LCOV - code coverage report
Current view: top level - include/llvm/Transforms/Utils - Evaluator.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 14 14 100.0 %
Date: 2018-05-20 00:06:23 Functions: 4 4 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- Evaluator.h - LLVM IR evaluator --------------------------*- C++ -*-===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : // Function evaluator for LLVM IR.
      11             : //
      12             : //===----------------------------------------------------------------------===//
      13             : 
      14             : #ifndef LLVM_TRANSFORMS_UTILS_EVALUATOR_H
      15             : #define LLVM_TRANSFORMS_UTILS_EVALUATOR_H
      16             : 
      17             : #include "llvm/ADT/DenseMap.h"
      18             : #include "llvm/ADT/SmallPtrSet.h"
      19             : #include "llvm/ADT/SmallVector.h"
      20             : #include "llvm/IR/BasicBlock.h"
      21             : #include "llvm/IR/GlobalVariable.h"
      22             : #include "llvm/IR/Value.h"
      23             : #include "llvm/Support/Casting.h"
      24             : #include <cassert>
      25             : #include <deque>
      26             : #include <memory>
      27             : 
      28             : namespace llvm {
      29             : 
      30             : class DataLayout;
      31             : class Function;
      32             : class TargetLibraryInfo;
      33             : 
      34             : /// This class evaluates LLVM IR, producing the Constant representing each SSA
      35             : /// instruction.  Changes to global variables are stored in a mapping that can
      36             : /// be iterated over after the evaluation is complete.  Once an evaluation call
      37             : /// fails, the evaluation object should not be reused.
      38             : class Evaluator {
      39             : public:
      40         207 :   Evaluator(const DataLayout &DL, const TargetLibraryInfo *TLI)
      41         414 :       : DL(DL), TLI(TLI) {
      42         207 :     ValueStack.emplace_back();
      43         207 :   }
      44             : 
      45         621 :   ~Evaluator() {
      46         251 :     for (auto &Tmp : AllocaTmps)
      47             :       // If there are still users of the alloca, the program is doing something
      48             :       // silly, e.g. storing the address of the alloca somewhere and using it
      49             :       // later.  Since this is undefined, we'll just make it be null.
      50          22 :       if (!Tmp->use_empty())
      51          16 :         Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
      52         207 :   }
      53             : 
      54             :   /// Evaluate a call to function F, returning true if successful, false if we
      55             :   /// can't evaluate it.  ActualArgs contains the formal arguments for the
      56             :   /// function.
      57             :   bool EvaluateFunction(Function *F, Constant *&RetVal,
      58             :                         const SmallVectorImpl<Constant*> &ActualArgs);
      59             : 
      60             :   /// Evaluate all instructions in block BB, returning true if successful, false
      61             :   /// if we can't evaluate it.  NewBB returns the next BB that control flows
      62             :   /// into, or null upon return.
      63             :   bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB);
      64             : 
      65        2398 :   Constant *getVal(Value *V) {
      66             :     if (Constant *CV = dyn_cast<Constant>(V)) return CV;
      67             :     Constant *R = ValueStack.back().lookup(V);
      68             :     assert(R && "Reference to an uncomputed value!");
      69         729 :     return R;
      70             :   }
      71             : 
      72         691 :   void setVal(Value *V, Constant *C) {
      73         691 :     ValueStack.back()[V] = C;
      74         691 :   }
      75             : 
      76             :   const DenseMap<Constant*, Constant*> &getMutatedMemory() const {
      77             :     return MutatedMemory;
      78             :   }
      79             : 
      80             :   const SmallPtrSetImpl<GlobalVariable*> &getInvariants() const {
      81             :     return Invariants;
      82             :   }
      83             : 
      84             : private:
      85             :   Constant *ComputeLoadResult(Constant *P);
      86             : 
      87             :   /// As we compute SSA register values, we store their contents here. The back
      88             :   /// of the deque contains the current function and the stack contains the
      89             :   /// values in the calling frames.
      90             :   std::deque<DenseMap<Value*, Constant*>> ValueStack;
      91             : 
      92             :   /// This is used to detect recursion.  In pathological situations we could hit
      93             :   /// exponential behavior, but at least there is nothing unbounded.
      94             :   SmallVector<Function*, 4> CallStack;
      95             : 
      96             :   /// For each store we execute, we update this map.  Loads check this to get
      97             :   /// the most up-to-date value.  If evaluation is successful, this state is
      98             :   /// committed to the process.
      99             :   DenseMap<Constant*, Constant*> MutatedMemory;
     100             : 
     101             :   /// To 'execute' an alloca, we create a temporary global variable to represent
     102             :   /// its body.  This vector is needed so we can delete the temporary globals
     103             :   /// when we are done.
     104             :   SmallVector<std::unique_ptr<GlobalVariable>, 32> AllocaTmps;
     105             : 
     106             :   /// These global variables have been marked invariant by the static
     107             :   /// constructor.
     108             :   SmallPtrSet<GlobalVariable*, 8> Invariants;
     109             : 
     110             :   /// These are constants we have checked and know to be simple enough to live
     111             :   /// in a static initializer of a global.
     112             :   SmallPtrSet<Constant*, 8> SimpleConstants;
     113             : 
     114             :   const DataLayout &DL;
     115             :   const TargetLibraryInfo *TLI;
     116             : };
     117             : 
     118             : } // end namespace llvm
     119             : 
     120             : #endif // LLVM_TRANSFORMS_UTILS_EVALUATOR_H

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