LCOV - code coverage report
Current view: top level - include/llvm/Transforms/Utils - Evaluator.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 15 15 100.0 %
Date: 2017-09-14 15:23:50 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/Constant.h"
      22             : #include "llvm/IR/GlobalVariable.h"
      23             : 
      24             : #include <deque>
      25             : #include <memory>
      26             : 
      27             : namespace llvm {
      28             : 
      29             : class DataLayout;
      30             : class Function;
      31             : class TargetLibraryInfo;
      32             : 
      33             : /// This class evaluates LLVM IR, producing the Constant representing each SSA
      34             : /// instruction.  Changes to global variables are stored in a mapping that can
      35             : /// be iterated over after the evaluation is complete.  Once an evaluation call
      36             : /// fails, the evaluation object should not be reused.
      37             : class Evaluator {
      38             : public:
      39         186 :   Evaluator(const DataLayout &DL, const TargetLibraryInfo *TLI)
      40        1302 :       : DL(DL), TLI(TLI) {
      41         186 :     ValueStack.emplace_back();
      42         186 :   }
      43             : 
      44        1302 :   ~Evaluator() {
      45         575 :     for (auto &Tmp : AllocaTmps)
      46             :       // If there are still users of the alloca, the program is doing something
      47             :       // silly, e.g. storing the address of the alloca somewhere and using it
      48             :       // later.  Since this is undefined, we'll just make it be null.
      49          34 :       if (!Tmp->use_empty())
      50          21 :         Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
      51         186 :   }
      52             : 
      53             :   /// Evaluate a call to function F, returning true if successful, false if we
      54             :   /// can't evaluate it.  ActualArgs contains the formal arguments for the
      55             :   /// function.
      56             :   bool EvaluateFunction(Function *F, Constant *&RetVal,
      57             :                         const SmallVectorImpl<Constant*> &ActualArgs);
      58             : 
      59             :   /// Evaluate all instructions in block BB, returning true if successful, false
      60             :   /// if we can't evaluate it.  NewBB returns the next BB that control flows
      61             :   /// into, or null upon return.
      62             :   bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB);
      63             : 
      64        1033 :   Constant *getVal(Value *V) {
      65             :     if (Constant *CV = dyn_cast<Constant>(V)) return CV;
      66        1200 :     Constant *R = ValueStack.back().lookup(V);
      67             :     assert(R && "Reference to an uncomputed value!");
      68         400 :     return R;
      69             :   }
      70             : 
      71         501 :   void setVal(Value *V, Constant *C) {
      72        1503 :     ValueStack.back()[V] = C;
      73         501 :   }
      74             : 
      75             :   const DenseMap<Constant*, Constant*> &getMutatedMemory() const {
      76             :     return MutatedMemory;
      77             :   }
      78             : 
      79             :   const SmallPtrSetImpl<GlobalVariable*> &getInvariants() const {
      80             :     return Invariants;
      81             :   }
      82             : 
      83             : private:
      84             :   Constant *ComputeLoadResult(Constant *P);
      85             : 
      86             :   /// As we compute SSA register values, we store their contents here. The back
      87             :   /// of the deque contains the current function and the stack contains the
      88             :   /// values in the calling frames.
      89             :   std::deque<DenseMap<Value*, Constant*>> ValueStack;
      90             : 
      91             :   /// This is used to detect recursion.  In pathological situations we could hit
      92             :   /// exponential behavior, but at least there is nothing unbounded.
      93             :   SmallVector<Function*, 4> CallStack;
      94             : 
      95             :   /// For each store we execute, we update this map.  Loads check this to get
      96             :   /// the most up-to-date value.  If evaluation is successful, this state is
      97             :   /// committed to the process.
      98             :   DenseMap<Constant*, Constant*> MutatedMemory;
      99             : 
     100             :   /// To 'execute' an alloca, we create a temporary global variable to represent
     101             :   /// its body.  This vector is needed so we can delete the temporary globals
     102             :   /// when we are done.
     103             :   SmallVector<std::unique_ptr<GlobalVariable>, 32> AllocaTmps;
     104             : 
     105             :   /// These global variables have been marked invariant by the static
     106             :   /// constructor.
     107             :   SmallPtrSet<GlobalVariable*, 8> Invariants;
     108             : 
     109             :   /// These are constants we have checked and know to be simple enough to live
     110             :   /// in a static initializer of a global.
     111             :   SmallPtrSet<Constant*, 8> SimpleConstants;
     112             : 
     113             :   const DataLayout &DL;
     114             :   const TargetLibraryInfo *TLI;
     115             : };
     116             : 
     117             : }
     118             : 
     119             : #endif

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