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1991e2a4df
Summary: This instruction encodes a loading operation that may fault, and a label to branch to if the load page-faults. The locations of potentially faulting loads and their "handler" destinations are recorded in a FaultMap section, meant to be consumed by LLVM's clients. Nothing generates FAULTING_LOAD_OP instructions yet, but they will be used in a future change. The documentation (FaultMaps.rst) needs improvement and I will update this diff with a more expanded version shortly. Depends on D10196 Reviewers: rnk, reames, AndyAyers, ab, atrick, pgavlin Reviewed By: atrick, pgavlin Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D10197 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239740 91177308-0d34-0410-b5e6-96231b3b80d8
115 lines
3.5 KiB
C++
115 lines
3.5 KiB
C++
//===---------------------------- FaultMaps.cpp ---------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/FaultMaps.h"
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#include "llvm/CodeGen/AsmPrinter.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCObjectFileInfo.h"
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#include "llvm/MC/MCStreamer.h"
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#include "llvm/Support/Debug.h"
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using namespace llvm;
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#define DEBUG_TYPE "faultmaps"
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static const int FaultMapVersion = 1;
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const char *FaultMaps::WFMP = "Fault Maps: ";
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FaultMaps::FaultMaps(AsmPrinter &AP) : AP(AP) {}
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void FaultMaps::recordFaultingOp(FaultType FaultTy,
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const MCSymbol *HandlerLabel) {
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MCContext &OutContext = AP.OutStreamer->getContext();
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MCSymbol *FaultingLabel = OutContext.createTempSymbol();
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AP.OutStreamer->EmitLabel(FaultingLabel);
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const MCExpr *FaultingOffset = MCBinaryExpr::createSub(
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MCSymbolRefExpr::create(FaultingLabel, OutContext),
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MCSymbolRefExpr::create(AP.CurrentFnSymForSize, OutContext), OutContext);
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const MCExpr *HandlerOffset = MCBinaryExpr::createSub(
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MCSymbolRefExpr::create(HandlerLabel, OutContext),
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MCSymbolRefExpr::create(AP.CurrentFnSymForSize, OutContext), OutContext);
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FunctionInfos[AP.CurrentFnSym].emplace_back(FaultTy, FaultingOffset,
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HandlerOffset);
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}
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void FaultMaps::serializeToFaultMapSection() {
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if (FunctionInfos.empty())
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return;
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MCContext &OutContext = AP.OutStreamer->getContext();
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MCStreamer &OS = *AP.OutStreamer;
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// Create the section.
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MCSection *FaultMapSection =
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OutContext.getObjectFileInfo()->getFaultMapSection();
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OS.SwitchSection(FaultMapSection);
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// Emit a dummy symbol to force section inclusion.
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OS.EmitLabel(OutContext.getOrCreateSymbol(Twine("__LLVM_FaultMaps")));
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DEBUG(dbgs() << "********** Fault Map Output **********\n");
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// Header
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OS.EmitIntValue(FaultMapVersion, 1); // Version.
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OS.EmitIntValue(0, 1); // Reserved.
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OS.EmitIntValue(0, 2); // Reserved.
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DEBUG(dbgs() << WFMP << "#functions = " << FunctionInfos.size() << "\n");
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OS.EmitIntValue(FunctionInfos.size(), 4);
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DEBUG(dbgs() << WFMP << "functions:\n");
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for (const auto &FFI : FunctionInfos)
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emitFunctionInfo(FFI.first, FFI.second);
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}
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void FaultMaps::emitFunctionInfo(const MCSymbol *FnLabel,
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const FunctionFaultInfos &FFI) {
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MCStreamer &OS = *AP.OutStreamer;
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DEBUG(dbgs() << WFMP << " function addr: " << *FnLabel << "\n");
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OS.EmitSymbolValue(FnLabel, 8);
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DEBUG(dbgs() << WFMP << " #faulting PCs: " << FFI.size() << "\n");
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OS.EmitIntValue(FFI.size(), 4);
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OS.EmitIntValue(0, 4); // Reserved
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for (auto &Fault : FFI) {
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DEBUG(dbgs() << WFMP << " fault type: "
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<< faultTypeToString(Fault.FaultType) << "\n");
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OS.EmitIntValue(Fault.FaultType, 4);
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DEBUG(dbgs() << WFMP << " faulting PC offset: "
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<< *Fault.FaultingOffsetExpr << "\n");
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OS.EmitValue(Fault.FaultingOffsetExpr, 4);
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DEBUG(dbgs() << WFMP << " fault handler PC offset: "
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<< *Fault.HandlerOffsetExpr << "\n");
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OS.EmitValue(Fault.HandlerOffsetExpr, 4);
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}
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}
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const char *FaultMaps::faultTypeToString(FaultMaps::FaultType FT) {
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switch (FT) {
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default:
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llvm_unreachable("unhandled fault type!");
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case FaultMaps::FaultingLoad:
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return "FaultingLoad";
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}
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}
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