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llvm-6502/lib/Target/AArch64/AArch64AsmPrinter.cpp
Lang Hames 26cc5bea39 [AArch64][Stackmaps] Optimize stackmap shadows on AArch64. 
Reduce the number of nops emitted for stackmap shadows on AArch64 by counting
non-stackmap instructions up to the next branch target towards the requested
shadow.

<rdar://problem/14959522>



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223156 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-02 21:36:24 +00:00

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//===-- AArch64AsmPrinter.cpp - AArch64 LLVM assembly writer --------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains a printer that converts from our internal representation
// of machine-dependent LLVM code to the AArch64 assembly language.
//
//===----------------------------------------------------------------------===//
#include "AArch64.h"
#include "AArch64MCInstLower.h"
#include "AArch64MachineFunctionInfo.h"
#include "AArch64RegisterInfo.h"
#include "AArch64Subtarget.h"
#include "InstPrinter/AArch64InstPrinter.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineModuleInfoImpls.h"
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstBuilder.h"
#include "llvm/MC/MCLinkerOptimizationHint.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/TargetRegistry.h"
using namespace llvm;
#define DEBUG_TYPE "asm-printer"
namespace {
class AArch64AsmPrinter : public AsmPrinter {
/// Subtarget - Keep a pointer to the AArch64Subtarget around so that we can
/// make the right decision when printing asm code for different targets.
const AArch64Subtarget *Subtarget;
AArch64MCInstLower MCInstLowering;
StackMaps SM;
public:
AArch64AsmPrinter(TargetMachine &TM, MCStreamer &Streamer)
: AsmPrinter(TM, Streamer),
Subtarget(&TM.getSubtarget<AArch64Subtarget>()),
MCInstLowering(OutContext, *this), SM(*this), AArch64FI(nullptr),
LOHLabelCounter(0) {}
const char *getPassName() const override {
return "AArch64 Assembly Printer";
}
/// \brief Wrapper for MCInstLowering.lowerOperand() for the
/// tblgen'erated pseudo lowering.
bool lowerOperand(const MachineOperand &MO, MCOperand &MCOp) const {
return MCInstLowering.lowerOperand(MO, MCOp);
}
void LowerSTACKMAP(MCStreamer &OutStreamer, StackMaps &SM,
const MachineInstr &MI);
void LowerPATCHPOINT(MCStreamer &OutStreamer, StackMaps &SM,
const MachineInstr &MI);
/// \brief tblgen'erated driver function for lowering simple MI->MC
/// pseudo instructions.
bool emitPseudoExpansionLowering(MCStreamer &OutStreamer,
const MachineInstr *MI);
void EmitInstruction(const MachineInstr *MI) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AsmPrinter::getAnalysisUsage(AU);
AU.setPreservesAll();
}
bool runOnMachineFunction(MachineFunction &F) override {
AArch64FI = F.getInfo<AArch64FunctionInfo>();
return AsmPrinter::runOnMachineFunction(F);
}
private:
MachineLocation getDebugValueLocation(const MachineInstr *MI) const;
void printOperand(const MachineInstr *MI, unsigned OpNum, raw_ostream &O);
bool printAsmMRegister(const MachineOperand &MO, char Mode, raw_ostream &O);
bool printAsmRegInClass(const MachineOperand &MO,
const TargetRegisterClass *RC, bool isVector,
raw_ostream &O);
bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNum,
unsigned AsmVariant, const char *ExtraCode,
raw_ostream &O) override;
bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNum,
unsigned AsmVariant, const char *ExtraCode,
raw_ostream &O) override;
void PrintDebugValueComment(const MachineInstr *MI, raw_ostream &OS);
void EmitFunctionBodyEnd() override;
MCSymbol *GetCPISymbol(unsigned CPID) const override;
void EmitEndOfAsmFile(Module &M) override;
AArch64FunctionInfo *AArch64FI;
/// \brief Emit the LOHs contained in AArch64FI.
void EmitLOHs();
typedef std::map<const MachineInstr *, MCSymbol *> MInstToMCSymbol;
MInstToMCSymbol LOHInstToLabel;
unsigned LOHLabelCounter;
};
} // end of anonymous namespace
//===----------------------------------------------------------------------===//
void AArch64AsmPrinter::EmitEndOfAsmFile(Module &M) {
if (Subtarget->isTargetMachO()) {
// 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
// implementation of multiple entry points). If this doesn't occur, the
// linker can safely perform dead code stripping. Since LLVM never
// generates code that does this, it is always safe to set.
OutStreamer.EmitAssemblerFlag(MCAF_SubsectionsViaSymbols);
SM.serializeToStackMapSection();
}
// Emit a .data.rel section containing any stubs that were created.
if (Subtarget->isTargetELF()) {
const TargetLoweringObjectFileELF &TLOFELF =
static_cast<const TargetLoweringObjectFileELF &>(getObjFileLowering());
MachineModuleInfoELF &MMIELF = MMI->getObjFileInfo<MachineModuleInfoELF>();
// Output stubs for external and common global variables.
MachineModuleInfoELF::SymbolListTy Stubs = MMIELF.GetGVStubList();
if (!Stubs.empty()) {
OutStreamer.SwitchSection(TLOFELF.getDataRelSection());
const DataLayout *TD = TM.getSubtargetImpl()->getDataLayout();
for (unsigned i = 0, e = Stubs.size(); i != e; ++i) {
OutStreamer.EmitLabel(Stubs[i].first);
OutStreamer.EmitSymbolValue(Stubs[i].second.getPointer(),
TD->getPointerSize(0));
}
Stubs.clear();
}
}
}
MachineLocation
AArch64AsmPrinter::getDebugValueLocation(const MachineInstr *MI) const {
MachineLocation Location;
assert(MI->getNumOperands() == 4 && "Invalid no. of machine operands!");
// Frame address. Currently handles register +- offset only.
if (MI->getOperand(0).isReg() && MI->getOperand(1).isImm())
Location.set(MI->getOperand(0).getReg(), MI->getOperand(1).getImm());
else {
DEBUG(dbgs() << "DBG_VALUE instruction ignored! " << *MI << "\n");
}
return Location;
}
void AArch64AsmPrinter::EmitLOHs() {
SmallVector<MCSymbol *, 3> MCArgs;
for (const auto &D : AArch64FI->getLOHContainer()) {
for (const MachineInstr *MI : D.getArgs()) {
MInstToMCSymbol::iterator LabelIt = LOHInstToLabel.find(MI);
assert(LabelIt != LOHInstToLabel.end() &&
"Label hasn't been inserted for LOH related instruction");
MCArgs.push_back(LabelIt->second);
}
OutStreamer.EmitLOHDirective(D.getKind(), MCArgs);
MCArgs.clear();
}
}
void AArch64AsmPrinter::EmitFunctionBodyEnd() {
if (!AArch64FI->getLOHRelated().empty())
EmitLOHs();
}
/// GetCPISymbol - Return the symbol for the specified constant pool entry.
MCSymbol *AArch64AsmPrinter::GetCPISymbol(unsigned CPID) const {
// Darwin uses a linker-private symbol name for constant-pools (to
// avoid addends on the relocation?), ELF has no such concept and
// uses a normal private symbol.
if (getDataLayout().getLinkerPrivateGlobalPrefix()[0])
return OutContext.GetOrCreateSymbol(
Twine(getDataLayout().getLinkerPrivateGlobalPrefix()) + "CPI" +
Twine(getFunctionNumber()) + "_" + Twine(CPID));
return OutContext.GetOrCreateSymbol(
Twine(getDataLayout().getPrivateGlobalPrefix()) + "CPI" +
Twine(getFunctionNumber()) + "_" + Twine(CPID));
}
void AArch64AsmPrinter::printOperand(const MachineInstr *MI, unsigned OpNum,
raw_ostream &O) {
const MachineOperand &MO = MI->getOperand(OpNum);
switch (MO.getType()) {
default:
llvm_unreachable("<unknown operand type>");
case MachineOperand::MO_Register: {
unsigned Reg = MO.getReg();
assert(TargetRegisterInfo::isPhysicalRegister(Reg));
assert(!MO.getSubReg() && "Subregs should be eliminated!");
O << AArch64InstPrinter::getRegisterName(Reg);
break;
}
case MachineOperand::MO_Immediate: {
int64_t Imm = MO.getImm();
O << '#' << Imm;
break;
}
}
}
bool AArch64AsmPrinter::printAsmMRegister(const MachineOperand &MO, char Mode,
raw_ostream &O) {
unsigned Reg = MO.getReg();
switch (Mode) {
default:
return true; // Unknown mode.
case 'w':
Reg = getWRegFromXReg(Reg);
break;
case 'x':
Reg = getXRegFromWReg(Reg);
break;
}
O << AArch64InstPrinter::getRegisterName(Reg);
return false;
}
// Prints the register in MO using class RC using the offset in the
// new register class. This should not be used for cross class
// printing.
bool AArch64AsmPrinter::printAsmRegInClass(const MachineOperand &MO,
const TargetRegisterClass *RC,
bool isVector, raw_ostream &O) {
assert(MO.isReg() && "Should only get here with a register!");
const AArch64RegisterInfo *RI = static_cast<const AArch64RegisterInfo *>(
TM.getSubtargetImpl()->getRegisterInfo());
unsigned Reg = MO.getReg();
unsigned RegToPrint = RC->getRegister(RI->getEncodingValue(Reg));
assert(RI->regsOverlap(RegToPrint, Reg));
O << AArch64InstPrinter::getRegisterName(
RegToPrint, isVector ? AArch64::vreg : AArch64::NoRegAltName);
return false;
}
bool AArch64AsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNum,
unsigned AsmVariant,
const char *ExtraCode, raw_ostream &O) {
const MachineOperand &MO = MI->getOperand(OpNum);
// First try the generic code, which knows about modifiers like 'c' and 'n'.
if (!AsmPrinter::PrintAsmOperand(MI, OpNum, AsmVariant, ExtraCode, O))
return false;
// Does this asm operand have a single letter operand modifier?
if (ExtraCode && ExtraCode[0]) {
if (ExtraCode[1] != 0)
return true; // Unknown modifier.
switch (ExtraCode[0]) {
default:
return true; // Unknown modifier.
case 'w': // Print W register
case 'x': // Print X register
if (MO.isReg())
return printAsmMRegister(MO, ExtraCode[0], O);
if (MO.isImm() && MO.getImm() == 0) {
unsigned Reg = ExtraCode[0] == 'w' ? AArch64::WZR : AArch64::XZR;
O << AArch64InstPrinter::getRegisterName(Reg);
return false;
}
printOperand(MI, OpNum, O);
return false;
case 'b': // Print B register.
case 'h': // Print H register.
case 's': // Print S register.
case 'd': // Print D register.
case 'q': // Print Q register.
if (MO.isReg()) {
const TargetRegisterClass *RC;
switch (ExtraCode[0]) {
case 'b':
RC = &AArch64::FPR8RegClass;
break;
case 'h':
RC = &AArch64::FPR16RegClass;
break;
case 's':
RC = &AArch64::FPR32RegClass;
break;
case 'd':
RC = &AArch64::FPR64RegClass;
break;
case 'q':
RC = &AArch64::FPR128RegClass;
break;
default:
return true;
}
return printAsmRegInClass(MO, RC, false /* vector */, O);
}
printOperand(MI, OpNum, O);
return false;
}
}
// According to ARM, we should emit x and v registers unless we have a
// modifier.
if (MO.isReg()) {
unsigned Reg = MO.getReg();
// If this is a w or x register, print an x register.
if (AArch64::GPR32allRegClass.contains(Reg) ||
AArch64::GPR64allRegClass.contains(Reg))
return printAsmMRegister(MO, 'x', O);
// If this is a b, h, s, d, or q register, print it as a v register.
return printAsmRegInClass(MO, &AArch64::FPR128RegClass, true /* vector */,
O);
}
printOperand(MI, OpNum, O);
return false;
}
bool AArch64AsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
unsigned OpNum,
unsigned AsmVariant,
const char *ExtraCode,
raw_ostream &O) {
if (ExtraCode && ExtraCode[0])
return true; // Unknown modifier.
const MachineOperand &MO = MI->getOperand(OpNum);
assert(MO.isReg() && "unexpected inline asm memory operand");
O << "[" << AArch64InstPrinter::getRegisterName(MO.getReg()) << "]";
return false;
}
void AArch64AsmPrinter::PrintDebugValueComment(const MachineInstr *MI,
raw_ostream &OS) {
unsigned NOps = MI->getNumOperands();
assert(NOps == 4);
OS << '\t' << MAI->getCommentString() << "DEBUG_VALUE: ";
// cast away const; DIetc do not take const operands for some reason.
DIVariable V(const_cast<MDNode *>(MI->getOperand(NOps - 1).getMetadata()));
OS << V.getName();
OS << " <- ";
// Frame address. Currently handles register +- offset only.
assert(MI->getOperand(0).isReg() && MI->getOperand(1).isImm());
OS << '[';
printOperand(MI, 0, OS);
OS << '+';
printOperand(MI, 1, OS);
OS << ']';
OS << "+";
printOperand(MI, NOps - 2, OS);
}
void AArch64AsmPrinter::LowerSTACKMAP(MCStreamer &OutStreamer, StackMaps &SM,
const MachineInstr &MI) {
unsigned NumNOPBytes = MI.getOperand(1).getImm();
SM.recordStackMap(MI);
assert(NumNOPBytes % 4 == 0 && "Invalid number of NOP bytes requested!");
// Scan ahead to trim the shadow.
const MachineBasicBlock &MBB = *MI.getParent();
MachineBasicBlock::const_iterator MII(MI);
++MII;
while (NumNOPBytes > 0) {
if (MII == MBB.end() || MII->isCall() ||
MII->getOpcode() == AArch64::DBG_VALUE ||
MII->getOpcode() == TargetOpcode::PATCHPOINT ||
MII->getOpcode() == TargetOpcode::STACKMAP)
break;
++MII;
NumNOPBytes -= 4;
}
// Emit nops.
for (unsigned i = 0; i < NumNOPBytes; i += 4)
EmitToStreamer(OutStreamer, MCInstBuilder(AArch64::HINT).addImm(0));
}
// Lower a patchpoint of the form:
// [<def>], <id>, <numBytes>, <target>, <numArgs>
void AArch64AsmPrinter::LowerPATCHPOINT(MCStreamer &OutStreamer, StackMaps &SM,
const MachineInstr &MI) {
SM.recordPatchPoint(MI);
PatchPointOpers Opers(&MI);
int64_t CallTarget = Opers.getMetaOper(PatchPointOpers::TargetPos).getImm();
unsigned EncodedBytes = 0;
if (CallTarget) {
assert((CallTarget & 0xFFFFFFFFFFFF) == CallTarget &&
"High 16 bits of call target should be zero.");
unsigned ScratchReg = MI.getOperand(Opers.getNextScratchIdx()).getReg();
EncodedBytes = 16;
// Materialize the jump address:
EmitToStreamer(OutStreamer, MCInstBuilder(AArch64::MOVZWi)
.addReg(ScratchReg)
.addImm((CallTarget >> 32) & 0xFFFF)
.addImm(32));
EmitToStreamer(OutStreamer, MCInstBuilder(AArch64::MOVKWi)
.addReg(ScratchReg)
.addReg(ScratchReg)
.addImm((CallTarget >> 16) & 0xFFFF)
.addImm(16));
EmitToStreamer(OutStreamer, MCInstBuilder(AArch64::MOVKWi)
.addReg(ScratchReg)
.addReg(ScratchReg)
.addImm(CallTarget & 0xFFFF)
.addImm(0));
EmitToStreamer(OutStreamer, MCInstBuilder(AArch64::BLR).addReg(ScratchReg));
}
// Emit padding.
unsigned NumBytes = Opers.getMetaOper(PatchPointOpers::NBytesPos).getImm();
assert(NumBytes >= EncodedBytes &&
"Patchpoint can't request size less than the length of a call.");
assert((NumBytes - EncodedBytes) % 4 == 0 &&
"Invalid number of NOP bytes requested!");
for (unsigned i = EncodedBytes; i < NumBytes; i += 4)
EmitToStreamer(OutStreamer, MCInstBuilder(AArch64::HINT).addImm(0));
}
// Simple pseudo-instructions have their lowering (with expansion to real
// instructions) auto-generated.
#include "AArch64GenMCPseudoLowering.inc"
void AArch64AsmPrinter::EmitInstruction(const MachineInstr *MI) {
// Do any auto-generated pseudo lowerings.
if (emitPseudoExpansionLowering(OutStreamer, MI))
return;
if (AArch64FI->getLOHRelated().count(MI)) {
// Generate a label for LOH related instruction
MCSymbol *LOHLabel = GetTempSymbol("loh", LOHLabelCounter++);
// Associate the instruction with the label
LOHInstToLabel[MI] = LOHLabel;
OutStreamer.EmitLabel(LOHLabel);
}
// Do any manual lowerings.
switch (MI->getOpcode()) {
default:
break;
case AArch64::DBG_VALUE: {
if (isVerbose() && OutStreamer.hasRawTextSupport()) {
SmallString<128> TmpStr;
raw_svector_ostream OS(TmpStr);
PrintDebugValueComment(MI, OS);
OutStreamer.EmitRawText(StringRef(OS.str()));
}
return;
}
// Tail calls use pseudo instructions so they have the proper code-gen
// attributes (isCall, isReturn, etc.). We lower them to the real
// instruction here.
case AArch64::TCRETURNri: {
MCInst TmpInst;
TmpInst.setOpcode(AArch64::BR);
TmpInst.addOperand(MCOperand::CreateReg(MI->getOperand(0).getReg()));
EmitToStreamer(OutStreamer, TmpInst);
return;
}
case AArch64::TCRETURNdi: {
MCOperand Dest;
MCInstLowering.lowerOperand(MI->getOperand(0), Dest);
MCInst TmpInst;
TmpInst.setOpcode(AArch64::B);
TmpInst.addOperand(Dest);
EmitToStreamer(OutStreamer, TmpInst);
return;
}
case AArch64::TLSDESC_BLR: {
MCOperand Callee, Sym;
MCInstLowering.lowerOperand(MI->getOperand(0), Callee);
MCInstLowering.lowerOperand(MI->getOperand(1), Sym);
// First emit a relocation-annotation. This expands to no code, but requests
// the following instruction gets an R_AARCH64_TLSDESC_CALL.
MCInst TLSDescCall;
TLSDescCall.setOpcode(AArch64::TLSDESCCALL);
TLSDescCall.addOperand(Sym);
EmitToStreamer(OutStreamer, TLSDescCall);
// Other than that it's just a normal indirect call to the function loaded
// from the descriptor.
MCInst BLR;
BLR.setOpcode(AArch64::BLR);
BLR.addOperand(Callee);
EmitToStreamer(OutStreamer, BLR);
return;
}
case TargetOpcode::STACKMAP:
return LowerSTACKMAP(OutStreamer, SM, *MI);
case TargetOpcode::PATCHPOINT:
return LowerPATCHPOINT(OutStreamer, SM, *MI);
}
// Finally, do the automated lowerings for everything else.
MCInst TmpInst;
MCInstLowering.Lower(MI, TmpInst);
EmitToStreamer(OutStreamer, TmpInst);
}
// Force static initialization.
extern "C" void LLVMInitializeAArch64AsmPrinter() {
RegisterAsmPrinter<AArch64AsmPrinter> X(TheAArch64leTarget);
RegisterAsmPrinter<AArch64AsmPrinter> Y(TheAArch64beTarget);
RegisterAsmPrinter<AArch64AsmPrinter> Z(TheARM64Target);
}
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