1 //===- MCExpr.cpp - Assembly Level Expression Implementation --------------===//
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 "llvm/MC/MCExpr.h"
11 #include "llvm/ADT/Statistic.h"
12 #include "llvm/ADT/StringSwitch.h"
13 #include "llvm/MC/MCAsmInfo.h"
14 #include "llvm/MC/MCAsmLayout.h"
15 #include "llvm/MC/MCAssembler.h"
16 #include "llvm/MC/MCContext.h"
17 #include "llvm/MC/MCObjectWriter.h"
18 #include "llvm/MC/MCSymbol.h"
19 #include "llvm/MC/MCValue.h"
20 #include "llvm/Support/Debug.h"
21 #include "llvm/Support/ErrorHandling.h"
22 #include "llvm/Support/raw_ostream.h"
23 using namespace llvm;
24
25 #define DEBUG_TYPE "mcexpr"
26
27 namespace {
28 namespace stats {
29 STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations");
30 }
31 }
32
print(raw_ostream & OS) const33 void MCExpr::print(raw_ostream &OS) const {
34 switch (getKind()) {
35 case MCExpr::Target:
36 return cast<MCTargetExpr>(this)->PrintImpl(OS);
37 case MCExpr::Constant:
38 OS << cast<MCConstantExpr>(*this).getValue();
39 return;
40
41 case MCExpr::SymbolRef: {
42 const MCSymbolRefExpr &SRE = cast<MCSymbolRefExpr>(*this);
43 const MCSymbol &Sym = SRE.getSymbol();
44 // Parenthesize names that start with $ so that they don't look like
45 // absolute names.
46 bool UseParens = Sym.getName()[0] == '$';
47 if (UseParens)
48 OS << '(' << Sym << ')';
49 else
50 OS << Sym;
51
52 if (SRE.getKind() != MCSymbolRefExpr::VK_None)
53 SRE.printVariantKind(OS);
54
55 return;
56 }
57
58 case MCExpr::Unary: {
59 const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this);
60 switch (UE.getOpcode()) {
61 case MCUnaryExpr::LNot: OS << '!'; break;
62 case MCUnaryExpr::Minus: OS << '-'; break;
63 case MCUnaryExpr::Not: OS << '~'; break;
64 case MCUnaryExpr::Plus: OS << '+'; break;
65 }
66 OS << *UE.getSubExpr();
67 return;
68 }
69
70 case MCExpr::Binary: {
71 const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this);
72
73 // Only print parens around the LHS if it is non-trivial.
74 if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) {
75 OS << *BE.getLHS();
76 } else {
77 OS << '(' << *BE.getLHS() << ')';
78 }
79
80 switch (BE.getOpcode()) {
81 case MCBinaryExpr::Add:
82 // Print "X-42" instead of "X+-42".
83 if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) {
84 if (RHSC->getValue() < 0) {
85 OS << RHSC->getValue();
86 return;
87 }
88 }
89
90 OS << '+';
91 break;
92 case MCBinaryExpr::And: OS << '&'; break;
93 case MCBinaryExpr::Div: OS << '/'; break;
94 case MCBinaryExpr::EQ: OS << "=="; break;
95 case MCBinaryExpr::GT: OS << '>'; break;
96 case MCBinaryExpr::GTE: OS << ">="; break;
97 case MCBinaryExpr::LAnd: OS << "&&"; break;
98 case MCBinaryExpr::LOr: OS << "||"; break;
99 case MCBinaryExpr::LT: OS << '<'; break;
100 case MCBinaryExpr::LTE: OS << "<="; break;
101 case MCBinaryExpr::Mod: OS << '%'; break;
102 case MCBinaryExpr::Mul: OS << '*'; break;
103 case MCBinaryExpr::NE: OS << "!="; break;
104 case MCBinaryExpr::Or: OS << '|'; break;
105 case MCBinaryExpr::Shl: OS << "<<"; break;
106 case MCBinaryExpr::Shr: OS << ">>"; break;
107 case MCBinaryExpr::Sub: OS << '-'; break;
108 case MCBinaryExpr::Xor: OS << '^'; break;
109 }
110
111 // Only print parens around the LHS if it is non-trivial.
112 if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) {
113 OS << *BE.getRHS();
114 } else {
115 OS << '(' << *BE.getRHS() << ')';
116 }
117 return;
118 }
119 }
120
121 llvm_unreachable("Invalid expression kind!");
122 }
123
124 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const125 void MCExpr::dump() const {
126 print(dbgs());
127 dbgs() << '\n';
128 }
129 #endif
130
131 /* *** */
132
Create(Opcode Opc,const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)133 const MCBinaryExpr *MCBinaryExpr::Create(Opcode Opc, const MCExpr *LHS,
134 const MCExpr *RHS, MCContext &Ctx) {
135 return new (Ctx) MCBinaryExpr(Opc, LHS, RHS);
136 }
137
Create(Opcode Opc,const MCExpr * Expr,MCContext & Ctx)138 const MCUnaryExpr *MCUnaryExpr::Create(Opcode Opc, const MCExpr *Expr,
139 MCContext &Ctx) {
140 return new (Ctx) MCUnaryExpr(Opc, Expr);
141 }
142
Create(int64_t Value,MCContext & Ctx)143 const MCConstantExpr *MCConstantExpr::Create(int64_t Value, MCContext &Ctx) {
144 return new (Ctx) MCConstantExpr(Value);
145 }
146
147 /* *** */
148
MCSymbolRefExpr(const MCSymbol * Symbol,VariantKind Kind,const MCAsmInfo * MAI)149 MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind,
150 const MCAsmInfo *MAI)
151 : MCExpr(MCExpr::SymbolRef), Kind(Kind),
152 UseParensForSymbolVariant(MAI->useParensForSymbolVariant()),
153 HasSubsectionsViaSymbols(MAI->hasSubsectionsViaSymbols()),
154 Symbol(Symbol) {
155 assert(Symbol);
156 }
157
Create(const MCSymbol * Sym,VariantKind Kind,MCContext & Ctx)158 const MCSymbolRefExpr *MCSymbolRefExpr::Create(const MCSymbol *Sym,
159 VariantKind Kind,
160 MCContext &Ctx) {
161 return new (Ctx) MCSymbolRefExpr(Sym, Kind, Ctx.getAsmInfo());
162 }
163
Create(StringRef Name,VariantKind Kind,MCContext & Ctx)164 const MCSymbolRefExpr *MCSymbolRefExpr::Create(StringRef Name, VariantKind Kind,
165 MCContext &Ctx) {
166 return Create(Ctx.GetOrCreateSymbol(Name), Kind, Ctx);
167 }
168
getVariantKindName(VariantKind Kind)169 StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
170 switch (Kind) {
171 case VK_Invalid: return "<<invalid>>";
172 case VK_None: return "<<none>>";
173
174 case VK_GOT: return "GOT";
175 case VK_GOTOFF: return "GOTOFF";
176 case VK_GOTPCREL: return "GOTPCREL";
177 case VK_GOTTPOFF: return "GOTTPOFF";
178 case VK_INDNTPOFF: return "INDNTPOFF";
179 case VK_NTPOFF: return "NTPOFF";
180 case VK_GOTNTPOFF: return "GOTNTPOFF";
181 case VK_PLT: return "PLT";
182 case VK_TLSGD: return "TLSGD";
183 case VK_TLSLD: return "TLSLD";
184 case VK_TLSLDM: return "TLSLDM";
185 case VK_TPOFF: return "TPOFF";
186 case VK_DTPOFF: return "DTPOFF";
187 case VK_TLVP: return "TLVP";
188 case VK_TLVPPAGE: return "TLVPPAGE";
189 case VK_TLVPPAGEOFF: return "TLVPPAGEOFF";
190 case VK_PAGE: return "PAGE";
191 case VK_PAGEOFF: return "PAGEOFF";
192 case VK_GOTPAGE: return "GOTPAGE";
193 case VK_GOTPAGEOFF: return "GOTPAGEOFF";
194 case VK_SECREL: return "SECREL32";
195 case VK_SIZE: return "SIZE";
196 case VK_WEAKREF: return "WEAKREF";
197 case VK_ARM_NONE: return "none";
198 case VK_ARM_TARGET1: return "target1";
199 case VK_ARM_TARGET2: return "target2";
200 case VK_ARM_PREL31: return "prel31";
201 case VK_ARM_SBREL: return "sbrel";
202 case VK_ARM_TLSLDO: return "tlsldo";
203 case VK_ARM_TLSCALL: return "tlscall";
204 case VK_ARM_TLSDESC: return "tlsdesc";
205 case VK_ARM_TLSDESCSEQ: return "tlsdescseq";
206 case VK_PPC_LO: return "l";
207 case VK_PPC_HI: return "h";
208 case VK_PPC_HA: return "ha";
209 case VK_PPC_HIGHER: return "higher";
210 case VK_PPC_HIGHERA: return "highera";
211 case VK_PPC_HIGHEST: return "highest";
212 case VK_PPC_HIGHESTA: return "highesta";
213 case VK_PPC_GOT_LO: return "got@l";
214 case VK_PPC_GOT_HI: return "got@h";
215 case VK_PPC_GOT_HA: return "got@ha";
216 case VK_PPC_TOCBASE: return "tocbase";
217 case VK_PPC_TOC: return "toc";
218 case VK_PPC_TOC_LO: return "toc@l";
219 case VK_PPC_TOC_HI: return "toc@h";
220 case VK_PPC_TOC_HA: return "toc@ha";
221 case VK_PPC_DTPMOD: return "dtpmod";
222 case VK_PPC_TPREL: return "tprel";
223 case VK_PPC_TPREL_LO: return "tprel@l";
224 case VK_PPC_TPREL_HI: return "tprel@h";
225 case VK_PPC_TPREL_HA: return "tprel@ha";
226 case VK_PPC_TPREL_HIGHER: return "tprel@higher";
227 case VK_PPC_TPREL_HIGHERA: return "tprel@highera";
228 case VK_PPC_TPREL_HIGHEST: return "tprel@highest";
229 case VK_PPC_TPREL_HIGHESTA: return "tprel@highesta";
230 case VK_PPC_DTPREL: return "dtprel";
231 case VK_PPC_DTPREL_LO: return "dtprel@l";
232 case VK_PPC_DTPREL_HI: return "dtprel@h";
233 case VK_PPC_DTPREL_HA: return "dtprel@ha";
234 case VK_PPC_DTPREL_HIGHER: return "dtprel@higher";
235 case VK_PPC_DTPREL_HIGHERA: return "dtprel@highera";
236 case VK_PPC_DTPREL_HIGHEST: return "dtprel@highest";
237 case VK_PPC_DTPREL_HIGHESTA: return "dtprel@highesta";
238 case VK_PPC_GOT_TPREL: return "got@tprel";
239 case VK_PPC_GOT_TPREL_LO: return "got@tprel@l";
240 case VK_PPC_GOT_TPREL_HI: return "got@tprel@h";
241 case VK_PPC_GOT_TPREL_HA: return "got@tprel@ha";
242 case VK_PPC_GOT_DTPREL: return "got@dtprel";
243 case VK_PPC_GOT_DTPREL_LO: return "got@dtprel@l";
244 case VK_PPC_GOT_DTPREL_HI: return "got@dtprel@h";
245 case VK_PPC_GOT_DTPREL_HA: return "got@dtprel@ha";
246 case VK_PPC_TLS: return "tls";
247 case VK_PPC_GOT_TLSGD: return "got@tlsgd";
248 case VK_PPC_GOT_TLSGD_LO: return "got@tlsgd@l";
249 case VK_PPC_GOT_TLSGD_HI: return "got@tlsgd@h";
250 case VK_PPC_GOT_TLSGD_HA: return "got@tlsgd@ha";
251 case VK_PPC_TLSGD: return "tlsgd";
252 case VK_PPC_GOT_TLSLD: return "got@tlsld";
253 case VK_PPC_GOT_TLSLD_LO: return "got@tlsld@l";
254 case VK_PPC_GOT_TLSLD_HI: return "got@tlsld@h";
255 case VK_PPC_GOT_TLSLD_HA: return "got@tlsld@ha";
256 case VK_PPC_TLSLD: return "tlsld";
257 case VK_PPC_LOCAL: return "local";
258 case VK_Mips_GPREL: return "GPREL";
259 case VK_Mips_GOT_CALL: return "GOT_CALL";
260 case VK_Mips_GOT16: return "GOT16";
261 case VK_Mips_GOT: return "GOT";
262 case VK_Mips_ABS_HI: return "ABS_HI";
263 case VK_Mips_ABS_LO: return "ABS_LO";
264 case VK_Mips_TLSGD: return "TLSGD";
265 case VK_Mips_TLSLDM: return "TLSLDM";
266 case VK_Mips_DTPREL_HI: return "DTPREL_HI";
267 case VK_Mips_DTPREL_LO: return "DTPREL_LO";
268 case VK_Mips_GOTTPREL: return "GOTTPREL";
269 case VK_Mips_TPREL_HI: return "TPREL_HI";
270 case VK_Mips_TPREL_LO: return "TPREL_LO";
271 case VK_Mips_GPOFF_HI: return "GPOFF_HI";
272 case VK_Mips_GPOFF_LO: return "GPOFF_LO";
273 case VK_Mips_GOT_DISP: return "GOT_DISP";
274 case VK_Mips_GOT_PAGE: return "GOT_PAGE";
275 case VK_Mips_GOT_OFST: return "GOT_OFST";
276 case VK_Mips_HIGHER: return "HIGHER";
277 case VK_Mips_HIGHEST: return "HIGHEST";
278 case VK_Mips_GOT_HI16: return "GOT_HI16";
279 case VK_Mips_GOT_LO16: return "GOT_LO16";
280 case VK_Mips_CALL_HI16: return "CALL_HI16";
281 case VK_Mips_CALL_LO16: return "CALL_LO16";
282 case VK_Mips_PCREL_HI16: return "PCREL_HI16";
283 case VK_Mips_PCREL_LO16: return "PCREL_LO16";
284 case VK_COFF_IMGREL32: return "IMGREL";
285 }
286 llvm_unreachable("Invalid variant kind");
287 }
288
289 MCSymbolRefExpr::VariantKind
getVariantKindForName(StringRef Name)290 MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
291 return StringSwitch<VariantKind>(Name.lower())
292 .Case("got", VK_GOT)
293 .Case("gotoff", VK_GOTOFF)
294 .Case("gotpcrel", VK_GOTPCREL)
295 .Case("got_prel", VK_GOTPCREL)
296 .Case("gottpoff", VK_GOTTPOFF)
297 .Case("indntpoff", VK_INDNTPOFF)
298 .Case("ntpoff", VK_NTPOFF)
299 .Case("gotntpoff", VK_GOTNTPOFF)
300 .Case("plt", VK_PLT)
301 .Case("tlsgd", VK_TLSGD)
302 .Case("tlsld", VK_TLSLD)
303 .Case("tlsldm", VK_TLSLDM)
304 .Case("tpoff", VK_TPOFF)
305 .Case("dtpoff", VK_DTPOFF)
306 .Case("tlvp", VK_TLVP)
307 .Case("tlvppage", VK_TLVPPAGE)
308 .Case("tlvppageoff", VK_TLVPPAGEOFF)
309 .Case("page", VK_PAGE)
310 .Case("pageoff", VK_PAGEOFF)
311 .Case("gotpage", VK_GOTPAGE)
312 .Case("gotpageoff", VK_GOTPAGEOFF)
313 .Case("imgrel", VK_COFF_IMGREL32)
314 .Case("secrel32", VK_SECREL)
315 .Case("size", VK_SIZE)
316 .Case("l", VK_PPC_LO)
317 .Case("h", VK_PPC_HI)
318 .Case("ha", VK_PPC_HA)
319 .Case("higher", VK_PPC_HIGHER)
320 .Case("highera", VK_PPC_HIGHERA)
321 .Case("highest", VK_PPC_HIGHEST)
322 .Case("highesta", VK_PPC_HIGHESTA)
323 .Case("got@l", VK_PPC_GOT_LO)
324 .Case("got@h", VK_PPC_GOT_HI)
325 .Case("got@ha", VK_PPC_GOT_HA)
326 .Case("local", VK_PPC_LOCAL)
327 .Case("tocbase", VK_PPC_TOCBASE)
328 .Case("toc", VK_PPC_TOC)
329 .Case("toc@l", VK_PPC_TOC_LO)
330 .Case("toc@h", VK_PPC_TOC_HI)
331 .Case("toc@ha", VK_PPC_TOC_HA)
332 .Case("tls", VK_PPC_TLS)
333 .Case("dtpmod", VK_PPC_DTPMOD)
334 .Case("tprel", VK_PPC_TPREL)
335 .Case("tprel@l", VK_PPC_TPREL_LO)
336 .Case("tprel@h", VK_PPC_TPREL_HI)
337 .Case("tprel@ha", VK_PPC_TPREL_HA)
338 .Case("tprel@higher", VK_PPC_TPREL_HIGHER)
339 .Case("tprel@highera", VK_PPC_TPREL_HIGHERA)
340 .Case("tprel@highest", VK_PPC_TPREL_HIGHEST)
341 .Case("tprel@highesta", VK_PPC_TPREL_HIGHESTA)
342 .Case("dtprel", VK_PPC_DTPREL)
343 .Case("dtprel@l", VK_PPC_DTPREL_LO)
344 .Case("dtprel@h", VK_PPC_DTPREL_HI)
345 .Case("dtprel@ha", VK_PPC_DTPREL_HA)
346 .Case("dtprel@higher", VK_PPC_DTPREL_HIGHER)
347 .Case("dtprel@highera", VK_PPC_DTPREL_HIGHERA)
348 .Case("dtprel@highest", VK_PPC_DTPREL_HIGHEST)
349 .Case("dtprel@highesta", VK_PPC_DTPREL_HIGHESTA)
350 .Case("got@tprel", VK_PPC_GOT_TPREL)
351 .Case("got@tprel@l", VK_PPC_GOT_TPREL_LO)
352 .Case("got@tprel@h", VK_PPC_GOT_TPREL_HI)
353 .Case("got@tprel@ha", VK_PPC_GOT_TPREL_HA)
354 .Case("got@dtprel", VK_PPC_GOT_DTPREL)
355 .Case("got@dtprel@l", VK_PPC_GOT_DTPREL_LO)
356 .Case("got@dtprel@h", VK_PPC_GOT_DTPREL_HI)
357 .Case("got@dtprel@ha", VK_PPC_GOT_DTPREL_HA)
358 .Case("got@tlsgd", VK_PPC_GOT_TLSGD)
359 .Case("got@tlsgd@l", VK_PPC_GOT_TLSGD_LO)
360 .Case("got@tlsgd@h", VK_PPC_GOT_TLSGD_HI)
361 .Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD_HA)
362 .Case("got@tlsld", VK_PPC_GOT_TLSLD)
363 .Case("got@tlsld@l", VK_PPC_GOT_TLSLD_LO)
364 .Case("got@tlsld@h", VK_PPC_GOT_TLSLD_HI)
365 .Case("got@tlsld@ha", VK_PPC_GOT_TLSLD_HA)
366 .Case("none", VK_ARM_NONE)
367 .Case("target1", VK_ARM_TARGET1)
368 .Case("target2", VK_ARM_TARGET2)
369 .Case("prel31", VK_ARM_PREL31)
370 .Case("sbrel", VK_ARM_SBREL)
371 .Case("tlsldo", VK_ARM_TLSLDO)
372 .Case("tlscall", VK_ARM_TLSCALL)
373 .Case("tlsdesc", VK_ARM_TLSDESC)
374 .Default(VK_Invalid);
375 }
376
printVariantKind(raw_ostream & OS) const377 void MCSymbolRefExpr::printVariantKind(raw_ostream &OS) const {
378 if (UseParensForSymbolVariant)
379 OS << '(' << MCSymbolRefExpr::getVariantKindName(getKind()) << ')';
380 else
381 OS << '@' << MCSymbolRefExpr::getVariantKindName(getKind());
382 }
383
384 /* *** */
385
anchor()386 void MCTargetExpr::anchor() {}
387
388 /* *** */
389
EvaluateAsAbsolute(int64_t & Res) const390 bool MCExpr::EvaluateAsAbsolute(int64_t &Res) const {
391 return EvaluateAsAbsolute(Res, nullptr, nullptr, nullptr);
392 }
393
EvaluateAsAbsolute(int64_t & Res,const MCAsmLayout & Layout) const394 bool MCExpr::EvaluateAsAbsolute(int64_t &Res,
395 const MCAsmLayout &Layout) const {
396 return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr);
397 }
398
EvaluateAsAbsolute(int64_t & Res,const MCAsmLayout & Layout,const SectionAddrMap & Addrs) const399 bool MCExpr::EvaluateAsAbsolute(int64_t &Res,
400 const MCAsmLayout &Layout,
401 const SectionAddrMap &Addrs) const {
402 return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs);
403 }
404
EvaluateAsAbsolute(int64_t & Res,const MCAssembler & Asm) const405 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const {
406 return EvaluateAsAbsolute(Res, &Asm, nullptr, nullptr);
407 }
408
evaluateKnownAbsolute(int64_t & Res,const MCAsmLayout & Layout) const409 bool MCExpr::evaluateKnownAbsolute(int64_t &Res,
410 const MCAsmLayout &Layout) const {
411 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr,
412 true);
413 }
414
EvaluateAsAbsolute(int64_t & Res,const MCAssembler * Asm,const MCAsmLayout * Layout,const SectionAddrMap * Addrs) const415 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
416 const MCAsmLayout *Layout,
417 const SectionAddrMap *Addrs) const {
418 // FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us
419 // absolutize differences across sections and that is what the MachO writer
420 // uses Addrs for.
421 return evaluateAsAbsolute(Res, Asm, Layout, Addrs, Addrs);
422 }
423
evaluateAsAbsolute(int64_t & Res,const MCAssembler * Asm,const MCAsmLayout * Layout,const SectionAddrMap * Addrs,bool InSet) const424 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
425 const MCAsmLayout *Layout,
426 const SectionAddrMap *Addrs, bool InSet) const {
427 MCValue Value;
428
429 // Fast path constants.
430 if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) {
431 Res = CE->getValue();
432 return true;
433 }
434
435 bool IsRelocatable =
436 EvaluateAsRelocatableImpl(Value, Asm, Layout, nullptr, Addrs, InSet);
437
438 // Record the current value.
439 Res = Value.getConstant();
440
441 return IsRelocatable && Value.isAbsolute();
442 }
443
444 /// \brief Helper method for \see EvaluateSymbolAdd().
AttemptToFoldSymbolOffsetDifference(const MCAssembler * Asm,const MCAsmLayout * Layout,const SectionAddrMap * Addrs,bool InSet,const MCSymbolRefExpr * & A,const MCSymbolRefExpr * & B,int64_t & Addend)445 static void AttemptToFoldSymbolOffsetDifference(
446 const MCAssembler *Asm, const MCAsmLayout *Layout,
447 const SectionAddrMap *Addrs, bool InSet, const MCSymbolRefExpr *&A,
448 const MCSymbolRefExpr *&B, int64_t &Addend) {
449 if (!A || !B)
450 return;
451
452 const MCSymbol &SA = A->getSymbol();
453 const MCSymbol &SB = B->getSymbol();
454
455 if (SA.isUndefined() || SB.isUndefined())
456 return;
457
458 if (!Asm->getWriter().IsSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet))
459 return;
460
461 const MCSymbolData &AD = Asm->getSymbolData(SA);
462 const MCSymbolData &BD = Asm->getSymbolData(SB);
463
464 if (AD.getFragment() == BD.getFragment()) {
465 Addend += (AD.getOffset() - BD.getOffset());
466
467 // Pointers to Thumb symbols need to have their low-bit set to allow
468 // for interworking.
469 if (Asm->isThumbFunc(&SA))
470 Addend |= 1;
471
472 // Clear the symbol expr pointers to indicate we have folded these
473 // operands.
474 A = B = nullptr;
475 return;
476 }
477
478 if (!Layout)
479 return;
480
481 const MCSectionData &SecA = *AD.getFragment()->getParent();
482 const MCSectionData &SecB = *BD.getFragment()->getParent();
483
484 if ((&SecA != &SecB) && !Addrs)
485 return;
486
487 // Eagerly evaluate.
488 Addend += (Layout->getSymbolOffset(&Asm->getSymbolData(A->getSymbol())) -
489 Layout->getSymbolOffset(&Asm->getSymbolData(B->getSymbol())));
490 if (Addrs && (&SecA != &SecB))
491 Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB));
492
493 // Pointers to Thumb symbols need to have their low-bit set to allow
494 // for interworking.
495 if (Asm->isThumbFunc(&SA))
496 Addend |= 1;
497
498 // Clear the symbol expr pointers to indicate we have folded these
499 // operands.
500 A = B = nullptr;
501 }
502
503 /// \brief Evaluate the result of an add between (conceptually) two MCValues.
504 ///
505 /// This routine conceptually attempts to construct an MCValue:
506 /// Result = (Result_A - Result_B + Result_Cst)
507 /// from two MCValue's LHS and RHS where
508 /// Result = LHS + RHS
509 /// and
510 /// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
511 ///
512 /// This routine attempts to aggresively fold the operands such that the result
513 /// is representable in an MCValue, but may not always succeed.
514 ///
515 /// \returns True on success, false if the result is not representable in an
516 /// MCValue.
517
518 /// NOTE: It is really important to have both the Asm and Layout arguments.
519 /// They might look redundant, but this function can be used before layout
520 /// is done (see the object streamer for example) and having the Asm argument
521 /// lets us avoid relaxations early.
522 static bool
EvaluateSymbolicAdd(const MCAssembler * Asm,const MCAsmLayout * Layout,const SectionAddrMap * Addrs,bool InSet,const MCValue & LHS,const MCSymbolRefExpr * RHS_A,const MCSymbolRefExpr * RHS_B,int64_t RHS_Cst,MCValue & Res)523 EvaluateSymbolicAdd(const MCAssembler *Asm, const MCAsmLayout *Layout,
524 const SectionAddrMap *Addrs, bool InSet, const MCValue &LHS,
525 const MCSymbolRefExpr *RHS_A, const MCSymbolRefExpr *RHS_B,
526 int64_t RHS_Cst, MCValue &Res) {
527 // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy
528 // about dealing with modifiers. This will ultimately bite us, one day.
529 const MCSymbolRefExpr *LHS_A = LHS.getSymA();
530 const MCSymbolRefExpr *LHS_B = LHS.getSymB();
531 int64_t LHS_Cst = LHS.getConstant();
532
533 // Fold the result constant immediately.
534 int64_t Result_Cst = LHS_Cst + RHS_Cst;
535
536 assert((!Layout || Asm) &&
537 "Must have an assembler object if layout is given!");
538
539 // If we have a layout, we can fold resolved differences.
540 if (Asm) {
541 // First, fold out any differences which are fully resolved. By
542 // reassociating terms in
543 // Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
544 // we have the four possible differences:
545 // (LHS_A - LHS_B),
546 // (LHS_A - RHS_B),
547 // (RHS_A - LHS_B),
548 // (RHS_A - RHS_B).
549 // Since we are attempting to be as aggressive as possible about folding, we
550 // attempt to evaluate each possible alternative.
551 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B,
552 Result_Cst);
553 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B,
554 Result_Cst);
555 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B,
556 Result_Cst);
557 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B,
558 Result_Cst);
559 }
560
561 // We can't represent the addition or subtraction of two symbols.
562 if ((LHS_A && RHS_A) || (LHS_B && RHS_B))
563 return false;
564
565 // At this point, we have at most one additive symbol and one subtractive
566 // symbol -- find them.
567 const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A;
568 const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B;
569
570 // If we have a negated symbol, then we must have also have a non-negated
571 // symbol in order to encode the expression.
572 if (B && !A)
573 return false;
574
575 Res = MCValue::get(A, B, Result_Cst);
576 return true;
577 }
578
EvaluateAsRelocatable(MCValue & Res,const MCAsmLayout * Layout,const MCFixup * Fixup) const579 bool MCExpr::EvaluateAsRelocatable(MCValue &Res,
580 const MCAsmLayout *Layout,
581 const MCFixup *Fixup) const {
582 MCAssembler *Assembler = Layout ? &Layout->getAssembler() : nullptr;
583 return EvaluateAsRelocatableImpl(Res, Assembler, Layout, Fixup, nullptr,
584 false);
585 }
586
evaluateAsValue(MCValue & Res,const MCAsmLayout & Layout) const587 bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const {
588 MCAssembler *Assembler = &Layout.getAssembler();
589 return EvaluateAsRelocatableImpl(Res, Assembler, &Layout, nullptr, nullptr,
590 true);
591 }
592
canExpand(const MCSymbol & Sym,const MCAssembler * Asm,bool InSet)593 static bool canExpand(const MCSymbol &Sym, const MCAssembler *Asm, bool InSet) {
594 if (InSet)
595 return true;
596 if (!Asm)
597 return false;
598 const MCSymbolData &SD = Asm->getSymbolData(Sym);
599 return !Asm->getWriter().isWeak(SD);
600 }
601
EvaluateAsRelocatableImpl(MCValue & Res,const MCAssembler * Asm,const MCAsmLayout * Layout,const MCFixup * Fixup,const SectionAddrMap * Addrs,bool InSet) const602 bool MCExpr::EvaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm,
603 const MCAsmLayout *Layout,
604 const MCFixup *Fixup,
605 const SectionAddrMap *Addrs,
606 bool InSet) const {
607 ++stats::MCExprEvaluate;
608
609 switch (getKind()) {
610 case Target:
611 return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout,
612 Fixup);
613
614 case Constant:
615 Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
616 return true;
617
618 case SymbolRef: {
619 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
620 const MCSymbol &Sym = SRE->getSymbol();
621
622 // Evaluate recursively if this is a variable.
623 if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None &&
624 canExpand(Sym, Asm, InSet)) {
625 bool IsMachO = SRE->hasSubsectionsViaSymbols();
626 if (Sym.getVariableValue()->EvaluateAsRelocatableImpl(
627 Res, Asm, Layout, Fixup, Addrs, InSet || IsMachO)) {
628 if (!IsMachO)
629 return true;
630
631 const MCSymbolRefExpr *A = Res.getSymA();
632 const MCSymbolRefExpr *B = Res.getSymB();
633 // FIXME: This is small hack. Given
634 // a = b + 4
635 // .long a
636 // the OS X assembler will completely drop the 4. We should probably
637 // include it in the relocation or produce an error if that is not
638 // possible.
639 if (!A && !B)
640 return true;
641 }
642 }
643
644 Res = MCValue::get(SRE, nullptr, 0);
645 return true;
646 }
647
648 case Unary: {
649 const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
650 MCValue Value;
651
652 if (!AUE->getSubExpr()->EvaluateAsRelocatableImpl(Value, Asm, Layout, Fixup,
653 Addrs, InSet))
654 return false;
655
656 switch (AUE->getOpcode()) {
657 case MCUnaryExpr::LNot:
658 if (!Value.isAbsolute())
659 return false;
660 Res = MCValue::get(!Value.getConstant());
661 break;
662 case MCUnaryExpr::Minus:
663 /// -(a - b + const) ==> (b - a - const)
664 if (Value.getSymA() && !Value.getSymB())
665 return false;
666 Res = MCValue::get(Value.getSymB(), Value.getSymA(),
667 -Value.getConstant());
668 break;
669 case MCUnaryExpr::Not:
670 if (!Value.isAbsolute())
671 return false;
672 Res = MCValue::get(~Value.getConstant());
673 break;
674 case MCUnaryExpr::Plus:
675 Res = Value;
676 break;
677 }
678
679 return true;
680 }
681
682 case Binary: {
683 const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
684 MCValue LHSValue, RHSValue;
685
686 if (!ABE->getLHS()->EvaluateAsRelocatableImpl(LHSValue, Asm, Layout, Fixup,
687 Addrs, InSet) ||
688 !ABE->getRHS()->EvaluateAsRelocatableImpl(RHSValue, Asm, Layout, Fixup,
689 Addrs, InSet))
690 return false;
691
692 // We only support a few operations on non-constant expressions, handle
693 // those first.
694 if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
695 switch (ABE->getOpcode()) {
696 default:
697 return false;
698 case MCBinaryExpr::Sub:
699 // Negate RHS and add.
700 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
701 RHSValue.getSymB(), RHSValue.getSymA(),
702 -RHSValue.getConstant(), Res);
703
704 case MCBinaryExpr::Add:
705 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
706 RHSValue.getSymA(), RHSValue.getSymB(),
707 RHSValue.getConstant(), Res);
708 }
709 }
710
711 // FIXME: We need target hooks for the evaluation. It may be limited in
712 // width, and gas defines the result of comparisons and right shifts
713 // differently from Apple as.
714 int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
715 int64_t Result = 0;
716 switch (ABE->getOpcode()) {
717 case MCBinaryExpr::Add: Result = LHS + RHS; break;
718 case MCBinaryExpr::And: Result = LHS & RHS; break;
719 case MCBinaryExpr::Div: Result = LHS / RHS; break;
720 case MCBinaryExpr::EQ: Result = LHS == RHS; break;
721 case MCBinaryExpr::GT: Result = LHS > RHS; break;
722 case MCBinaryExpr::GTE: Result = LHS >= RHS; break;
723 case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
724 case MCBinaryExpr::LOr: Result = LHS || RHS; break;
725 case MCBinaryExpr::LT: Result = LHS < RHS; break;
726 case MCBinaryExpr::LTE: Result = LHS <= RHS; break;
727 case MCBinaryExpr::Mod: Result = LHS % RHS; break;
728 case MCBinaryExpr::Mul: Result = LHS * RHS; break;
729 case MCBinaryExpr::NE: Result = LHS != RHS; break;
730 case MCBinaryExpr::Or: Result = LHS | RHS; break;
731 case MCBinaryExpr::Shl: Result = LHS << RHS; break;
732 case MCBinaryExpr::Shr: Result = LHS >> RHS; break;
733 case MCBinaryExpr::Sub: Result = LHS - RHS; break;
734 case MCBinaryExpr::Xor: Result = LHS ^ RHS; break;
735 }
736
737 Res = MCValue::get(Result);
738 return true;
739 }
740 }
741
742 llvm_unreachable("Invalid assembly expression kind!");
743 }
744
FindAssociatedSection() const745 const MCSection *MCExpr::FindAssociatedSection() const {
746 switch (getKind()) {
747 case Target:
748 // We never look through target specific expressions.
749 return cast<MCTargetExpr>(this)->FindAssociatedSection();
750
751 case Constant:
752 return MCSymbol::AbsolutePseudoSection;
753
754 case SymbolRef: {
755 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
756 const MCSymbol &Sym = SRE->getSymbol();
757
758 if (Sym.isDefined())
759 return &Sym.getSection();
760
761 return nullptr;
762 }
763
764 case Unary:
765 return cast<MCUnaryExpr>(this)->getSubExpr()->FindAssociatedSection();
766
767 case Binary: {
768 const MCBinaryExpr *BE = cast<MCBinaryExpr>(this);
769 const MCSection *LHS_S = BE->getLHS()->FindAssociatedSection();
770 const MCSection *RHS_S = BE->getRHS()->FindAssociatedSection();
771
772 // If either section is absolute, return the other.
773 if (LHS_S == MCSymbol::AbsolutePseudoSection)
774 return RHS_S;
775 if (RHS_S == MCSymbol::AbsolutePseudoSection)
776 return LHS_S;
777
778 // Not always correct, but probably the best we can do without more context.
779 if (BE->getOpcode() == MCBinaryExpr::Sub)
780 return MCSymbol::AbsolutePseudoSection;
781
782 // Otherwise, return the first non-null section.
783 return LHS_S ? LHS_S : RHS_S;
784 }
785 }
786
787 llvm_unreachable("Invalid assembly expression kind!");
788 }
789