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