1 //===- ProfDataUtils.cpp - Utility functions for MD_prof Metadata ---------===//
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 file implements utilities for working with Profiling Metadata.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "llvm/IR/ProfDataUtils.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/ADT/Twine.h"
16 #include "llvm/IR/Constants.h"
17 #include "llvm/IR/Function.h"
18 #include "llvm/IR/Instructions.h"
19 #include "llvm/IR/LLVMContext.h"
20 #include "llvm/IR/MDBuilder.h"
21 #include "llvm/IR/Metadata.h"
22 #include "llvm/Support/BranchProbability.h"
23 #include "llvm/Support/CommandLine.h"
24
25 using namespace llvm;
26
27 namespace {
28
29 // MD_prof nodes have the following layout
30 //
31 // In general:
32 // { String name, Array of i32 }
33 //
34 // In terms of Types:
35 // { MDString, [i32, i32, ...]}
36 //
37 // Concretely for Branch Weights
38 // { "branch_weights", [i32 1, i32 10000]}
39 //
40 // We maintain some constants here to ensure that we access the branch weights
41 // correctly, and can change the behavior in the future if the layout changes
42
43 // The index at which the weights vector starts
44 constexpr unsigned WeightsIdx = 1;
45
46 // the minimum number of operands for MD_prof nodes with branch weights
47 constexpr unsigned MinBWOps = 3;
48
49 // We may want to add support for other MD_prof types, so provide an abstraction
50 // for checking the metadata type.
isTargetMD(const MDNode * ProfData,const char * Name,unsigned MinOps)51 bool isTargetMD(const MDNode *ProfData, const char *Name, unsigned MinOps) {
52 // TODO: This routine may be simplified if MD_prof used an enum instead of a
53 // string to differentiate the types of MD_prof nodes.
54 if (!ProfData || !Name || MinOps < 2)
55 return false;
56
57 unsigned NOps = ProfData->getNumOperands();
58 if (NOps < MinOps)
59 return false;
60
61 auto *ProfDataName = dyn_cast<MDString>(ProfData->getOperand(0));
62 if (!ProfDataName)
63 return false;
64
65 return ProfDataName->getString().equals(Name);
66 }
67
68 } // namespace
69
70 namespace llvm {
71
hasProfMD(const Instruction & I)72 bool hasProfMD(const Instruction &I) {
73 return nullptr != I.getMetadata(LLVMContext::MD_prof);
74 }
75
isBranchWeightMD(const MDNode * ProfileData)76 bool isBranchWeightMD(const MDNode *ProfileData) {
77 return isTargetMD(ProfileData, "branch_weights", MinBWOps);
78 }
79
hasBranchWeightMD(const Instruction & I)80 bool hasBranchWeightMD(const Instruction &I) {
81 auto *ProfileData = I.getMetadata(LLVMContext::MD_prof);
82 return isBranchWeightMD(ProfileData);
83 }
84
hasValidBranchWeightMD(const Instruction & I)85 bool hasValidBranchWeightMD(const Instruction &I) {
86 return getValidBranchWeightMDNode(I);
87 }
88
getBranchWeightMDNode(const Instruction & I)89 MDNode *getBranchWeightMDNode(const Instruction &I) {
90 auto *ProfileData = I.getMetadata(LLVMContext::MD_prof);
91 if (!isBranchWeightMD(ProfileData))
92 return nullptr;
93 return ProfileData;
94 }
95
getValidBranchWeightMDNode(const Instruction & I)96 MDNode *getValidBranchWeightMDNode(const Instruction &I) {
97 auto *ProfileData = getBranchWeightMDNode(I);
98 if (ProfileData && ProfileData->getNumOperands() == 1 + I.getNumSuccessors())
99 return ProfileData;
100 return nullptr;
101 }
102
extractFromBranchWeightMD(const MDNode * ProfileData,SmallVectorImpl<uint32_t> & Weights)103 void extractFromBranchWeightMD(const MDNode *ProfileData,
104 SmallVectorImpl<uint32_t> &Weights) {
105 assert(isBranchWeightMD(ProfileData) && "wrong metadata");
106
107 unsigned NOps = ProfileData->getNumOperands();
108 assert(WeightsIdx < NOps && "Weights Index must be less than NOps.");
109 Weights.resize(NOps - WeightsIdx);
110
111 for (unsigned Idx = WeightsIdx, E = NOps; Idx != E; ++Idx) {
112 ConstantInt *Weight =
113 mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(Idx));
114 assert(Weight && "Malformed branch_weight in MD_prof node");
115 assert(Weight->getValue().getActiveBits() <= 32 &&
116 "Too many bits for uint32_t");
117 Weights[Idx - WeightsIdx] = Weight->getZExtValue();
118 }
119 }
120
extractBranchWeights(const MDNode * ProfileData,SmallVectorImpl<uint32_t> & Weights)121 bool extractBranchWeights(const MDNode *ProfileData,
122 SmallVectorImpl<uint32_t> &Weights) {
123 if (!isBranchWeightMD(ProfileData))
124 return false;
125 extractFromBranchWeightMD(ProfileData, Weights);
126 return true;
127 }
128
extractBranchWeights(const Instruction & I,SmallVectorImpl<uint32_t> & Weights)129 bool extractBranchWeights(const Instruction &I,
130 SmallVectorImpl<uint32_t> &Weights) {
131 auto *ProfileData = I.getMetadata(LLVMContext::MD_prof);
132 return extractBranchWeights(ProfileData, Weights);
133 }
134
extractBranchWeights(const Instruction & I,uint64_t & TrueVal,uint64_t & FalseVal)135 bool extractBranchWeights(const Instruction &I, uint64_t &TrueVal,
136 uint64_t &FalseVal) {
137 assert((I.getOpcode() == Instruction::Br ||
138 I.getOpcode() == Instruction::Select) &&
139 "Looking for branch weights on something besides branch, select, or "
140 "switch");
141
142 SmallVector<uint32_t, 2> Weights;
143 auto *ProfileData = I.getMetadata(LLVMContext::MD_prof);
144 if (!extractBranchWeights(ProfileData, Weights))
145 return false;
146
147 if (Weights.size() > 2)
148 return false;
149
150 TrueVal = Weights[0];
151 FalseVal = Weights[1];
152 return true;
153 }
154
extractProfTotalWeight(const MDNode * ProfileData,uint64_t & TotalVal)155 bool extractProfTotalWeight(const MDNode *ProfileData, uint64_t &TotalVal) {
156 TotalVal = 0;
157 if (!ProfileData)
158 return false;
159
160 auto *ProfDataName = dyn_cast<MDString>(ProfileData->getOperand(0));
161 if (!ProfDataName)
162 return false;
163
164 if (ProfDataName->getString().equals("branch_weights")) {
165 for (unsigned Idx = 1; Idx < ProfileData->getNumOperands(); Idx++) {
166 auto *V = mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(Idx));
167 assert(V && "Malformed branch_weight in MD_prof node");
168 TotalVal += V->getValue().getZExtValue();
169 }
170 return true;
171 }
172
173 if (ProfDataName->getString().equals("VP") &&
174 ProfileData->getNumOperands() > 3) {
175 TotalVal = mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(2))
176 ->getValue()
177 .getZExtValue();
178 return true;
179 }
180 return false;
181 }
182
extractProfTotalWeight(const Instruction & I,uint64_t & TotalVal)183 bool extractProfTotalWeight(const Instruction &I, uint64_t &TotalVal) {
184 return extractProfTotalWeight(I.getMetadata(LLVMContext::MD_prof), TotalVal);
185 }
186
setBranchWeights(Instruction & I,ArrayRef<uint32_t> Weights)187 void setBranchWeights(Instruction &I, ArrayRef<uint32_t> Weights) {
188 MDBuilder MDB(I.getContext());
189 MDNode *BranchWeights = MDB.createBranchWeights(Weights);
190 I.setMetadata(LLVMContext::MD_prof, BranchWeights);
191 }
192
193 } // namespace llvm
194