InlineAsm.cpp revision 2928c83b010f7cfdb0f819199d806f6942a7d995 
1//===-- InlineAsm.cpp - Implement the InlineAsm class ---------------------===//
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// This file implements the InlineAsm class.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/InlineAsm.h"
15#include "llvm/DerivedTypes.h"
16#include <algorithm>
17#include <cctype>
18using namespace llvm;
19
20// Implement the first virtual method in this class in this file so the
21// InlineAsm vtable is emitted here.
22InlineAsm::~InlineAsm() {
23}
24
25
26// NOTE: when memoizing the function type, we have to be careful to handle the
27// case when the type gets refined.
28
29InlineAsm *InlineAsm::get(const FunctionType *Ty, StringRef AsmString,
30                          StringRef Constraints, bool hasSideEffects,
31                          bool isAlignStack) {
32  // FIXME: memoize!
33  return new InlineAsm(Ty, AsmString, Constraints, hasSideEffects,
34                       isAlignStack);
35}
36
37InlineAsm::InlineAsm(const FunctionType *Ty, StringRef asmString,
38                     StringRef constraints, bool hasSideEffects,
39                     bool isAlignStack)
40  : Value(PointerType::getUnqual(Ty),
41          Value::InlineAsmVal),
42    AsmString(asmString),
43    Constraints(constraints), HasSideEffects(hasSideEffects),
44    IsAlignStack(isAlignStack) {
45
46  // Do various checks on the constraint string and type.
47  assert(Verify(Ty, constraints) && "Function type not legal for constraints!");
48}
49
50const FunctionType *InlineAsm::getFunctionType() const {
51  return cast<FunctionType>(getType()->getElementType());
52}
53
54/// Parse - Analyze the specified string (e.g. "==&{eax}") and fill in the
55/// fields in this structure.  If the constraint string is not understood,
56/// return true, otherwise return false.
57bool InlineAsm::ConstraintInfo::Parse(StringRef Str,
58                     std::vector<InlineAsm::ConstraintInfo> &ConstraintsSoFar) {
59  StringRef::iterator I = Str.begin(), E = Str.end();
60
61  // Initialize
62  Type = isInput;
63  isEarlyClobber = false;
64  MatchingInput = -1;
65  isCommutative = false;
66  isIndirect = false;
67
68  // Parse prefixes.
69  if (*I == '~') {
70    Type = isClobber;
71    ++I;
72  } else if (*I == '=') {
73    ++I;
74    Type = isOutput;
75  }
76
77  if (*I == '*') {
78    isIndirect = true;
79    ++I;
80  }
81
82  if (I == E) return true;  // Just a prefix, like "==" or "~".
83
84  // Parse the modifiers.
85  bool DoneWithModifiers = false;
86  while (!DoneWithModifiers) {
87    switch (*I) {
88    default:
89      DoneWithModifiers = true;
90      break;
91    case '&':     // Early clobber.
92      if (Type != isOutput ||      // Cannot early clobber anything but output.
93          isEarlyClobber)          // Reject &&&&&&
94        return true;
95      isEarlyClobber = true;
96      break;
97    case '%':     // Commutative.
98      if (Type == isClobber ||     // Cannot commute clobbers.
99          isCommutative)           // Reject %%%%%
100        return true;
101      isCommutative = true;
102      break;
103    case '#':     // Comment.
104    case '*':     // Register preferencing.
105      return true;     // Not supported.
106    }
107
108    if (!DoneWithModifiers) {
109      ++I;
110      if (I == E) return true;   // Just prefixes and modifiers!
111    }
112  }
113
114  // Parse the various constraints.
115  while (I != E) {
116    if (*I == '{') {   // Physical register reference.
117      // Find the end of the register name.
118      StringRef::iterator ConstraintEnd = std::find(I+1, E, '}');
119      if (ConstraintEnd == E) return true;  // "{foo"
120      Codes.push_back(std::string(I, ConstraintEnd+1));
121      I = ConstraintEnd+1;
122    } else if (isdigit(*I)) {     // Matching Constraint
123      // Maximal munch numbers.
124      StringRef::iterator NumStart = I;
125      while (I != E && isdigit(*I))
126        ++I;
127      Codes.push_back(std::string(NumStart, I));
128      unsigned N = atoi(Codes.back().c_str());
129      // Check that this is a valid matching constraint!
130      if (N >= ConstraintsSoFar.size() || ConstraintsSoFar[N].Type != isOutput||
131          Type != isInput)
132        return true;  // Invalid constraint number.
133
134      // If Operand N already has a matching input, reject this.  An output
135      // can't be constrained to the same value as multiple inputs.
136      if (ConstraintsSoFar[N].hasMatchingInput())
137        return true;
138
139      // Note that operand #n has a matching input.
140      ConstraintsSoFar[N].MatchingInput = ConstraintsSoFar.size();
141    } else {
142      // Single letter constraint.
143      Codes.push_back(std::string(I, I+1));
144      ++I;
145    }
146  }
147
148  return false;
149}
150
151std::vector<InlineAsm::ConstraintInfo>
152InlineAsm::ParseConstraints(StringRef Constraints) {
153  std::vector<ConstraintInfo> Result;
154
155  // Scan the constraints string.
156  for (StringRef::iterator I = Constraints.begin(),
157         E = Constraints.end(); I != E; ) {
158    ConstraintInfo Info;
159
160    // Find the end of this constraint.
161    StringRef::iterator ConstraintEnd = std::find(I, E, ',');
162
163    if (ConstraintEnd == I ||  // Empty constraint like ",,"
164        Info.Parse(std::string(I, ConstraintEnd), Result)) {
165      Result.clear();          // Erroneous constraint?
166      break;
167    }
168
169    Result.push_back(Info);
170
171    // ConstraintEnd may be either the next comma or the end of the string.  In
172    // the former case, we skip the comma.
173    I = ConstraintEnd;
174    if (I != E) {
175      ++I;
176      if (I == E) { Result.clear(); break; }    // don't allow "xyz,"
177    }
178  }
179
180  return Result;
181}
182
183
184/// Verify - Verify that the specified constraint string is reasonable for the
185/// specified function type, and otherwise validate the constraint string.
186bool InlineAsm::Verify(const FunctionType *Ty, StringRef ConstStr) {
187  if (Ty->isVarArg()) return false;
188
189  std::vector<ConstraintInfo> Constraints = ParseConstraints(ConstStr);
190
191  // Error parsing constraints.
192  if (Constraints.empty() && !ConstStr.empty()) return false;
193
194  unsigned NumOutputs = 0, NumInputs = 0, NumClobbers = 0;
195  unsigned NumIndirect = 0;
196
197  for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
198    switch (Constraints[i].Type) {
199    case InlineAsm::isOutput:
200      if ((NumInputs-NumIndirect) != 0 || NumClobbers != 0)
201        return false;  // outputs before inputs and clobbers.
202      if (!Constraints[i].isIndirect) {
203        ++NumOutputs;
204        break;
205      }
206      ++NumIndirect;
207      // FALLTHROUGH for Indirect Outputs.
208    case InlineAsm::isInput:
209      if (NumClobbers) return false;               // inputs before clobbers.
210      ++NumInputs;
211      break;
212    case InlineAsm::isClobber:
213      ++NumClobbers;
214      break;
215    }
216  }
217
218  switch (NumOutputs) {
219  case 0:
220    if (Ty->getReturnType() != Type::getVoidTy(Ty->getContext())) return false;
221    break;
222  case 1:
223    if (isa<StructType>(Ty->getReturnType())) return false;
224    break;
225  default:
226    const StructType *STy = dyn_cast<StructType>(Ty->getReturnType());
227    if (STy == 0 || STy->getNumElements() != NumOutputs)
228      return false;
229    break;
230  }
231
232  if (Ty->getNumParams() != NumInputs) return false;
233  return true;
234}
235
236