1 //===-- MipsMCExpr.cpp - Mips specific MC expression classes --------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "MipsMCExpr.h"
11 #include "llvm/BinaryFormat/ELF.h"
12 #include "llvm/MC/MCAsmInfo.h"
13 #include "llvm/MC/MCAssembler.h"
14 #include "llvm/MC/MCContext.h"
15 #include "llvm/MC/MCStreamer.h"
16 #include "llvm/MC/MCSymbolELF.h"
17 #include "llvm/MC/MCValue.h"
18 #include "llvm/Support/Casting.h"
19 #include "llvm/Support/ErrorHandling.h"
20 #include "llvm/Support/MathExtras.h"
21 #include "llvm/Support/raw_ostream.h"
22 #include <cstdint>
23 
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "mipsmcexpr"
27 
28 const MipsMCExpr *MipsMCExpr::create(MipsMCExpr::MipsExprKind Kind,
29                                      const MCExpr *Expr, MCContext &Ctx) {
30   return new (Ctx) MipsMCExpr(Kind, Expr);
31 }
32 
33 const MipsMCExpr *MipsMCExpr::createGpOff(MipsMCExpr::MipsExprKind Kind,
34                                           const MCExpr *Expr, MCContext &Ctx) {
35   return create(Kind, create(MEK_NEG, create(MEK_GPREL, Expr, Ctx), Ctx), Ctx);
36 }
37 
38 void MipsMCExpr::printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const {
39   int64_t AbsVal;
40 
41   switch (Kind) {
42   case MEK_None:
43   case MEK_Special:
44     llvm_unreachable("MEK_None and MEK_Special are invalid");
45     break;
46   case MEK_DTPREL:
47     // MEK_DTPREL is used for marking TLS DIEExpr only
48     // and contains a regular sub-expression.
49     getSubExpr()->print(OS, MAI, true);
50     return;
51   case MEK_CALL_HI16:
52     OS << "%call_hi";
53     break;
54   case MEK_CALL_LO16:
55     OS << "%call_lo";
56     break;
57   case MEK_DTPREL_HI:
58     OS << "%dtprel_hi";
59     break;
60   case MEK_DTPREL_LO:
61     OS << "%dtprel_lo";
62     break;
63   case MEK_GOT:
64     OS << "%got";
65     break;
66   case MEK_GOTTPREL:
67     OS << "%gottprel";
68     break;
69   case MEK_GOT_CALL:
70     OS << "%call16";
71     break;
72   case MEK_GOT_DISP:
73     OS << "%got_disp";
74     break;
75   case MEK_GOT_HI16:
76     OS << "%got_hi";
77     break;
78   case MEK_GOT_LO16:
79     OS << "%got_lo";
80     break;
81   case MEK_GOT_PAGE:
82     OS << "%got_page";
83     break;
84   case MEK_GOT_OFST:
85     OS << "%got_ofst";
86     break;
87   case MEK_GPREL:
88     OS << "%gp_rel";
89     break;
90   case MEK_HI:
91     OS << "%hi";
92     break;
93   case MEK_HIGHER:
94     OS << "%higher";
95     break;
96   case MEK_HIGHEST:
97     OS << "%highest";
98     break;
99   case MEK_LO:
100     OS << "%lo";
101     break;
102   case MEK_NEG:
103     OS << "%neg";
104     break;
105   case MEK_PCREL_HI16:
106     OS << "%pcrel_hi";
107     break;
108   case MEK_PCREL_LO16:
109     OS << "%pcrel_lo";
110     break;
111   case MEK_TLSGD:
112     OS << "%tlsgd";
113     break;
114   case MEK_TLSLDM:
115     OS << "%tlsldm";
116     break;
117   case MEK_TPREL_HI:
118     OS << "%tprel_hi";
119     break;
120   case MEK_TPREL_LO:
121     OS << "%tprel_lo";
122     break;
123   }
124 
125   OS << '(';
126   if (Expr->evaluateAsAbsolute(AbsVal))
127     OS << AbsVal;
128   else
129     Expr->print(OS, MAI, true);
130   OS << ')';
131 }
132 
133 bool
134 MipsMCExpr::evaluateAsRelocatableImpl(MCValue &Res,
135                                       const MCAsmLayout *Layout,
136                                       const MCFixup *Fixup) const {
137   // Look for the %hi(%neg(%gp_rel(X))) and %lo(%neg(%gp_rel(X))) special cases.
138   if (isGpOff()) {
139     const MCExpr *SubExpr =
140         cast<MipsMCExpr>(cast<MipsMCExpr>(getSubExpr())->getSubExpr())
141             ->getSubExpr();
142     if (!SubExpr->evaluateAsRelocatable(Res, Layout, Fixup))
143       return false;
144 
145     Res = MCValue::get(Res.getSymA(), Res.getSymB(), Res.getConstant(),
146                        MEK_Special);
147     return true;
148   }
149 
150   if (!getSubExpr()->evaluateAsRelocatable(Res, Layout, Fixup))
151     return false;
152 
153   if (Res.getRefKind() != MCSymbolRefExpr::VK_None)
154     return false;
155 
156   // evaluateAsAbsolute() and evaluateAsValue() require that we evaluate the
157   // %hi/%lo/etc. here. Fixup is a null pointer when either of these is the
158   // caller.
159   if (Res.isAbsolute() && Fixup == nullptr) {
160     int64_t AbsVal = Res.getConstant();
161     switch (Kind) {
162     case MEK_None:
163     case MEK_Special:
164       llvm_unreachable("MEK_None and MEK_Special are invalid");
165     case MEK_DTPREL:
166       // MEK_DTPREL is used for marking TLS DIEExpr only
167       // and contains a regular sub-expression.
168       return getSubExpr()->evaluateAsRelocatable(Res, Layout, Fixup);
169     case MEK_DTPREL_HI:
170     case MEK_DTPREL_LO:
171     case MEK_GOT:
172     case MEK_GOTTPREL:
173     case MEK_GOT_CALL:
174     case MEK_GOT_DISP:
175     case MEK_GOT_HI16:
176     case MEK_GOT_LO16:
177     case MEK_GOT_OFST:
178     case MEK_GOT_PAGE:
179     case MEK_GPREL:
180     case MEK_PCREL_HI16:
181     case MEK_PCREL_LO16:
182     case MEK_TLSGD:
183     case MEK_TLSLDM:
184     case MEK_TPREL_HI:
185     case MEK_TPREL_LO:
186       return false;
187     case MEK_LO:
188     case MEK_CALL_LO16:
189       AbsVal = SignExtend64<16>(AbsVal);
190       break;
191     case MEK_CALL_HI16:
192     case MEK_HI:
193       AbsVal = SignExtend64<16>((AbsVal + 0x8000) >> 16);
194       break;
195     case MEK_HIGHER:
196       AbsVal = SignExtend64<16>((AbsVal + 0x80008000LL) >> 32);
197       break;
198     case MEK_HIGHEST:
199       AbsVal = SignExtend64<16>((AbsVal + 0x800080008000LL) >> 48);
200       break;
201     case MEK_NEG:
202       AbsVal = -AbsVal;
203       break;
204     }
205     Res = MCValue::get(AbsVal);
206     return true;
207   }
208 
209   // We want to defer it for relocatable expressions since the constant is
210   // applied to the whole symbol value.
211   //
212   // The value of getKind() that is given to MCValue is only intended to aid
213   // debugging when inspecting MCValue objects. It shouldn't be relied upon
214   // for decision making.
215   Res = MCValue::get(Res.getSymA(), Res.getSymB(), Res.getConstant(), getKind());
216 
217   return true;
218 }
219 
220 void MipsMCExpr::visitUsedExpr(MCStreamer &Streamer) const {
221   Streamer.visitUsedExpr(*getSubExpr());
222 }
223 
224 static void fixELFSymbolsInTLSFixupsImpl(const MCExpr *Expr, MCAssembler &Asm) {
225   switch (Expr->getKind()) {
226   case MCExpr::Target:
227     fixELFSymbolsInTLSFixupsImpl(cast<MipsMCExpr>(Expr)->getSubExpr(), Asm);
228     break;
229   case MCExpr::Constant:
230     break;
231   case MCExpr::Binary: {
232     const MCBinaryExpr *BE = cast<MCBinaryExpr>(Expr);
233     fixELFSymbolsInTLSFixupsImpl(BE->getLHS(), Asm);
234     fixELFSymbolsInTLSFixupsImpl(BE->getRHS(), Asm);
235     break;
236   }
237   case MCExpr::SymbolRef: {
238     // We're known to be under a TLS fixup, so any symbol should be
239     // modified. There should be only one.
240     const MCSymbolRefExpr &SymRef = *cast<MCSymbolRefExpr>(Expr);
241     cast<MCSymbolELF>(SymRef.getSymbol()).setType(ELF::STT_TLS);
242     break;
243   }
244   case MCExpr::Unary:
245     fixELFSymbolsInTLSFixupsImpl(cast<MCUnaryExpr>(Expr)->getSubExpr(), Asm);
246     break;
247   }
248 }
249 
250 void MipsMCExpr::fixELFSymbolsInTLSFixups(MCAssembler &Asm) const {
251   switch (getKind()) {
252   case MEK_None:
253   case MEK_Special:
254     llvm_unreachable("MEK_None and MEK_Special are invalid");
255     break;
256   case MEK_CALL_HI16:
257   case MEK_CALL_LO16:
258   case MEK_GOT:
259   case MEK_GOT_CALL:
260   case MEK_GOT_DISP:
261   case MEK_GOT_HI16:
262   case MEK_GOT_LO16:
263   case MEK_GOT_OFST:
264   case MEK_GOT_PAGE:
265   case MEK_GPREL:
266   case MEK_HI:
267   case MEK_HIGHER:
268   case MEK_HIGHEST:
269   case MEK_LO:
270   case MEK_NEG:
271   case MEK_PCREL_HI16:
272   case MEK_PCREL_LO16:
273     // If we do have nested target-specific expressions, they will be in
274     // a consecutive chain.
275     if (const MipsMCExpr *E = dyn_cast<const MipsMCExpr>(getSubExpr()))
276       E->fixELFSymbolsInTLSFixups(Asm);
277     break;
278   case MEK_DTPREL:
279   case MEK_DTPREL_HI:
280   case MEK_DTPREL_LO:
281   case MEK_TLSLDM:
282   case MEK_TLSGD:
283   case MEK_GOTTPREL:
284   case MEK_TPREL_HI:
285   case MEK_TPREL_LO:
286     fixELFSymbolsInTLSFixupsImpl(getSubExpr(), Asm);
287     break;
288   }
289 }
290 
291 bool MipsMCExpr::isGpOff(MipsExprKind &Kind) const {
292   if (getKind() == MEK_HI || getKind() == MEK_LO) {
293     if (const MipsMCExpr *S1 = dyn_cast<const MipsMCExpr>(getSubExpr())) {
294       if (const MipsMCExpr *S2 = dyn_cast<const MipsMCExpr>(S1->getSubExpr())) {
295         if (S1->getKind() == MEK_NEG && S2->getKind() == MEK_GPREL) {
296           Kind = getKind();
297           return true;
298         }
299       }
300     }
301   }
302   return false;
303 }
304