1 //===- llvm/CodeGen/PseudoProbePrinter.cpp - Pseudo Probe Emission -------===//
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 contains support for writing pseudo probe info into asm files.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "PseudoProbePrinter.h"
14 #include "llvm/CodeGen/AsmPrinter.h"
15 #include "llvm/IR/DebugInfoMetadata.h"
16 #include "llvm/IR/Module.h"
17 #include "llvm/IR/PseudoProbe.h"
18 #include "llvm/MC/MCPseudoProbe.h"
19 #include "llvm/MC/MCStreamer.h"
20
21 using namespace llvm;
22
23 #define DEBUG_TYPE "pseudoprobe"
24
25 PseudoProbeHandler::~PseudoProbeHandler() = default;
26
PseudoProbeHandler(AsmPrinter * A,Module * M)27 PseudoProbeHandler::PseudoProbeHandler(AsmPrinter *A, Module *M) : Asm(A) {
28 NamedMDNode *FuncInfo = M->getNamedMetadata(PseudoProbeDescMetadataName);
29 assert(FuncInfo && "Pseudo probe descriptors are missing");
30 for (const auto *Operand : FuncInfo->operands()) {
31 const auto *MD = cast<MDNode>(Operand);
32 auto GUID =
33 mdconst::dyn_extract<ConstantInt>(MD->getOperand(0))->getZExtValue();
34 auto Name = cast<MDString>(MD->getOperand(2))->getString();
35 // We may see pairs with same name but different GUIDs here in LTO mode, due
36 // to static same-named functions inlined from other modules into this
37 // module. Function profiles with the same name will be merged no matter
38 // whether they are collected on the same function. Therefore we just pick
39 // up the last <Name, GUID> pair here to represent the same-named function
40 // collection and all probes from the collection will be merged into a
41 // single profile eventually.
42 Names[Name] = GUID;
43 }
44
45 LLVM_DEBUG(dump());
46 }
47
emitPseudoProbe(uint64_t Guid,uint64_t Index,uint64_t Type,uint64_t Attr,const DILocation * DebugLoc)48 void PseudoProbeHandler::emitPseudoProbe(uint64_t Guid, uint64_t Index,
49 uint64_t Type, uint64_t Attr,
50 const DILocation *DebugLoc) {
51 // Gather all the inlined-at nodes.
52 // When it's done ReversedInlineStack looks like ([66, B], [88, A])
53 // which means, Function A inlines function B at calliste with a probe id 88,
54 // and B inlines C at probe 66 where C is represented by Guid.
55 SmallVector<InlineSite, 8> ReversedInlineStack;
56 auto *InlinedAt = DebugLoc ? DebugLoc->getInlinedAt() : nullptr;
57 while (InlinedAt) {
58 const DISubprogram *SP = InlinedAt->getScope()->getSubprogram();
59 // Use linkage name for C++ if possible.
60 auto Name = SP->getLinkageName();
61 if (Name.empty())
62 Name = SP->getName();
63 assert(Names.count(Name) && "Pseudo probe descriptor missing for function");
64 uint64_t CallerGuid = Names[Name];
65 uint64_t CallerProbeId = PseudoProbeDwarfDiscriminator::extractProbeIndex(
66 InlinedAt->getDiscriminator());
67 ReversedInlineStack.emplace_back(CallerGuid, CallerProbeId);
68 InlinedAt = InlinedAt->getInlinedAt();
69 }
70
71 SmallVector<InlineSite, 8> InlineStack(ReversedInlineStack.rbegin(),
72 ReversedInlineStack.rend());
73 Asm->OutStreamer->emitPseudoProbe(Guid, Index, Type, Attr, InlineStack);
74 }
75
76 #ifndef NDEBUG
dump() const77 void PseudoProbeHandler::dump() const {
78 dbgs() << "\n=============================\n";
79 dbgs() << "\nFunction Name to GUID map:\n";
80 dbgs() << "\n=============================\n";
81 for (const auto &Item : Names)
82 dbgs() << "Func: " << Item.first << " GUID: " << Item.second << "\n";
83 }
84 #endif
85