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117b53ae38
Currently, an AsmPrinterHandler has several methods that allow to
dynamically hook in unwind or debug info emission, e.g. at begin/end of
every function or instruction. The class hierarchy and the actually
overridden functions are as follows:
(SymSz=setSymbolSize, mFE=markFunctionEnd, BBS=BasicBlockSection,
FL=Funclet; b=beginX, e=endX)
SymSz Mod Fn mFE BBS FL Inst
AsmPrinterHandler - - - - - - -
` PseudoProbeHandler - - - - - - -
` WinCFGuard - e e - - - -
` EHStreamer - - - - - - -
` DwarfCFIException - e be - be - -
` ARMException - - be e - - -
` AIXException - - e - - - -
` WinException - e be e - be -
` WasmException - e be - - - -
` DebugHandlerBase - b be - be - be
` BTFDebug - e - - - - b
` CodeViewDebug - be - - - - b
` DWARFDebug yes be - - - - b
Doing virtual function calls per instruction is costly and useless when
the called function does nothing.
This commit performs the following clean-up/improvements:
- PseudoProbeHandler is no longer an AsmPrinterHandler -- it used
nothing of its functionality to hook in at the possible points. This
avoids virtual function calls when a pseudo probe printer is present.
- DebugHandlerBase is no longer an AsmPrinterHandler, but a separate
base class. DebugHandlerBase is the only remaining "hook" for begin/end
instruction and setSymbolSize (only used by DWARFDebug). begin/end for
function and basic block sections are never overriden and therefore are
no longer virtual. (Originally I intended there to be only one debug
handler, but BPF as the only target supports two at the same time: DWARF
and BTF.)
- AsmPrinterHandler no longer has begin/end instruction and
setSymbolSize hooks -- these were only used by DebugHandlerBase. This
avoid iterating over handlers in every instruction.
AsmPrinterHandler Mod Fn mFE BBS FL
` WinCFGuard e e - - -
` EHStreamer - - - - -
` DwarfCFIException e be - be -
` ARMException - be e - -
` AIXException - e - - -
` WinException e be e - be
` WasmException e be - - -
SymSz Mod Fn BBS Inst
DebugHandlerBase - b be be be
` BTFDebug - e b
` CodeViewDebug - be b
` DWARFDebug yes be b
PseudoProbeHandler (no shared methods)
To continue allowing external users (e.g., Julia) to hook in at every
instruction, a new method addDebugHandler is exposed.
This results in a performance improvement, especially in the -O0 -g0
case with unwind information (e.g., JIT baseline).
55 lines
2.4 KiB
C++
55 lines
2.4 KiB
C++
//===- 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/Function.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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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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auto Name = InlinedAt->getSubprogramLinkageName();
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// Use caching to avoid redundant md5 computation for build speed.
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uint64_t &CallerGuid = NameGuidMap[Name];
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if (!CallerGuid)
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CallerGuid = Function::getGUID(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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uint64_t Discriminator = 0;
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// For now only block probes have FS discriminators. See
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// MIRFSDiscriminator.cpp for more details.
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if (EnableFSDiscriminator && DebugLoc &&
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(Type == (uint64_t)PseudoProbeType::Block))
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Discriminator = DebugLoc->getDiscriminator();
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assert((EnableFSDiscriminator || Discriminator == 0) &&
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"Discriminator should not be set in non-FSAFDO mode");
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SmallVector<InlineSite, 8> InlineStack(llvm::reverse(ReversedInlineStack));
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Asm->OutStreamer->emitPseudoProbe(Guid, Index, Type, Attr, Discriminator,
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InlineStack, Asm->CurrentFnSym);
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}
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