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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     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)
dump() const134 void MCExpr::dump() const {
135   print(dbgs());
136   dbgs() << '\n';
137 }
138 #endif
139 
140 /* *** */
141 
Create(Opcode Opc,const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)142 const MCBinaryExpr *MCBinaryExpr::Create(Opcode Opc, const MCExpr *LHS,
143                                          const MCExpr *RHS, MCContext &Ctx) {
144   return new (Ctx) MCBinaryExpr(Opc, LHS, RHS);
145 }
146 
Create(Opcode Opc,const MCExpr * Expr,MCContext & Ctx)147 const MCUnaryExpr *MCUnaryExpr::Create(Opcode Opc, const MCExpr *Expr,
148                                        MCContext &Ctx) {
149   return new (Ctx) MCUnaryExpr(Opc, Expr);
150 }
151 
Create(int64_t Value,MCContext & Ctx)152 const MCConstantExpr *MCConstantExpr::Create(int64_t Value, MCContext &Ctx) {
153   return new (Ctx) MCConstantExpr(Value);
154 }
155 
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);
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_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_HIGHER: return "higher";
203   case VK_PPC_HIGHERA: return "highera";
204   case VK_PPC_HIGHEST: return "highest";
205   case VK_PPC_HIGHESTA: return "highesta";
206   case VK_PPC_GOT_LO: return "got@l";
207   case VK_PPC_GOT_HI: return "got@h";
208   case VK_PPC_GOT_HA: return "got@ha";
209   case VK_PPC_TOCBASE: return "tocbase";
210   case VK_PPC_TOC: return "toc";
211   case VK_PPC_TOC_LO: return "toc@l";
212   case VK_PPC_TOC_HI: return "toc@h";
213   case VK_PPC_TOC_HA: return "toc@ha";
214   case VK_PPC_DTPMOD: return "dtpmod";
215   case VK_PPC_TPREL: return "tprel";
216   case VK_PPC_TPREL_LO: return "tprel@l";
217   case VK_PPC_TPREL_HI: return "tprel@h";
218   case VK_PPC_TPREL_HA: return "tprel@ha";
219   case VK_PPC_TPREL_HIGHER: return "tprel@higher";
220   case VK_PPC_TPREL_HIGHERA: return "tprel@highera";
221   case VK_PPC_TPREL_HIGHEST: return "tprel@highest";
222   case VK_PPC_TPREL_HIGHESTA: return "tprel@highesta";
223   case VK_PPC_DTPREL: return "dtprel";
224   case VK_PPC_DTPREL_LO: return "dtprel@l";
225   case VK_PPC_DTPREL_HI: return "dtprel@h";
226   case VK_PPC_DTPREL_HA: return "dtprel@ha";
227   case VK_PPC_DTPREL_HIGHER: return "dtprel@higher";
228   case VK_PPC_DTPREL_HIGHERA: return "dtprel@highera";
229   case VK_PPC_DTPREL_HIGHEST: return "dtprel@highest";
230   case VK_PPC_DTPREL_HIGHESTA: return "dtprel@highesta";
231   case VK_PPC_GOT_TPREL: return "got@tprel";
232   case VK_PPC_GOT_TPREL_LO: return "got@tprel@l";
233   case VK_PPC_GOT_TPREL_HI: return "got@tprel@h";
234   case VK_PPC_GOT_TPREL_HA: return "got@tprel@ha";
235   case VK_PPC_GOT_DTPREL: return "got@dtprel";
236   case VK_PPC_GOT_DTPREL_LO: return "got@dtprel@l";
237   case VK_PPC_GOT_DTPREL_HI: return "got@dtprel@h";
238   case VK_PPC_GOT_DTPREL_HA: return "got@dtprel@ha";
239   case VK_PPC_TLS: return "tls";
240   case VK_PPC_GOT_TLSGD: return "got@tlsgd";
241   case VK_PPC_GOT_TLSGD_LO: return "got@tlsgd@l";
242   case VK_PPC_GOT_TLSGD_HI: return "got@tlsgd@h";
243   case VK_PPC_GOT_TLSGD_HA: return "got@tlsgd@ha";
244   case VK_PPC_TLSGD: return "tlsgd";
245   case VK_PPC_GOT_TLSLD: return "got@tlsld";
246   case VK_PPC_GOT_TLSLD_LO: return "got@tlsld@l";
247   case VK_PPC_GOT_TLSLD_HI: return "got@tlsld@h";
248   case VK_PPC_GOT_TLSLD_HA: return "got@tlsld@ha";
249   case VK_PPC_TLSLD: return "tlsld";
250   case VK_Mips_GPREL: return "GPREL";
251   case VK_Mips_GOT_CALL: return "GOT_CALL";
252   case VK_Mips_GOT16: return "GOT16";
253   case VK_Mips_GOT: return "GOT";
254   case VK_Mips_ABS_HI: return "ABS_HI";
255   case VK_Mips_ABS_LO: return "ABS_LO";
256   case VK_Mips_TLSGD: return "TLSGD";
257   case VK_Mips_TLSLDM: return "TLSLDM";
258   case VK_Mips_DTPREL_HI: return "DTPREL_HI";
259   case VK_Mips_DTPREL_LO: return "DTPREL_LO";
260   case VK_Mips_GOTTPREL: return "GOTTPREL";
261   case VK_Mips_TPREL_HI: return "TPREL_HI";
262   case VK_Mips_TPREL_LO: return "TPREL_LO";
263   case VK_Mips_GPOFF_HI: return "GPOFF_HI";
264   case VK_Mips_GPOFF_LO: return "GPOFF_LO";
265   case VK_Mips_GOT_DISP: return "GOT_DISP";
266   case VK_Mips_GOT_PAGE: return "GOT_PAGE";
267   case VK_Mips_GOT_OFST: return "GOT_OFST";
268   case VK_Mips_HIGHER:   return "HIGHER";
269   case VK_Mips_HIGHEST:  return "HIGHEST";
270   case VK_Mips_GOT_HI16: return "GOT_HI16";
271   case VK_Mips_GOT_LO16: return "GOT_LO16";
272   case VK_Mips_CALL_HI16: return "CALL_HI16";
273   case VK_Mips_CALL_LO16: return "CALL_LO16";
274   case VK_COFF_IMGREL32: return "IMGREL32";
275   }
276   llvm_unreachable("Invalid variant kind");
277 }
278 
279 MCSymbolRefExpr::VariantKind
getVariantKindForName(StringRef Name)280 MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
281   return StringSwitch<VariantKind>(Name)
282     .Case("GOT", VK_GOT)
283     .Case("got", VK_GOT)
284     .Case("GOTOFF", VK_GOTOFF)
285     .Case("gotoff", VK_GOTOFF)
286     .Case("GOTPCREL", VK_GOTPCREL)
287     .Case("gotpcrel", VK_GOTPCREL)
288     .Case("GOTTPOFF", VK_GOTTPOFF)
289     .Case("gottpoff", VK_GOTTPOFF)
290     .Case("INDNTPOFF", VK_INDNTPOFF)
291     .Case("indntpoff", VK_INDNTPOFF)
292     .Case("NTPOFF", VK_NTPOFF)
293     .Case("ntpoff", VK_NTPOFF)
294     .Case("GOTNTPOFF", VK_GOTNTPOFF)
295     .Case("gotntpoff", VK_GOTNTPOFF)
296     .Case("PLT", VK_PLT)
297     .Case("plt", VK_PLT)
298     .Case("TLSGD", VK_TLSGD)
299     .Case("tlsgd", VK_TLSGD)
300     .Case("TLSLD", VK_TLSLD)
301     .Case("tlsld", VK_TLSLD)
302     .Case("TLSLDM", VK_TLSLDM)
303     .Case("tlsldm", VK_TLSLDM)
304     .Case("TPOFF", VK_TPOFF)
305     .Case("tpoff", VK_TPOFF)
306     .Case("DTPOFF", VK_DTPOFF)
307     .Case("dtpoff", VK_DTPOFF)
308     .Case("TLVP", VK_TLVP)
309     .Case("tlvp", VK_TLVP)
310     .Case("IMGREL", VK_COFF_IMGREL32)
311     .Case("imgrel", VK_COFF_IMGREL32)
312     .Case("SECREL32", VK_SECREL)
313     .Case("secrel32", VK_SECREL)
314     .Case("L", VK_PPC_LO)
315     .Case("l", VK_PPC_LO)
316     .Case("H", VK_PPC_HI)
317     .Case("h", VK_PPC_HI)
318     .Case("HA", VK_PPC_HA)
319     .Case("ha", VK_PPC_HA)
320     .Case("HIGHER", VK_PPC_HIGHER)
321     .Case("higher", VK_PPC_HIGHER)
322     .Case("HIGHERA", VK_PPC_HIGHERA)
323     .Case("highera", VK_PPC_HIGHERA)
324     .Case("HIGHEST", VK_PPC_HIGHEST)
325     .Case("highest", VK_PPC_HIGHEST)
326     .Case("HIGHESTA", VK_PPC_HIGHESTA)
327     .Case("highesta", VK_PPC_HIGHESTA)
328     .Case("GOT@L", VK_PPC_GOT_LO)
329     .Case("got@l", VK_PPC_GOT_LO)
330     .Case("GOT@H", VK_PPC_GOT_HI)
331     .Case("got@h", VK_PPC_GOT_HI)
332     .Case("GOT@HA", VK_PPC_GOT_HA)
333     .Case("got@ha", VK_PPC_GOT_HA)
334     .Case("TOCBASE", VK_PPC_TOCBASE)
335     .Case("tocbase", VK_PPC_TOCBASE)
336     .Case("TOC", VK_PPC_TOC)
337     .Case("toc", VK_PPC_TOC)
338     .Case("TOC@L", VK_PPC_TOC_LO)
339     .Case("toc@l", VK_PPC_TOC_LO)
340     .Case("TOC@H", VK_PPC_TOC_HI)
341     .Case("toc@h", VK_PPC_TOC_HI)
342     .Case("TOC@HA", VK_PPC_TOC_HA)
343     .Case("toc@ha", VK_PPC_TOC_HA)
344     .Case("TLS", VK_PPC_TLS)
345     .Case("tls", VK_PPC_TLS)
346     .Case("DTPMOD", VK_PPC_DTPMOD)
347     .Case("dtpmod", VK_PPC_DTPMOD)
348     .Case("TPREL", VK_PPC_TPREL)
349     .Case("tprel", VK_PPC_TPREL)
350     .Case("TPREL@L", VK_PPC_TPREL_LO)
351     .Case("tprel@l", VK_PPC_TPREL_LO)
352     .Case("TPREL@H", VK_PPC_TPREL_HI)
353     .Case("tprel@h", VK_PPC_TPREL_HI)
354     .Case("TPREL@HA", VK_PPC_TPREL_HA)
355     .Case("tprel@ha", VK_PPC_TPREL_HA)
356     .Case("TPREL@HIGHER", VK_PPC_TPREL_HIGHER)
357     .Case("tprel@higher", VK_PPC_TPREL_HIGHER)
358     .Case("TPREL@HIGHERA", VK_PPC_TPREL_HIGHERA)
359     .Case("tprel@highera", VK_PPC_TPREL_HIGHERA)
360     .Case("TPREL@HIGHEST", VK_PPC_TPREL_HIGHEST)
361     .Case("tprel@highest", VK_PPC_TPREL_HIGHEST)
362     .Case("TPREL@HIGHESTA", VK_PPC_TPREL_HIGHESTA)
363     .Case("tprel@highesta", VK_PPC_TPREL_HIGHESTA)
364     .Case("DTPREL", VK_PPC_DTPREL)
365     .Case("dtprel", VK_PPC_DTPREL)
366     .Case("DTPREL@L", VK_PPC_DTPREL_LO)
367     .Case("dtprel@l", VK_PPC_DTPREL_LO)
368     .Case("DTPREL@H", VK_PPC_DTPREL_HI)
369     .Case("dtprel@h", VK_PPC_DTPREL_HI)
370     .Case("DTPREL@HA", VK_PPC_DTPREL_HA)
371     .Case("dtprel@ha", VK_PPC_DTPREL_HA)
372     .Case("DTPREL@HIGHER", VK_PPC_DTPREL_HIGHER)
373     .Case("dtprel@higher", VK_PPC_DTPREL_HIGHER)
374     .Case("DTPREL@HIGHERA", VK_PPC_DTPREL_HIGHERA)
375     .Case("dtprel@highera", VK_PPC_DTPREL_HIGHERA)
376     .Case("DTPREL@HIGHEST", VK_PPC_DTPREL_HIGHEST)
377     .Case("dtprel@highest", VK_PPC_DTPREL_HIGHEST)
378     .Case("DTPREL@HIGHESTA", VK_PPC_DTPREL_HIGHESTA)
379     .Case("dtprel@highesta", VK_PPC_DTPREL_HIGHESTA)
380     .Case("GOT@TPREL", VK_PPC_GOT_TPREL)
381     .Case("got@tprel", VK_PPC_GOT_TPREL)
382     .Case("GOT@TPREL@L", VK_PPC_GOT_TPREL_LO)
383     .Case("got@tprel@l", VK_PPC_GOT_TPREL_LO)
384     .Case("GOT@TPREL@H", VK_PPC_GOT_TPREL_HI)
385     .Case("got@tprel@h", VK_PPC_GOT_TPREL_HI)
386     .Case("GOT@TPREL@HA", VK_PPC_GOT_TPREL_HA)
387     .Case("got@tprel@ha", VK_PPC_GOT_TPREL_HA)
388     .Case("GOT@DTPREL", VK_PPC_GOT_DTPREL)
389     .Case("got@dtprel", VK_PPC_GOT_DTPREL)
390     .Case("GOT@DTPREL@L", VK_PPC_GOT_DTPREL_LO)
391     .Case("got@dtprel@l", VK_PPC_GOT_DTPREL_LO)
392     .Case("GOT@DTPREL@H", VK_PPC_GOT_DTPREL_HI)
393     .Case("got@dtprel@h", VK_PPC_GOT_DTPREL_HI)
394     .Case("GOT@DTPREL@HA", VK_PPC_GOT_DTPREL_HA)
395     .Case("got@dtprel@ha", VK_PPC_GOT_DTPREL_HA)
396     .Case("GOT@TLSGD", VK_PPC_GOT_TLSGD)
397     .Case("got@tlsgd", VK_PPC_GOT_TLSGD)
398     .Case("GOT@TLSGD@L", VK_PPC_GOT_TLSGD_LO)
399     .Case("got@tlsgd@l", VK_PPC_GOT_TLSGD_LO)
400     .Case("GOT@TLSGD@H", VK_PPC_GOT_TLSGD_HI)
401     .Case("got@tlsgd@h", VK_PPC_GOT_TLSGD_HI)
402     .Case("GOT@TLSGD@HA", VK_PPC_GOT_TLSGD_HA)
403     .Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD_HA)
404     .Case("GOT@TLSLD", VK_PPC_GOT_TLSLD)
405     .Case("got@tlsld", VK_PPC_GOT_TLSLD)
406     .Case("GOT@TLSLD@L", VK_PPC_GOT_TLSLD_LO)
407     .Case("got@tlsld@l", VK_PPC_GOT_TLSLD_LO)
408     .Case("GOT@TLSLD@H", VK_PPC_GOT_TLSLD_HI)
409     .Case("got@tlsld@h", VK_PPC_GOT_TLSLD_HI)
410     .Case("GOT@TLSLD@HA", VK_PPC_GOT_TLSLD_HA)
411     .Case("got@tlsld@ha", VK_PPC_GOT_TLSLD_HA)
412     .Default(VK_Invalid);
413 }
414 
415 /* *** */
416 
anchor()417 void MCTargetExpr::anchor() {}
418 
419 /* *** */
420 
EvaluateAsAbsolute(int64_t & Res) const421 bool MCExpr::EvaluateAsAbsolute(int64_t &Res) const {
422   return EvaluateAsAbsolute(Res, 0, 0, 0);
423 }
424 
EvaluateAsAbsolute(int64_t & Res,const MCAsmLayout & Layout) const425 bool MCExpr::EvaluateAsAbsolute(int64_t &Res,
426                                 const MCAsmLayout &Layout) const {
427   return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, 0);
428 }
429 
EvaluateAsAbsolute(int64_t & Res,const MCAsmLayout & Layout,const SectionAddrMap & Addrs) const430 bool MCExpr::EvaluateAsAbsolute(int64_t &Res,
431                                 const MCAsmLayout &Layout,
432                                 const SectionAddrMap &Addrs) const {
433   return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs);
434 }
435 
EvaluateAsAbsolute(int64_t & Res,const MCAssembler & Asm) const436 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const {
437   return EvaluateAsAbsolute(Res, &Asm, 0, 0);
438 }
439 
EvaluateAsAbsolute(int64_t & Res,const MCAssembler * Asm,const MCAsmLayout * Layout,const SectionAddrMap * Addrs) const440 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
441                                 const MCAsmLayout *Layout,
442                                 const SectionAddrMap *Addrs) const {
443   MCValue Value;
444 
445   // Fast path constants.
446   if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) {
447     Res = CE->getValue();
448     return true;
449   }
450 
451   // FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us
452   // absolutize differences across sections and that is what the MachO writer
453   // uses Addrs for.
454   bool IsRelocatable =
455     EvaluateAsRelocatableImpl(Value, Asm, Layout, Addrs, /*InSet*/ Addrs);
456 
457   // Record the current value.
458   Res = Value.getConstant();
459 
460   return IsRelocatable && Value.isAbsolute();
461 }
462 
463 /// \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)464 static void AttemptToFoldSymbolOffsetDifference(const MCAssembler *Asm,
465                                                 const MCAsmLayout *Layout,
466                                                 const SectionAddrMap *Addrs,
467                                                 bool InSet,
468                                                 const MCSymbolRefExpr *&A,
469                                                 const MCSymbolRefExpr *&B,
470                                                 int64_t &Addend) {
471   if (!A || !B)
472     return;
473 
474   const MCSymbol &SA = A->getSymbol();
475   const MCSymbol &SB = B->getSymbol();
476 
477   if (SA.isUndefined() || SB.isUndefined())
478     return;
479 
480   if (!Asm->getWriter().IsSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet))
481     return;
482 
483   MCSymbolData &AD = Asm->getSymbolData(SA);
484   MCSymbolData &BD = Asm->getSymbolData(SB);
485 
486   if (AD.getFragment() == BD.getFragment()) {
487     Addend += (AD.getOffset() - BD.getOffset());
488 
489     // Pointers to Thumb symbols need to have their low-bit set to allow
490     // for interworking.
491     if (Asm->isThumbFunc(&SA))
492       Addend |= 1;
493 
494     // Clear the symbol expr pointers to indicate we have folded these
495     // operands.
496     A = B = 0;
497     return;
498   }
499 
500   if (!Layout)
501     return;
502 
503   const MCSectionData &SecA = *AD.getFragment()->getParent();
504   const MCSectionData &SecB = *BD.getFragment()->getParent();
505 
506   if ((&SecA != &SecB) && !Addrs)
507     return;
508 
509   // Eagerly evaluate.
510   Addend += (Layout->getSymbolOffset(&Asm->getSymbolData(A->getSymbol())) -
511              Layout->getSymbolOffset(&Asm->getSymbolData(B->getSymbol())));
512   if (Addrs && (&SecA != &SecB))
513     Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB));
514 
515   // Pointers to Thumb symbols need to have their low-bit set to allow
516   // for interworking.
517   if (Asm->isThumbFunc(&SA))
518     Addend |= 1;
519 
520   // Clear the symbol expr pointers to indicate we have folded these
521   // operands.
522   A = B = 0;
523 }
524 
525 /// \brief Evaluate the result of an add between (conceptually) two MCValues.
526 ///
527 /// This routine conceptually attempts to construct an MCValue:
528 ///   Result = (Result_A - Result_B + Result_Cst)
529 /// from two MCValue's LHS and RHS where
530 ///   Result = LHS + RHS
531 /// and
532 ///   Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
533 ///
534 /// This routine attempts to aggresively fold the operands such that the result
535 /// is representable in an MCValue, but may not always succeed.
536 ///
537 /// \returns True on success, false if the result is not representable in an
538 /// MCValue.
539 
540 /// NOTE: It is really important to have both the Asm and Layout arguments.
541 /// They might look redundant, but this function can be used before layout
542 /// is done (see the object streamer for example) and having the Asm argument
543 /// 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)544 static bool EvaluateSymbolicAdd(const MCAssembler *Asm,
545                                 const MCAsmLayout *Layout,
546                                 const SectionAddrMap *Addrs,
547                                 bool InSet,
548                                 const MCValue &LHS,const MCSymbolRefExpr *RHS_A,
549                                 const MCSymbolRefExpr *RHS_B, int64_t RHS_Cst,
550                                 MCValue &Res) {
551   // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy
552   // about dealing with modifiers. This will ultimately bite us, one day.
553   const MCSymbolRefExpr *LHS_A = LHS.getSymA();
554   const MCSymbolRefExpr *LHS_B = LHS.getSymB();
555   int64_t LHS_Cst = LHS.getConstant();
556 
557   // Fold the result constant immediately.
558   int64_t Result_Cst = LHS_Cst + RHS_Cst;
559 
560   assert((!Layout || Asm) &&
561          "Must have an assembler object if layout is given!");
562 
563   // If we have a layout, we can fold resolved differences.
564   if (Asm) {
565     // First, fold out any differences which are fully resolved. By
566     // reassociating terms in
567     //   Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
568     // we have the four possible differences:
569     //   (LHS_A - LHS_B),
570     //   (LHS_A - RHS_B),
571     //   (RHS_A - LHS_B),
572     //   (RHS_A - RHS_B).
573     // Since we are attempting to be as aggressive as possible about folding, we
574     // attempt to evaluate each possible alternative.
575     AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B,
576                                         Result_Cst);
577     AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B,
578                                         Result_Cst);
579     AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B,
580                                         Result_Cst);
581     AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B,
582                                         Result_Cst);
583   }
584 
585   // We can't represent the addition or subtraction of two symbols.
586   if ((LHS_A && RHS_A) || (LHS_B && RHS_B))
587     return false;
588 
589   // At this point, we have at most one additive symbol and one subtractive
590   // symbol -- find them.
591   const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A;
592   const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B;
593 
594   // If we have a negated symbol, then we must have also have a non-negated
595   // symbol in order to encode the expression.
596   if (B && !A)
597     return false;
598 
599   Res = MCValue::get(A, B, Result_Cst);
600   return true;
601 }
602 
EvaluateAsRelocatable(MCValue & Res,const MCAsmLayout & Layout) const603 bool MCExpr::EvaluateAsRelocatable(MCValue &Res,
604                                    const MCAsmLayout &Layout) const {
605   return EvaluateAsRelocatableImpl(Res, &Layout.getAssembler(), &Layout,
606                                    0, false);
607 }
608 
EvaluateAsRelocatableImpl(MCValue & Res,const MCAssembler * Asm,const MCAsmLayout * Layout,const SectionAddrMap * Addrs,bool InSet) const609 bool MCExpr::EvaluateAsRelocatableImpl(MCValue &Res,
610                                        const MCAssembler *Asm,
611                                        const MCAsmLayout *Layout,
612                                        const SectionAddrMap *Addrs,
613                                        bool InSet) const {
614   ++stats::MCExprEvaluate;
615 
616   switch (getKind()) {
617   case Target:
618     return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout);
619 
620   case Constant:
621     Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
622     return true;
623 
624   case SymbolRef: {
625     const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
626     const MCSymbol &Sym = SRE->getSymbol();
627 
628     // Evaluate recursively if this is a variable.
629     if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None) {
630       bool Ret = Sym.getVariableValue()->EvaluateAsRelocatableImpl(Res, Asm,
631                                                                    Layout,
632                                                                    Addrs,
633                                                                    true);
634       // If we failed to simplify this to a constant, let the target
635       // handle it.
636       if (Ret && !Res.getSymA() && !Res.getSymB())
637         return true;
638     }
639 
640     Res = MCValue::get(SRE, 0, 0);
641     return true;
642   }
643 
644   case Unary: {
645     const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
646     MCValue Value;
647 
648     if (!AUE->getSubExpr()->EvaluateAsRelocatableImpl(Value, Asm, Layout,
649                                                       Addrs, InSet))
650       return false;
651 
652     switch (AUE->getOpcode()) {
653     case MCUnaryExpr::LNot:
654       if (!Value.isAbsolute())
655         return false;
656       Res = MCValue::get(!Value.getConstant());
657       break;
658     case MCUnaryExpr::Minus:
659       /// -(a - b + const) ==> (b - a - const)
660       if (Value.getSymA() && !Value.getSymB())
661         return false;
662       Res = MCValue::get(Value.getSymB(), Value.getSymA(),
663                          -Value.getConstant());
664       break;
665     case MCUnaryExpr::Not:
666       if (!Value.isAbsolute())
667         return false;
668       Res = MCValue::get(~Value.getConstant());
669       break;
670     case MCUnaryExpr::Plus:
671       Res = Value;
672       break;
673     }
674 
675     return true;
676   }
677 
678   case Binary: {
679     const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
680     MCValue LHSValue, RHSValue;
681 
682     if (!ABE->getLHS()->EvaluateAsRelocatableImpl(LHSValue, Asm, Layout,
683                                                   Addrs, InSet) ||
684         !ABE->getRHS()->EvaluateAsRelocatableImpl(RHSValue, Asm, Layout,
685                                                   Addrs, InSet))
686       return false;
687 
688     // We only support a few operations on non-constant expressions, handle
689     // those first.
690     if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
691       switch (ABE->getOpcode()) {
692       default:
693         return false;
694       case MCBinaryExpr::Sub:
695         // Negate RHS and add.
696         return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
697                                    RHSValue.getSymB(), RHSValue.getSymA(),
698                                    -RHSValue.getConstant(),
699                                    Res);
700 
701       case MCBinaryExpr::Add:
702         return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
703                                    RHSValue.getSymA(), RHSValue.getSymB(),
704                                    RHSValue.getConstant(),
705                                    Res);
706       }
707     }
708 
709     // FIXME: We need target hooks for the evaluation. It may be limited in
710     // width, and gas defines the result of comparisons and right shifts
711     // differently from Apple as.
712     int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
713     int64_t Result = 0;
714     switch (ABE->getOpcode()) {
715     case MCBinaryExpr::Add:  Result = LHS + RHS; break;
716     case MCBinaryExpr::And:  Result = LHS & RHS; break;
717     case MCBinaryExpr::Div:  Result = LHS / RHS; break;
718     case MCBinaryExpr::EQ:   Result = LHS == RHS; break;
719     case MCBinaryExpr::GT:   Result = LHS > RHS; break;
720     case MCBinaryExpr::GTE:  Result = LHS >= RHS; break;
721     case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
722     case MCBinaryExpr::LOr:  Result = LHS || RHS; break;
723     case MCBinaryExpr::LT:   Result = LHS < RHS; break;
724     case MCBinaryExpr::LTE:  Result = LHS <= RHS; break;
725     case MCBinaryExpr::Mod:  Result = LHS % RHS; break;
726     case MCBinaryExpr::Mul:  Result = LHS * RHS; break;
727     case MCBinaryExpr::NE:   Result = LHS != RHS; break;
728     case MCBinaryExpr::Or:   Result = LHS | RHS; break;
729     case MCBinaryExpr::Shl:  Result = LHS << RHS; break;
730     case MCBinaryExpr::Shr:  Result = LHS >> RHS; break;
731     case MCBinaryExpr::Sub:  Result = LHS - RHS; break;
732     case MCBinaryExpr::Xor:  Result = LHS ^ RHS; break;
733     }
734 
735     Res = MCValue::get(Result);
736     return true;
737   }
738   }
739 
740   llvm_unreachable("Invalid assembly expression kind!");
741 }
742 
FindAssociatedSection() const743 const MCSection *MCExpr::FindAssociatedSection() const {
744   switch (getKind()) {
745   case Target:
746     // We never look through target specific expressions.
747     return cast<MCTargetExpr>(this)->FindAssociatedSection();
748 
749   case Constant:
750     return MCSymbol::AbsolutePseudoSection;
751 
752   case SymbolRef: {
753     const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
754     const MCSymbol &Sym = SRE->getSymbol();
755 
756     if (Sym.isDefined())
757       return &Sym.getSection();
758 
759     return 0;
760   }
761 
762   case Unary:
763     return cast<MCUnaryExpr>(this)->getSubExpr()->FindAssociatedSection();
764 
765   case Binary: {
766     const MCBinaryExpr *BE = cast<MCBinaryExpr>(this);
767     const MCSection *LHS_S = BE->getLHS()->FindAssociatedSection();
768     const MCSection *RHS_S = BE->getRHS()->FindAssociatedSection();
769 
770     // If either section is absolute, return the other.
771     if (LHS_S == MCSymbol::AbsolutePseudoSection)
772       return RHS_S;
773     if (RHS_S == MCSymbol::AbsolutePseudoSection)
774       return LHS_S;
775 
776     // Otherwise, return the first non-null section.
777     return LHS_S ? LHS_S : RHS_S;
778   }
779   }
780 
781   llvm_unreachable("Invalid assembly expression kind!");
782 }
783