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//===- llvm/CodeGen/PseudoProbePrinter.cpp - Pseudo Probe Emission -------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing pseudo probe info into asm files.
//
//===----------------------------------------------------------------------===//
#include "PseudoProbePrinter.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PseudoProbe.h"
#include "llvm/MC/MCPseudoProbe.h"
#include "llvm/MC/MCStreamer.h"
using namespace llvm;
#define DEBUG_TYPE "pseudoprobe"
PseudoProbeHandler::~PseudoProbeHandler() = default;
PseudoProbeHandler::PseudoProbeHandler(AsmPrinter *A, Module *M) : Asm(A) {
NamedMDNode *FuncInfo = M->getNamedMetadata(PseudoProbeDescMetadataName);
assert(FuncInfo && "Pseudo probe descriptors are missing");
for (const auto *Operand : FuncInfo->operands()) {
const auto *MD = cast<MDNode>(Operand);
auto GUID =
mdconst::dyn_extract<ConstantInt>(MD->getOperand(0))->getZExtValue();
auto Name = cast<MDString>(MD->getOperand(2))->getString();
// We may see pairs with same name but different GUIDs here in LTO mode, due
// to static same-named functions inlined from other modules into this
// module. Function profiles with the same name will be merged no matter
// whether they are collected on the same function. Therefore we just pick
// up the last <Name, GUID> pair here to represent the same-named function
// collection and all probes from the collection will be merged into a
// single profile eventually.
Names[Name] = GUID;
}
LLVM_DEBUG(dump());
}
void PseudoProbeHandler::emitPseudoProbe(uint64_t Guid, uint64_t Index,
uint64_t Type, uint64_t Attr,
const DILocation *DebugLoc) {
// Gather all the inlined-at nodes.
// When it's done ReversedInlineStack looks like ([66, B], [88, A])
// which means, Function A inlines function B at calliste with a probe id 88,
// and B inlines C at probe 66 where C is represented by Guid.
SmallVector<InlineSite, 8> ReversedInlineStack;
auto *InlinedAt = DebugLoc ? DebugLoc->getInlinedAt() : nullptr;
while (InlinedAt) {
const DISubprogram *SP = InlinedAt->getScope()->getSubprogram();
// Use linkage name for C++ if possible.
auto Name = SP->getLinkageName();
if (Name.empty())
Name = SP->getName();
assert(Names.count(Name) && "Pseudo probe descriptor missing for function");
uint64_t CallerGuid = Names[Name];
uint64_t CallerProbeId = PseudoProbeDwarfDiscriminator::extractProbeIndex(
InlinedAt->getDiscriminator());
ReversedInlineStack.emplace_back(CallerGuid, CallerProbeId);
InlinedAt = InlinedAt->getInlinedAt();
}
SmallVector<InlineSite, 8> InlineStack(ReversedInlineStack.rbegin(),
ReversedInlineStack.rend());
Asm->OutStreamer->emitPseudoProbe(Guid, Index, Type, Attr, InlineStack);
}
#ifndef NDEBUG
void PseudoProbeHandler::dump() const {
dbgs() << "\n=============================\n";
dbgs() << "\nFunction Name to GUID map:\n";
dbgs() << "\n=============================\n";
for (const auto &Item : Names)
dbgs() << "Func: " << Item.first << " GUID: " << Item.second << "\n";
}
#endif
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