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 "SafeStackColoring.h"
13 #include "llvm/ADT/DenseMap.h"
14 #include "llvm/ADT/SmallVector.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     StackColoring::LiveRange Range;
31 
32     StackRegion(unsigned Start, unsigned End,
33                 const StackColoring::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     StackColoring::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 StackColoring::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