1 //===-- MipsASMBackend.cpp - Mips Asm Backend ----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the MipsAsmBackend and MipsELFObjectWriter classes.
12 //===----------------------------------------------------------------------===//
15 #include "MipsBaseInfo.h"
16 #include "MipsFixupKinds.h"
17 #include "MCTargetDesc/MipsMCTargetDesc.h"
18 #include "llvm/MC/MCAsmBackend.h"
19 #include "llvm/MC/MCAssembler.h"
20 #include "llvm/MC/MCDirectives.h"
21 #include "llvm/MC/MCELFObjectWriter.h"
22 #include "llvm/MC/MCFixupKindInfo.h"
23 #include "llvm/MC/MCObjectWriter.h"
24 #include "llvm/MC/MCSubtargetInfo.h"
25 #include "llvm/Support/ErrorHandling.h"
26 #include "llvm/Support/raw_ostream.h"
30 // Prepare value for the target space for it
31 static unsigned adjustFixupValue(unsigned Kind, uint64_t Value) {
33 // Add/subtract and shift
39 case Mips::fixup_Mips_LO16:
41 case Mips::fixup_Mips_PC16:
42 // So far we are only using this type for branches.
43 // For branches we start 1 instruction after the branch
44 // so the displacement will be one instruction size less.
46 // The displacement is then divided by 4 to give us an 18 bit
50 case Mips::fixup_Mips_26:
51 // So far we are only using this type for jumps.
52 // The displacement is then divided by 4 to give us an 28 bit
56 case Mips::fixup_Mips_HI16:
57 case Mips::fixup_Mips_GOT_Local:
58 // Get the higher 16-bits. Also add 1 if bit 15 is 1.
59 Value = ((Value + 0x8000) >> 16) & 0xffff;
67 class MipsAsmBackend : public MCAsmBackend {
68 Triple::OSType OSType;
69 bool IsLittle; // Big or little endian
72 MipsAsmBackend(const Target &T, Triple::OSType _OSType, bool _isLittle) :
73 MCAsmBackend(), OSType(_OSType), IsLittle(_isLittle) {}
75 MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
76 return createMipsELFObjectWriter(OS, OSType, IsLittle);
79 /// ApplyFixup - Apply the \arg Value for given \arg Fixup into the provided
80 /// data fragment, at the offset specified by the fixup and following the
81 /// fixup kind as appropriate.
82 void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
83 uint64_t Value) const {
84 MCFixupKind Kind = Fixup.getKind();
85 Value = adjustFixupValue((unsigned)Kind, Value);
86 int64_t SymOffset = MipsGetSymAndOffset(Fixup).second;
88 if (!Value && !SymOffset)
89 return; // Doesn't change encoding.
91 // Where do we start in the object
92 unsigned Offset = Fixup.getOffset();
93 // Number of bytes we need to fixup
94 unsigned NumBytes = (getFixupKindInfo(Kind).TargetSize + 7) / 8;
95 // Used to point to big endian bytes
98 switch ((unsigned)Kind) {
99 case Mips::fixup_Mips_16:
102 case Mips::fixup_Mips_64:
110 // Grab current value, if any, from bits.
113 for (unsigned i = 0; i != NumBytes; ++i) {
114 unsigned Idx = IsLittle ? i : (FullSize - 1 - i);
115 CurVal |= (uint64_t)((uint8_t)Data[Offset + Idx]) << (i*8);
118 uint64_t Mask = ((uint64_t)(-1) >> (64 - getFixupKindInfo(Kind).TargetSize));
119 CurVal |= (Value + SymOffset) & Mask;
121 // Write out the fixed up bytes back to the code/data bits.
122 for (unsigned i = 0; i != NumBytes; ++i) {
123 unsigned Idx = IsLittle ? i : (FullSize - 1 - i);
124 Data[Offset + Idx] = (uint8_t)((CurVal >> (i*8)) & 0xff);
128 unsigned getNumFixupKinds() const { return Mips::NumTargetFixupKinds; }
130 const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const {
131 const static MCFixupKindInfo Infos[Mips::NumTargetFixupKinds] = {
132 // This table *must* be in same the order of fixup_* kinds in
135 // name offset bits flags
136 { "fixup_Mips_16", 0, 16, 0 },
137 { "fixup_Mips_32", 0, 32, 0 },
138 { "fixup_Mips_REL32", 0, 32, 0 },
139 { "fixup_Mips_26", 0, 26, 0 },
140 { "fixup_Mips_HI16", 0, 16, 0 },
141 { "fixup_Mips_LO16", 0, 16, 0 },
142 { "fixup_Mips_GPREL16", 0, 16, 0 },
143 { "fixup_Mips_LITERAL", 0, 16, 0 },
144 { "fixup_Mips_GOT_Global", 0, 16, 0 },
145 { "fixup_Mips_GOT_Local", 0, 16, 0 },
146 { "fixup_Mips_PC16", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
147 { "fixup_Mips_CALL16", 0, 16, 0 },
148 { "fixup_Mips_GPREL32", 0, 32, 0 },
149 { "fixup_Mips_SHIFT5", 6, 5, 0 },
150 { "fixup_Mips_SHIFT6", 6, 5, 0 },
151 { "fixup_Mips_64", 0, 64, 0 },
152 { "fixup_Mips_TLSGD", 0, 16, 0 },
153 { "fixup_Mips_GOTTPREL", 0, 16, 0 },
154 { "fixup_Mips_TPREL_HI", 0, 16, 0 },
155 { "fixup_Mips_TPREL_LO", 0, 16, 0 },
156 { "fixup_Mips_TLSLDM", 0, 16, 0 },
157 { "fixup_Mips_DTPREL_HI", 0, 16, 0 },
158 { "fixup_Mips_DTPREL_LO", 0, 16, 0 },
159 { "fixup_Mips_Branch_PCRel", 0, 16, MCFixupKindInfo::FKF_IsPCRel }
162 if (Kind < FirstTargetFixupKind)
163 return MCAsmBackend::getFixupKindInfo(Kind);
165 assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
167 return Infos[Kind - FirstTargetFixupKind];
170 /// @name Target Relaxation Interfaces
173 /// MayNeedRelaxation - Check whether the given instruction may need
176 /// \param Inst - The instruction to test.
177 bool mayNeedRelaxation(const MCInst &Inst) const {
181 /// fixupNeedsRelaxation - Target specific predicate for whether a given
182 /// fixup requires the associated instruction to be relaxed.
183 bool fixupNeedsRelaxation(const MCFixup &Fixup,
185 const MCInstFragment *DF,
186 const MCAsmLayout &Layout) const {
188 assert(0 && "RelaxInstruction() unimplemented");
192 /// RelaxInstruction - Relax the instruction in the given fragment
193 /// to the next wider instruction.
195 /// \param Inst - The instruction to relax, which may be the same
197 /// \parm Res [output] - On return, the relaxed instruction.
198 void relaxInstruction(const MCInst &Inst, MCInst &Res) const {
203 /// WriteNopData - Write an (optimal) nop sequence of Count bytes
204 /// to the given output. If the target cannot generate such a sequence,
205 /// it should return an error.
207 /// \return - True on success.
208 bool writeNopData(uint64_t Count, MCObjectWriter *OW) const {
216 MCAsmBackend *llvm::createMipsAsmBackendEL(const Target &T, StringRef TT) {
217 return new MipsAsmBackend(T, Triple(TT).getOS(),
221 MCAsmBackend *llvm::createMipsAsmBackendEB(const Target &T, StringRef TT) {
222 return new MipsAsmBackend(T, Triple(TT).getOS(),