1 //===---- CGLoopInfo.cpp - 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 #include "CGLoopInfo.h"
11 #include "llvm/IR/BasicBlock.h"
12 #include "llvm/IR/Constants.h"
13 #include "llvm/IR/InstrTypes.h"
14 #include "llvm/IR/Instructions.h"
15 #include "llvm/IR/Metadata.h"
16 using namespace clang;
17 using namespace CodeGen;
18 using namespace llvm;
19
createMetadata(LLVMContext & Ctx,const LoopAttributes & Attrs)20 static MDNode *createMetadata(LLVMContext &Ctx, const LoopAttributes &Attrs) {
21
22 if (!Attrs.IsParallel && Attrs.VectorizerWidth == 0 &&
23 Attrs.VectorizerUnroll == 0 &&
24 Attrs.VectorizerEnable == LoopAttributes::VecUnspecified)
25 return nullptr;
26
27 SmallVector<Metadata *, 4> Args;
28 // Reserve operand 0 for loop id self reference.
29 auto TempNode = MDNode::getTemporary(Ctx, None);
30 Args.push_back(TempNode.get());
31
32 // Setting vectorizer.width
33 if (Attrs.VectorizerWidth > 0) {
34 Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.vectorize.width"),
35 ConstantAsMetadata::get(ConstantInt::get(
36 Type::getInt32Ty(Ctx), Attrs.VectorizerWidth))};
37 Args.push_back(MDNode::get(Ctx, Vals));
38 }
39
40 // Setting vectorizer.unroll
41 if (Attrs.VectorizerUnroll > 0) {
42 Metadata *Vals[] = {MDString::get(Ctx, "llvm.loop.interleave.count"),
43 ConstantAsMetadata::get(ConstantInt::get(
44 Type::getInt32Ty(Ctx), Attrs.VectorizerUnroll))};
45 Args.push_back(MDNode::get(Ctx, Vals));
46 }
47
48 // Setting vectorizer.enable
49 if (Attrs.VectorizerEnable != LoopAttributes::VecUnspecified) {
50 Metadata *Vals[] = {
51 MDString::get(Ctx, "llvm.loop.vectorize.enable"),
52 ConstantAsMetadata::get(ConstantInt::get(
53 Type::getInt1Ty(Ctx),
54 (Attrs.VectorizerEnable == LoopAttributes::VecEnable)))};
55 Args.push_back(MDNode::get(Ctx, Vals));
56 }
57
58 // Set the first operand to itself.
59 MDNode *LoopID = MDNode::get(Ctx, Args);
60 LoopID->replaceOperandWith(0, LoopID);
61 return LoopID;
62 }
63
LoopAttributes(bool IsParallel)64 LoopAttributes::LoopAttributes(bool IsParallel)
65 : IsParallel(IsParallel), VectorizerEnable(LoopAttributes::VecUnspecified),
66 VectorizerWidth(0), VectorizerUnroll(0) {}
67
clear()68 void LoopAttributes::clear() {
69 IsParallel = false;
70 VectorizerWidth = 0;
71 VectorizerUnroll = 0;
72 VectorizerEnable = LoopAttributes::VecUnspecified;
73 }
74
LoopInfo(BasicBlock * Header,const LoopAttributes & Attrs)75 LoopInfo::LoopInfo(BasicBlock *Header, const LoopAttributes &Attrs)
76 : LoopID(nullptr), Header(Header), Attrs(Attrs) {
77 LoopID = createMetadata(Header->getContext(), Attrs);
78 }
79
push(BasicBlock * Header)80 void LoopInfoStack::push(BasicBlock *Header) {
81 Active.push_back(LoopInfo(Header, StagedAttrs));
82 // Clear the attributes so nested loops do not inherit them.
83 StagedAttrs.clear();
84 }
85
pop()86 void LoopInfoStack::pop() {
87 assert(!Active.empty() && "No active loops to pop");
88 Active.pop_back();
89 }
90
InsertHelper(Instruction * I) const91 void LoopInfoStack::InsertHelper(Instruction *I) const {
92 if (!hasInfo())
93 return;
94
95 const LoopInfo &L = getInfo();
96 if (!L.getLoopID())
97 return;
98
99 if (TerminatorInst *TI = dyn_cast<TerminatorInst>(I)) {
100 for (unsigned i = 0, ie = TI->getNumSuccessors(); i < ie; ++i)
101 if (TI->getSuccessor(i) == L.getHeader()) {
102 TI->setMetadata("llvm.loop", L.getLoopID());
103 break;
104 }
105 return;
106 }
107
108 if (L.getAttributes().IsParallel && I->mayReadOrWriteMemory())
109 I->setMetadata("llvm.mem.parallel_loop_access", L.getLoopID());
110 }
111