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/IR/InlineAsm.h"
15 #include "ConstantsContext.h"
16 #include "LLVMContextImpl.h"
17 #include "llvm/IR/DerivedTypes.h"
18 #include <algorithm>
19 #include <cctype>
20 using namespace llvm;
21 
22 // Implement the first virtual method in this class in this file so the
23 // InlineAsm vtable is emitted here.
24 InlineAsm::~InlineAsm() {
25 }
26 
27 
28 InlineAsm *InlineAsm::get(FunctionType *Ty, StringRef AsmString,
29                           StringRef Constraints, bool hasSideEffects,
30                           bool isAlignStack, AsmDialect asmDialect) {
31   InlineAsmKeyType Key(AsmString, Constraints, hasSideEffects, isAlignStack,
32                        asmDialect);
33   LLVMContextImpl *pImpl = Ty->getContext().pImpl;
34   return pImpl->InlineAsms.getOrCreate(PointerType::getUnqual(Ty), Key);
35 }
36 
37 InlineAsm::InlineAsm(PointerType *Ty, const std::string &asmString,
38                      const std::string &constraints, bool hasSideEffects,
39                      bool isAlignStack, AsmDialect asmDialect)
40   : Value(Ty, Value::InlineAsmVal),
41     AsmString(asmString), Constraints(constraints),
42     HasSideEffects(hasSideEffects), IsAlignStack(isAlignStack),
43     Dialect(asmDialect) {
44 
45   // Do various checks on the constraint string and type.
46   assert(Verify(getFunctionType(), constraints) &&
47          "Function type not legal for constraints!");
48 }
49 
50 void InlineAsm::destroyConstant() {
51   getType()->getContext().pImpl->InlineAsms.remove(this);
52   delete this;
53 }
54 
55 FunctionType *InlineAsm::getFunctionType() const {
56   return cast<FunctionType>(getType()->getElementType());
57 }
58 
59 ///Default constructor.
60 InlineAsm::ConstraintInfo::ConstraintInfo() :
61   Type(isInput), isEarlyClobber(false),
62   MatchingInput(-1), isCommutative(false),
63   isIndirect(false), isMultipleAlternative(false),
64   currentAlternativeIndex(0) {
65 }
66 
67 /// Parse - Analyze the specified string (e.g. "==&{eax}") and fill in the
68 /// fields in this structure.  If the constraint string is not understood,
69 /// return true, otherwise return false.
70 bool InlineAsm::ConstraintInfo::Parse(StringRef Str,
71                      InlineAsm::ConstraintInfoVector &ConstraintsSoFar) {
72   StringRef::iterator I = Str.begin(), E = Str.end();
73   unsigned multipleAlternativeCount = Str.count('|') + 1;
74   unsigned multipleAlternativeIndex = 0;
75   ConstraintCodeVector *pCodes = &Codes;
76 
77   // Initialize
78   isMultipleAlternative = (multipleAlternativeCount > 1 ? true : false);
79   if (isMultipleAlternative) {
80     multipleAlternatives.resize(multipleAlternativeCount);
81     pCodes = &multipleAlternatives[0].Codes;
82   }
83   Type = isInput;
84   isEarlyClobber = false;
85   MatchingInput = -1;
86   isCommutative = false;
87   isIndirect = false;
88   currentAlternativeIndex = 0;
89 
90   // Parse prefixes.
91   if (*I == '~') {
92     Type = isClobber;
93     ++I;
94 
95     // '{' must immediately follow '~'.
96     if (I != E && *I != '{')
97       return true;
98   } else if (*I == '=') {
99     ++I;
100     Type = isOutput;
101   }
102 
103   if (*I == '*') {
104     isIndirect = true;
105     ++I;
106   }
107 
108   if (I == E) return true;  // Just a prefix, like "==" or "~".
109 
110   // Parse the modifiers.
111   bool DoneWithModifiers = false;
112   while (!DoneWithModifiers) {
113     switch (*I) {
114     default:
115       DoneWithModifiers = true;
116       break;
117     case '&':     // Early clobber.
118       if (Type != isOutput ||      // Cannot early clobber anything but output.
119           isEarlyClobber)          // Reject &&&&&&
120         return true;
121       isEarlyClobber = true;
122       break;
123     case '%':     // Commutative.
124       if (Type == isClobber ||     // Cannot commute clobbers.
125           isCommutative)           // Reject %%%%%
126         return true;
127       isCommutative = true;
128       break;
129     case '#':     // Comment.
130     case '*':     // Register preferencing.
131       return true;     // Not supported.
132     }
133 
134     if (!DoneWithModifiers) {
135       ++I;
136       if (I == E) return true;   // Just prefixes and modifiers!
137     }
138   }
139 
140   // Parse the various constraints.
141   while (I != E) {
142     if (*I == '{') {   // Physical register reference.
143       // Find the end of the register name.
144       StringRef::iterator ConstraintEnd = std::find(I+1, E, '}');
145       if (ConstraintEnd == E) return true;  // "{foo"
146       pCodes->push_back(std::string(I, ConstraintEnd+1));
147       I = ConstraintEnd+1;
148     } else if (isdigit(static_cast<unsigned char>(*I))) { // Matching Constraint
149       // Maximal munch numbers.
150       StringRef::iterator NumStart = I;
151       while (I != E && isdigit(static_cast<unsigned char>(*I)))
152         ++I;
153       pCodes->push_back(std::string(NumStart, I));
154       unsigned N = atoi(pCodes->back().c_str());
155       // Check that this is a valid matching constraint!
156       if (N >= ConstraintsSoFar.size() || ConstraintsSoFar[N].Type != isOutput||
157           Type != isInput)
158         return true;  // Invalid constraint number.
159 
160       // If Operand N already has a matching input, reject this.  An output
161       // can't be constrained to the same value as multiple inputs.
162       if (isMultipleAlternative) {
163         InlineAsm::SubConstraintInfo &scInfo =
164           ConstraintsSoFar[N].multipleAlternatives[multipleAlternativeIndex];
165         if (scInfo.MatchingInput != -1)
166           return true;
167         // Note that operand #n has a matching input.
168         scInfo.MatchingInput = ConstraintsSoFar.size();
169       } else {
170         if (ConstraintsSoFar[N].hasMatchingInput())
171           return true;
172         // Note that operand #n has a matching input.
173         ConstraintsSoFar[N].MatchingInput = ConstraintsSoFar.size();
174         }
175     } else if (*I == '|') {
176       multipleAlternativeIndex++;
177       pCodes = &multipleAlternatives[multipleAlternativeIndex].Codes;
178       ++I;
179     } else if (*I == '^') {
180       // Multi-letter constraint
181       // FIXME: For now assuming these are 2-character constraints.
182       pCodes->push_back(std::string(I+1, I+3));
183       I += 3;
184     } else {
185       // Single letter constraint.
186       pCodes->push_back(std::string(I, I+1));
187       ++I;
188     }
189   }
190 
191   return false;
192 }
193 
194 /// selectAlternative - Point this constraint to the alternative constraint
195 /// indicated by the index.
196 void InlineAsm::ConstraintInfo::selectAlternative(unsigned index) {
197   if (index < multipleAlternatives.size()) {
198     currentAlternativeIndex = index;
199     InlineAsm::SubConstraintInfo &scInfo =
200       multipleAlternatives[currentAlternativeIndex];
201     MatchingInput = scInfo.MatchingInput;
202     Codes = scInfo.Codes;
203   }
204 }
205 
206 InlineAsm::ConstraintInfoVector
207 InlineAsm::ParseConstraints(StringRef Constraints) {
208   ConstraintInfoVector Result;
209 
210   // Scan the constraints string.
211   for (StringRef::iterator I = Constraints.begin(),
212          E = Constraints.end(); I != E; ) {
213     ConstraintInfo Info;
214 
215     // Find the end of this constraint.
216     StringRef::iterator ConstraintEnd = std::find(I, E, ',');
217 
218     if (ConstraintEnd == I ||  // Empty constraint like ",,"
219         Info.Parse(StringRef(I, ConstraintEnd-I), Result)) {
220       Result.clear();          // Erroneous constraint?
221       break;
222     }
223 
224     Result.push_back(Info);
225 
226     // ConstraintEnd may be either the next comma or the end of the string.  In
227     // the former case, we skip the comma.
228     I = ConstraintEnd;
229     if (I != E) {
230       ++I;
231       if (I == E) { Result.clear(); break; }    // don't allow "xyz,"
232     }
233   }
234 
235   return Result;
236 }
237 
238 /// Verify - Verify that the specified constraint string is reasonable for the
239 /// specified function type, and otherwise validate the constraint string.
240 bool InlineAsm::Verify(FunctionType *Ty, StringRef ConstStr) {
241   if (Ty->isVarArg()) return false;
242 
243   ConstraintInfoVector Constraints = ParseConstraints(ConstStr);
244 
245   // Error parsing constraints.
246   if (Constraints.empty() && !ConstStr.empty()) return false;
247 
248   unsigned NumOutputs = 0, NumInputs = 0, NumClobbers = 0;
249   unsigned NumIndirect = 0;
250 
251   for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
252     switch (Constraints[i].Type) {
253     case InlineAsm::isOutput:
254       if ((NumInputs-NumIndirect) != 0 || NumClobbers != 0)
255         return false;  // outputs before inputs and clobbers.
256       if (!Constraints[i].isIndirect) {
257         ++NumOutputs;
258         break;
259       }
260       ++NumIndirect;
261       // FALLTHROUGH for Indirect Outputs.
262     case InlineAsm::isInput:
263       if (NumClobbers) return false;               // inputs before clobbers.
264       ++NumInputs;
265       break;
266     case InlineAsm::isClobber:
267       ++NumClobbers;
268       break;
269     }
270   }
271 
272   switch (NumOutputs) {
273   case 0:
274     if (!Ty->getReturnType()->isVoidTy()) return false;
275     break;
276   case 1:
277     if (Ty->getReturnType()->isStructTy()) return false;
278     break;
279   default:
280     StructType *STy = dyn_cast<StructType>(Ty->getReturnType());
281     if (!STy || STy->getNumElements() != NumOutputs)
282       return false;
283     break;
284   }
285 
286   if (Ty->getNumParams() != NumInputs) return false;
287   return true;
288 }
289 
290