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
85