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//===- lib/MC/MCPseudoProbe.cpp - Pseudo probe encoding support ----------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCPseudoProbe.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/MC/MCStreamer.h"
#define DEBUG_TYPE "mcpseudoprobe"
using namespace llvm;
#ifndef NDEBUG
int MCPseudoProbeTable::DdgPrintIndent = 0;
#endif
static const MCExpr *buildSymbolDiff(MCObjectStreamer *MCOS, const MCSymbol *A,
const MCSymbol *B) {
MCContext &Context = MCOS->getContext();
MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
const MCExpr *ARef = MCSymbolRefExpr::create(A, Variant, Context);
const MCExpr *BRef = MCSymbolRefExpr::create(B, Variant, Context);
const MCExpr *AddrDelta =
MCBinaryExpr::create(MCBinaryExpr::Sub, ARef, BRef, Context);
return AddrDelta;
}
void MCPseudoProbe::emit(MCObjectStreamer *MCOS,
const MCPseudoProbe *LastProbe) const {
// Emit Index
MCOS->emitULEB128IntValue(Index);
// Emit Type and the flag:
// Type (bit 0 to 3), with bit 4 to 6 for attributes.
// Flag (bit 7, 0 - code address, 1 - address delta). This indicates whether
// the following field is a symbolic code address or an address delta.
assert(Type <= 0xF && "Probe type too big to encode, exceeding 15");
assert(Attributes <= 0x7 &&
"Probe attributes too big to encode, exceeding 7");
uint8_t PackedType = Type | (Attributes << 4);
uint8_t Flag = LastProbe ? ((int8_t)MCPseudoProbeFlag::AddressDelta << 7) : 0;
MCOS->emitInt8(Flag | PackedType);
if (LastProbe) {
// Emit the delta between the address label and LastProbe.
const MCExpr *AddrDelta =
buildSymbolDiff(MCOS, Label, LastProbe->getLabel());
int64_t Delta;
if (AddrDelta->evaluateAsAbsolute(Delta, MCOS->getAssemblerPtr())) {
MCOS->emitSLEB128IntValue(Delta);
} else {
MCOS->insert(new MCPseudoProbeAddrFragment(AddrDelta));
}
} else {
// Emit label as a symbolic code address.
MCOS->emitSymbolValue(
Label, MCOS->getContext().getAsmInfo()->getCodePointerSize());
}
LLVM_DEBUG({
dbgs().indent(MCPseudoProbeTable::DdgPrintIndent);
dbgs() << "Probe: " << Index << "\n";
});
}
MCPseudoProbeInlineTree::~MCPseudoProbeInlineTree() {
for (auto &Inlinee : Inlinees)
delete Inlinee.second;
}
MCPseudoProbeInlineTree *
MCPseudoProbeInlineTree::getOrAddNode(InlineSite Site) {
auto Iter = Inlinees.find(Site);
if (Iter == Inlinees.end()) {
auto *Node = new MCPseudoProbeInlineTree(std::get<0>(Site));
Inlinees[Site] = Node;
return Node;
} else {
return Iter->second;
}
}
void MCPseudoProbeInlineTree::addPseudoProbe(
const MCPseudoProbe &Probe, const MCPseudoProbeInlineStack &InlineStack) {
// The function should not be called on the root.
assert(isRoot() && "Should not be called on root");
// When it comes here, the input look like:
// Probe: GUID of C, ...
// InlineStack: [88, A], [66, B]
// which means, Function A inlines function B at call site with a probe id of
// 88, and B inlines C at probe 66. The tri-tree expects a tree path like {[0,
// A], [88, B], [66, C]} to locate the tree node where the probe should be
// added. Note that the edge [0, A] means A is the top-level function we are
// emitting probes for.
// Make a [0, A] edge.
// An empty inline stack means the function that the probe originates from
// is a top-level function.
InlineSite Top;
if (InlineStack.empty()) {
Top = InlineSite(Probe.getGuid(), 0);
} else {
Top = InlineSite(std::get<0>(InlineStack.front()), 0);
}
auto *Cur = getOrAddNode(Top);
// Make interior edges by walking the inline stack. Once it's done, Cur should
// point to the node that the probe originates from.
if (!InlineStack.empty()) {
auto Iter = InlineStack.begin();
auto Index = std::get<1>(*Iter);
Iter++;
for (; Iter != InlineStack.end(); Iter++) {
// Make an edge by using the previous probe id and current GUID.
Cur = Cur->getOrAddNode(InlineSite(std::get<0>(*Iter), Index));
Index = std::get<1>(*Iter);
}
Cur = Cur->getOrAddNode(InlineSite(Probe.getGuid(), Index));
}
Cur->Probes.push_back(Probe);
}
void MCPseudoProbeInlineTree::emit(MCObjectStreamer *MCOS,
const MCPseudoProbe *&LastProbe) {
LLVM_DEBUG({
dbgs().indent(MCPseudoProbeTable::DdgPrintIndent);
dbgs() << "Group [\n";
MCPseudoProbeTable::DdgPrintIndent += 2;
});
// Emit probes grouped by GUID.
if (Guid != 0) {
LLVM_DEBUG({
dbgs().indent(MCPseudoProbeTable::DdgPrintIndent);
dbgs() << "GUID: " << Guid << "\n";
});
// Emit Guid
MCOS->emitInt64(Guid);
// Emit number of probes in this node
MCOS->emitULEB128IntValue(Probes.size());
// Emit number of direct inlinees
MCOS->emitULEB128IntValue(Inlinees.size());
// Emit probes in this group
for (const auto &Probe : Probes) {
Probe.emit(MCOS, LastProbe);
LastProbe = &Probe;
}
} else {
assert(Probes.empty() && "Root should not have probes");
}
// Emit descendent
for (const auto &Inlinee : Inlinees) {
if (Guid) {
// Emit probe index
MCOS->emitULEB128IntValue(std::get<1>(Inlinee.first));
LLVM_DEBUG({
dbgs().indent(MCPseudoProbeTable::DdgPrintIndent);
dbgs() << "InlineSite: " << std::get<1>(Inlinee.first) << "\n";
});
}
// Emit the group
Inlinee.second->emit(MCOS, LastProbe);
}
LLVM_DEBUG({
MCPseudoProbeTable::DdgPrintIndent -= 2;
dbgs().indent(MCPseudoProbeTable::DdgPrintIndent);
dbgs() << "]\n";
});
}
void MCPseudoProbeSection::emit(MCObjectStreamer *MCOS) {
MCContext &Ctx = MCOS->getContext();
for (auto &ProbeSec : MCProbeDivisions) {
const MCPseudoProbe *LastProbe = nullptr;
if (auto *S =
Ctx.getObjectFileInfo()->getPseudoProbeSection(ProbeSec.first)) {
// Switch to the .pseudoprobe section or a comdat group.
MCOS->SwitchSection(S);
// Emit probes grouped by GUID.
ProbeSec.second.emit(MCOS, LastProbe);
}
}
}
//
// This emits the pseudo probe tables.
//
void MCPseudoProbeTable::emit(MCObjectStreamer *MCOS) {
MCContext &Ctx = MCOS->getContext();
auto &ProbeTable = Ctx.getMCPseudoProbeTable();
// Bail out early so we don't switch to the pseudo_probe section needlessly
// and in doing so create an unnecessary (if empty) section.
auto &ProbeSections = ProbeTable.getProbeSections();
if (ProbeSections.empty())
return;
LLVM_DEBUG(MCPseudoProbeTable::DdgPrintIndent = 0);
// Put out the probe.
ProbeSections.emit(MCOS);
}
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