1 //===---- CGLoopInfo.h - LLVM CodeGen for loop metadata -*- C++ -*---------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This is the internal state used for llvm translation for loop statement
11 // metadata.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_CLANG_LIB_CODEGEN_CGLOOPINFO_H
16 #define LLVM_CLANG_LIB_CODEGEN_CGLOOPINFO_H
17 
18 #include "llvm/ADT/ArrayRef.h"
19 #include "llvm/ADT/DenseMap.h"
20 #include "llvm/ADT/SmallVector.h"
21 #include "llvm/IR/Value.h"
22 #include "llvm/Support/Compiler.h"
23 
24 namespace llvm {
25 class BasicBlock;
26 class Instruction;
27 class MDNode;
28 } // end namespace llvm
29 
30 namespace clang {
31 class Attr;
32 namespace CodeGen {
33 
34 /// \brief Attributes that may be specified on loops.
35 struct LoopAttributes {
36   explicit LoopAttributes(bool IsParallel = false);
37   void clear();
38 
39   /// \brief Generate llvm.loop.parallel metadata for loads and stores.
40   bool IsParallel;
41 
42   /// \brief State of loop vectorization or unrolling.
43   enum LVEnableState { Unspecified, Enable, Disable };
44 
45   /// \brief Value for llvm.loop.vectorize.enable metadata.
46   LVEnableState VectorizeEnable;
47 
48   /// \brief Value for llvm.loop.vectorize.width metadata.
49   unsigned VectorizeWidth;
50 
51   /// \brief Value for llvm.loop.interleave.count metadata.
52   unsigned InterleaveCount;
53 };
54 
55 /// \brief Information used when generating a structured loop.
56 class LoopInfo {
57 public:
58   /// \brief Construct a new LoopInfo for the loop with entry Header.
59   LoopInfo(llvm::BasicBlock *Header, const LoopAttributes &Attrs);
60 
61   /// \brief Get the loop id metadata for this loop.
62   llvm::MDNode *getLoopID() const { return LoopID; }
63 
64   /// \brief Get the header block of this loop.
65   llvm::BasicBlock *getHeader() const { return Header; }
66 
67   /// \brief Get the set of attributes active for this loop.
68   const LoopAttributes &getAttributes() const { return Attrs; }
69 
70 private:
71   /// \brief Loop ID metadata.
72   llvm::MDNode *LoopID;
73   /// \brief Header block of this loop.
74   llvm::BasicBlock *Header;
75   /// \brief The attributes for this loop.
76   LoopAttributes Attrs;
77 };
78 
79 /// \brief A stack of loop information corresponding to loop nesting levels.
80 /// This stack can be used to prepare attributes which are applied when a loop
81 /// is emitted.
82 class LoopInfoStack {
83   LoopInfoStack(const LoopInfoStack &) = delete;
84   void operator=(const LoopInfoStack &) = delete;
85 
86 public:
87   LoopInfoStack() {}
88 
89   /// \brief Begin a new structured loop. The set of staged attributes will be
90   /// applied to the loop and then cleared.
91   void push(llvm::BasicBlock *Header,
92             llvm::ArrayRef<const Attr *> Attrs = llvm::None);
93 
94   /// \brief End the current loop.
95   void pop();
96 
97   /// \brief Return the top loop id metadata.
98   llvm::MDNode *getCurLoopID() const { return getInfo().getLoopID(); }
99 
100   /// \brief Return true if the top loop is parallel.
101   bool getCurLoopParallel() const {
102     return hasInfo() ? getInfo().getAttributes().IsParallel : false;
103   }
104 
105   /// \brief Function called by the CodeGenFunction when an instruction is
106   /// created.
107   void InsertHelper(llvm::Instruction *I) const;
108 
109   /// \brief Set the next pushed loop as parallel.
110   void setParallel(bool Enable = true) { StagedAttrs.IsParallel = Enable; }
111 
112   /// \brief Set the next pushed loop 'vectorize.enable'
113   void setVectorizeEnable(bool Enable = true) {
114     StagedAttrs.VectorizeEnable =
115         Enable ? LoopAttributes::Enable : LoopAttributes::Disable;
116   }
117 
118   /// \brief Set the vectorize width for the next loop pushed.
119   void setVectorizeWidth(unsigned W) { StagedAttrs.VectorizeWidth = W; }
120 
121   /// \brief Set the interleave count for the next loop pushed.
122   void setInterleaveCount(unsigned C) { StagedAttrs.InterleaveCount = C; }
123 
124 private:
125   /// \brief Returns true if there is LoopInfo on the stack.
126   bool hasInfo() const { return !Active.empty(); }
127   /// \brief Return the LoopInfo for the current loop. HasInfo should be called
128   /// first to ensure LoopInfo is present.
129   const LoopInfo &getInfo() const { return Active.back(); }
130   /// \brief The set of attributes that will be applied to the next pushed loop.
131   LoopAttributes StagedAttrs;
132   /// \brief Stack of active loops.
133   llvm::SmallVector<LoopInfo, 4> Active;
134 };
135 
136 } // end namespace CodeGen
137 } // end namespace clang
138 
139 #endif
140