MCExpr.cpp revision d2849572463da994c685b3bd7a60d5a7566c01e3 
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"
23using namespace llvm;
24
25namespace {
26namespace stats {
27STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations");
28}
29}
30
31void 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    if (UseParens)
46      OS << '(' << Sym << ')';
47    else
48      OS << Sym;
49
50    if (SRE.getKind() == MCSymbolRefExpr::VK_ARM_NONE ||
51        SRE.getKind() == MCSymbolRefExpr::VK_ARM_PLT ||
52        SRE.getKind() == MCSymbolRefExpr::VK_ARM_TLSGD ||
53        SRE.getKind() == MCSymbolRefExpr::VK_ARM_GOT ||
54        SRE.getKind() == MCSymbolRefExpr::VK_ARM_GOTOFF ||
55        SRE.getKind() == MCSymbolRefExpr::VK_ARM_TPOFF ||
56        SRE.getKind() == MCSymbolRefExpr::VK_ARM_GOTTPOFF ||
57        SRE.getKind() == MCSymbolRefExpr::VK_ARM_TARGET1 ||
58        SRE.getKind() == MCSymbolRefExpr::VK_ARM_TARGET2 ||
59        SRE.getKind() == MCSymbolRefExpr::VK_ARM_PREL31)
60      OS << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
61    else if (SRE.getKind() != MCSymbolRefExpr::VK_None)
62      OS << '@' << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
63
64    return;
65  }
66
67  case MCExpr::Unary: {
68    const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this);
69    switch (UE.getOpcode()) {
70    case MCUnaryExpr::LNot:  OS << '!'; break;
71    case MCUnaryExpr::Minus: OS << '-'; break;
72    case MCUnaryExpr::Not:   OS << '~'; break;
73    case MCUnaryExpr::Plus:  OS << '+'; break;
74    }
75    OS << *UE.getSubExpr();
76    return;
77  }
78
79  case MCExpr::Binary: {
80    const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this);
81
82    // Only print parens around the LHS if it is non-trivial.
83    if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) {
84      OS << *BE.getLHS();
85    } else {
86      OS << '(' << *BE.getLHS() << ')';
87    }
88
89    switch (BE.getOpcode()) {
90    case MCBinaryExpr::Add:
91      // Print "X-42" instead of "X+-42".
92      if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) {
93        if (RHSC->getValue() < 0) {
94          OS << RHSC->getValue();
95          return;
96        }
97      }
98
99      OS <<  '+';
100      break;
101    case MCBinaryExpr::And:  OS <<  '&'; break;
102    case MCBinaryExpr::Div:  OS <<  '/'; break;
103    case MCBinaryExpr::EQ:   OS << "=="; break;
104    case MCBinaryExpr::GT:   OS <<  '>'; break;
105    case MCBinaryExpr::GTE:  OS << ">="; break;
106    case MCBinaryExpr::LAnd: OS << "&&"; break;
107    case MCBinaryExpr::LOr:  OS << "||"; break;
108    case MCBinaryExpr::LT:   OS <<  '<'; break;
109    case MCBinaryExpr::LTE:  OS << "<="; break;
110    case MCBinaryExpr::Mod:  OS <<  '%'; break;
111    case MCBinaryExpr::Mul:  OS <<  '*'; break;
112    case MCBinaryExpr::NE:   OS << "!="; break;
113    case MCBinaryExpr::Or:   OS <<  '|'; break;
114    case MCBinaryExpr::Shl:  OS << "<<"; break;
115    case MCBinaryExpr::Shr:  OS << ">>"; break;
116    case MCBinaryExpr::Sub:  OS <<  '-'; break;
117    case MCBinaryExpr::Xor:  OS <<  '^'; break;
118    }
119
120    // Only print parens around the LHS if it is non-trivial.
121    if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) {
122      OS << *BE.getRHS();
123    } else {
124      OS << '(' << *BE.getRHS() << ')';
125    }
126    return;
127  }
128  }
129
130  llvm_unreachable("Invalid expression kind!");
131}
132
133#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
134void MCExpr::dump() const {
135  print(dbgs());
136  dbgs() << '\n';
137}
138#endif
139
140/* *** */
141
142const MCBinaryExpr *MCBinaryExpr::Create(Opcode Opc, const MCExpr *LHS,
143                                         const MCExpr *RHS, MCContext &Ctx) {
144  return new (Ctx) MCBinaryExpr(Opc, LHS, RHS);
145}
146
147const MCUnaryExpr *MCUnaryExpr::Create(Opcode Opc, const MCExpr *Expr,
148                                       MCContext &Ctx) {
149  return new (Ctx) MCUnaryExpr(Opc, Expr);
150}
151
152const MCConstantExpr *MCConstantExpr::Create(int64_t Value, MCContext &Ctx) {
153  return new (Ctx) MCConstantExpr(Value);
154}
155
156/* *** */
157
158const MCSymbolRefExpr *MCSymbolRefExpr::Create(const MCSymbol *Sym,
159                                               VariantKind Kind,
160                                               MCContext &Ctx) {
161  return new (Ctx) MCSymbolRefExpr(Sym, Kind);
162}
163
164const MCSymbolRefExpr *MCSymbolRefExpr::Create(StringRef Name, VariantKind Kind,
165                                               MCContext &Ctx) {
166  return Create(Ctx.GetOrCreateSymbol(Name), Kind, Ctx);
167}
168
169StringRef 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_SECREL: return "SECREL32";
189  case VK_ARM_NONE: return "(NONE)";
190  case VK_ARM_PLT: return "(PLT)";
191  case VK_ARM_GOT: return "(GOT)";
192  case VK_ARM_GOTOFF: return "(GOTOFF)";
193  case VK_ARM_TPOFF: return "(tpoff)";
194  case VK_ARM_GOTTPOFF: return "(gottpoff)";
195  case VK_ARM_TLSGD: return "(tlsgd)";
196  case VK_ARM_TARGET1: return "(target1)";
197  case VK_ARM_TARGET2: return "(target2)";
198  case VK_ARM_PREL31: return "(prel31)";
199  case VK_PPC_LO: return "l";
200  case VK_PPC_HI: return "h";
201  case VK_PPC_HA: return "ha";
202  case VK_PPC_TOCBASE: return "tocbase";
203  case VK_PPC_TOC: return "toc";
204  case VK_PPC_TOC_LO: return "toc@l";
205  case VK_PPC_TOC_HA: return "toc@ha";
206  case VK_PPC_TPREL_LO: return "tprel@l";
207  case VK_PPC_TPREL_HA: return "tprel@ha";
208  case VK_PPC_DTPREL_LO: return "dtprel@l";
209  case VK_PPC_DTPREL_HA: return "dtprel@ha";
210  case VK_PPC_GOT_TPREL_LO: return "got@tprel@l";
211  case VK_PPC_GOT_TPREL_HA: return "got@tprel@ha";
212  case VK_PPC_TLS: return "tls";
213  case VK_PPC_GOT_TLSGD_LO: return "got@tlsgd@l";
214  case VK_PPC_GOT_TLSGD_HA: return "got@tlsgd@ha";
215  case VK_PPC_TLSGD: return "tlsgd";
216  case VK_PPC_GOT_TLSLD_LO: return "got@tlsld@l";
217  case VK_PPC_GOT_TLSLD_HA: return "got@tlsld@ha";
218  case VK_PPC_TLSLD: return "tlsld";
219  case VK_Mips_GPREL: return "GPREL";
220  case VK_Mips_GOT_CALL: return "GOT_CALL";
221  case VK_Mips_GOT16: return "GOT16";
222  case VK_Mips_GOT: return "GOT";
223  case VK_Mips_ABS_HI: return "ABS_HI";
224  case VK_Mips_ABS_LO: return "ABS_LO";
225  case VK_Mips_TLSGD: return "TLSGD";
226  case VK_Mips_TLSLDM: return "TLSLDM";
227  case VK_Mips_DTPREL_HI: return "DTPREL_HI";
228  case VK_Mips_DTPREL_LO: return "DTPREL_LO";
229  case VK_Mips_GOTTPREL: return "GOTTPREL";
230  case VK_Mips_TPREL_HI: return "TPREL_HI";
231  case VK_Mips_TPREL_LO: return "TPREL_LO";
232  case VK_Mips_GPOFF_HI: return "GPOFF_HI";
233  case VK_Mips_GPOFF_LO: return "GPOFF_LO";
234  case VK_Mips_GOT_DISP: return "GOT_DISP";
235  case VK_Mips_GOT_PAGE: return "GOT_PAGE";
236  case VK_Mips_GOT_OFST: return "GOT_OFST";
237  case VK_Mips_HIGHER:   return "HIGHER";
238  case VK_Mips_HIGHEST:  return "HIGHEST";
239  case VK_Mips_GOT_HI16: return "GOT_HI16";
240  case VK_Mips_GOT_LO16: return "GOT_LO16";
241  case VK_Mips_CALL_HI16: return "CALL_HI16";
242  case VK_Mips_CALL_LO16: return "CALL_LO16";
243  case VK_COFF_IMGREL32: return "IMGREL32";
244  }
245  llvm_unreachable("Invalid variant kind");
246}
247
248MCSymbolRefExpr::VariantKind
249MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
250  return StringSwitch<VariantKind>(Name)
251    .Case("GOT", VK_GOT)
252    .Case("got", VK_GOT)
253    .Case("GOTOFF", VK_GOTOFF)
254    .Case("gotoff", VK_GOTOFF)
255    .Case("GOTPCREL", VK_GOTPCREL)
256    .Case("gotpcrel", VK_GOTPCREL)
257    .Case("GOTTPOFF", VK_GOTTPOFF)
258    .Case("gottpoff", VK_GOTTPOFF)
259    .Case("INDNTPOFF", VK_INDNTPOFF)
260    .Case("indntpoff", VK_INDNTPOFF)
261    .Case("NTPOFF", VK_NTPOFF)
262    .Case("ntpoff", VK_NTPOFF)
263    .Case("GOTNTPOFF", VK_GOTNTPOFF)
264    .Case("gotntpoff", VK_GOTNTPOFF)
265    .Case("PLT", VK_PLT)
266    .Case("plt", VK_PLT)
267    .Case("TLSGD", VK_TLSGD)
268    .Case("tlsgd", VK_TLSGD)
269    .Case("TLSLD", VK_TLSLD)
270    .Case("tlsld", VK_TLSLD)
271    .Case("TLSLDM", VK_TLSLDM)
272    .Case("tlsldm", VK_TLSLDM)
273    .Case("TPOFF", VK_TPOFF)
274    .Case("tpoff", VK_TPOFF)
275    .Case("DTPOFF", VK_DTPOFF)
276    .Case("dtpoff", VK_DTPOFF)
277    .Case("TLVP", VK_TLVP)
278    .Case("tlvp", VK_TLVP)
279    .Case("IMGREL", VK_COFF_IMGREL32)
280    .Case("imgrel", VK_COFF_IMGREL32)
281    .Case("SECREL32", VK_SECREL)
282    .Case("secrel32", VK_SECREL)
283    .Case("L", VK_PPC_LO)
284    .Case("l", VK_PPC_LO)
285    .Case("H", VK_PPC_HI)
286    .Case("h", VK_PPC_HI)
287    .Case("HA", VK_PPC_HA)
288    .Case("ha", VK_PPC_HA)
289    .Case("TOCBASE", VK_PPC_TOCBASE)
290    .Case("tocbase", VK_PPC_TOCBASE)
291    .Case("TOC", VK_PPC_TOC)
292    .Case("toc", VK_PPC_TOC)
293    .Case("TOC@L", VK_PPC_TOC_LO)
294    .Case("toc@l", VK_PPC_TOC_LO)
295    .Case("TOC@HA", VK_PPC_TOC_HA)
296    .Case("toc@ha", VK_PPC_TOC_HA)
297    .Case("TLS", VK_PPC_TLS)
298    .Case("tls", VK_PPC_TLS)
299    .Case("TPREL@L", VK_PPC_TPREL_LO)
300    .Case("tprel@l", VK_PPC_TPREL_LO)
301    .Case("TPREL@HA", VK_PPC_TPREL_HA)
302    .Case("tprel@ha", VK_PPC_TPREL_HA)
303    .Case("DTPREL@L", VK_PPC_DTPREL_LO)
304    .Case("dtprel@l", VK_PPC_DTPREL_LO)
305    .Case("DTPREL@HA", VK_PPC_DTPREL_HA)
306    .Case("dtprel@ha", VK_PPC_DTPREL_HA)
307    .Case("GOT@TPREL@L", VK_PPC_GOT_TPREL_LO)
308    .Case("got@tprel@l", VK_PPC_GOT_TPREL_LO)
309    .Case("GOT@TPREL@HA", VK_PPC_GOT_TPREL_HA)
310    .Case("got@tprel@ha", VK_PPC_GOT_TPREL_HA)
311    .Case("GOT@TLSGD@L", VK_PPC_GOT_TLSGD_LO)
312    .Case("got@tlsgd@l", VK_PPC_GOT_TLSGD_LO)
313    .Case("GOT@TLSGD@HA", VK_PPC_GOT_TLSGD_HA)
314    .Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD_HA)
315    .Case("GOT@TLSLD@L", VK_PPC_GOT_TLSLD_LO)
316    .Case("got@tlsld@l", VK_PPC_GOT_TLSLD_LO)
317    .Case("GOT@TLSLD@HA", VK_PPC_GOT_TLSLD_HA)
318    .Case("got@tlsld@ha", VK_PPC_GOT_TLSLD_HA)
319    .Default(VK_Invalid);
320}
321
322/* *** */
323
324void MCTargetExpr::anchor() {}
325
326/* *** */
327
328bool MCExpr::EvaluateAsAbsolute(int64_t &Res) const {
329  return EvaluateAsAbsolute(Res, 0, 0, 0);
330}
331
332bool MCExpr::EvaluateAsAbsolute(int64_t &Res,
333                                const MCAsmLayout &Layout) const {
334  return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, 0);
335}
336
337bool MCExpr::EvaluateAsAbsolute(int64_t &Res,
338                                const MCAsmLayout &Layout,
339                                const SectionAddrMap &Addrs) const {
340  return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs);
341}
342
343bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const {
344  return EvaluateAsAbsolute(Res, &Asm, 0, 0);
345}
346
347bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
348                                const MCAsmLayout *Layout,
349                                const SectionAddrMap *Addrs) const {
350  MCValue Value;
351
352  // Fast path constants.
353  if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) {
354    Res = CE->getValue();
355    return true;
356  }
357
358  // FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us
359  // absolutize differences across sections and that is what the MachO writer
360  // uses Addrs for.
361  bool IsRelocatable =
362    EvaluateAsRelocatableImpl(Value, Asm, Layout, Addrs, /*InSet*/ Addrs);
363
364  // Record the current value.
365  Res = Value.getConstant();
366
367  return IsRelocatable && Value.isAbsolute();
368}
369
370/// \brief Helper method for \see EvaluateSymbolAdd().
371static void AttemptToFoldSymbolOffsetDifference(const MCAssembler *Asm,
372                                                const MCAsmLayout *Layout,
373                                                const SectionAddrMap *Addrs,
374                                                bool InSet,
375                                                const MCSymbolRefExpr *&A,
376                                                const MCSymbolRefExpr *&B,
377                                                int64_t &Addend) {
378  if (!A || !B)
379    return;
380
381  const MCSymbol &SA = A->getSymbol();
382  const MCSymbol &SB = B->getSymbol();
383
384  if (SA.isUndefined() || SB.isUndefined())
385    return;
386
387  if (!Asm->getWriter().IsSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet))
388    return;
389
390  MCSymbolData &AD = Asm->getSymbolData(SA);
391  MCSymbolData &BD = Asm->getSymbolData(SB);
392
393  if (AD.getFragment() == BD.getFragment()) {
394    Addend += (AD.getOffset() - BD.getOffset());
395
396    // Pointers to Thumb symbols need to have their low-bit set to allow
397    // for interworking.
398    if (Asm->isThumbFunc(&SA))
399      Addend |= 1;
400
401    // Clear the symbol expr pointers to indicate we have folded these
402    // operands.
403    A = B = 0;
404    return;
405  }
406
407  if (!Layout)
408    return;
409
410  const MCSectionData &SecA = *AD.getFragment()->getParent();
411  const MCSectionData &SecB = *BD.getFragment()->getParent();
412
413  if ((&SecA != &SecB) && !Addrs)
414    return;
415
416  // Eagerly evaluate.
417  Addend += (Layout->getSymbolOffset(&Asm->getSymbolData(A->getSymbol())) -
418             Layout->getSymbolOffset(&Asm->getSymbolData(B->getSymbol())));
419  if (Addrs && (&SecA != &SecB))
420    Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB));
421
422  // Pointers to Thumb symbols need to have their low-bit set to allow
423  // for interworking.
424  if (Asm->isThumbFunc(&SA))
425    Addend |= 1;
426
427  // Clear the symbol expr pointers to indicate we have folded these
428  // operands.
429  A = B = 0;
430}
431
432/// \brief Evaluate the result of an add between (conceptually) two MCValues.
433///
434/// This routine conceptually attempts to construct an MCValue:
435///   Result = (Result_A - Result_B + Result_Cst)
436/// from two MCValue's LHS and RHS where
437///   Result = LHS + RHS
438/// and
439///   Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
440///
441/// This routine attempts to aggresively fold the operands such that the result
442/// is representable in an MCValue, but may not always succeed.
443///
444/// \returns True on success, false if the result is not representable in an
445/// MCValue.
446
447/// NOTE: It is really important to have both the Asm and Layout arguments.
448/// They might look redundant, but this function can be used before layout
449/// is done (see the object streamer for example) and having the Asm argument
450/// lets us avoid relaxations early.
451static bool EvaluateSymbolicAdd(const MCAssembler *Asm,
452                                const MCAsmLayout *Layout,
453                                const SectionAddrMap *Addrs,
454                                bool InSet,
455                                const MCValue &LHS,const MCSymbolRefExpr *RHS_A,
456                                const MCSymbolRefExpr *RHS_B, int64_t RHS_Cst,
457                                MCValue &Res) {
458  // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy
459  // about dealing with modifiers. This will ultimately bite us, one day.
460  const MCSymbolRefExpr *LHS_A = LHS.getSymA();
461  const MCSymbolRefExpr *LHS_B = LHS.getSymB();
462  int64_t LHS_Cst = LHS.getConstant();
463
464  // Fold the result constant immediately.
465  int64_t Result_Cst = LHS_Cst + RHS_Cst;
466
467  assert((!Layout || Asm) &&
468         "Must have an assembler object if layout is given!");
469
470  // If we have a layout, we can fold resolved differences.
471  if (Asm) {
472    // First, fold out any differences which are fully resolved. By
473    // reassociating terms in
474    //   Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
475    // we have the four possible differences:
476    //   (LHS_A - LHS_B),
477    //   (LHS_A - RHS_B),
478    //   (RHS_A - LHS_B),
479    //   (RHS_A - RHS_B).
480    // Since we are attempting to be as aggressive as possible about folding, we
481    // attempt to evaluate each possible alternative.
482    AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B,
483                                        Result_Cst);
484    AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B,
485                                        Result_Cst);
486    AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B,
487                                        Result_Cst);
488    AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B,
489                                        Result_Cst);
490  }
491
492  // We can't represent the addition or subtraction of two symbols.
493  if ((LHS_A && RHS_A) || (LHS_B && RHS_B))
494    return false;
495
496  // At this point, we have at most one additive symbol and one subtractive
497  // symbol -- find them.
498  const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A;
499  const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B;
500
501  // If we have a negated symbol, then we must have also have a non-negated
502  // symbol in order to encode the expression.
503  if (B && !A)
504    return false;
505
506  Res = MCValue::get(A, B, Result_Cst);
507  return true;
508}
509
510bool MCExpr::EvaluateAsRelocatable(MCValue &Res,
511                                   const MCAsmLayout &Layout) const {
512  return EvaluateAsRelocatableImpl(Res, &Layout.getAssembler(), &Layout,
513                                   0, false);
514}
515
516bool MCExpr::EvaluateAsRelocatableImpl(MCValue &Res,
517                                       const MCAssembler *Asm,
518                                       const MCAsmLayout *Layout,
519                                       const SectionAddrMap *Addrs,
520                                       bool InSet) const {
521  ++stats::MCExprEvaluate;
522
523  switch (getKind()) {
524  case Target:
525    return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout);
526
527  case Constant:
528    Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
529    return true;
530
531  case SymbolRef: {
532    const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
533    const MCSymbol &Sym = SRE->getSymbol();
534
535    // Evaluate recursively if this is a variable.
536    if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None) {
537      bool Ret = Sym.getVariableValue()->EvaluateAsRelocatableImpl(Res, Asm,
538                                                                   Layout,
539                                                                   Addrs,
540                                                                   true);
541      // If we failed to simplify this to a constant, let the target
542      // handle it.
543      if (Ret && !Res.getSymA() && !Res.getSymB())
544        return true;
545    }
546
547    Res = MCValue::get(SRE, 0, 0);
548    return true;
549  }
550
551  case Unary: {
552    const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
553    MCValue Value;
554
555    if (!AUE->getSubExpr()->EvaluateAsRelocatableImpl(Value, Asm, Layout,
556                                                      Addrs, InSet))
557      return false;
558
559    switch (AUE->getOpcode()) {
560    case MCUnaryExpr::LNot:
561      if (!Value.isAbsolute())
562        return false;
563      Res = MCValue::get(!Value.getConstant());
564      break;
565    case MCUnaryExpr::Minus:
566      /// -(a - b + const) ==> (b - a - const)
567      if (Value.getSymA() && !Value.getSymB())
568        return false;
569      Res = MCValue::get(Value.getSymB(), Value.getSymA(),
570                         -Value.getConstant());
571      break;
572    case MCUnaryExpr::Not:
573      if (!Value.isAbsolute())
574        return false;
575      Res = MCValue::get(~Value.getConstant());
576      break;
577    case MCUnaryExpr::Plus:
578      Res = Value;
579      break;
580    }
581
582    return true;
583  }
584
585  case Binary: {
586    const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
587    MCValue LHSValue, RHSValue;
588
589    if (!ABE->getLHS()->EvaluateAsRelocatableImpl(LHSValue, Asm, Layout,
590                                                  Addrs, InSet) ||
591        !ABE->getRHS()->EvaluateAsRelocatableImpl(RHSValue, Asm, Layout,
592                                                  Addrs, InSet))
593      return false;
594
595    // We only support a few operations on non-constant expressions, handle
596    // those first.
597    if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
598      switch (ABE->getOpcode()) {
599      default:
600        return false;
601      case MCBinaryExpr::Sub:
602        // Negate RHS and add.
603        return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
604                                   RHSValue.getSymB(), RHSValue.getSymA(),
605                                   -RHSValue.getConstant(),
606                                   Res);
607
608      case MCBinaryExpr::Add:
609        return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
610                                   RHSValue.getSymA(), RHSValue.getSymB(),
611                                   RHSValue.getConstant(),
612                                   Res);
613      }
614    }
615
616    // FIXME: We need target hooks for the evaluation. It may be limited in
617    // width, and gas defines the result of comparisons and right shifts
618    // differently from Apple as.
619    int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
620    int64_t Result = 0;
621    switch (ABE->getOpcode()) {
622    case MCBinaryExpr::Add:  Result = LHS + RHS; break;
623    case MCBinaryExpr::And:  Result = LHS & RHS; break;
624    case MCBinaryExpr::Div:  Result = LHS / RHS; break;
625    case MCBinaryExpr::EQ:   Result = LHS == RHS; break;
626    case MCBinaryExpr::GT:   Result = LHS > RHS; break;
627    case MCBinaryExpr::GTE:  Result = LHS >= RHS; break;
628    case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
629    case MCBinaryExpr::LOr:  Result = LHS || RHS; break;
630    case MCBinaryExpr::LT:   Result = LHS < RHS; break;
631    case MCBinaryExpr::LTE:  Result = LHS <= RHS; break;
632    case MCBinaryExpr::Mod:  Result = LHS % RHS; break;
633    case MCBinaryExpr::Mul:  Result = LHS * RHS; break;
634    case MCBinaryExpr::NE:   Result = LHS != RHS; break;
635    case MCBinaryExpr::Or:   Result = LHS | RHS; break;
636    case MCBinaryExpr::Shl:  Result = LHS << RHS; break;
637    case MCBinaryExpr::Shr:  Result = LHS >> RHS; break;
638    case MCBinaryExpr::Sub:  Result = LHS - RHS; break;
639    case MCBinaryExpr::Xor:  Result = LHS ^ RHS; break;
640    }
641
642    Res = MCValue::get(Result);
643    return true;
644  }
645  }
646
647  llvm_unreachable("Invalid assembly expression kind!");
648}
649
650const MCSection *MCExpr::FindAssociatedSection() const {
651  switch (getKind()) {
652  case Target:
653    // We never look through target specific expressions.
654    return cast<MCTargetExpr>(this)->FindAssociatedSection();
655
656  case Constant:
657    return MCSymbol::AbsolutePseudoSection;
658
659  case SymbolRef: {
660    const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
661    const MCSymbol &Sym = SRE->getSymbol();
662
663    if (Sym.isDefined())
664      return &Sym.getSection();
665
666    return 0;
667  }
668
669  case Unary:
670    return cast<MCUnaryExpr>(this)->getSubExpr()->FindAssociatedSection();
671
672  case Binary: {
673    const MCBinaryExpr *BE = cast<MCBinaryExpr>(this);
674    const MCSection *LHS_S = BE->getLHS()->FindAssociatedSection();
675    const MCSection *RHS_S = BE->getRHS()->FindAssociatedSection();
676
677    // If either section is absolute, return the other.
678    if (LHS_S == MCSymbol::AbsolutePseudoSection)
679      return RHS_S;
680    if (RHS_S == MCSymbol::AbsolutePseudoSection)
681      return LHS_S;
682
683    // Otherwise, return the first non-null section.
684    return LHS_S ? LHS_S : RHS_S;
685  }
686  }
687
688  llvm_unreachable("Invalid assembly expression kind!");
689}
690