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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/MC/MCAsmInfo.h"
12 #include "llvm/MC/MCAssembler.h"
13 #include "llvm/MC/MCContext.h"
14 #include "llvm/MC/MCObjectStreamer.h"
15 #include "llvm/MC/MCSymbolELF.h"
16 #include "llvm/Support/ELF.h"
17 
18 using namespace llvm;
19 
20 #define DEBUG_TYPE "mipsmcexpr"
21 
create(MipsMCExpr::MipsExprKind Kind,const MCExpr * Expr,MCContext & Ctx)22 const MipsMCExpr *MipsMCExpr::create(MipsMCExpr::MipsExprKind Kind,
23                                      const MCExpr *Expr, MCContext &Ctx) {
24   return new (Ctx) MipsMCExpr(Kind, Expr);
25 }
26 
createGpOff(MipsMCExpr::MipsExprKind Kind,const MCExpr * Expr,MCContext & Ctx)27 const MipsMCExpr *MipsMCExpr::createGpOff(MipsMCExpr::MipsExprKind Kind,
28                                           const MCExpr *Expr, MCContext &Ctx) {
29   return create(Kind, create(MEK_NEG, create(MEK_GPREL, Expr, Ctx), Ctx), Ctx);
30 }
31 
printImpl(raw_ostream & OS,const MCAsmInfo * MAI) const32 void MipsMCExpr::printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const {
33   int64_t AbsVal;
34 
35   switch (Kind) {
36   case MEK_None:
37   case MEK_Special:
38     llvm_unreachable("MEK_None and MEK_Special are invalid");
39     break;
40   case MEK_CALL_HI16:
41     OS << "%call_hi";
42     break;
43   case MEK_CALL_LO16:
44     OS << "%call_lo";
45     break;
46   case MEK_DTPREL_HI:
47     OS << "%dtprel_hi";
48     break;
49   case MEK_DTPREL_LO:
50     OS << "%dtprel_lo";
51     break;
52   case MEK_GOT:
53     OS << "%got";
54     break;
55   case MEK_GOTTPREL:
56     OS << "%gottprel";
57     break;
58   case MEK_GOT_CALL:
59     OS << "%call16";
60     break;
61   case MEK_GOT_DISP:
62     OS << "%got_disp";
63     break;
64   case MEK_GOT_HI16:
65     OS << "%got_hi";
66     break;
67   case MEK_GOT_LO16:
68     OS << "%got_lo";
69     break;
70   case MEK_GOT_PAGE:
71     OS << "%got_page";
72     break;
73   case MEK_GOT_OFST:
74     OS << "%got_ofst";
75     break;
76   case MEK_GPREL:
77     OS << "%gp_rel";
78     break;
79   case MEK_HI:
80     OS << "%hi";
81     break;
82   case MEK_HIGHER:
83     OS << "%higher";
84     break;
85   case MEK_HIGHEST:
86     OS << "%highest";
87     break;
88   case MEK_LO:
89     OS << "%lo";
90     break;
91   case MEK_NEG:
92     OS << "%neg";
93     break;
94   case MEK_PCREL_HI16:
95     OS << "%pcrel_hi";
96     break;
97   case MEK_PCREL_LO16:
98     OS << "%pcrel_lo";
99     break;
100   case MEK_TLSGD:
101     OS << "%tlsgd";
102     break;
103   case MEK_TLSLDM:
104     OS << "%tlsldm";
105     break;
106   case MEK_TPREL_HI:
107     OS << "%tprel_hi";
108     break;
109   case MEK_TPREL_LO:
110     OS << "%tprel_lo";
111     break;
112   }
113 
114   OS << '(';
115   if (Expr->evaluateAsAbsolute(AbsVal))
116     OS << AbsVal;
117   else
118     Expr->print(OS, MAI, true);
119   OS << ')';
120 }
121 
122 bool
evaluateAsRelocatableImpl(MCValue & Res,const MCAsmLayout * Layout,const MCFixup * Fixup) const123 MipsMCExpr::evaluateAsRelocatableImpl(MCValue &Res,
124                                       const MCAsmLayout *Layout,
125                                       const MCFixup *Fixup) const {
126   // Look for the %hi(%neg(%gp_rel(X))) and %lo(%neg(%gp_rel(X))) special cases.
127   if (isGpOff()) {
128     const MCExpr *SubExpr =
129         cast<MipsMCExpr>(cast<MipsMCExpr>(getSubExpr())->getSubExpr())
130             ->getSubExpr();
131     if (!SubExpr->evaluateAsRelocatable(Res, Layout, Fixup))
132       return false;
133 
134     Res = MCValue::get(Res.getSymA(), Res.getSymB(), Res.getConstant(),
135                        MEK_Special);
136     return true;
137   }
138 
139   if (!getSubExpr()->evaluateAsRelocatable(Res, Layout, Fixup))
140     return false;
141 
142   if (Res.getRefKind() != MCSymbolRefExpr::VK_None)
143     return false;
144 
145   // evaluateAsAbsolute() and evaluateAsValue() require that we evaluate the
146   // %hi/%lo/etc. here. Fixup is a null pointer when either of these is the
147   // caller.
148   if (Res.isAbsolute() && Fixup == nullptr) {
149     int64_t AbsVal = Res.getConstant();
150     switch (Kind) {
151     case MEK_None:
152     case MEK_Special:
153       llvm_unreachable("MEK_None and MEK_Special are invalid");
154     case MEK_DTPREL_HI:
155     case MEK_DTPREL_LO:
156     case MEK_GOT:
157     case MEK_GOTTPREL:
158     case MEK_GOT_CALL:
159     case MEK_GOT_DISP:
160     case MEK_GOT_HI16:
161     case MEK_GOT_LO16:
162     case MEK_GOT_OFST:
163     case MEK_GOT_PAGE:
164     case MEK_GPREL:
165     case MEK_PCREL_HI16:
166     case MEK_PCREL_LO16:
167     case MEK_TLSGD:
168     case MEK_TLSLDM:
169     case MEK_TPREL_HI:
170     case MEK_TPREL_LO:
171       return false;
172     case MEK_LO:
173     case MEK_CALL_LO16:
174       AbsVal = SignExtend64<16>(AbsVal);
175       break;
176     case MEK_CALL_HI16:
177     case MEK_HI:
178       AbsVal = SignExtend64<16>((AbsVal + 0x8000) >> 16);
179       break;
180     case MEK_HIGHER:
181       AbsVal = SignExtend64<16>((AbsVal + 0x80008000LL) >> 32);
182       break;
183     case MEK_HIGHEST:
184       AbsVal = SignExtend64<16>((AbsVal + 0x800080008000LL) >> 48);
185       break;
186     case MEK_NEG:
187       AbsVal = -AbsVal;
188       break;
189     }
190     Res = MCValue::get(AbsVal);
191     return true;
192   }
193 
194   // We want to defer it for relocatable expressions since the constant is
195   // applied to the whole symbol value.
196   //
197   // The value of getKind() that is given to MCValue is only intended to aid
198   // debugging when inspecting MCValue objects. It shouldn't be relied upon
199   // for decision making.
200   Res = MCValue::get(Res.getSymA(), Res.getSymB(), Res.getConstant(), getKind());
201 
202   return true;
203 }
204 
visitUsedExpr(MCStreamer & Streamer) const205 void MipsMCExpr::visitUsedExpr(MCStreamer &Streamer) const {
206   Streamer.visitUsedExpr(*getSubExpr());
207 }
208 
fixELFSymbolsInTLSFixupsImpl(const MCExpr * Expr,MCAssembler & Asm)209 static void fixELFSymbolsInTLSFixupsImpl(const MCExpr *Expr, MCAssembler &Asm) {
210   switch (Expr->getKind()) {
211   case MCExpr::Target:
212     fixELFSymbolsInTLSFixupsImpl(cast<MipsMCExpr>(Expr)->getSubExpr(), Asm);
213     break;
214   case MCExpr::Constant:
215     break;
216   case MCExpr::Binary: {
217     const MCBinaryExpr *BE = cast<MCBinaryExpr>(Expr);
218     fixELFSymbolsInTLSFixupsImpl(BE->getLHS(), Asm);
219     fixELFSymbolsInTLSFixupsImpl(BE->getRHS(), Asm);
220     break;
221   }
222   case MCExpr::SymbolRef: {
223     // We're known to be under a TLS fixup, so any symbol should be
224     // modified. There should be only one.
225     const MCSymbolRefExpr &SymRef = *cast<MCSymbolRefExpr>(Expr);
226     cast<MCSymbolELF>(SymRef.getSymbol()).setType(ELF::STT_TLS);
227     break;
228   }
229   case MCExpr::Unary:
230     fixELFSymbolsInTLSFixupsImpl(cast<MCUnaryExpr>(Expr)->getSubExpr(), Asm);
231     break;
232   }
233 }
234 
fixELFSymbolsInTLSFixups(MCAssembler & Asm) const235 void MipsMCExpr::fixELFSymbolsInTLSFixups(MCAssembler &Asm) const {
236   switch (getKind()) {
237   case MEK_None:
238   case MEK_Special:
239     llvm_unreachable("MEK_None and MEK_Special are invalid");
240     break;
241   case MEK_CALL_HI16:
242   case MEK_CALL_LO16:
243   case MEK_DTPREL_HI:
244   case MEK_DTPREL_LO:
245   case MEK_GOT:
246   case MEK_GOT_CALL:
247   case MEK_GOT_DISP:
248   case MEK_GOT_HI16:
249   case MEK_GOT_LO16:
250   case MEK_GOT_OFST:
251   case MEK_GOT_PAGE:
252   case MEK_GPREL:
253   case MEK_HI:
254   case MEK_HIGHER:
255   case MEK_HIGHEST:
256   case MEK_LO:
257   case MEK_NEG:
258   case MEK_PCREL_HI16:
259   case MEK_PCREL_LO16:
260   case MEK_TLSLDM:
261     // If we do have nested target-specific expressions, they will be in
262     // a consecutive chain.
263     if (const MipsMCExpr *E = dyn_cast<const MipsMCExpr>(getSubExpr()))
264       E->fixELFSymbolsInTLSFixups(Asm);
265     break;
266   case MEK_GOTTPREL:
267   case MEK_TLSGD:
268   case MEK_TPREL_HI:
269   case MEK_TPREL_LO:
270     fixELFSymbolsInTLSFixupsImpl(getSubExpr(), Asm);
271     break;
272   }
273 }
274 
isGpOff(MipsExprKind & Kind) const275 bool MipsMCExpr::isGpOff(MipsExprKind &Kind) const {
276   if (getKind() == MEK_HI || getKind() == MEK_LO) {
277     if (const MipsMCExpr *S1 = dyn_cast<const MipsMCExpr>(getSubExpr())) {
278       if (const MipsMCExpr *S2 = dyn_cast<const MipsMCExpr>(S1->getSubExpr())) {
279         if (S1->getKind() == MEK_NEG && S2->getKind() == MEK_GPREL) {
280           Kind = getKind();
281           return true;
282         }
283       }
284     }
285   }
286   return false;
287 }
288