;
+  BBEntry = NewBB = new BasicBlock();
+  if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
+
+  bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
+  
+  // Loop over all instructions, and copy them over, DCE'ing as we go.  This
+  // loop doesn't include the terminator.
+  for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
+       II != IE; ++II) {
+    // If this instruction constant folds, don't bother cloning the instruction,
+    // instead, just add the constant to the value map.
+    if (Constant *C = ConstantFoldMappedInstruction(II)) {
+      ValueMap[II] = C;
+      continue;
+    }
+    
+    Instruction *NewInst = II->clone();
+    if (II->hasName())
+      NewInst->setName(II->getName()+NameSuffix);
+    NewBB->getInstList().push_back(NewInst);
+    ValueMap[II] = NewInst;                // Add instruction map to value.
+    
+    hasCalls |= isa<CallInst>(II);
+    if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
+      if (isa<ConstantInt>(AI->getArraySize()))
+        hasStaticAllocas = true;
+      else
+        hasDynamicAllocas = true;
+    }
+  }
+  
+  if (CodeInfo) {
+    CodeInfo->ContainsCalls          |= hasCalls;
+    CodeInfo->ContainsUnwinds        |= isa<UnwindInst>(BB->getTerminator());
+    CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
+    CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 
+      BB != &BB->getParent()->front();
+  }
+  
+  if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
+    Returns.push_back(RI);
+  
+  // Recursively clone any reachable successor blocks.
+  const TerminatorInst *TI = BB->getTerminator();
+  for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
+    CloneBlock(TI->getSuccessor(i));
+}
+
+/// ConstantFoldMappedInstruction - Constant fold the specified instruction,
+/// mapping its operands through ValueMap if they are available.
+Constant *PruningFunctionCloner::
+ConstantFoldMappedInstruction(const Instruction *I) {
+  if (isa<BinaryOperator>(I) || isa<ShiftInst>(I)) {
+    if (Constant *Op0 = dyn_cast_or_null<Constant>(MapValue(I->getOperand(0),
+                                                            ValueMap)))
+      if (Constant *Op1 = dyn_cast_or_null<Constant>(MapValue(I->getOperand(1),
+                                                              ValueMap)))
+        return ConstantExpr::get(I->getOpcode(), Op0, Op1);
+    return 0;
+  }
+
+  std::vector<Constant*> Ops;
+  for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
+    if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
+                                                           ValueMap)))
+      Ops.push_back(Op);
+    else
+      return 0;  // All operands not constant!
+
+  return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Ops);
+}
+
+
+/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
+/// except that it does some simple constant prop and DCE on the fly.  The
+/// effect of this is to copy significantly less code in cases where (for
+/// example) a function call with constant arguments is inlined, and those
+/// constant arguments cause a significant amount of code in the callee to be
+/// dead.  Since this doesn't produce an exactly copy of the input, it can't be
+/// used for things like CloneFunction or CloneModule.
+void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
+                                     std::map<const Value*, Value*> &ValueMap,
+                                     std::vector<ReturnInst*> &Returns,
+                                     const char *NameSuffix, 
+                                     ClonedCodeInfo *CodeInfo) {
+  assert(NameSuffix && "NameSuffix cannot be null!");
+  
+#ifndef NDEBUG
+  for (Function::const_arg_iterator I = OldFunc->arg_begin(), 
+       E = OldFunc->arg_end(); I != E; ++I)
+    assert(ValueMap.count(I) && "No mapping from source argument specified!");
+#endif
+  
+  PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns, 
+                            NameSuffix, CodeInfo);
+
+  // Clone the entry block, and anything recursively reachable from it.
+  PFC.CloneBlock(&OldFunc->getEntryBlock());
+  
+  // Loop over all of the basic blocks in the old function.  If the block was
+  // reachable, we have cloned it and the old block is now in the value map:
+  // insert it into the new function in the right order.  If not, ignore it.
+  //
+  for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
+       BI != BE; ++BI) {
+    BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
+    if (NewBB == 0) continue;  // Dead block.
+    
+    // Add the new block to the new function.
+    NewFunc->getBasicBlockList().push_back(NewBB);
+    
+    // Loop over all of the instructions in the block, fixing up operand
+    // references as we go.  This uses ValueMap to do all the hard work.
+    //
+    BasicBlock::iterator I = NewBB->begin();
+    
+    // Handle PHI nodes specially, as we have to remove references to dead
+    // blocks.
+    if (PHINode *PN = dyn_cast<PHINode>(I)) {
+      unsigned NumPreds = PN->getNumIncomingValues();
+      for (; (PN = dyn_cast<PHINode>(I)); ++I) {
+        for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
+          if (BasicBlock *MappedBlock = 
+                   cast<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
+            Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
+            assert(InVal && "Unknown input value?");
+            PN->setIncomingValue(pred, InVal);
+            PN->setIncomingBlock(pred, MappedBlock);
+          } else {
+            PN->removeIncomingValue(pred, false);
+            --pred, --e;  // Revisit the next entry.
+          }
+        }
+      }
+    }
+    
+    // Otherwise, remap the rest of the instructions normally.
+    for (; I != NewBB->end(); ++I)
+      RemapInstruction(I, ValueMap);
+  }
+}
+
+
diff --git a/lib/Transforms/Utils/ValueMapper.cpp b/lib/Transforms/Utils/ValueMapper.cpp
index b309f9c0e2..d4be6e47ef 100644
--- a/lib/Transforms/Utils/ValueMapper.cpp
+++ b/lib/Transforms/Utils/ValueMapper.cpp
@@ -30,7 +30,7 @@ Value *llvm::MapValue(const Value *V, std::map<const Value*, Value*> &VM) {
   if (Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V))) {
     if (isa<ConstantIntegral>(C) || isa<ConstantFP>(C) ||
         isa<ConstantPointerNull>(C) || isa<ConstantAggregateZero>(C) ||
-        isa<UndefValue>(C) || isa<InlineAsm>(V))
+        isa<UndefValue>(C))
       return VMSlot = C;           // Primitive constants map directly
     else if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) {
       for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) {
@@ -130,8 +130,6 @@ Value *llvm::MapValue(const Value *V, std::map<const Value*, Value*> &VM) {
     }
   }
 
-  V->dump();
-  assert(0 && "Unknown value type: why didn't it get resolved?!");
   return 0;
 }