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//===-- X86AsmPrinter.h - X86 implementation of AsmPrinter ------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIB_TARGET_X86_X86ASMPRINTER_H
#define LLVM_LIB_TARGET_X86_X86ASMPRINTER_H
#include "X86Subtarget.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/FaultMaps.h"
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/Target/TargetMachine.h"
// Implemented in X86MCInstLower.cpp
namespace {
class X86MCInstLower;
}
namespace llvm {
class MCStreamer;
class MCSymbol;
class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
const X86Subtarget *Subtarget;
StackMaps SM;
FaultMaps FM;
std::unique_ptr<MCCodeEmitter> CodeEmitter;
// This utility class tracks the length of a stackmap instruction's 'shadow'.
// It is used by the X86AsmPrinter to ensure that the stackmap shadow
// invariants (i.e. no other stackmaps, patchpoints, or control flow within
// the shadow) are met, while outputting a minimal number of NOPs for padding.
//
// To minimise the number of NOPs used, the shadow tracker counts the number
// of instruction bytes output since the last stackmap. Only if there are too
// few instruction bytes to cover the shadow are NOPs used for padding.
class StackMapShadowTracker {
public:
void startFunction(MachineFunction &MF) {
this->MF = &MF;
}
void count(MCInst &Inst, const MCSubtargetInfo &STI,
MCCodeEmitter *CodeEmitter);
// Called to signal the start of a shadow of RequiredSize bytes.
void reset(unsigned RequiredSize) {
RequiredShadowSize = RequiredSize;
CurrentShadowSize = 0;
InShadow = true;
}
// Called before every stackmap/patchpoint, and at the end of basic blocks,
// to emit any necessary padding-NOPs.
void emitShadowPadding(MCStreamer &OutStreamer, const MCSubtargetInfo &STI);
private:
const MachineFunction *MF;
bool InShadow = false;
// RequiredShadowSize holds the length of the shadow specified in the most
// recently encountered STACKMAP instruction.
// CurrentShadowSize counts the number of bytes encoded since the most
// recently encountered STACKMAP, stopping when that number is greater than
// or equal to RequiredShadowSize.
unsigned RequiredShadowSize = 0, CurrentShadowSize = 0;
};
StackMapShadowTracker SMShadowTracker;
// This describes the kind of sled we're storing in the XRay table.
enum class SledKind : uint8_t {
FUNCTION_ENTER = 0,
FUNCTION_EXIT = 1,
TAIL_CALL = 2,
};
// The table will contain these structs that point to the sled, the function
// containing the sled, and what kind of sled (and whether they should always
// be instrumented).
struct XRayFunctionEntry {
const MCSymbol *Sled;
const MCSymbol *Function;
SledKind Kind;
bool AlwaysInstrument;
const class Function *Fn;
};
// All the sleds to be emitted.
std::vector<XRayFunctionEntry> Sleds;
// All instructions emitted by the X86AsmPrinter should use this helper
// method.
//
// This helper function invokes the SMShadowTracker on each instruction before
// outputting it to the OutStream. This allows the shadow tracker to minimise
// the number of NOPs used for stackmap padding.
void EmitAndCountInstruction(MCInst &Inst);
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 LowerPATCHABLE_OP(const MachineInstr &MI, X86MCInstLower &MCIL);
void LowerTlsAddr(X86MCInstLower &MCInstLowering, const MachineInstr &MI);
// XRay-specific lowering for X86.
void LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr &MI,
X86MCInstLower &MCIL);
void LowerPATCHABLE_RET(const MachineInstr &MI, X86MCInstLower &MCIL);
void LowerPATCHABLE_TAIL_CALL(const MachineInstr &MI, X86MCInstLower &MCIL);
// Helper function that emits the XRay sleds we've collected for a particular
// function.
void EmitXRayTable();
// Helper function to record a given XRay sled.
void recordSled(MCSymbol *Sled, const MachineInstr &MI, SledKind Kind);
public:
explicit X86AsmPrinter(TargetMachine &TM,
std::unique_ptr<MCStreamer> Streamer)
: AsmPrinter(TM, std::move(Streamer)), SM(*this), FM(*this) {}
const char *getPassName() const override {
return "X86 Assembly / Object Emitter";
}
const X86Subtarget &getSubtarget() const { return *Subtarget; }
void EmitStartOfAsmFile(Module &M) override;
void EmitEndOfAsmFile(Module &M) override;
void EmitInstruction(const MachineInstr *MI) override;
void EmitBasicBlockEnd(const MachineBasicBlock &MBB) override {
SMShadowTracker.emitShadowPadding(*OutStreamer, getSubtargetInfo());
}
bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
unsigned AsmVariant, const char *ExtraCode,
raw_ostream &OS) override;
bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
unsigned AsmVariant, const char *ExtraCode,
raw_ostream &OS) override;
/// \brief Return the symbol for the specified constant pool entry.
MCSymbol *GetCPISymbol(unsigned CPID) const override;
bool doInitialization(Module &M) override {
SMShadowTracker.reset(0);
SM.reset();
return AsmPrinter::doInitialization(M);
}
bool runOnMachineFunction(MachineFunction &F) override;
};
} // end namespace llvm
#endif
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