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 "ConstantsContext.h"
15 #include "LLVMContextImpl.h"
16 #include "llvm/ADT/StringRef.h"
17 #include "llvm/IR/DerivedTypes.h"
18 #include "llvm/IR/InlineAsm.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 // Implement the first virtual method in this class in this file so the
44 // InlineAsm vtable is emitted here.
45 InlineAsm::~InlineAsm() = default;
46 
47 InlineAsm *InlineAsm::get(FunctionType *FTy, StringRef AsmString,
48                           StringRef Constraints, bool hasSideEffects,
49                           bool isAlignStack, AsmDialect asmDialect) {
50   InlineAsmKeyType Key(AsmString, Constraints, FTy, hasSideEffects,
51                        isAlignStack, asmDialect);
52   LLVMContextImpl *pImpl = FTy->getContext().pImpl;
53   return pImpl->InlineAsms.getOrCreate(PointerType::getUnqual(FTy), Key);
54 }
55 
56 void InlineAsm::destroyConstant() {
57   getType()->getContext().pImpl->InlineAsms.remove(this);
58   delete this;
59 }
60 
61 FunctionType *InlineAsm::getFunctionType() const {
62   return FTy;
63 }
64 
65 /// Parse - Analyze the specified string (e.g. "==&{eax}") and fill in the
66 /// fields in this structure.  If the constraint string is not understood,
67 /// return true, otherwise return false.
68 bool InlineAsm::ConstraintInfo::Parse(StringRef Str,
69                      InlineAsm::ConstraintInfoVector &ConstraintsSoFar) {
70   StringRef::iterator I = Str.begin(), E = Str.end();
71   unsigned multipleAlternativeCount = Str.count('|') + 1;
72   unsigned multipleAlternativeIndex = 0;
73   ConstraintCodeVector *pCodes = &Codes;
74 
75   // Initialize
76   isMultipleAlternative = multipleAlternativeCount > 1;
77   if (isMultipleAlternative) {
78     multipleAlternatives.resize(multipleAlternativeCount);
79     pCodes = &multipleAlternatives[0].Codes;
80   }
81   Type = isInput;
82   isEarlyClobber = false;
83   MatchingInput = -1;
84   isCommutative = false;
85   isIndirect = false;
86   currentAlternativeIndex = 0;
87 
88   // Parse prefixes.
89   if (*I == '~') {
90     Type = isClobber;
91     ++I;
92 
93     // '{' must immediately follow '~'.
94     if (I != E && *I != '{')
95       return true;
96   } else if (*I == '=') {
97     ++I;
98     Type = isOutput;
99   }
100 
101   if (*I == '*') {
102     isIndirect = true;
103     ++I;
104   }
105 
106   if (I == E) return true;  // Just a prefix, like "==" or "~".
107 
108   // Parse the modifiers.
109   bool DoneWithModifiers = false;
110   while (!DoneWithModifiers) {
111     switch (*I) {
112     default:
113       DoneWithModifiers = true;
114       break;
115     case '&':     // Early clobber.
116       if (Type != isOutput ||      // Cannot early clobber anything but output.
117           isEarlyClobber)          // Reject &&&&&&
118         return true;
119       isEarlyClobber = true;
120       break;
121     case '%':     // Commutative.
122       if (Type == isClobber ||     // Cannot commute clobbers.
123           isCommutative)           // Reject %%%%%
124         return true;
125       isCommutative = true;
126       break;
127     case '#':     // Comment.
128     case '*':     // Register preferencing.
129       return true;     // Not supported.
130     }
131 
132     if (!DoneWithModifiers) {
133       ++I;
134       if (I == E) return true;   // Just prefixes and modifiers!
135     }
136   }
137 
138   // Parse the various constraints.
139   while (I != E) {
140     if (*I == '{') {   // Physical register reference.
141       // Find the end of the register name.
142       StringRef::iterator ConstraintEnd = std::find(I+1, E, '}');
143       if (ConstraintEnd == E) return true;  // "{foo"
144       pCodes->push_back(StringRef(I, ConstraintEnd+1 - I));
145       I = ConstraintEnd+1;
146     } else if (isdigit(static_cast<unsigned char>(*I))) { // Matching Constraint
147       // Maximal munch numbers.
148       StringRef::iterator NumStart = I;
149       while (I != E && isdigit(static_cast<unsigned char>(*I)))
150         ++I;
151       pCodes->push_back(StringRef(NumStart, I - NumStart));
152       unsigned N = atoi(pCodes->back().c_str());
153       // Check that this is a valid matching constraint!
154       if (N >= ConstraintsSoFar.size() || ConstraintsSoFar[N].Type != isOutput||
155           Type != isInput)
156         return true;  // Invalid constraint number.
157 
158       // If Operand N already has a matching input, reject this.  An output
159       // can't be constrained to the same value as multiple inputs.
160       if (isMultipleAlternative) {
161         if (multipleAlternativeIndex >=
162             ConstraintsSoFar[N].multipleAlternatives.size())
163           return true;
164         InlineAsm::SubConstraintInfo &scInfo =
165           ConstraintsSoFar[N].multipleAlternatives[multipleAlternativeIndex];
166         if (scInfo.MatchingInput != -1)
167           return true;
168         // Note that operand #n has a matching input.
169         scInfo.MatchingInput = ConstraintsSoFar.size();
170       } else {
171         if (ConstraintsSoFar[N].hasMatchingInput() &&
172             (size_t)ConstraintsSoFar[N].MatchingInput !=
173                 ConstraintsSoFar.size())
174           return true;
175         // Note that operand #n has a matching input.
176         ConstraintsSoFar[N].MatchingInput = ConstraintsSoFar.size();
177         }
178     } else if (*I == '|') {
179       multipleAlternativeIndex++;
180       pCodes = &multipleAlternatives[multipleAlternativeIndex].Codes;
181       ++I;
182     } else if (*I == '^') {
183       // Multi-letter constraint
184       // FIXME: For now assuming these are 2-character constraints.
185       pCodes->push_back(StringRef(I+1, 2));
186       I += 3;
187     } else {
188       // Single letter constraint.
189       pCodes->push_back(StringRef(I, 1));
190       ++I;
191     }
192   }
193 
194   return false;
195 }
196 
197 /// selectAlternative - Point this constraint to the alternative constraint
198 /// indicated by the index.
199 void InlineAsm::ConstraintInfo::selectAlternative(unsigned index) {
200   if (index < multipleAlternatives.size()) {
201     currentAlternativeIndex = index;
202     InlineAsm::SubConstraintInfo &scInfo =
203       multipleAlternatives[currentAlternativeIndex];
204     MatchingInput = scInfo.MatchingInput;
205     Codes = scInfo.Codes;
206   }
207 }
208 
209 InlineAsm::ConstraintInfoVector
210 InlineAsm::ParseConstraints(StringRef Constraints) {
211   ConstraintInfoVector Result;
212 
213   // Scan the constraints string.
214   for (StringRef::iterator I = Constraints.begin(),
215          E = Constraints.end(); I != E; ) {
216     ConstraintInfo Info;
217 
218     // Find the end of this constraint.
219     StringRef::iterator ConstraintEnd = std::find(I, E, ',');
220 
221     if (ConstraintEnd == I ||  // Empty constraint like ",,"
222         Info.Parse(StringRef(I, ConstraintEnd-I), Result)) {
223       Result.clear();          // Erroneous constraint?
224       break;
225     }
226 
227     Result.push_back(Info);
228 
229     // ConstraintEnd may be either the next comma or the end of the string.  In
230     // the former case, we skip the comma.
231     I = ConstraintEnd;
232     if (I != E) {
233       ++I;
234       if (I == E) {
235         Result.clear();
236         break;
237       } // don't allow "xyz,"
238     }
239   }
240 
241   return Result;
242 }
243 
244 /// Verify - Verify that the specified constraint string is reasonable for the
245 /// specified function type, and otherwise validate the constraint string.
246 bool InlineAsm::Verify(FunctionType *Ty, StringRef ConstStr) {
247   if (Ty->isVarArg()) return false;
248 
249   ConstraintInfoVector Constraints = ParseConstraints(ConstStr);
250 
251   // Error parsing constraints.
252   if (Constraints.empty() && !ConstStr.empty()) return false;
253 
254   unsigned NumOutputs = 0, NumInputs = 0, NumClobbers = 0;
255   unsigned NumIndirect = 0;
256 
257   for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
258     switch (Constraints[i].Type) {
259     case InlineAsm::isOutput:
260       if ((NumInputs-NumIndirect) != 0 || NumClobbers != 0)
261         return false;  // outputs before inputs and clobbers.
262       if (!Constraints[i].isIndirect) {
263         ++NumOutputs;
264         break;
265       }
266       ++NumIndirect;
267       LLVM_FALLTHROUGH; // We fall through for Indirect Outputs.
268     case InlineAsm::isInput:
269       if (NumClobbers) return false;               // inputs before clobbers.
270       ++NumInputs;
271       break;
272     case InlineAsm::isClobber:
273       ++NumClobbers;
274       break;
275     }
276   }
277 
278   switch (NumOutputs) {
279   case 0:
280     if (!Ty->getReturnType()->isVoidTy()) return false;
281     break;
282   case 1:
283     if (Ty->getReturnType()->isStructTy()) return false;
284     break;
285   default:
286     StructType *STy = dyn_cast<StructType>(Ty->getReturnType());
287     if (!STy || STy->getNumElements() != NumOutputs)
288       return false;
289     break;
290   }
291 
292   if (Ty->getNumParams() != NumInputs) return false;
293   return true;
294 }
295