1 //===-- MipsMCExpr.cpp - Mips specific MC expression classes --------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "MipsMCExpr.h"
10 #include "llvm/BinaryFormat/ELF.h"
11 #include "llvm/MC/MCAsmInfo.h"
12 #include "llvm/MC/MCAssembler.h"
13 #include "llvm/MC/MCContext.h"
14 #include "llvm/MC/MCStreamer.h"
15 #include "llvm/MC/MCSymbolELF.h"
16 #include "llvm/MC/MCValue.h"
17 #include "llvm/Support/Casting.h"
18 #include "llvm/Support/ErrorHandling.h"
19 #include "llvm/Support/MathExtras.h"
20 #include "llvm/Support/raw_ostream.h"
21 #include <cstdint>
22 
23 using namespace llvm;
24 
25 #define DEBUG_TYPE "mipsmcexpr"
26 
create(MipsMCExpr::MipsExprKind Kind,const MCExpr * Expr,MCContext & Ctx)27 const MipsMCExpr *MipsMCExpr::create(MipsMCExpr::MipsExprKind Kind,
28                                      const MCExpr *Expr, MCContext &Ctx) {
29   return new (Ctx) MipsMCExpr(Kind, Expr);
30 }
31 
createGpOff(MipsMCExpr::MipsExprKind Kind,const MCExpr * Expr,MCContext & Ctx)32 const MipsMCExpr *MipsMCExpr::createGpOff(MipsMCExpr::MipsExprKind Kind,
33                                           const MCExpr *Expr, MCContext &Ctx) {
34   return create(Kind, create(MEK_NEG, create(MEK_GPREL, Expr, Ctx), Ctx), Ctx);
35 }
36 
printImpl(raw_ostream & OS,const MCAsmInfo * MAI) const37 void MipsMCExpr::printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const {
38   int64_t AbsVal;
39 
40   switch (Kind) {
41   case MEK_None:
42   case MEK_Special:
43     llvm_unreachable("MEK_None and MEK_Special are invalid");
44     break;
45   case MEK_DTPREL:
46     // MEK_DTPREL is used for marking TLS DIEExpr only
47     // and contains a regular sub-expression.
48     getSubExpr()->print(OS, MAI, true);
49     return;
50   case MEK_CALL_HI16:
51     OS << "%call_hi";
52     break;
53   case MEK_CALL_LO16:
54     OS << "%call_lo";
55     break;
56   case MEK_DTPREL_HI:
57     OS << "%dtprel_hi";
58     break;
59   case MEK_DTPREL_LO:
60     OS << "%dtprel_lo";
61     break;
62   case MEK_GOT:
63     OS << "%got";
64     break;
65   case MEK_GOTTPREL:
66     OS << "%gottprel";
67     break;
68   case MEK_GOT_CALL:
69     OS << "%call16";
70     break;
71   case MEK_GOT_DISP:
72     OS << "%got_disp";
73     break;
74   case MEK_GOT_HI16:
75     OS << "%got_hi";
76     break;
77   case MEK_GOT_LO16:
78     OS << "%got_lo";
79     break;
80   case MEK_GOT_PAGE:
81     OS << "%got_page";
82     break;
83   case MEK_GOT_OFST:
84     OS << "%got_ofst";
85     break;
86   case MEK_GPREL:
87     OS << "%gp_rel";
88     break;
89   case MEK_HI:
90     OS << "%hi";
91     break;
92   case MEK_HIGHER:
93     OS << "%higher";
94     break;
95   case MEK_HIGHEST:
96     OS << "%highest";
97     break;
98   case MEK_LO:
99     OS << "%lo";
100     break;
101   case MEK_NEG:
102     OS << "%neg";
103     break;
104   case MEK_PCREL_HI16:
105     OS << "%pcrel_hi";
106     break;
107   case MEK_PCREL_LO16:
108     OS << "%pcrel_lo";
109     break;
110   case MEK_TLSGD:
111     OS << "%tlsgd";
112     break;
113   case MEK_TLSLDM:
114     OS << "%tlsldm";
115     break;
116   case MEK_TPREL_HI:
117     OS << "%tprel_hi";
118     break;
119   case MEK_TPREL_LO:
120     OS << "%tprel_lo";
121     break;
122   }
123 
124   OS << '(';
125   if (Expr->evaluateAsAbsolute(AbsVal))
126     OS << AbsVal;
127   else
128     Expr->print(OS, MAI, true);
129   OS << ')';
130 }
131 
132 bool
evaluateAsRelocatableImpl(MCValue & Res,const MCAsmLayout * Layout,const MCFixup * Fixup) const133 MipsMCExpr::evaluateAsRelocatableImpl(MCValue &Res,
134                                       const MCAsmLayout *Layout,
135                                       const MCFixup *Fixup) const {
136   // Look for the %hi(%neg(%gp_rel(X))) and %lo(%neg(%gp_rel(X))) special cases.
137   if (isGpOff()) {
138     const MCExpr *SubExpr =
139         cast<MipsMCExpr>(cast<MipsMCExpr>(getSubExpr())->getSubExpr())
140             ->getSubExpr();
141     if (!SubExpr->evaluateAsRelocatable(Res, Layout, Fixup))
142       return false;
143 
144     Res = MCValue::get(Res.getSymA(), Res.getSymB(), Res.getConstant(),
145                        MEK_Special);
146     return true;
147   }
148 
149   if (!getSubExpr()->evaluateAsRelocatable(Res, Layout, Fixup))
150     return false;
151 
152   if (Res.getRefKind() != MCSymbolRefExpr::VK_None)
153     return false;
154 
155   // evaluateAsAbsolute() and evaluateAsValue() require that we evaluate the
156   // %hi/%lo/etc. here. Fixup is a null pointer when either of these is the
157   // caller.
158   if (Res.isAbsolute() && Fixup == nullptr) {
159     int64_t AbsVal = Res.getConstant();
160     switch (Kind) {
161     case MEK_None:
162     case MEK_Special:
163       llvm_unreachable("MEK_None and MEK_Special are invalid");
164     case MEK_DTPREL:
165       // MEK_DTPREL is used for marking TLS DIEExpr only
166       // and contains a regular sub-expression.
167       return getSubExpr()->evaluateAsRelocatable(Res, Layout, Fixup);
168     case MEK_DTPREL_HI:
169     case MEK_DTPREL_LO:
170     case MEK_GOT:
171     case MEK_GOTTPREL:
172     case MEK_GOT_CALL:
173     case MEK_GOT_DISP:
174     case MEK_GOT_HI16:
175     case MEK_GOT_LO16:
176     case MEK_GOT_OFST:
177     case MEK_GOT_PAGE:
178     case MEK_GPREL:
179     case MEK_PCREL_HI16:
180     case MEK_PCREL_LO16:
181     case MEK_TLSGD:
182     case MEK_TLSLDM:
183     case MEK_TPREL_HI:
184     case MEK_TPREL_LO:
185       return false;
186     case MEK_LO:
187     case MEK_CALL_LO16:
188       AbsVal = SignExtend64<16>(AbsVal);
189       break;
190     case MEK_CALL_HI16:
191     case MEK_HI:
192       AbsVal = SignExtend64<16>((AbsVal + 0x8000) >> 16);
193       break;
194     case MEK_HIGHER:
195       AbsVal = SignExtend64<16>((AbsVal + 0x80008000LL) >> 32);
196       break;
197     case MEK_HIGHEST:
198       AbsVal = SignExtend64<16>((AbsVal + 0x800080008000LL) >> 48);
199       break;
200     case MEK_NEG:
201       AbsVal = -AbsVal;
202       break;
203     }
204     Res = MCValue::get(AbsVal);
205     return true;
206   }
207 
208   // We want to defer it for relocatable expressions since the constant is
209   // applied to the whole symbol value.
210   //
211   // The value of getKind() that is given to MCValue is only intended to aid
212   // debugging when inspecting MCValue objects. It shouldn't be relied upon
213   // for decision making.
214   Res =
215       MCValue::get(Res.getSymA(), Res.getSymB(), Res.getConstant(), getKind());
216 
217   return true;
218 }
219 
visitUsedExpr(MCStreamer & Streamer) const220 void MipsMCExpr::visitUsedExpr(MCStreamer &Streamer) const {
221   Streamer.visitUsedExpr(*getSubExpr());
222 }
223 
fixELFSymbolsInTLSFixupsImpl(const MCExpr * Expr,MCAssembler & Asm)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 
fixELFSymbolsInTLSFixups(MCAssembler & Asm) const250 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 
isGpOff(MipsExprKind & Kind) const291 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