[CodeGen] Introduce a FAULTING_LOAD_OP pseudo-op.
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
llvm-svn: 239740
diff --git a/llvm/lib/CodeGen/CMakeLists.txt b/llvm/lib/CodeGen/CMakeLists.txt
index 6d2af90..2f65253 100644
--- a/llvm/lib/CodeGen/CMakeLists.txt
+++ b/llvm/lib/CodeGen/CMakeLists.txt
@@ -20,6 +20,7 @@
ExecutionDepsFix.cpp
ExpandISelPseudos.cpp
ExpandPostRAPseudos.cpp
+ FaultMaps.cpp
GCMetadata.cpp
GCMetadataPrinter.cpp
GCRootLowering.cpp
diff --git a/llvm/lib/CodeGen/FaultMaps.cpp b/llvm/lib/CodeGen/FaultMaps.cpp
new file mode 100644
index 0000000..2f84951
--- /dev/null
+++ b/llvm/lib/CodeGen/FaultMaps.cpp
@@ -0,0 +1,114 @@
+//===---------------------------- FaultMaps.cpp ---------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/FaultMaps.h"
+
+#include "llvm/CodeGen/AsmPrinter.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/Support/Debug.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "faultmaps"
+
+static const int FaultMapVersion = 1;
+const char *FaultMaps::WFMP = "Fault Maps: ";
+
+FaultMaps::FaultMaps(AsmPrinter &AP) : AP(AP) {}
+
+void FaultMaps::recordFaultingOp(FaultType FaultTy,
+ const MCSymbol *HandlerLabel) {
+ MCContext &OutContext = AP.OutStreamer->getContext();
+ MCSymbol *FaultingLabel = OutContext.createTempSymbol();
+
+ AP.OutStreamer->EmitLabel(FaultingLabel);
+
+ const MCExpr *FaultingOffset = MCBinaryExpr::createSub(
+ MCSymbolRefExpr::create(FaultingLabel, OutContext),
+ MCSymbolRefExpr::create(AP.CurrentFnSymForSize, OutContext), OutContext);
+
+ const MCExpr *HandlerOffset = MCBinaryExpr::createSub(
+ MCSymbolRefExpr::create(HandlerLabel, OutContext),
+ MCSymbolRefExpr::create(AP.CurrentFnSymForSize, OutContext), OutContext);
+
+ FunctionInfos[AP.CurrentFnSym].emplace_back(FaultTy, FaultingOffset,
+ HandlerOffset);
+}
+
+void FaultMaps::serializeToFaultMapSection() {
+ if (FunctionInfos.empty())
+ return;
+
+ MCContext &OutContext = AP.OutStreamer->getContext();
+ MCStreamer &OS = *AP.OutStreamer;
+
+ // Create the section.
+ MCSection *FaultMapSection =
+ OutContext.getObjectFileInfo()->getFaultMapSection();
+ OS.SwitchSection(FaultMapSection);
+
+ // Emit a dummy symbol to force section inclusion.
+ OS.EmitLabel(OutContext.getOrCreateSymbol(Twine("__LLVM_FaultMaps")));
+
+ DEBUG(dbgs() << "********** Fault Map Output **********\n");
+
+ // Header
+ OS.EmitIntValue(FaultMapVersion, 1); // Version.
+ OS.EmitIntValue(0, 1); // Reserved.
+ OS.EmitIntValue(0, 2); // Reserved.
+
+ DEBUG(dbgs() << WFMP << "#functions = " << FunctionInfos.size() << "\n");
+ OS.EmitIntValue(FunctionInfos.size(), 4);
+
+ DEBUG(dbgs() << WFMP << "functions:\n");
+
+ for (const auto &FFI : FunctionInfos)
+ emitFunctionInfo(FFI.first, FFI.second);
+}
+
+void FaultMaps::emitFunctionInfo(const MCSymbol *FnLabel,
+ const FunctionFaultInfos &FFI) {
+ MCStreamer &OS = *AP.OutStreamer;
+
+ DEBUG(dbgs() << WFMP << " function addr: " << *FnLabel << "\n");
+ OS.EmitSymbolValue(FnLabel, 8);
+
+ DEBUG(dbgs() << WFMP << " #faulting PCs: " << FFI.size() << "\n");
+ OS.EmitIntValue(FFI.size(), 4);
+
+ OS.EmitIntValue(0, 4); // Reserved
+
+ for (auto &Fault : FFI) {
+ DEBUG(dbgs() << WFMP << " fault type: "
+ << faultTypeToString(Fault.FaultType) << "\n");
+ OS.EmitIntValue(Fault.FaultType, 4);
+
+ DEBUG(dbgs() << WFMP << " faulting PC offset: "
+ << *Fault.FaultingOffsetExpr << "\n");
+ OS.EmitValue(Fault.FaultingOffsetExpr, 4);
+
+ DEBUG(dbgs() << WFMP << " fault handler PC offset: "
+ << *Fault.HandlerOffsetExpr << "\n");
+ OS.EmitValue(Fault.HandlerOffsetExpr, 4);
+ }
+}
+
+
+const char *FaultMaps::faultTypeToString(FaultMaps::FaultType FT) {
+ switch (FT) {
+ default:
+ llvm_unreachable("unhandled fault type!");
+
+ case FaultMaps::FaultingLoad:
+ return "FaultingLoad";
+ }
+}
diff --git a/llvm/lib/MC/MCObjectFileInfo.cpp b/llvm/lib/MC/MCObjectFileInfo.cpp
index 83a08e2..3ef87b5 100644
--- a/llvm/lib/MC/MCObjectFileInfo.cpp
+++ b/llvm/lib/MC/MCObjectFileInfo.cpp
@@ -238,6 +238,9 @@
StackMapSection = Ctx->getMachOSection("__LLVM_STACKMAPS", "__llvm_stackmaps",
0, SectionKind::getMetadata());
+ FaultMapSection = Ctx->getMachOSection("__LLVM_FAULTMAPS", "__llvm_faultmaps",
+ 0, SectionKind::getMetadata());
+
TLSExtraDataSection = TLSTLVSection;
}
@@ -518,6 +521,9 @@
StackMapSection =
Ctx->getELFSection(".llvm_stackmaps", ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
+
+ FaultMapSection =
+ Ctx->getELFSection(".llvm_faultmaps", ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
}
void MCObjectFileInfo::initCOFFMCObjectFileInfo(Triple T) {
diff --git a/llvm/lib/Target/X86/X86AsmPrinter.cpp b/llvm/lib/Target/X86/X86AsmPrinter.cpp
index 64fc6d0..3b11e69 100644
--- a/llvm/lib/Target/X86/X86AsmPrinter.cpp
+++ b/llvm/lib/Target/X86/X86AsmPrinter.cpp
@@ -674,6 +674,7 @@
}
SM.serializeToStackMapSection();
+ FM.serializeToFaultMapSection();
// Funny Darwin hack: This flag tells the linker that no global symbols
// contain code that falls through to other global symbols (e.g. the obvious
@@ -726,8 +727,10 @@
}
}
- if (TT.isOSBinFormatELF())
+ if (TT.isOSBinFormatELF()) {
SM.serializeToStackMapSection();
+ FM.serializeToFaultMapSection();
+ }
}
//===----------------------------------------------------------------------===//
diff --git a/llvm/lib/Target/X86/X86AsmPrinter.h b/llvm/lib/Target/X86/X86AsmPrinter.h
index 3beeb17..acba211 100644
--- a/llvm/lib/Target/X86/X86AsmPrinter.h
+++ b/llvm/lib/Target/X86/X86AsmPrinter.h
@@ -12,6 +12,7 @@
#include "X86Subtarget.h"
#include "llvm/CodeGen/AsmPrinter.h"
+#include "llvm/CodeGen/FaultMaps.h"
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/Target/TargetMachine.h"
@@ -27,6 +28,7 @@
class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
const X86Subtarget *Subtarget;
StackMaps SM;
+ FaultMaps FM;
void GenerateExportDirective(const MCSymbol *Sym, bool IsData);
@@ -83,13 +85,15 @@
void LowerSTACKMAP(const MachineInstr &MI);
void LowerPATCHPOINT(const MachineInstr &MI, X86MCInstLower &MCIL);
void LowerSTATEPOINT(const MachineInstr &MI, X86MCInstLower &MCIL);
+ void LowerFAULTING_LOAD_OP(const MachineInstr &MI, X86MCInstLower &MCIL);
void LowerTlsAddr(X86MCInstLower &MCInstLowering, const MachineInstr &MI);
public:
explicit X86AsmPrinter(TargetMachine &TM,
std::unique_ptr<MCStreamer> Streamer)
- : AsmPrinter(TM, std::move(Streamer)), SM(*this), SMShadowTracker(TM) {}
+ : AsmPrinter(TM, std::move(Streamer)), SM(*this), FM(*this),
+ SMShadowTracker(TM) {}
const char *getPassName() const override {
return "X86 Assembly / Object Emitter";
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index e47ab17..655e06a 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -864,6 +864,28 @@
SM.recordStatepoint(MI);
}
+void X86AsmPrinter::LowerFAULTING_LOAD_OP(const MachineInstr &MI,
+ X86MCInstLower &MCIL) {
+ // FAULTING_LOAD_OP <def>, <handler label>, <load opcode>, <load operands>
+
+ unsigned LoadDefRegister = MI.getOperand(0).getReg();
+ MCSymbol *HandlerLabel = MI.getOperand(1).getMCSymbol();
+ unsigned LoadOpcode = MI.getOperand(2).getImm();
+ unsigned LoadOperandsBeginIdx = 3;
+
+ FM.recordFaultingOp(FaultMaps::FaultingLoad, HandlerLabel);
+
+ MCInst LoadMI;
+ LoadMI.setOpcode(LoadOpcode);
+ LoadMI.addOperand(MCOperand::createReg(LoadDefRegister));
+ for (auto I = MI.operands_begin() + LoadOperandsBeginIdx,
+ E = MI.operands_end();
+ I != E; ++I)
+ if (auto MaybeOperand = MCIL.LowerMachineOperand(&MI, *I))
+ LoadMI.addOperand(MaybeOperand.getValue());
+
+ OutStreamer->EmitInstruction(LoadMI, getSubtargetInfo());
+}
// Lower a stackmap of the form:
// <id>, <shadowBytes>, ...
@@ -1119,6 +1141,9 @@
case TargetOpcode::STATEPOINT:
return LowerSTATEPOINT(*MI, MCInstLowering);
+ case TargetOpcode::FAULTING_LOAD_OP:
+ return LowerFAULTING_LOAD_OP(*MI, MCInstLowering);
+
case TargetOpcode::STACKMAP:
return LowerSTACKMAP(*MI);