MCExpr.cpp revision b4d1721eff7b43577e5f2e53f885973fb6c43683 
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/MCObjectFormat.h"
18#include "llvm/MC/MCSymbol.h"
19#include "llvm/MC/MCValue.h"
20#include "llvm/Support/Debug.h"
21#include "llvm/Support/raw_ostream.h"
22#include "llvm/Target/TargetAsmBackend.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
43    if (SRE.getKind() == MCSymbolRefExpr::VK_ARM_HI16 ||
44        SRE.getKind() == MCSymbolRefExpr::VK_ARM_LO16)
45      OS << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
46
47    // Parenthesize names that start with $ so that they don't look like
48    // absolute names.
49    if (Sym.getName()[0] == '$')
50      OS << '(' << Sym << ')';
51    else
52      OS << Sym;
53
54    if (SRE.getKind() == MCSymbolRefExpr::VK_ARM_PLT)
55      OS << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
56    else if (SRE.getKind() != MCSymbolRefExpr::VK_None &&
57             SRE.getKind() != MCSymbolRefExpr::VK_ARM_HI16 &&
58             SRE.getKind() != MCSymbolRefExpr::VK_ARM_LO16)
59      OS << '@' << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
60
61    return;
62  }
63
64  case MCExpr::Unary: {
65    const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this);
66    switch (UE.getOpcode()) {
67    default: assert(0 && "Invalid opcode!");
68    case MCUnaryExpr::LNot:  OS << '!'; break;
69    case MCUnaryExpr::Minus: OS << '-'; break;
70    case MCUnaryExpr::Not:   OS << '~'; break;
71    case MCUnaryExpr::Plus:  OS << '+'; break;
72    }
73    OS << *UE.getSubExpr();
74    return;
75  }
76
77  case MCExpr::Binary: {
78    const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this);
79
80    // Only print parens around the LHS if it is non-trivial.
81    if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) {
82      OS << *BE.getLHS();
83    } else {
84      OS << '(' << *BE.getLHS() << ')';
85    }
86
87    switch (BE.getOpcode()) {
88    default: assert(0 && "Invalid opcode!");
89    case MCBinaryExpr::Add:
90      // Print "X-42" instead of "X+-42".
91      if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) {
92        if (RHSC->getValue() < 0) {
93          OS << RHSC->getValue();
94          return;
95        }
96      }
97
98      OS <<  '+';
99      break;
100    case MCBinaryExpr::And:  OS <<  '&'; break;
101    case MCBinaryExpr::Div:  OS <<  '/'; break;
102    case MCBinaryExpr::EQ:   OS << "=="; break;
103    case MCBinaryExpr::GT:   OS <<  '>'; break;
104    case MCBinaryExpr::GTE:  OS << ">="; break;
105    case MCBinaryExpr::LAnd: OS << "&&"; break;
106    case MCBinaryExpr::LOr:  OS << "||"; break;
107    case MCBinaryExpr::LT:   OS <<  '<'; break;
108    case MCBinaryExpr::LTE:  OS << "<="; break;
109    case MCBinaryExpr::Mod:  OS <<  '%'; break;
110    case MCBinaryExpr::Mul:  OS <<  '*'; break;
111    case MCBinaryExpr::NE:   OS << "!="; break;
112    case MCBinaryExpr::Or:   OS <<  '|'; break;
113    case MCBinaryExpr::Shl:  OS << "<<"; break;
114    case MCBinaryExpr::Shr:  OS << ">>"; break;
115    case MCBinaryExpr::Sub:  OS <<  '-'; break;
116    case MCBinaryExpr::Xor:  OS <<  '^'; break;
117    }
118
119    // Only print parens around the LHS if it is non-trivial.
120    if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) {
121      OS << *BE.getRHS();
122    } else {
123      OS << '(' << *BE.getRHS() << ')';
124    }
125    return;
126  }
127  }
128
129  assert(0 && "Invalid expression kind!");
130}
131
132void MCExpr::dump() const {
133  print(dbgs());
134  dbgs() << '\n';
135}
136
137/* *** */
138
139const MCBinaryExpr *MCBinaryExpr::Create(Opcode Opc, const MCExpr *LHS,
140                                         const MCExpr *RHS, MCContext &Ctx) {
141  return new (Ctx) MCBinaryExpr(Opc, LHS, RHS);
142}
143
144const MCUnaryExpr *MCUnaryExpr::Create(Opcode Opc, const MCExpr *Expr,
145                                       MCContext &Ctx) {
146  return new (Ctx) MCUnaryExpr(Opc, Expr);
147}
148
149const MCConstantExpr *MCConstantExpr::Create(int64_t Value, MCContext &Ctx) {
150  return new (Ctx) MCConstantExpr(Value);
151}
152
153/* *** */
154
155const MCSymbolRefExpr *MCSymbolRefExpr::Create(const MCSymbol *Sym,
156                                               VariantKind Kind,
157                                               MCContext &Ctx) {
158  return new (Ctx) MCSymbolRefExpr(Sym, Kind);
159}
160
161const MCSymbolRefExpr *MCSymbolRefExpr::Create(StringRef Name, VariantKind Kind,
162                                               MCContext &Ctx) {
163  return Create(Ctx.GetOrCreateSymbol(Name), Kind, Ctx);
164}
165
166StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
167  switch (Kind) {
168  default:
169  case VK_Invalid: return "<<invalid>>";
170  case VK_None: return "<<none>>";
171
172  case VK_GOT: return "GOT";
173  case VK_GOTOFF: return "GOTOFF";
174  case VK_GOTPCREL: return "GOTPCREL";
175  case VK_GOTTPOFF: return "GOTTPOFF";
176  case VK_INDNTPOFF: return "INDNTPOFF";
177  case VK_NTPOFF: return "NTPOFF";
178  case VK_GOTNTPOFF: return "GOTNTPOFF";
179  case VK_PLT: return "PLT";
180  case VK_TLSGD: return "TLSGD";
181  case VK_TLSLD: return "TLSLD";
182  case VK_TLSLDM: return "TLSLDM";
183  case VK_TPOFF: return "TPOFF";
184  case VK_DTPOFF: return "DTPOFF";
185  case VK_ARM_HI16: return ":upper16:";
186  case VK_ARM_LO16: return ":lower16:";
187  case VK_ARM_PLT: return "(PLT)";
188  case VK_TLVP: return "TLVP";
189  }
190}
191
192MCSymbolRefExpr::VariantKind
193MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
194  return StringSwitch<VariantKind>(Name)
195    .Case("GOT", VK_GOT)
196    .Case("GOTOFF", VK_GOTOFF)
197    .Case("GOTPCREL", VK_GOTPCREL)
198    .Case("GOTTPOFF", VK_GOTTPOFF)
199    .Case("INDNTPOFF", VK_INDNTPOFF)
200    .Case("NTPOFF", VK_NTPOFF)
201    .Case("GOTNTPOFF", VK_GOTNTPOFF)
202    .Case("PLT", VK_PLT)
203    .Case("TLSGD", VK_TLSGD)
204    .Case("TLSLD", VK_TLSLD)
205    .Case("TLSLDM", VK_TLSLDM)
206    .Case("TPOFF", VK_TPOFF)
207    .Case("DTPOFF", VK_DTPOFF)
208    .Case("TLVP", VK_TLVP)
209    .Default(VK_Invalid);
210}
211
212/* *** */
213
214void MCTargetExpr::Anchor() {}
215
216/* *** */
217
218bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAsmLayout *Layout) const {
219  MCValue Value;
220
221  // Fast path constants.
222  if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) {
223    Res = CE->getValue();
224    return true;
225  }
226
227  if (!EvaluateAsRelocatable(Value, Layout) || !Value.isAbsolute()) {
228    // EvaluateAsAbsolute is defined to return the "current value" of
229    // the expression if we are given a Layout object, even in cases
230    // when the value is not fixed.
231    if (Layout) {
232      Res = Value.getConstant();
233      if (Value.getSymA()) {
234	Res += Layout->getSymbolAddress(
235          &Layout->getAssembler().getSymbolData(Value.getSymA()->getSymbol()));
236      }
237      if (Value.getSymB()) {
238	Res -= Layout->getSymbolAddress(
239          &Layout->getAssembler().getSymbolData(Value.getSymB()->getSymbol()));
240      }
241    }
242    return false;
243  }
244
245  Res = Value.getConstant();
246  return true;
247}
248
249static bool EvaluateSymbolicAdd(const MCAsmLayout *Layout, bool InSet,
250                                const MCValue &LHS,const MCSymbolRefExpr *RHS_A,
251                                const MCSymbolRefExpr *RHS_B, int64_t RHS_Cst,
252                                MCValue &Res) {
253  // We can't add or subtract two symbols.
254  if ((LHS.getSymA() && RHS_A) ||
255      (LHS.getSymB() && RHS_B))
256    return false;
257
258  const MCSymbolRefExpr *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
259  const MCSymbolRefExpr *B = LHS.getSymB() ? LHS.getSymB() : RHS_B;
260  if (B) {
261    // If we have a negated symbol, then we must have also have a non-negated
262    // symbol in order to encode the expression. We can do this check later to
263    // permit expressions which eventually fold to a representable form -- such
264    // as (a + (0 - b)) -- if necessary.
265    if (!A)
266      return false;
267  }
268
269  // Absolutize symbol differences between defined symbols when we have a
270  // layout object and the target requests it.
271
272  if (Layout && A && B) {
273    const MCSymbol &SA = A->getSymbol();
274    const MCSymbol &SB = B->getSymbol();
275    const MCObjectFormat &F =
276      Layout->getAssembler().getBackend().getObjectFormat();
277    if (SA.isDefined() && SB.isDefined() && F.isAbsolute(InSet, SA, SB)) {
278      const MCAssembler &Asm = Layout->getAssembler();
279      MCSymbolData &AD = Asm.getSymbolData(A->getSymbol());
280      MCSymbolData &BD = Asm.getSymbolData(B->getSymbol());
281      Res = MCValue::get(+ Layout->getSymbolAddress(&AD)
282                         - Layout->getSymbolAddress(&BD)
283                         + LHS.getConstant()
284                         + RHS_Cst);
285      return true;
286    }
287  }
288
289
290  Res = MCValue::get(A, B, LHS.getConstant() + RHS_Cst);
291  return true;
292}
293
294bool MCExpr::EvaluateAsRelocatable(MCValue &Res,
295                                   const MCAsmLayout *Layout) const {
296  return EvaluateAsRelocatableImpl(Res, Layout, false);
297}
298
299bool MCExpr::EvaluateAsRelocatableImpl(MCValue &Res,
300                                       const MCAsmLayout *Layout,
301                                       bool InSet) const {
302  ++stats::MCExprEvaluate;
303
304  switch (getKind()) {
305  case Target:
306    return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout);
307
308  case Constant:
309    Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
310    return true;
311
312  case SymbolRef: {
313    const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
314    const MCSymbol &Sym = SRE->getSymbol();
315
316    // Evaluate recursively if this is a variable.
317    if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None)
318      return Sym.getVariableValue()->EvaluateAsRelocatableImpl(Res, Layout,
319                                                               true);
320
321    Res = MCValue::get(SRE, 0, 0);
322    return true;
323  }
324
325  case Unary: {
326    const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
327    MCValue Value;
328
329    if (!AUE->getSubExpr()->EvaluateAsRelocatableImpl(Value, Layout, InSet))
330      return false;
331
332    switch (AUE->getOpcode()) {
333    case MCUnaryExpr::LNot:
334      if (!Value.isAbsolute())
335        return false;
336      Res = MCValue::get(!Value.getConstant());
337      break;
338    case MCUnaryExpr::Minus:
339      /// -(a - b + const) ==> (b - a - const)
340      if (Value.getSymA() && !Value.getSymB())
341        return false;
342      Res = MCValue::get(Value.getSymB(), Value.getSymA(),
343                         -Value.getConstant());
344      break;
345    case MCUnaryExpr::Not:
346      if (!Value.isAbsolute())
347        return false;
348      Res = MCValue::get(~Value.getConstant());
349      break;
350    case MCUnaryExpr::Plus:
351      Res = Value;
352      break;
353    }
354
355    return true;
356  }
357
358  case Binary: {
359    const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
360    MCValue LHSValue, RHSValue;
361
362    if (!ABE->getLHS()->EvaluateAsRelocatableImpl(LHSValue, Layout, InSet) ||
363        !ABE->getRHS()->EvaluateAsRelocatableImpl(RHSValue, Layout, InSet))
364      return false;
365
366    // We only support a few operations on non-constant expressions, handle
367    // those first.
368    if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
369      switch (ABE->getOpcode()) {
370      default:
371        return false;
372      case MCBinaryExpr::Sub:
373        // Negate RHS and add.
374        return EvaluateSymbolicAdd(Layout, InSet, LHSValue,
375                                   RHSValue.getSymB(), RHSValue.getSymA(),
376                                   -RHSValue.getConstant(),
377                                   Res);
378
379      case MCBinaryExpr::Add:
380        return EvaluateSymbolicAdd(Layout, InSet, LHSValue,
381                                   RHSValue.getSymA(), RHSValue.getSymB(),
382                                   RHSValue.getConstant(),
383                                   Res);
384      }
385    }
386
387    // FIXME: We need target hooks for the evaluation. It may be limited in
388    // width, and gas defines the result of comparisons and right shifts
389    // differently from Apple as.
390    int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
391    int64_t Result = 0;
392    switch (ABE->getOpcode()) {
393    case MCBinaryExpr::Add:  Result = LHS + RHS; break;
394    case MCBinaryExpr::And:  Result = LHS & RHS; break;
395    case MCBinaryExpr::Div:  Result = LHS / RHS; break;
396    case MCBinaryExpr::EQ:   Result = LHS == RHS; break;
397    case MCBinaryExpr::GT:   Result = LHS > RHS; break;
398    case MCBinaryExpr::GTE:  Result = LHS >= RHS; break;
399    case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
400    case MCBinaryExpr::LOr:  Result = LHS || RHS; break;
401    case MCBinaryExpr::LT:   Result = LHS < RHS; break;
402    case MCBinaryExpr::LTE:  Result = LHS <= RHS; break;
403    case MCBinaryExpr::Mod:  Result = LHS % RHS; break;
404    case MCBinaryExpr::Mul:  Result = LHS * RHS; break;
405    case MCBinaryExpr::NE:   Result = LHS != RHS; break;
406    case MCBinaryExpr::Or:   Result = LHS | RHS; break;
407    case MCBinaryExpr::Shl:  Result = LHS << RHS; break;
408    case MCBinaryExpr::Shr:  Result = LHS >> RHS; break;
409    case MCBinaryExpr::Sub:  Result = LHS - RHS; break;
410    case MCBinaryExpr::Xor:  Result = LHS ^ RHS; break;
411    }
412
413    Res = MCValue::get(Result);
414    return true;
415  }
416  }
417
418  assert(0 && "Invalid assembly expression kind!");
419  return false;
420}
421