llvm/lib/CodeGen/SafeStackLayout.h

   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 #include "llvm/Support/Alignment.h"
  16
  17 namespace llvm {
  18
  19 class raw_ostream;
  20 class Value;
  21
  22 namespace safestack {
  23
  24 /// Compute the layout of an unsafe stack frame.
  25 class StackLayout {
  26   Align MaxAlignment;
  27
  28   struct StackRegion {
  29     unsigned Start;
  30     unsigned End;
  31     StackLifetime::LiveRange Range;
  32
  33     StackRegion(unsigned Start, unsigned End,
  34                 const StackLifetime::LiveRange &Range)
  35         : Start(Start), End(End), Range(Range) {}
  36   };
  37
  38   /// The list of current stack regions, sorted by StackRegion::Start.
  39   SmallVector<StackRegion, 16> Regions;
  40
  41   struct StackObject {
  42     const Value *Handle;
  43     unsigned Size;
  44     Align Alignment;
  45     StackLifetime::LiveRange Range;
  46   };
  47
  48   SmallVector<StackObject, 8> StackObjects;
  49
  50   DenseMap<const Value *, unsigned> ObjectOffsets;
  51   DenseMap<const Value *, Align> ObjectAlignments;
  52
  53   void layoutObject(StackObject &Obj);
  54
  55 public:
  56   StackLayout(Align StackAlignment) : MaxAlignment(StackAlignment) {}
  57
  58   /// Add an object to the stack frame. Value pointer is opaque and used as a
  59   /// handle to retrieve the object's offset in the frame later.
  60   void addObject(const Value *V, unsigned Size, Align Alignment,
  61                  const StackLifetime::LiveRange &Range);
  62
  63   /// Run the layout computation for all previously added objects.
  64   void computeLayout();
  65
  66   /// Returns the offset to the object start in the stack frame.
  67   unsigned getObjectOffset(const Value *V) { return ObjectOffsets[V]; }
  68
  69   /// Returns the alignment of the object
  70   Align getObjectAlignment(const Value *V) { return ObjectAlignments[V]; }
  71
  72   /// Returns the size of the entire frame.
  73   unsigned getFrameSize() { return Regions.empty() ? 0 : Regions.back().End; }
  74
  75   /// Returns the alignment of the frame.
  76   Align getFrameAlignment() { return MaxAlignment; }
  77
  78   void print(raw_ostream &OS);
  79 };
  80
  81 } // end namespace safestack
  82
  83 } // end namespace llvm
  84
  85 #endif // LLVM_LIB_CODEGEN_SAFESTACKLAYOUT_H