1 //===- InlineAsm.cpp - Implement the InlineAsm class ----------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the InlineAsm class.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/IR/InlineAsm.h"
14 #include "ConstantsContext.h"
15 #include "LLVMContextImpl.h"
16 #include "llvm/ADT/StringRef.h"
17 #include "llvm/IR/DerivedTypes.h"
18 #include "llvm/IR/LLVMContext.h"
19 #include "llvm/IR/Value.h"
20 #include "llvm/Support/Casting.h"
21 #include "llvm/Support/Compiler.h"
22 #include <algorithm>
23 #include <cassert>
24 #include <cctype>
25 #include <cstddef>
26 #include <cstdlib>
27 
28 using namespace llvm;
29 
30 InlineAsm::InlineAsm(FunctionType *FTy, const std::string &asmString,
31                      const std::string &constraints, bool hasSideEffects,
32                      bool isAlignStack, AsmDialect asmDialect, bool canThrow)
33     : Value(PointerType::getUnqual(FTy), Value::InlineAsmVal),
34       AsmString(asmString), Constraints(constraints), FTy(FTy),
35       HasSideEffects(hasSideEffects), IsAlignStack(isAlignStack),
36       Dialect(asmDialect), CanThrow(canThrow) {
37   // Do various checks on the constraint string and type.
38   assert(Verify(getFunctionType(), constraints) &&
39          "Function type not legal for constraints!");
40 }
41 
42 InlineAsm *InlineAsm::get(FunctionType *FTy, StringRef AsmString,
43                           StringRef Constraints, bool hasSideEffects,
44                           bool isAlignStack, AsmDialect asmDialect,
45                           bool canThrow) {
46   InlineAsmKeyType Key(AsmString, Constraints, FTy, hasSideEffects,
47                        isAlignStack, asmDialect, canThrow);
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(std::string(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(std::string(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(std::string(StringRef(I + 1, 2)));
184       I += 3;
185     } else if (*I == '@') {
186       // Multi-letter constraint
187       ++I;
188       unsigned char C = static_cast<unsigned char>(*I);
189       assert(isdigit(C) && "Expected a digit!");
190       int N = C - '0';
191       assert(N > 0 && "Found a zero letter constraint!");
192       ++I;
193       pCodes->push_back(std::string(StringRef(I, N)));
194       I += N;
195     } else {
196       // Single letter constraint.
197       pCodes->push_back(std::string(StringRef(I, 1)));
198       ++I;
199     }
200   }
201 
202   return false;
203 }
204 
205 /// selectAlternative - Point this constraint to the alternative constraint
206 /// indicated by the index.
207 void InlineAsm::ConstraintInfo::selectAlternative(unsigned index) {
208   if (index < multipleAlternatives.size()) {
209     currentAlternativeIndex = index;
210     InlineAsm::SubConstraintInfo &scInfo =
211       multipleAlternatives[currentAlternativeIndex];
212     MatchingInput = scInfo.MatchingInput;
213     Codes = scInfo.Codes;
214   }
215 }
216 
217 InlineAsm::ConstraintInfoVector
218 InlineAsm::ParseConstraints(StringRef Constraints) {
219   ConstraintInfoVector Result;
220 
221   // Scan the constraints string.
222   for (StringRef::iterator I = Constraints.begin(),
223          E = Constraints.end(); I != E; ) {
224     ConstraintInfo Info;
225 
226     // Find the end of this constraint.
227     StringRef::iterator ConstraintEnd = std::find(I, E, ',');
228 
229     if (ConstraintEnd == I ||  // Empty constraint like ",,"
230         Info.Parse(StringRef(I, ConstraintEnd-I), Result)) {
231       Result.clear();          // Erroneous constraint?
232       break;
233     }
234 
235     Result.push_back(Info);
236 
237     // ConstraintEnd may be either the next comma or the end of the string.  In
238     // the former case, we skip the comma.
239     I = ConstraintEnd;
240     if (I != E) {
241       ++I;
242       if (I == E) {
243         Result.clear();
244         break;
245       } // don't allow "xyz,"
246     }
247   }
248 
249   return Result;
250 }
251 
252 /// Verify - Verify that the specified constraint string is reasonable for the
253 /// specified function type, and otherwise validate the constraint string.
254 bool InlineAsm::Verify(FunctionType *Ty, StringRef ConstStr) {
255   if (Ty->isVarArg()) return false;
256 
257   ConstraintInfoVector Constraints = ParseConstraints(ConstStr);
258 
259   // Error parsing constraints.
260   if (Constraints.empty() && !ConstStr.empty()) return false;
261 
262   unsigned NumOutputs = 0, NumInputs = 0, NumClobbers = 0;
263   unsigned NumIndirect = 0;
264 
265   for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
266     switch (Constraints[i].Type) {
267     case InlineAsm::isOutput:
268       if ((NumInputs-NumIndirect) != 0 || NumClobbers != 0)
269         return false;  // outputs before inputs and clobbers.
270       if (!Constraints[i].isIndirect) {
271         ++NumOutputs;
272         break;
273       }
274       ++NumIndirect;
275       LLVM_FALLTHROUGH; // We fall through for Indirect Outputs.
276     case InlineAsm::isInput:
277       if (NumClobbers) return false;               // inputs before clobbers.
278       ++NumInputs;
279       break;
280     case InlineAsm::isClobber:
281       ++NumClobbers;
282       break;
283     }
284   }
285 
286   switch (NumOutputs) {
287   case 0:
288     if (!Ty->getReturnType()->isVoidTy()) return false;
289     break;
290   case 1:
291     if (Ty->getReturnType()->isStructTy()) return false;
292     break;
293   default:
294     StructType *STy = dyn_cast<StructType>(Ty->getReturnType());
295     if (!STy || STy->getNumElements() != NumOutputs)
296       return false;
297     break;
298   }
299 
300   if (Ty->getNumParams() != NumInputs) return false;
301   return true;
302 }
303