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
  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   Align 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;
  43     Align Alignment;
  44     StackLifetime::LiveRange Range;
  45   };
  46
  47   SmallVector<StackObject, 8> StackObjects;
  48
  49   DenseMap<const Value *, unsigned> ObjectOffsets;
  50   DenseMap<const Value *, Align> ObjectAlignments;
  51
  52   void layoutObject(StackObject &Obj);
  53
  54 public:
  55   StackLayout(Align StackAlignment) : MaxAlignment(StackAlignment) {}
  56
  57   /// Add an object to the stack frame. Value pointer is opaque and used as a
  58   /// handle to retrieve the object's offset in the frame later.
  59   void addObject(const Value *V, unsigned Size, Align Alignment,
  60                  const StackLifetime::LiveRange &Range);
  61
  62   /// Run the layout computation for all previously added objects.
  63   void computeLayout();
  64
  65   /// Returns the offset to the object start in the stack frame.
  66   unsigned getObjectOffset(const Value *V) { return ObjectOffsets[V]; }
  67
  68   /// Returns the alignment of the object
  69   Align getObjectAlignment(const Value *V) { return ObjectAlignments[V]; }
  70
  71   /// Returns the size of the entire frame.
  72   unsigned getFrameSize() { return Regions.empty() ? 0 : Regions.back().End; }
  73
  74   /// Returns the alignment of the frame.
  75   Align getFrameAlignment() { return MaxAlignment; }
  76
  77   void print(raw_ostream &OS);
  78 };
  79
  80 } // end namespace safestack
  81
  82 } // end namespace llvm
  83
  84 #endif // LLVM_LIB_CODEGEN_SAFESTACKLAYOUT_H