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//===-- llvm/CodeGen/DwarfExpression.cpp - Dwarf Debug Framework ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing dwarf debug info into asm files.
//
//===----------------------------------------------------------------------===//
#include "DwarfExpression.h"
#include "DwarfDebug.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
using namespace llvm;
const TargetRegisterInfo *DwarfExpression::getTRI() const {
return AP.TM.getSubtargetImpl()->getRegisterInfo();
}
unsigned DwarfExpression::getDwarfVersion() const {
return AP.getDwarfDebug()->getDwarfVersion();
}
void DwarfExpression::AddReg(int DwarfReg, const char *Comment) {
assert(DwarfReg >= 0 && "invalid negative dwarf register number");
if (DwarfReg < 32) {
EmitOp(dwarf::DW_OP_reg0 + DwarfReg, Comment);
} else {
EmitOp(dwarf::DW_OP_regx, Comment);
EmitUnsigned(DwarfReg);
}
}
void DwarfExpression::AddRegIndirect(int DwarfReg, int Offset, bool Deref) {
assert(DwarfReg >= 0 && "invalid negative dwarf register number");
if (DwarfReg < 32) {
EmitOp(dwarf::DW_OP_breg0 + DwarfReg);
} else {
EmitOp(dwarf::DW_OP_bregx);
EmitUnsigned(DwarfReg);
}
EmitSigned(Offset);
if (Deref)
EmitOp(dwarf::DW_OP_deref);
}
void DwarfExpression::AddOpPiece(unsigned SizeInBits, unsigned OffsetInBits) {
assert(SizeInBits > 0 && "piece has size zero");
const unsigned SizeOfByte = 8;
if (OffsetInBits > 0 || SizeInBits % SizeOfByte) {
EmitOp(dwarf::DW_OP_bit_piece);
EmitUnsigned(SizeInBits);
EmitUnsigned(OffsetInBits);
} else {
EmitOp(dwarf::DW_OP_piece);
unsigned ByteSize = SizeInBits / SizeOfByte;
EmitUnsigned(ByteSize);
}
}
void DwarfExpression::AddShr(unsigned ShiftBy) {
EmitOp(dwarf::DW_OP_constu);
EmitUnsigned(ShiftBy);
EmitOp(dwarf::DW_OP_shr);
}
bool DwarfExpression::AddMachineRegIndirect(unsigned MachineReg, int Offset) {
int DwarfReg = getTRI()->getDwarfRegNum(MachineReg, false);
if (DwarfReg < 0)
return false;
if (MachineReg == getFrameRegister()) {
// If variable offset is based in frame register then use fbreg.
EmitOp(dwarf::DW_OP_fbreg);
EmitSigned(Offset);
} else {
AddRegIndirect(DwarfReg, Offset);
}
return true;
}
void DwarfExpression::AddMachineRegPiece(unsigned MachineReg,
unsigned PieceSizeInBits,
unsigned PieceOffsetInBits) {
const TargetRegisterInfo *TRI = getTRI();
int Reg = TRI->getDwarfRegNum(MachineReg, false);
// If this is a valid register number, emit it.
if (Reg >= 0) {
AddReg(Reg);
if (PieceSizeInBits)
AddOpPiece(PieceSizeInBits, PieceOffsetInBits);
return;
}
// Walk up the super-register chain until we find a valid number.
// For example, EAX on x86_64 is a 32-bit piece of RAX with offset 0.
for (MCSuperRegIterator SR(MachineReg, TRI); SR.isValid(); ++SR) {
Reg = TRI->getDwarfRegNum(*SR, false);
if (Reg >= 0) {
unsigned Idx = TRI->getSubRegIndex(*SR, MachineReg);
unsigned Size = TRI->getSubRegIdxSize(Idx);
unsigned RegOffset = TRI->getSubRegIdxOffset(Idx);
AddReg(Reg, "super-register");
if (PieceOffsetInBits == RegOffset) {
AddOpPiece(Size, RegOffset);
} else {
// If this is part of a variable in a sub-register at a
// non-zero offset, we need to manually shift the value into
// place, since the DW_OP_piece describes the part of the
// variable, not the position of the subregister.
if (RegOffset)
AddShr(RegOffset);
AddOpPiece(Size, PieceOffsetInBits);
}
return;
}
}
// Otherwise, attempt to find a covering set of sub-register numbers.
// For example, Q0 on ARM is a composition of D0+D1.
//
// Keep track of the current position so we can emit the more
// efficient DW_OP_piece.
unsigned CurPos = PieceOffsetInBits;
// The size of the register in bits, assuming 8 bits per byte.
unsigned RegSize = TRI->getMinimalPhysRegClass(MachineReg)->getSize() * 8;
// Keep track of the bits in the register we already emitted, so we
// can avoid emitting redundant aliasing subregs.
SmallBitVector Coverage(RegSize, false);
for (MCSubRegIterator SR(MachineReg, TRI); SR.isValid(); ++SR) {
unsigned Idx = TRI->getSubRegIndex(MachineReg, *SR);
unsigned Size = TRI->getSubRegIdxSize(Idx);
unsigned Offset = TRI->getSubRegIdxOffset(Idx);
Reg = TRI->getDwarfRegNum(*SR, false);
// Intersection between the bits we already emitted and the bits
// covered by this subregister.
SmallBitVector Intersection(RegSize, false);
Intersection.set(Offset, Offset + Size);
Intersection ^= Coverage;
// If this sub-register has a DWARF number and we haven't covered
// its range, emit a DWARF piece for it.
if (Reg >= 0 && Intersection.any()) {
AddReg(Reg, "sub-register");
AddOpPiece(Size, Offset == CurPos ? 0 : Offset);
CurPos = Offset + Size;
// Mark it as emitted.
Coverage.set(Offset, Offset + Size);
}
}
if (CurPos == PieceOffsetInBits)
// FIXME: We have no reasonable way of handling errors in here.
EmitOp(dwarf::DW_OP_nop, "nop (could not find a dwarf register number)");
}
void DwarfExpression::AddSignedConstant(int Value) {
EmitOp(dwarf::DW_OP_consts);
EmitSigned(Value);
// The proper way to describe a constant value is
// DW_OP_constu <const>, DW_OP_stack_value.
// Unfortunately, DW_OP_stack_value was not available until DWARF-4,
// so we will continue to generate DW_OP_constu <const> for DWARF-2
// and DWARF-3. Technically, this is incorrect since DW_OP_const <const>
// actually describes a value at a constant addess, not a constant value.
// However, in the past there was no better way to describe a constant
// value, so the producers and consumers started to rely on heuristics
// to disambiguate the value vs. location status of the expression.
// See PR21176 for more details.
if (getDwarfVersion() >= 4)
EmitOp(dwarf::DW_OP_stack_value);
}
void DwarfExpression::AddUnsignedConstant(unsigned Value) {
EmitOp(dwarf::DW_OP_constu);
EmitUnsigned(Value);
// cf. comment in DwarfExpression::AddSignedConstant().
if (getDwarfVersion() >= 4)
EmitOp(dwarf::DW_OP_stack_value);
}
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