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      1 //===- SafeStackLayout.h - SafeStack frame layout --------------*- C++ -*--===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 
      9 #ifndef LLVM_LIB_CODEGEN_SAFESTACKLAYOUT_H
     10 #define LLVM_LIB_CODEGEN_SAFESTACKLAYOUT_H
     11 
     12 #include "llvm/ADT/DenseMap.h"
     13 #include "llvm/ADT/SmallVector.h"
     14 #include "llvm/Analysis/StackLifetime.h"
     15 
     16 namespace llvm {
     17 
     18 class raw_ostream;
     19 class Value;
     20 
     21 namespace safestack {
     22 
     23 /// Compute the layout of an unsafe stack frame.
     24 class StackLayout {
     25   unsigned MaxAlignment;
     26 
     27   struct StackRegion {
     28     unsigned Start;
     29     unsigned End;
     30     StackLifetime::LiveRange Range;
     31 
     32     StackRegion(unsigned Start, unsigned End,
     33                 const StackLifetime::LiveRange &Range)
     34         : Start(Start), End(End), Range(Range) {}
     35   };
     36 
     37   /// The list of current stack regions, sorted by StackRegion::Start.
     38   SmallVector<StackRegion, 16> Regions;
     39 
     40   struct StackObject {
     41     const Value *Handle;
     42     unsigned Size, Alignment;
     43     StackLifetime::LiveRange Range;
     44   };
     45 
     46   SmallVector<StackObject, 8> StackObjects;
     47 
     48   DenseMap<const Value *, unsigned> ObjectOffsets;
     49   DenseMap<const Value *, unsigned> ObjectAlignments;
     50 
     51   void layoutObject(StackObject &Obj);
     52 
     53 public:
     54   StackLayout(unsigned StackAlignment) : MaxAlignment(StackAlignment) {}
     55 
     56   /// Add an object to the stack frame. Value pointer is opaque and used as a
     57   /// handle to retrieve the object's offset in the frame later.
     58   void addObject(const Value *V, unsigned Size, unsigned Alignment,
     59                  const StackLifetime::LiveRange &Range);
     60 
     61   /// Run the layout computation for all previously added objects.
     62   void computeLayout();
     63 
     64   /// Returns the offset to the object start in the stack frame.
     65   unsigned getObjectOffset(const Value *V) { return ObjectOffsets[V]; }
     66 
     67   /// Returns the alignment of the object
     68   unsigned getObjectAlignment(const Value *V) { return ObjectAlignments[V]; }
     69 
     70   /// Returns the size of the entire frame.
     71   unsigned getFrameSize() { return Regions.empty() ? 0 : Regions.back().End; }
     72 
     73   /// Returns the alignment of the frame.
     74   unsigned getFrameAlignment() { return MaxAlignment; }
     75 
     76   void print(raw_ostream &OS);
     77 };
     78 
     79 } // end namespace safestack
     80 
     81 } // end namespace llvm
     82 
     83 #endif // LLVM_LIB_CODEGEN_SAFESTACKLAYOUT_H
     84