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 <cstdlib>
26 
27 using namespace llvm;
28 
29 InlineAsm::InlineAsm(FunctionType *FTy, const std::string &asmString,
30                      const std::string &constraints, bool hasSideEffects,
31                      bool isAlignStack, AsmDialect asmDialect, bool canThrow)
32     : Value(PointerType::getUnqual(FTy), Value::InlineAsmVal),
33       AsmString(asmString), Constraints(constraints), FTy(FTy),
34       HasSideEffects(hasSideEffects), IsAlignStack(isAlignStack),
35       Dialect(asmDialect), CanThrow(canThrow) {
36   // Do various checks on the constraint string and type.
37   assert(Verify(getFunctionType(), constraints) &&
38          "Function type not legal for constraints!");
39 }
40 
41 InlineAsm *InlineAsm::get(FunctionType *FTy, StringRef AsmString,
42                           StringRef Constraints, bool hasSideEffects,
43                           bool isAlignStack, AsmDialect asmDialect,
44                           bool canThrow) {
45   InlineAsmKeyType Key(AsmString, Constraints, FTy, hasSideEffects,
46                        isAlignStack, asmDialect, canThrow);
47   LLVMContextImpl *pImpl = FTy->getContext().pImpl;
48   return pImpl->InlineAsms.getOrCreate(PointerType::getUnqual(FTy), Key);
49 }
50 
51 void InlineAsm::destroyConstant() {
52   getType()->getContext().pImpl->InlineAsms.remove(this);
53   delete this;
54 }
55 
56 FunctionType *InlineAsm::getFunctionType() const {
57   return FTy;
58 }
59 
60 /// Parse - Analyze the specified string (e.g. "==&{eax}") and fill in the
61 /// fields in this structure.  If the constraint string is not understood,
62 /// return true, otherwise return false.
63 bool InlineAsm::ConstraintInfo::Parse(StringRef Str,
64                      InlineAsm::ConstraintInfoVector &ConstraintsSoFar) {
65   StringRef::iterator I = Str.begin(), E = Str.end();
66   unsigned multipleAlternativeCount = Str.count('|') + 1;
67   unsigned multipleAlternativeIndex = 0;
68   ConstraintCodeVector *pCodes = &Codes;
69 
70   // Initialize
71   isMultipleAlternative = multipleAlternativeCount > 1;
72   if (isMultipleAlternative) {
73     multipleAlternatives.resize(multipleAlternativeCount);
74     pCodes = &multipleAlternatives[0].Codes;
75   }
76   Type = isInput;
77   isEarlyClobber = false;
78   MatchingInput = -1;
79   isCommutative = false;
80   isIndirect = false;
81   currentAlternativeIndex = 0;
82 
83   // Parse prefixes.
84   if (*I == '~') {
85     Type = isClobber;
86     ++I;
87 
88     // '{' must immediately follow '~'.
89     if (I != E && *I != '{')
90       return true;
91   } else if (*I == '=') {
92     ++I;
93     Type = isOutput;
94   }
95 
96   if (*I == '*') {
97     isIndirect = true;
98     ++I;
99   }
100 
101   if (I == E) return true;  // Just a prefix, like "==" or "~".
102 
103   // Parse the modifiers.
104   bool DoneWithModifiers = false;
105   while (!DoneWithModifiers) {
106     switch (*I) {
107     default:
108       DoneWithModifiers = true;
109       break;
110     case '&':     // Early clobber.
111       if (Type != isOutput ||      // Cannot early clobber anything but output.
112           isEarlyClobber)          // Reject &&&&&&
113         return true;
114       isEarlyClobber = true;
115       break;
116     case '%':     // Commutative.
117       if (Type == isClobber ||     // Cannot commute clobbers.
118           isCommutative)           // Reject %%%%%
119         return true;
120       isCommutative = true;
121       break;
122     case '#':     // Comment.
123     case '*':     // Register preferencing.
124       return true;     // Not supported.
125     }
126 
127     if (!DoneWithModifiers) {
128       ++I;
129       if (I == E) return true;   // Just prefixes and modifiers!
130     }
131   }
132 
133   // Parse the various constraints.
134   while (I != E) {
135     if (*I == '{') {   // Physical register reference.
136       // Find the end of the register name.
137       StringRef::iterator ConstraintEnd = std::find(I+1, E, '}');
138       if (ConstraintEnd == E) return true;  // "{foo"
139       pCodes->push_back(std::string(StringRef(I, ConstraintEnd + 1 - I)));
140       I = ConstraintEnd+1;
141     } else if (isdigit(static_cast<unsigned char>(*I))) { // Matching Constraint
142       // Maximal munch numbers.
143       StringRef::iterator NumStart = I;
144       while (I != E && isdigit(static_cast<unsigned char>(*I)))
145         ++I;
146       pCodes->push_back(std::string(StringRef(NumStart, I - NumStart)));
147       unsigned N = atoi(pCodes->back().c_str());
148       // Check that this is a valid matching constraint!
149       if (N >= ConstraintsSoFar.size() || ConstraintsSoFar[N].Type != isOutput||
150           Type != isInput)
151         return true;  // Invalid constraint number.
152 
153       // If Operand N already has a matching input, reject this.  An output
154       // can't be constrained to the same value as multiple inputs.
155       if (isMultipleAlternative) {
156         if (multipleAlternativeIndex >=
157             ConstraintsSoFar[N].multipleAlternatives.size())
158           return true;
159         InlineAsm::SubConstraintInfo &scInfo =
160           ConstraintsSoFar[N].multipleAlternatives[multipleAlternativeIndex];
161         if (scInfo.MatchingInput != -1)
162           return true;
163         // Note that operand #n has a matching input.
164         scInfo.MatchingInput = ConstraintsSoFar.size();
165         assert(scInfo.MatchingInput >= 0);
166       } else {
167         if (ConstraintsSoFar[N].hasMatchingInput() &&
168             (size_t)ConstraintsSoFar[N].MatchingInput !=
169                 ConstraintsSoFar.size())
170           return true;
171         // Note that operand #n has a matching input.
172         ConstraintsSoFar[N].MatchingInput = ConstraintsSoFar.size();
173         assert(ConstraintsSoFar[N].MatchingInput >= 0);
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(StringRef(I + 1, 2)));
183       I += 3;
184     } else if (*I == '@') {
185       // Multi-letter constraint
186       ++I;
187       unsigned char C = static_cast<unsigned char>(*I);
188       assert(isdigit(C) && "Expected a digit!");
189       int N = C - '0';
190       assert(N > 0 && "Found a zero letter constraint!");
191       ++I;
192       pCodes->push_back(std::string(StringRef(I, N)));
193       I += N;
194     } else {
195       // Single letter constraint.
196       pCodes->push_back(std::string(StringRef(I, 1)));
197       ++I;
198     }
199   }
200 
201   return false;
202 }
203 
204 /// selectAlternative - Point this constraint to the alternative constraint
205 /// indicated by the index.
206 void InlineAsm::ConstraintInfo::selectAlternative(unsigned index) {
207   if (index < multipleAlternatives.size()) {
208     currentAlternativeIndex = index;
209     InlineAsm::SubConstraintInfo &scInfo =
210       multipleAlternatives[currentAlternativeIndex];
211     MatchingInput = scInfo.MatchingInput;
212     Codes = scInfo.Codes;
213   }
214 }
215 
216 InlineAsm::ConstraintInfoVector
217 InlineAsm::ParseConstraints(StringRef Constraints) {
218   ConstraintInfoVector Result;
219 
220   // Scan the constraints string.
221   for (StringRef::iterator I = Constraints.begin(),
222          E = Constraints.end(); I != E; ) {
223     ConstraintInfo Info;
224 
225     // Find the end of this constraint.
226     StringRef::iterator ConstraintEnd = std::find(I, E, ',');
227 
228     if (ConstraintEnd == I ||  // Empty constraint like ",,"
229         Info.Parse(StringRef(I, ConstraintEnd-I), Result)) {
230       Result.clear();          // Erroneous constraint?
231       break;
232     }
233 
234     Result.push_back(Info);
235 
236     // ConstraintEnd may be either the next comma or the end of the string.  In
237     // the former case, we skip the comma.
238     I = ConstraintEnd;
239     if (I != E) {
240       ++I;
241       if (I == E) {
242         Result.clear();
243         break;
244       } // don't allow "xyz,"
245     }
246   }
247 
248   return Result;
249 }
250 
251 /// Verify - Verify that the specified constraint string is reasonable for the
252 /// specified function type, and otherwise validate the constraint string.
253 bool InlineAsm::Verify(FunctionType *Ty, StringRef ConstStr) {
254   if (Ty->isVarArg()) return false;
255 
256   ConstraintInfoVector Constraints = ParseConstraints(ConstStr);
257 
258   // Error parsing constraints.
259   if (Constraints.empty() && !ConstStr.empty()) return false;
260 
261   unsigned NumOutputs = 0, NumInputs = 0, NumClobbers = 0;
262   unsigned NumIndirect = 0;
263 
264   for (const ConstraintInfo &Constraint : Constraints) {
265     switch (Constraint.Type) {
266     case InlineAsm::isOutput:
267       if ((NumInputs-NumIndirect) != 0 || NumClobbers != 0)
268         return false;  // outputs before inputs and clobbers.
269       if (!Constraint.isIndirect) {
270         ++NumOutputs;
271         break;
272       }
273       ++NumIndirect;
274       LLVM_FALLTHROUGH; // We fall through for Indirect Outputs.
275     case InlineAsm::isInput:
276       if (NumClobbers) return false;               // inputs before clobbers.
277       ++NumInputs;
278       break;
279     case InlineAsm::isClobber:
280       ++NumClobbers;
281       break;
282     }
283   }
284 
285   switch (NumOutputs) {
286   case 0:
287     if (!Ty->getReturnType()->isVoidTy()) return false;
288     break;
289   case 1:
290     if (Ty->getReturnType()->isStructTy()) return false;
291     break;
292   default:
293     StructType *STy = dyn_cast<StructType>(Ty->getReturnType());
294     if (!STy || STy->getNumElements() != NumOutputs)
295       return false;
296     break;
297   }
298 
299   if (Ty->getNumParams() != NumInputs) return false;
300   return true;
301 }
302