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/ADT/StringRef.h"
18 #include "llvm/IR/DerivedTypes.h"
19 #include "llvm/IR/LLVMContext.h"
20 #include "llvm/IR/Value.h"
21 #include "llvm/Support/Casting.h"
22 #include "llvm/Support/Compiler.h"
23 #include <algorithm>
24 #include <cassert>
25 #include <cctype>
26 #include <cstddef>
27 #include <cstdlib>
28 
29 using namespace llvm;
30 
31 InlineAsm::InlineAsm(FunctionType *FTy, const std::string &asmString,
32                      const std::string &constraints, bool hasSideEffects,
33                      bool isAlignStack, AsmDialect asmDialect)
34     : Value(PointerType::getUnqual(FTy), Value::InlineAsmVal),
35       AsmString(asmString), Constraints(constraints), FTy(FTy),
36       HasSideEffects(hasSideEffects), IsAlignStack(isAlignStack),
37       Dialect(asmDialect) {
38   // Do various checks on the constraint string and type.
39   assert(Verify(getFunctionType(), constraints) &&
40          "Function type not legal for constraints!");
41 }
42 
43 InlineAsm *InlineAsm::get(FunctionType *FTy, StringRef AsmString,
44                           StringRef Constraints, bool hasSideEffects,
45                           bool isAlignStack, AsmDialect asmDialect) {
46   InlineAsmKeyType Key(AsmString, Constraints, FTy, hasSideEffects,
47                        isAlignStack, asmDialect);
48   LLVMContextImpl *pImpl = FTy->getContext().pImpl;
49   return pImpl->InlineAsms.getOrCreate(PointerType::getUnqual(FTy), Key);
50 }
51 
52 void InlineAsm::destroyConstant() {
53   getType()->getContext().pImpl->InlineAsms.remove(this);
54   delete this;
55 }
56 
57 FunctionType *InlineAsm::getFunctionType() const {
58   return FTy;
59 }
60 
61 /// Parse - Analyze the specified string (e.g. "==&{eax}") and fill in the
62 /// fields in this structure.  If the constraint string is not understood,
63 /// return true, otherwise return false.
64 bool InlineAsm::ConstraintInfo::Parse(StringRef Str,
65                      InlineAsm::ConstraintInfoVector &ConstraintsSoFar) {
66   StringRef::iterator I = Str.begin(), E = Str.end();
67   unsigned multipleAlternativeCount = Str.count('|') + 1;
68   unsigned multipleAlternativeIndex = 0;
69   ConstraintCodeVector *pCodes = &Codes;
70 
71   // Initialize
72   isMultipleAlternative = multipleAlternativeCount > 1;
73   if (isMultipleAlternative) {
74     multipleAlternatives.resize(multipleAlternativeCount);
75     pCodes = &multipleAlternatives[0].Codes;
76   }
77   Type = isInput;
78   isEarlyClobber = false;
79   MatchingInput = -1;
80   isCommutative = false;
81   isIndirect = false;
82   currentAlternativeIndex = 0;
83 
84   // Parse prefixes.
85   if (*I == '~') {
86     Type = isClobber;
87     ++I;
88 
89     // '{' must immediately follow '~'.
90     if (I != E && *I != '{')
91       return true;
92   } else if (*I == '=') {
93     ++I;
94     Type = isOutput;
95   }
96 
97   if (*I == '*') {
98     isIndirect = true;
99     ++I;
100   }
101 
102   if (I == E) return true;  // Just a prefix, like "==" or "~".
103 
104   // Parse the modifiers.
105   bool DoneWithModifiers = false;
106   while (!DoneWithModifiers) {
107     switch (*I) {
108     default:
109       DoneWithModifiers = true;
110       break;
111     case '&':     // Early clobber.
112       if (Type != isOutput ||      // Cannot early clobber anything but output.
113           isEarlyClobber)          // Reject &&&&&&
114         return true;
115       isEarlyClobber = true;
116       break;
117     case '%':     // Commutative.
118       if (Type == isClobber ||     // Cannot commute clobbers.
119           isCommutative)           // Reject %%%%%
120         return true;
121       isCommutative = true;
122       break;
123     case '#':     // Comment.
124     case '*':     // Register preferencing.
125       return true;     // Not supported.
126     }
127 
128     if (!DoneWithModifiers) {
129       ++I;
130       if (I == E) return true;   // Just prefixes and modifiers!
131     }
132   }
133 
134   // Parse the various constraints.
135   while (I != E) {
136     if (*I == '{') {   // Physical register reference.
137       // Find the end of the register name.
138       StringRef::iterator ConstraintEnd = std::find(I+1, E, '}');
139       if (ConstraintEnd == E) return true;  // "{foo"
140       pCodes->push_back(StringRef(I, ConstraintEnd+1 - I));
141       I = ConstraintEnd+1;
142     } else if (isdigit(static_cast<unsigned char>(*I))) { // Matching Constraint
143       // Maximal munch numbers.
144       StringRef::iterator NumStart = I;
145       while (I != E && isdigit(static_cast<unsigned char>(*I)))
146         ++I;
147       pCodes->push_back(StringRef(NumStart, I - NumStart));
148       unsigned N = atoi(pCodes->back().c_str());
149       // Check that this is a valid matching constraint!
150       if (N >= ConstraintsSoFar.size() || ConstraintsSoFar[N].Type != isOutput||
151           Type != isInput)
152         return true;  // Invalid constraint number.
153 
154       // If Operand N already has a matching input, reject this.  An output
155       // can't be constrained to the same value as multiple inputs.
156       if (isMultipleAlternative) {
157         if (multipleAlternativeIndex >=
158             ConstraintsSoFar[N].multipleAlternatives.size())
159           return true;
160         InlineAsm::SubConstraintInfo &scInfo =
161           ConstraintsSoFar[N].multipleAlternatives[multipleAlternativeIndex];
162         if (scInfo.MatchingInput != -1)
163           return true;
164         // Note that operand #n has a matching input.
165         scInfo.MatchingInput = ConstraintsSoFar.size();
166         assert(scInfo.MatchingInput >= 0);
167       } else {
168         if (ConstraintsSoFar[N].hasMatchingInput() &&
169             (size_t)ConstraintsSoFar[N].MatchingInput !=
170                 ConstraintsSoFar.size())
171           return true;
172         // Note that operand #n has a matching input.
173         ConstraintsSoFar[N].MatchingInput = ConstraintsSoFar.size();
174         assert(ConstraintsSoFar[N].MatchingInput >= 0);
175         }
176     } else if (*I == '|') {
177       multipleAlternativeIndex++;
178       pCodes = &multipleAlternatives[multipleAlternativeIndex].Codes;
179       ++I;
180     } else if (*I == '^') {
181       // Multi-letter constraint
182       // FIXME: For now assuming these are 2-character constraints.
183       pCodes->push_back(StringRef(I+1, 2));
184       I += 3;
185     } else {
186       // Single letter constraint.
187       pCodes->push_back(StringRef(I, 1));
188       ++I;
189     }
190   }
191 
192   return false;
193 }
194 
195 /// selectAlternative - Point this constraint to the alternative constraint
196 /// indicated by the index.
197 void InlineAsm::ConstraintInfo::selectAlternative(unsigned index) {
198   if (index < multipleAlternatives.size()) {
199     currentAlternativeIndex = index;
200     InlineAsm::SubConstraintInfo &scInfo =
201       multipleAlternatives[currentAlternativeIndex];
202     MatchingInput = scInfo.MatchingInput;
203     Codes = scInfo.Codes;
204   }
205 }
206 
207 InlineAsm::ConstraintInfoVector
208 InlineAsm::ParseConstraints(StringRef Constraints) {
209   ConstraintInfoVector Result;
210 
211   // Scan the constraints string.
212   for (StringRef::iterator I = Constraints.begin(),
213          E = Constraints.end(); I != E; ) {
214     ConstraintInfo Info;
215 
216     // Find the end of this constraint.
217     StringRef::iterator ConstraintEnd = std::find(I, E, ',');
218 
219     if (ConstraintEnd == I ||  // Empty constraint like ",,"
220         Info.Parse(StringRef(I, ConstraintEnd-I), Result)) {
221       Result.clear();          // Erroneous constraint?
222       break;
223     }
224 
225     Result.push_back(Info);
226 
227     // ConstraintEnd may be either the next comma or the end of the string.  In
228     // the former case, we skip the comma.
229     I = ConstraintEnd;
230     if (I != E) {
231       ++I;
232       if (I == E) {
233         Result.clear();
234         break;
235       } // don't allow "xyz,"
236     }
237   }
238 
239   return Result;
240 }
241 
242 /// Verify - Verify that the specified constraint string is reasonable for the
243 /// specified function type, and otherwise validate the constraint string.
244 bool InlineAsm::Verify(FunctionType *Ty, StringRef ConstStr) {
245   if (Ty->isVarArg()) return false;
246 
247   ConstraintInfoVector Constraints = ParseConstraints(ConstStr);
248 
249   // Error parsing constraints.
250   if (Constraints.empty() && !ConstStr.empty()) return false;
251 
252   unsigned NumOutputs = 0, NumInputs = 0, NumClobbers = 0;
253   unsigned NumIndirect = 0;
254 
255   for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
256     switch (Constraints[i].Type) {
257     case InlineAsm::isOutput:
258       if ((NumInputs-NumIndirect) != 0 || NumClobbers != 0)
259         return false;  // outputs before inputs and clobbers.
260       if (!Constraints[i].isIndirect) {
261         ++NumOutputs;
262         break;
263       }
264       ++NumIndirect;
265       LLVM_FALLTHROUGH; // We fall through for Indirect Outputs.
266     case InlineAsm::isInput:
267       if (NumClobbers) return false;               // inputs before clobbers.
268       ++NumInputs;
269       break;
270     case InlineAsm::isClobber:
271       ++NumClobbers;
272       break;
273     }
274   }
275 
276   switch (NumOutputs) {
277   case 0:
278     if (!Ty->getReturnType()->isVoidTy()) return false;
279     break;
280   case 1:
281     if (Ty->getReturnType()->isStructTy()) return false;
282     break;
283   default:
284     StructType *STy = dyn_cast<StructType>(Ty->getReturnType());
285     if (!STy || STy->getNumElements() != NumOutputs)
286       return false;
287     break;
288   }
289 
290   if (Ty->getNumParams() != NumInputs) return false;
291   return true;
292 }
293