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 #define DEBUG_TYPE "mcexpr"
11 #include "llvm/MC/MCExpr.h"
12 #include "llvm/ADT/Statistic.h"
13 #include "llvm/ADT/StringSwitch.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 namespace {
26 namespace stats {
27 STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations");
28 }
29 }
30
print(raw_ostream & OS) const31 void MCExpr::print(raw_ostream &OS) const {
32 switch (getKind()) {
33 case MCExpr::Target:
34 return cast<MCTargetExpr>(this)->PrintImpl(OS);
35 case MCExpr::Constant:
36 OS << cast<MCConstantExpr>(*this).getValue();
37 return;
38
39 case MCExpr::SymbolRef: {
40 const MCSymbolRefExpr &SRE = cast<MCSymbolRefExpr>(*this);
41 const MCSymbol &Sym = SRE.getSymbol();
42 // Parenthesize names that start with $ so that they don't look like
43 // absolute names.
44 bool UseParens = Sym.getName()[0] == '$';
45
46 if (SRE.getKind() == MCSymbolRefExpr::VK_PPC_DARWIN_HA16 ||
47 SRE.getKind() == MCSymbolRefExpr::VK_PPC_DARWIN_LO16) {
48 OS << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
49 UseParens = true;
50 }
51
52 if (UseParens)
53 OS << '(' << Sym << ')';
54 else
55 OS << Sym;
56
57 if (SRE.getKind() == MCSymbolRefExpr::VK_ARM_NONE ||
58 SRE.getKind() == MCSymbolRefExpr::VK_ARM_PLT ||
59 SRE.getKind() == MCSymbolRefExpr::VK_ARM_TLSGD ||
60 SRE.getKind() == MCSymbolRefExpr::VK_ARM_GOT ||
61 SRE.getKind() == MCSymbolRefExpr::VK_ARM_GOTOFF ||
62 SRE.getKind() == MCSymbolRefExpr::VK_ARM_TPOFF ||
63 SRE.getKind() == MCSymbolRefExpr::VK_ARM_GOTTPOFF ||
64 SRE.getKind() == MCSymbolRefExpr::VK_ARM_TARGET1 ||
65 SRE.getKind() == MCSymbolRefExpr::VK_ARM_TARGET2 ||
66 SRE.getKind() == MCSymbolRefExpr::VK_ARM_PREL31)
67 OS << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
68 else if (SRE.getKind() != MCSymbolRefExpr::VK_None &&
69 SRE.getKind() != MCSymbolRefExpr::VK_PPC_DARWIN_HA16 &&
70 SRE.getKind() != MCSymbolRefExpr::VK_PPC_DARWIN_LO16)
71 OS << '@' << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
72
73 return;
74 }
75
76 case MCExpr::Unary: {
77 const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this);
78 switch (UE.getOpcode()) {
79 case MCUnaryExpr::LNot: OS << '!'; break;
80 case MCUnaryExpr::Minus: OS << '-'; break;
81 case MCUnaryExpr::Not: OS << '~'; break;
82 case MCUnaryExpr::Plus: OS << '+'; break;
83 }
84 OS << *UE.getSubExpr();
85 return;
86 }
87
88 case MCExpr::Binary: {
89 const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this);
90
91 // Only print parens around the LHS if it is non-trivial.
92 if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) {
93 OS << *BE.getLHS();
94 } else {
95 OS << '(' << *BE.getLHS() << ')';
96 }
97
98 switch (BE.getOpcode()) {
99 case MCBinaryExpr::Add:
100 // Print "X-42" instead of "X+-42".
101 if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) {
102 if (RHSC->getValue() < 0) {
103 OS << RHSC->getValue();
104 return;
105 }
106 }
107
108 OS << '+';
109 break;
110 case MCBinaryExpr::And: OS << '&'; break;
111 case MCBinaryExpr::Div: OS << '/'; break;
112 case MCBinaryExpr::EQ: OS << "=="; break;
113 case MCBinaryExpr::GT: OS << '>'; break;
114 case MCBinaryExpr::GTE: OS << ">="; break;
115 case MCBinaryExpr::LAnd: OS << "&&"; break;
116 case MCBinaryExpr::LOr: OS << "||"; break;
117 case MCBinaryExpr::LT: OS << '<'; break;
118 case MCBinaryExpr::LTE: OS << "<="; break;
119 case MCBinaryExpr::Mod: OS << '%'; break;
120 case MCBinaryExpr::Mul: OS << '*'; break;
121 case MCBinaryExpr::NE: OS << "!="; break;
122 case MCBinaryExpr::Or: OS << '|'; break;
123 case MCBinaryExpr::Shl: OS << "<<"; break;
124 case MCBinaryExpr::Shr: OS << ">>"; break;
125 case MCBinaryExpr::Sub: OS << '-'; break;
126 case MCBinaryExpr::Xor: OS << '^'; break;
127 }
128
129 // Only print parens around the LHS if it is non-trivial.
130 if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) {
131 OS << *BE.getRHS();
132 } else {
133 OS << '(' << *BE.getRHS() << ')';
134 }
135 return;
136 }
137 }
138
139 llvm_unreachable("Invalid expression kind!");
140 }
141
142 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const143 void MCExpr::dump() const {
144 print(dbgs());
145 dbgs() << '\n';
146 }
147 #endif
148
149 /* *** */
150
Create(Opcode Opc,const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)151 const MCBinaryExpr *MCBinaryExpr::Create(Opcode Opc, const MCExpr *LHS,
152 const MCExpr *RHS, MCContext &Ctx) {
153 return new (Ctx) MCBinaryExpr(Opc, LHS, RHS);
154 }
155
Create(Opcode Opc,const MCExpr * Expr,MCContext & Ctx)156 const MCUnaryExpr *MCUnaryExpr::Create(Opcode Opc, const MCExpr *Expr,
157 MCContext &Ctx) {
158 return new (Ctx) MCUnaryExpr(Opc, Expr);
159 }
160
Create(int64_t Value,MCContext & Ctx)161 const MCConstantExpr *MCConstantExpr::Create(int64_t Value, MCContext &Ctx) {
162 return new (Ctx) MCConstantExpr(Value);
163 }
164
165 /* *** */
166
Create(const MCSymbol * Sym,VariantKind Kind,MCContext & Ctx)167 const MCSymbolRefExpr *MCSymbolRefExpr::Create(const MCSymbol *Sym,
168 VariantKind Kind,
169 MCContext &Ctx) {
170 return new (Ctx) MCSymbolRefExpr(Sym, Kind);
171 }
172
Create(StringRef Name,VariantKind Kind,MCContext & Ctx)173 const MCSymbolRefExpr *MCSymbolRefExpr::Create(StringRef Name, VariantKind Kind,
174 MCContext &Ctx) {
175 return Create(Ctx.GetOrCreateSymbol(Name), Kind, Ctx);
176 }
177
getVariantKindName(VariantKind Kind)178 StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
179 switch (Kind) {
180 case VK_Invalid: return "<<invalid>>";
181 case VK_None: return "<<none>>";
182
183 case VK_GOT: return "GOT";
184 case VK_GOTOFF: return "GOTOFF";
185 case VK_GOTPCREL: return "GOTPCREL";
186 case VK_GOTTPOFF: return "GOTTPOFF";
187 case VK_INDNTPOFF: return "INDNTPOFF";
188 case VK_NTPOFF: return "NTPOFF";
189 case VK_GOTNTPOFF: return "GOTNTPOFF";
190 case VK_PLT: return "PLT";
191 case VK_TLSGD: return "TLSGD";
192 case VK_TLSLD: return "TLSLD";
193 case VK_TLSLDM: return "TLSLDM";
194 case VK_TPOFF: return "TPOFF";
195 case VK_DTPOFF: return "DTPOFF";
196 case VK_TLVP: return "TLVP";
197 case VK_SECREL: return "SECREL";
198 case VK_ARM_NONE: return "(NONE)";
199 case VK_ARM_PLT: return "(PLT)";
200 case VK_ARM_GOT: return "(GOT)";
201 case VK_ARM_GOTOFF: return "(GOTOFF)";
202 case VK_ARM_TPOFF: return "(tpoff)";
203 case VK_ARM_GOTTPOFF: return "(gottpoff)";
204 case VK_ARM_TLSGD: return "(tlsgd)";
205 case VK_ARM_TARGET1: return "(target1)";
206 case VK_ARM_TARGET2: return "(target2)";
207 case VK_ARM_PREL31: return "(prel31)";
208 case VK_PPC_TOC: return "tocbase";
209 case VK_PPC_TOC_ENTRY: return "toc";
210 case VK_PPC_DARWIN_HA16: return "ha16";
211 case VK_PPC_DARWIN_LO16: return "lo16";
212 case VK_PPC_GAS_HA16: return "ha";
213 case VK_PPC_GAS_LO16: return "l";
214 case VK_PPC_TPREL16_HA: return "tprel@ha";
215 case VK_PPC_TPREL16_LO: return "tprel@l";
216 case VK_PPC_DTPREL16_HA: return "dtprel@ha";
217 case VK_PPC_DTPREL16_LO: return "dtprel@l";
218 case VK_PPC_TOC16_HA: return "toc@ha";
219 case VK_PPC_TOC16_LO: return "toc@l";
220 case VK_PPC_GOT_TPREL16_HA: return "got@tprel@ha";
221 case VK_PPC_GOT_TPREL16_LO: return "got@tprel@l";
222 case VK_PPC_TLS: return "tls";
223 case VK_PPC_GOT_TLSGD16_HA: return "got@tlsgd@ha";
224 case VK_PPC_GOT_TLSGD16_LO: return "got@tlsgd@l";
225 case VK_PPC_GOT_TLSLD16_HA: return "got@tlsld@ha";
226 case VK_PPC_GOT_TLSLD16_LO: return "got@tlsld@l";
227 case VK_PPC_TLSGD: return "tlsgd";
228 case VK_PPC_TLSLD: return "tlsld";
229 case VK_Mips_GPREL: return "GPREL";
230 case VK_Mips_GOT_CALL: return "GOT_CALL";
231 case VK_Mips_GOT16: return "GOT16";
232 case VK_Mips_GOT: return "GOT";
233 case VK_Mips_ABS_HI: return "ABS_HI";
234 case VK_Mips_ABS_LO: return "ABS_LO";
235 case VK_Mips_TLSGD: return "TLSGD";
236 case VK_Mips_TLSLDM: return "TLSLDM";
237 case VK_Mips_DTPREL_HI: return "DTPREL_HI";
238 case VK_Mips_DTPREL_LO: return "DTPREL_LO";
239 case VK_Mips_GOTTPREL: return "GOTTPREL";
240 case VK_Mips_TPREL_HI: return "TPREL_HI";
241 case VK_Mips_TPREL_LO: return "TPREL_LO";
242 case VK_Mips_GPOFF_HI: return "GPOFF_HI";
243 case VK_Mips_GPOFF_LO: return "GPOFF_LO";
244 case VK_Mips_GOT_DISP: return "GOT_DISP";
245 case VK_Mips_GOT_PAGE: return "GOT_PAGE";
246 case VK_Mips_GOT_OFST: return "GOT_OFST";
247 case VK_Mips_HIGHER: return "HIGHER";
248 case VK_Mips_HIGHEST: return "HIGHEST";
249 case VK_Mips_GOT_HI16: return "GOT_HI16";
250 case VK_Mips_GOT_LO16: return "GOT_LO16";
251 case VK_Mips_CALL_HI16: return "CALL_HI16";
252 case VK_Mips_CALL_LO16: return "CALL_LO16";
253 }
254 llvm_unreachable("Invalid variant kind");
255 }
256
257 MCSymbolRefExpr::VariantKind
getVariantKindForName(StringRef Name)258 MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
259 return StringSwitch<VariantKind>(Name)
260 .Case("GOT", VK_GOT)
261 .Case("got", VK_GOT)
262 .Case("GOTOFF", VK_GOTOFF)
263 .Case("gotoff", VK_GOTOFF)
264 .Case("GOTPCREL", VK_GOTPCREL)
265 .Case("gotpcrel", VK_GOTPCREL)
266 .Case("GOTTPOFF", VK_GOTTPOFF)
267 .Case("gottpoff", VK_GOTTPOFF)
268 .Case("INDNTPOFF", VK_INDNTPOFF)
269 .Case("indntpoff", VK_INDNTPOFF)
270 .Case("NTPOFF", VK_NTPOFF)
271 .Case("ntpoff", VK_NTPOFF)
272 .Case("GOTNTPOFF", VK_GOTNTPOFF)
273 .Case("gotntpoff", VK_GOTNTPOFF)
274 .Case("PLT", VK_PLT)
275 .Case("plt", VK_PLT)
276 .Case("TLSGD", VK_TLSGD)
277 .Case("tlsgd", VK_TLSGD)
278 .Case("TLSLD", VK_TLSLD)
279 .Case("tlsld", VK_TLSLD)
280 .Case("TLSLDM", VK_TLSLDM)
281 .Case("tlsldm", VK_TLSLDM)
282 .Case("TPOFF", VK_TPOFF)
283 .Case("tpoff", VK_TPOFF)
284 .Case("DTPOFF", VK_DTPOFF)
285 .Case("dtpoff", VK_DTPOFF)
286 .Case("TLVP", VK_TLVP)
287 .Case("tlvp", VK_TLVP)
288 .Default(VK_Invalid);
289 }
290
291 /* *** */
292
anchor()293 void MCTargetExpr::anchor() {}
294
295 /* *** */
296
EvaluateAsAbsolute(int64_t & Res) const297 bool MCExpr::EvaluateAsAbsolute(int64_t &Res) const {
298 return EvaluateAsAbsolute(Res, 0, 0, 0);
299 }
300
EvaluateAsAbsolute(int64_t & Res,const MCAsmLayout & Layout) const301 bool MCExpr::EvaluateAsAbsolute(int64_t &Res,
302 const MCAsmLayout &Layout) const {
303 return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, 0);
304 }
305
EvaluateAsAbsolute(int64_t & Res,const MCAsmLayout & Layout,const SectionAddrMap & Addrs) const306 bool MCExpr::EvaluateAsAbsolute(int64_t &Res,
307 const MCAsmLayout &Layout,
308 const SectionAddrMap &Addrs) const {
309 return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs);
310 }
311
EvaluateAsAbsolute(int64_t & Res,const MCAssembler & Asm) const312 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const {
313 return EvaluateAsAbsolute(Res, &Asm, 0, 0);
314 }
315
EvaluateAsAbsolute(int64_t & Res,const MCAssembler * Asm,const MCAsmLayout * Layout,const SectionAddrMap * Addrs) const316 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
317 const MCAsmLayout *Layout,
318 const SectionAddrMap *Addrs) const {
319 MCValue Value;
320
321 // Fast path constants.
322 if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) {
323 Res = CE->getValue();
324 return true;
325 }
326
327 // FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us
328 // absolutize differences across sections and that is what the MachO writer
329 // uses Addrs for.
330 bool IsRelocatable =
331 EvaluateAsRelocatableImpl(Value, Asm, Layout, Addrs, /*InSet*/ Addrs);
332
333 // Record the current value.
334 Res = Value.getConstant();
335
336 return IsRelocatable && Value.isAbsolute();
337 }
338
339 /// \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)340 static void AttemptToFoldSymbolOffsetDifference(const MCAssembler *Asm,
341 const MCAsmLayout *Layout,
342 const SectionAddrMap *Addrs,
343 bool InSet,
344 const MCSymbolRefExpr *&A,
345 const MCSymbolRefExpr *&B,
346 int64_t &Addend) {
347 if (!A || !B)
348 return;
349
350 const MCSymbol &SA = A->getSymbol();
351 const MCSymbol &SB = B->getSymbol();
352
353 if (SA.isUndefined() || SB.isUndefined())
354 return;
355
356 if (!Asm->getWriter().IsSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet))
357 return;
358
359 MCSymbolData &AD = Asm->getSymbolData(SA);
360 MCSymbolData &BD = Asm->getSymbolData(SB);
361
362 if (AD.getFragment() == BD.getFragment()) {
363 Addend += (AD.getOffset() - BD.getOffset());
364
365 // Pointers to Thumb symbols need to have their low-bit set to allow
366 // for interworking.
367 if (Asm->isThumbFunc(&SA))
368 Addend |= 1;
369
370 // Clear the symbol expr pointers to indicate we have folded these
371 // operands.
372 A = B = 0;
373 return;
374 }
375
376 if (!Layout)
377 return;
378
379 const MCSectionData &SecA = *AD.getFragment()->getParent();
380 const MCSectionData &SecB = *BD.getFragment()->getParent();
381
382 if ((&SecA != &SecB) && !Addrs)
383 return;
384
385 // Eagerly evaluate.
386 Addend += (Layout->getSymbolOffset(&Asm->getSymbolData(A->getSymbol())) -
387 Layout->getSymbolOffset(&Asm->getSymbolData(B->getSymbol())));
388 if (Addrs && (&SecA != &SecB))
389 Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB));
390
391 // Pointers to Thumb symbols need to have their low-bit set to allow
392 // for interworking.
393 if (Asm->isThumbFunc(&SA))
394 Addend |= 1;
395
396 // Clear the symbol expr pointers to indicate we have folded these
397 // operands.
398 A = B = 0;
399 }
400
401 /// \brief Evaluate the result of an add between (conceptually) two MCValues.
402 ///
403 /// This routine conceptually attempts to construct an MCValue:
404 /// Result = (Result_A - Result_B + Result_Cst)
405 /// from two MCValue's LHS and RHS where
406 /// Result = LHS + RHS
407 /// and
408 /// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
409 ///
410 /// This routine attempts to aggresively fold the operands such that the result
411 /// is representable in an MCValue, but may not always succeed.
412 ///
413 /// \returns True on success, false if the result is not representable in an
414 /// MCValue.
415
416 /// NOTE: It is really important to have both the Asm and Layout arguments.
417 /// They might look redundant, but this function can be used before layout
418 /// is done (see the object streamer for example) and having the Asm argument
419 /// lets us avoid relaxations early.
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)420 static bool EvaluateSymbolicAdd(const MCAssembler *Asm,
421 const MCAsmLayout *Layout,
422 const SectionAddrMap *Addrs,
423 bool InSet,
424 const MCValue &LHS,const MCSymbolRefExpr *RHS_A,
425 const MCSymbolRefExpr *RHS_B, int64_t RHS_Cst,
426 MCValue &Res) {
427 // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy
428 // about dealing with modifiers. This will ultimately bite us, one day.
429 const MCSymbolRefExpr *LHS_A = LHS.getSymA();
430 const MCSymbolRefExpr *LHS_B = LHS.getSymB();
431 int64_t LHS_Cst = LHS.getConstant();
432
433 // Fold the result constant immediately.
434 int64_t Result_Cst = LHS_Cst + RHS_Cst;
435
436 assert((!Layout || Asm) &&
437 "Must have an assembler object if layout is given!");
438
439 // If we have a layout, we can fold resolved differences.
440 if (Asm) {
441 // First, fold out any differences which are fully resolved. By
442 // reassociating terms in
443 // Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
444 // we have the four possible differences:
445 // (LHS_A - LHS_B),
446 // (LHS_A - RHS_B),
447 // (RHS_A - LHS_B),
448 // (RHS_A - RHS_B).
449 // Since we are attempting to be as aggressive as possible about folding, we
450 // attempt to evaluate each possible alternative.
451 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B,
452 Result_Cst);
453 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B,
454 Result_Cst);
455 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B,
456 Result_Cst);
457 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B,
458 Result_Cst);
459 }
460
461 // We can't represent the addition or subtraction of two symbols.
462 if ((LHS_A && RHS_A) || (LHS_B && RHS_B))
463 return false;
464
465 // At this point, we have at most one additive symbol and one subtractive
466 // symbol -- find them.
467 const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A;
468 const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B;
469
470 // If we have a negated symbol, then we must have also have a non-negated
471 // symbol in order to encode the expression.
472 if (B && !A)
473 return false;
474
475 Res = MCValue::get(A, B, Result_Cst);
476 return true;
477 }
478
EvaluateAsRelocatable(MCValue & Res,const MCAsmLayout & Layout) const479 bool MCExpr::EvaluateAsRelocatable(MCValue &Res,
480 const MCAsmLayout &Layout) const {
481 return EvaluateAsRelocatableImpl(Res, &Layout.getAssembler(), &Layout,
482 0, false);
483 }
484
EvaluateAsRelocatableImpl(MCValue & Res,const MCAssembler * Asm,const MCAsmLayout * Layout,const SectionAddrMap * Addrs,bool InSet) const485 bool MCExpr::EvaluateAsRelocatableImpl(MCValue &Res,
486 const MCAssembler *Asm,
487 const MCAsmLayout *Layout,
488 const SectionAddrMap *Addrs,
489 bool InSet) const {
490 ++stats::MCExprEvaluate;
491
492 switch (getKind()) {
493 case Target:
494 return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout);
495
496 case Constant:
497 Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
498 return true;
499
500 case SymbolRef: {
501 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
502 const MCSymbol &Sym = SRE->getSymbol();
503
504 // Evaluate recursively if this is a variable.
505 if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None) {
506 bool Ret = Sym.getVariableValue()->EvaluateAsRelocatableImpl(Res, Asm,
507 Layout,
508 Addrs,
509 true);
510 // If we failed to simplify this to a constant, let the target
511 // handle it.
512 if (Ret && !Res.getSymA() && !Res.getSymB())
513 return true;
514 }
515
516 Res = MCValue::get(SRE, 0, 0);
517 return true;
518 }
519
520 case Unary: {
521 const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
522 MCValue Value;
523
524 if (!AUE->getSubExpr()->EvaluateAsRelocatableImpl(Value, Asm, Layout,
525 Addrs, InSet))
526 return false;
527
528 switch (AUE->getOpcode()) {
529 case MCUnaryExpr::LNot:
530 if (!Value.isAbsolute())
531 return false;
532 Res = MCValue::get(!Value.getConstant());
533 break;
534 case MCUnaryExpr::Minus:
535 /// -(a - b + const) ==> (b - a - const)
536 if (Value.getSymA() && !Value.getSymB())
537 return false;
538 Res = MCValue::get(Value.getSymB(), Value.getSymA(),
539 -Value.getConstant());
540 break;
541 case MCUnaryExpr::Not:
542 if (!Value.isAbsolute())
543 return false;
544 Res = MCValue::get(~Value.getConstant());
545 break;
546 case MCUnaryExpr::Plus:
547 Res = Value;
548 break;
549 }
550
551 return true;
552 }
553
554 case Binary: {
555 const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
556 MCValue LHSValue, RHSValue;
557
558 if (!ABE->getLHS()->EvaluateAsRelocatableImpl(LHSValue, Asm, Layout,
559 Addrs, InSet) ||
560 !ABE->getRHS()->EvaluateAsRelocatableImpl(RHSValue, Asm, Layout,
561 Addrs, InSet))
562 return false;
563
564 // We only support a few operations on non-constant expressions, handle
565 // those first.
566 if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
567 switch (ABE->getOpcode()) {
568 default:
569 return false;
570 case MCBinaryExpr::Sub:
571 // Negate RHS and add.
572 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
573 RHSValue.getSymB(), RHSValue.getSymA(),
574 -RHSValue.getConstant(),
575 Res);
576
577 case MCBinaryExpr::Add:
578 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
579 RHSValue.getSymA(), RHSValue.getSymB(),
580 RHSValue.getConstant(),
581 Res);
582 }
583 }
584
585 // FIXME: We need target hooks for the evaluation. It may be limited in
586 // width, and gas defines the result of comparisons and right shifts
587 // differently from Apple as.
588 int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
589 int64_t Result = 0;
590 switch (ABE->getOpcode()) {
591 case MCBinaryExpr::Add: Result = LHS + RHS; break;
592 case MCBinaryExpr::And: Result = LHS & RHS; break;
593 case MCBinaryExpr::Div: Result = LHS / RHS; break;
594 case MCBinaryExpr::EQ: Result = LHS == RHS; break;
595 case MCBinaryExpr::GT: Result = LHS > RHS; break;
596 case MCBinaryExpr::GTE: Result = LHS >= RHS; break;
597 case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
598 case MCBinaryExpr::LOr: Result = LHS || RHS; break;
599 case MCBinaryExpr::LT: Result = LHS < RHS; break;
600 case MCBinaryExpr::LTE: Result = LHS <= RHS; break;
601 case MCBinaryExpr::Mod: Result = LHS % RHS; break;
602 case MCBinaryExpr::Mul: Result = LHS * RHS; break;
603 case MCBinaryExpr::NE: Result = LHS != RHS; break;
604 case MCBinaryExpr::Or: Result = LHS | RHS; break;
605 case MCBinaryExpr::Shl: Result = LHS << RHS; break;
606 case MCBinaryExpr::Shr: Result = LHS >> RHS; break;
607 case MCBinaryExpr::Sub: Result = LHS - RHS; break;
608 case MCBinaryExpr::Xor: Result = LHS ^ RHS; break;
609 }
610
611 Res = MCValue::get(Result);
612 return true;
613 }
614 }
615
616 llvm_unreachable("Invalid assembly expression kind!");
617 }
618
FindAssociatedSection() const619 const MCSection *MCExpr::FindAssociatedSection() const {
620 switch (getKind()) {
621 case Target:
622 // We never look through target specific expressions.
623 return cast<MCTargetExpr>(this)->FindAssociatedSection();
624
625 case Constant:
626 return MCSymbol::AbsolutePseudoSection;
627
628 case SymbolRef: {
629 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
630 const MCSymbol &Sym = SRE->getSymbol();
631
632 if (Sym.isDefined())
633 return &Sym.getSection();
634
635 return 0;
636 }
637
638 case Unary:
639 return cast<MCUnaryExpr>(this)->getSubExpr()->FindAssociatedSection();
640
641 case Binary: {
642 const MCBinaryExpr *BE = cast<MCBinaryExpr>(this);
643 const MCSection *LHS_S = BE->getLHS()->FindAssociatedSection();
644 const MCSection *RHS_S = BE->getRHS()->FindAssociatedSection();
645
646 // If either section is absolute, return the other.
647 if (LHS_S == MCSymbol::AbsolutePseudoSection)
648 return RHS_S;
649 if (RHS_S == MCSymbol::AbsolutePseudoSection)
650 return LHS_S;
651
652 // Otherwise, return the first non-null section.
653 return LHS_S ? LHS_S : RHS_S;
654 }
655 }
656
657 llvm_unreachable("Invalid assembly expression kind!");
658 }
659