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