1 //===---- CGLoopInfo.h - LLVM CodeGen for loop metadata -*- 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 // This is the internal state used for llvm translation for loop statement
10 // metadata.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_LIB_CODEGEN_CGLOOPINFO_H
15 #define LLVM_CLANG_LIB_CODEGEN_CGLOOPINFO_H
16 
17 #include "llvm/ADT/ArrayRef.h"
18 #include "llvm/ADT/SmallVector.h"
19 #include "llvm/IR/DebugLoc.h"
20 #include "llvm/IR/Value.h"
21 #include "llvm/Support/Compiler.h"
22 
23 namespace llvm {
24 class BasicBlock;
25 class Instruction;
26 class MDNode;
27 } // end namespace llvm
28 
29 namespace clang {
30 class Attr;
31 class ASTContext;
32 class CodeGenOptions;
33 namespace CodeGen {
34 
35 /// Attributes that may be specified on loops.
36 struct LoopAttributes {
37   explicit LoopAttributes(bool IsParallel = false);
38   void clear();
39 
40   /// Generate llvm.loop.parallel metadata for loads and stores.
41   bool IsParallel;
42 
43   /// State of loop vectorization or unrolling.
44   enum LVEnableState { Unspecified, Enable, Disable, Full };
45 
46   /// Value for llvm.loop.vectorize.enable metadata.
47   LVEnableState VectorizeEnable;
48 
49   /// Value for llvm.loop.unroll.* metadata (enable, disable, or full).
50   LVEnableState UnrollEnable;
51 
52   /// Value for llvm.loop.unroll_and_jam.* metadata (enable, disable, or full).
53   LVEnableState UnrollAndJamEnable;
54 
55   /// Value for llvm.loop.vectorize.predicate metadata
56   LVEnableState VectorizePredicateEnable;
57 
58   /// Value for llvm.loop.vectorize.width metadata.
59   unsigned VectorizeWidth;
60 
61   // Value for llvm.loop.vectorize.scalable.enable
62   LVEnableState VectorizeScalable;
63 
64   /// Value for llvm.loop.interleave.count metadata.
65   unsigned InterleaveCount;
66 
67   /// llvm.unroll.
68   unsigned UnrollCount;
69 
70   /// llvm.unroll.
71   unsigned UnrollAndJamCount;
72 
73   /// Value for llvm.loop.distribute.enable metadata.
74   LVEnableState DistributeEnable;
75 
76   /// Value for llvm.loop.pipeline.disable metadata.
77   bool PipelineDisabled;
78 
79   /// Value for llvm.loop.pipeline.iicount metadata.
80   unsigned PipelineInitiationInterval;
81 
82   /// Value for whether the loop is required to make progress.
83   bool MustProgress;
84 };
85 
86 /// Information used when generating a structured loop.
87 class LoopInfo {
88 public:
89   /// Construct a new LoopInfo for the loop with entry Header.
90   LoopInfo(llvm::BasicBlock *Header, const LoopAttributes &Attrs,
91            const llvm::DebugLoc &StartLoc, const llvm::DebugLoc &EndLoc,
92            LoopInfo *Parent);
93 
94   /// Get the loop id metadata for this loop.
95   llvm::MDNode *getLoopID() const { return TempLoopID.get(); }
96 
97   /// Get the header block of this loop.
98   llvm::BasicBlock *getHeader() const { return Header; }
99 
100   /// Get the set of attributes active for this loop.
101   const LoopAttributes &getAttributes() const { return Attrs; }
102 
103   /// Return this loop's access group or nullptr if it does not have one.
104   llvm::MDNode *getAccessGroup() const { return AccGroup; }
105 
106   /// Create the loop's metadata. Must be called after its nested loops have
107   /// been processed.
108   void finish();
109 
110 private:
111   /// Loop ID metadata.
112   llvm::TempMDTuple TempLoopID;
113   /// Header block of this loop.
114   llvm::BasicBlock *Header;
115   /// The attributes for this loop.
116   LoopAttributes Attrs;
117   /// The access group for memory accesses parallel to this loop.
118   llvm::MDNode *AccGroup = nullptr;
119   /// Start location of this loop.
120   llvm::DebugLoc StartLoc;
121   /// End location of this loop.
122   llvm::DebugLoc EndLoc;
123   /// The next outer loop, or nullptr if this is the outermost loop.
124   LoopInfo *Parent;
125   /// If this loop has unroll-and-jam metadata, this can be set by the inner
126   /// loop's LoopInfo to set the llvm.loop.unroll_and_jam.followup_inner
127   /// metadata.
128   llvm::MDNode *UnrollAndJamInnerFollowup = nullptr;
129 
130   /// Create a LoopID without any transformations.
131   llvm::MDNode *
132   createLoopPropertiesMetadata(llvm::ArrayRef<llvm::Metadata *> LoopProperties);
133 
134   /// Create a LoopID for transformations.
135   ///
136   /// The methods call each other in case multiple transformations are applied
137   /// to a loop. The transformation first to be applied will use LoopID of the
138   /// next transformation in its followup attribute.
139   ///
140   /// @param Attrs             The loop's transformations.
141   /// @param LoopProperties    Non-transformation properties such as debug
142   ///                          location, parallel accesses and disabled
143   ///                          transformations. These are added to the returned
144   ///                          LoopID.
145   /// @param HasUserTransforms [out] Set to true if the returned MDNode encodes
146   ///                          at least one transformation.
147   ///
148   /// @return A LoopID (metadata node) that can be used for the llvm.loop
149   ///         annotation or followup-attribute.
150   /// @{
151   llvm::MDNode *
152   createPipeliningMetadata(const LoopAttributes &Attrs,
153                            llvm::ArrayRef<llvm::Metadata *> LoopProperties,
154                            bool &HasUserTransforms);
155   llvm::MDNode *
156   createPartialUnrollMetadata(const LoopAttributes &Attrs,
157                               llvm::ArrayRef<llvm::Metadata *> LoopProperties,
158                               bool &HasUserTransforms);
159   llvm::MDNode *
160   createUnrollAndJamMetadata(const LoopAttributes &Attrs,
161                              llvm::ArrayRef<llvm::Metadata *> LoopProperties,
162                              bool &HasUserTransforms);
163   llvm::MDNode *
164   createLoopVectorizeMetadata(const LoopAttributes &Attrs,
165                               llvm::ArrayRef<llvm::Metadata *> LoopProperties,
166                               bool &HasUserTransforms);
167   llvm::MDNode *
168   createLoopDistributeMetadata(const LoopAttributes &Attrs,
169                                llvm::ArrayRef<llvm::Metadata *> LoopProperties,
170                                bool &HasUserTransforms);
171   llvm::MDNode *
172   createFullUnrollMetadata(const LoopAttributes &Attrs,
173                            llvm::ArrayRef<llvm::Metadata *> LoopProperties,
174                            bool &HasUserTransforms);
175   /// @}
176 
177   /// Create a LoopID for this loop, including transformation-unspecific
178   /// metadata such as debug location.
179   ///
180   /// @param Attrs             This loop's attributes and transformations.
181   /// @param LoopProperties    Additional non-transformation properties to add
182   ///                          to the LoopID, such as transformation-specific
183   ///                          metadata that are not covered by @p Attrs.
184   /// @param HasUserTransforms [out] Set to true if the returned MDNode encodes
185   ///                          at least one transformation.
186   ///
187   /// @return A LoopID (metadata node) that can be used for the llvm.loop
188   ///         annotation.
189   llvm::MDNode *createMetadata(const LoopAttributes &Attrs,
190                                llvm::ArrayRef<llvm::Metadata *> LoopProperties,
191                                bool &HasUserTransforms);
192 };
193 
194 /// A stack of loop information corresponding to loop nesting levels.
195 /// This stack can be used to prepare attributes which are applied when a loop
196 /// is emitted.
197 class LoopInfoStack {
198   LoopInfoStack(const LoopInfoStack &) = delete;
199   void operator=(const LoopInfoStack &) = delete;
200 
201 public:
202   LoopInfoStack() {}
203 
204   /// Begin a new structured loop. The set of staged attributes will be
205   /// applied to the loop and then cleared.
206   void push(llvm::BasicBlock *Header, const llvm::DebugLoc &StartLoc,
207             const llvm::DebugLoc &EndLoc);
208 
209   /// Begin a new structured loop. Stage attributes from the Attrs list.
210   /// The staged attributes are applied to the loop and then cleared.
211   void push(llvm::BasicBlock *Header, clang::ASTContext &Ctx,
212             const clang::CodeGenOptions &CGOpts,
213             llvm::ArrayRef<const Attr *> Attrs, const llvm::DebugLoc &StartLoc,
214             const llvm::DebugLoc &EndLoc, bool MustProgress = false);
215 
216   /// End the current loop.
217   void pop();
218 
219   /// Return the top loop id metadata.
220   llvm::MDNode *getCurLoopID() const { return getInfo().getLoopID(); }
221 
222   /// Return true if the top loop is parallel.
223   bool getCurLoopParallel() const {
224     return hasInfo() ? getInfo().getAttributes().IsParallel : false;
225   }
226 
227   /// Function called by the CodeGenFunction when an instruction is
228   /// created.
229   void InsertHelper(llvm::Instruction *I) const;
230 
231   /// Set the next pushed loop as parallel.
232   void setParallel(bool Enable = true) { StagedAttrs.IsParallel = Enable; }
233 
234   /// Set the next pushed loop 'vectorize.enable'
235   void setVectorizeEnable(bool Enable = true) {
236     StagedAttrs.VectorizeEnable =
237         Enable ? LoopAttributes::Enable : LoopAttributes::Disable;
238   }
239 
240   /// Set the next pushed loop as a distribution candidate.
241   void setDistributeState(bool Enable = true) {
242     StagedAttrs.DistributeEnable =
243         Enable ? LoopAttributes::Enable : LoopAttributes::Disable;
244   }
245 
246   /// Set the next pushed loop unroll state.
247   void setUnrollState(const LoopAttributes::LVEnableState &State) {
248     StagedAttrs.UnrollEnable = State;
249   }
250 
251   /// Set the next pushed vectorize predicate state.
252   void setVectorizePredicateState(const LoopAttributes::LVEnableState &State) {
253     StagedAttrs.VectorizePredicateEnable = State;
254   }
255 
256   /// Set the next pushed loop unroll_and_jam state.
257   void setUnrollAndJamState(const LoopAttributes::LVEnableState &State) {
258     StagedAttrs.UnrollAndJamEnable = State;
259   }
260 
261   /// Set the vectorize width for the next loop pushed.
262   void setVectorizeWidth(unsigned W) { StagedAttrs.VectorizeWidth = W; }
263 
264   void setVectorizeScalable(const LoopAttributes::LVEnableState &State) {
265     StagedAttrs.VectorizeScalable = State;
266   }
267 
268   /// Set the interleave count for the next loop pushed.
269   void setInterleaveCount(unsigned C) { StagedAttrs.InterleaveCount = C; }
270 
271   /// Set the unroll count for the next loop pushed.
272   void setUnrollCount(unsigned C) { StagedAttrs.UnrollCount = C; }
273 
274   /// \brief Set the unroll count for the next loop pushed.
275   void setUnrollAndJamCount(unsigned C) { StagedAttrs.UnrollAndJamCount = C; }
276 
277   /// Set the pipeline disabled state.
278   void setPipelineDisabled(bool S) { StagedAttrs.PipelineDisabled = S; }
279 
280   /// Set the pipeline initiation interval.
281   void setPipelineInitiationInterval(unsigned C) {
282     StagedAttrs.PipelineInitiationInterval = C;
283   }
284 
285   /// Set no progress for the next loop pushed.
286   void setMustProgress(bool P) { StagedAttrs.MustProgress = P; }
287 
288 private:
289   /// Returns true if there is LoopInfo on the stack.
290   bool hasInfo() const { return !Active.empty(); }
291   /// Return the LoopInfo for the current loop. HasInfo should be called
292   /// first to ensure LoopInfo is present.
293   const LoopInfo &getInfo() const { return *Active.back(); }
294   /// The set of attributes that will be applied to the next pushed loop.
295   LoopAttributes StagedAttrs;
296   /// Stack of active loops.
297   llvm::SmallVector<std::unique_ptr<LoopInfo>, 4> Active;
298 };
299 
300 } // end namespace CodeGen
301 } // end namespace clang
302 
303 #endif
304