forked from OSchip/llvm-project
156 lines
5.8 KiB
C++
156 lines
5.8 KiB
C++
//===- PseudoProbeInserter.cpp - Insert annotation for callsite profiling -===//
|
|
//
|
|
// 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 implements PseudoProbeInserter pass, which inserts pseudo probe
|
|
// annotations for call instructions with a pseudo-probe-specific dwarf
|
|
// discriminator. such discriminator indicates that the call instruction comes
|
|
// with a pseudo probe, and the discriminator value holds information to
|
|
// identify the corresponding counter.
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/CodeGen/MachineBasicBlock.h"
|
|
#include "llvm/CodeGen/MachineFunctionPass.h"
|
|
#include "llvm/CodeGen/MachineInstr.h"
|
|
#include "llvm/CodeGen/TargetInstrInfo.h"
|
|
#include "llvm/IR/DebugInfoMetadata.h"
|
|
#include "llvm/IR/PseudoProbe.h"
|
|
#include "llvm/InitializePasses.h"
|
|
#include "llvm/MC/MCPseudoProbe.h"
|
|
#include "llvm/Target/TargetMachine.h"
|
|
#include <unordered_set>
|
|
|
|
#define DEBUG_TYPE "pseudo-probe-inserter"
|
|
|
|
using namespace llvm;
|
|
|
|
namespace {
|
|
class PseudoProbeInserter : public MachineFunctionPass {
|
|
public:
|
|
static char ID;
|
|
|
|
PseudoProbeInserter() : MachineFunctionPass(ID) {
|
|
initializePseudoProbeInserterPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
StringRef getPassName() const override { return "Pseudo Probe Inserter"; }
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override {
|
|
AU.setPreservesAll();
|
|
MachineFunctionPass::getAnalysisUsage(AU);
|
|
}
|
|
|
|
bool doInitialization(Module &M) override {
|
|
ShouldRun = M.getNamedMetadata(PseudoProbeDescMetadataName);
|
|
return false;
|
|
}
|
|
|
|
bool runOnMachineFunction(MachineFunction &MF) override {
|
|
if (!ShouldRun)
|
|
return false;
|
|
const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
|
|
bool Changed = false;
|
|
for (MachineBasicBlock &MBB : MF) {
|
|
MachineInstr *FirstInstr = nullptr;
|
|
for (MachineInstr &MI : MBB) {
|
|
if (!MI.isPseudo())
|
|
FirstInstr = &MI;
|
|
if (MI.isCall()) {
|
|
if (DILocation *DL = MI.getDebugLoc()) {
|
|
auto Value = DL->getDiscriminator();
|
|
if (DILocation::isPseudoProbeDiscriminator(Value)) {
|
|
BuildMI(MBB, MI, DL, TII->get(TargetOpcode::PSEUDO_PROBE))
|
|
.addImm(getFuncGUID(MF.getFunction().getParent(), DL))
|
|
.addImm(
|
|
PseudoProbeDwarfDiscriminator::extractProbeIndex(Value))
|
|
.addImm(
|
|
PseudoProbeDwarfDiscriminator::extractProbeType(Value))
|
|
.addImm(PseudoProbeDwarfDiscriminator::extractProbeAttributes(
|
|
Value));
|
|
Changed = true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Walk the block backwards, move PSEUDO_PROBE before the first real
|
|
// instruction to fix out-of-order probes. There is a problem with probes
|
|
// as the terminator of the block. During the offline counts processing,
|
|
// the samples collected on the first physical instruction following a
|
|
// probe will be counted towards the probe. This logically equals to
|
|
// treating the instruction next to a probe as if it is from the same
|
|
// block of the probe. This is accurate most of the time unless the
|
|
// instruction can be reached from multiple flows, which means it actually
|
|
// starts a new block. Samples collected on such probes may cause
|
|
// imprecision with the counts inference algorithm. Fortunately, if
|
|
// there are still other native instructions preceding the probe we can
|
|
// use them as a place holder to collect samples for the probe.
|
|
if (FirstInstr) {
|
|
auto MII = MBB.rbegin();
|
|
while (MII != MBB.rend()) {
|
|
// Skip all pseudo probes followed by a real instruction since they
|
|
// are not dangling.
|
|
if (!MII->isPseudo())
|
|
break;
|
|
auto Cur = MII++;
|
|
if (Cur->getOpcode() != TargetOpcode::PSEUDO_PROBE)
|
|
continue;
|
|
// Move the dangling probe before FirstInstr.
|
|
auto *ProbeInstr = &*Cur;
|
|
MBB.remove(ProbeInstr);
|
|
MBB.insert(FirstInstr, ProbeInstr);
|
|
Changed = true;
|
|
}
|
|
} else {
|
|
// Probes not surrounded by any real instructions in the same block are
|
|
// called dangling probes. Since there's no good way to pick up a sample
|
|
// collection point for dangling probes at compile time, they are being
|
|
// removed so that the profile correlation tool will not report any
|
|
// samples collected for them and it's up to the counts inference tool
|
|
// to get them a reasonable count.
|
|
SmallVector<MachineInstr *, 4> ToBeRemoved;
|
|
for (MachineInstr &MI : MBB) {
|
|
if (MI.isPseudoProbe())
|
|
ToBeRemoved.push_back(&MI);
|
|
}
|
|
|
|
for (auto *MI : ToBeRemoved)
|
|
MI->eraseFromParent();
|
|
|
|
Changed |= !ToBeRemoved.empty();
|
|
}
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
private:
|
|
uint64_t getFuncGUID(Module *M, DILocation *DL) {
|
|
auto *SP = DL->getScope()->getSubprogram();
|
|
auto Name = SP->getLinkageName();
|
|
if (Name.empty())
|
|
Name = SP->getName();
|
|
return Function::getGUID(Name);
|
|
}
|
|
|
|
bool ShouldRun = false;
|
|
};
|
|
} // namespace
|
|
|
|
char PseudoProbeInserter::ID = 0;
|
|
INITIALIZE_PASS_BEGIN(PseudoProbeInserter, DEBUG_TYPE,
|
|
"Insert pseudo probe annotations for value profiling",
|
|
false, false)
|
|
INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
|
|
INITIALIZE_PASS_END(PseudoProbeInserter, DEBUG_TYPE,
|
|
"Insert pseudo probe annotations for value profiling",
|
|
false, false)
|
|
|
|
FunctionPass *llvm::createPseudoProbeInserter() {
|
|
return new PseudoProbeInserter();
|
|
}
|