llvm/lib/IR/InlineAsm.cpp

   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 "llvm/Support/Errc.h"
  23 #include <algorithm>
  24 #include <cassert>
  25 #include <cctype>
  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 #ifndef NDEBUG
  38   // Do various checks on the constraint string and type.
  39   cantFail(verify(getFunctionType(), constraints));
  40 #endif
  41 }
  42
  43 InlineAsm *InlineAsm::get(FunctionType *FTy, StringRef AsmString,
  44                           StringRef Constraints, bool hasSideEffects,
  45                           bool isAlignStack, AsmDialect asmDialect,
  46                           bool canThrow) {
  47   InlineAsmKeyType Key(AsmString, Constraints, FTy, hasSideEffects,
  48                        isAlignStack, asmDialect, canThrow);
  49   LLVMContextImpl *pImpl = FTy->getContext().pImpl;
  50   return pImpl->InlineAsms.getOrCreate(PointerType::getUnqual(FTy), Key);
  51 }
  52
  53 void InlineAsm::destroyConstant() {
  54   getType()->getContext().pImpl->InlineAsms.remove(this);
  55   delete this;
  56 }
  57
  58 FunctionType *InlineAsm::getFunctionType() const {
  59   return FTy;
  60 }
  61
  62 void InlineAsm::collectAsmStrs(SmallVectorImpl<StringRef> &AsmStrs) const {
  63   StringRef AsmStr(AsmString);
  64   AsmStrs.clear();
  65
  66   // TODO: 1) Unify delimiter for inline asm, we also meet other delimiters
  67   // for example "\0A", ";".
  68   // 2) Enhance StringRef. Some of the special delimiter ("\0") can't be
  69   // split in StringRef. Also empty StringRef can not call split (will stuck).
  70   if (AsmStr.empty())
  71     return;
  72   AsmStr.split(AsmStrs, "\n\t", -1, false);
  73 }
  74
  75 /// Parse - Analyze the specified string (e.g. "==&{eax}") and fill in the
  76 /// fields in this structure.  If the constraint string is not understood,
  77 /// return true, otherwise return false.
  78 bool InlineAsm::ConstraintInfo::Parse(StringRef Str,
  79                      InlineAsm::ConstraintInfoVector &ConstraintsSoFar) {
  80   StringRef::iterator I = Str.begin(), E = Str.end();
  81   unsigned multipleAlternativeCount = Str.count('|') + 1;
  82   unsigned multipleAlternativeIndex = 0;
  83   ConstraintCodeVector *pCodes = &Codes;
  84
  85   // Initialize
  86   isMultipleAlternative = multipleAlternativeCount > 1;
  87   if (isMultipleAlternative) {
  88     multipleAlternatives.resize(multipleAlternativeCount);
  89     pCodes = &multipleAlternatives[0].Codes;
  90   }
  91   Type = isInput;
  92   isEarlyClobber = false;
  93   MatchingInput = -1;
  94   isCommutative = false;
  95   isIndirect = false;
  96   currentAlternativeIndex = 0;
  97
  98   // Parse prefixes.
  99   if (*I == '~') {
 100     Type = isClobber;
 101     ++I;
 102
 103     // '{' must immediately follow '~'.
 104     if (I != E && *I != '{')
 105       return true;
 106   } else if (*I == '=') {
 107     ++I;
 108     Type = isOutput;
 109   } else if (*I == '!') {
 110     ++I;
 111     Type = isLabel;
 112   }
 113
 114   if (*I == '*') {
 115     isIndirect = true;
 116     ++I;
 117   }
 118
 119   if (I == E) return true;  // Just a prefix, like "==" or "~".
 120
 121   // Parse the modifiers.
 122   bool DoneWithModifiers = false;
 123   while (!DoneWithModifiers) {
 124     switch (*I) {
 125     default:
 126       DoneWithModifiers = true;
 127       break;
 128     case '&':     // Early clobber.
 129       if (Type != isOutput ||      // Cannot early clobber anything but output.
 130           isEarlyClobber)          // Reject &&&&&&
 131         return true;
 132       isEarlyClobber = true;
 133       break;
 134     case '%':     // Commutative.
 135       if (Type == isClobber ||     // Cannot commute clobbers.
 136           isCommutative)           // Reject %%%%%
 137         return true;
 138       isCommutative = true;
 139       break;
 140     case '#':     // Comment.
 141     case '*':     // Register preferencing.
 142       return true;     // Not supported.
 143     }
 144
 145     if (!DoneWithModifiers) {
 146       ++I;
 147       if (I == E) return true;   // Just prefixes and modifiers!
 148     }
 149   }
 150
 151   // Parse the various constraints.
 152   while (I != E) {
 153     if (*I == '{') {   // Physical register reference.
 154       // Find the end of the register name.
 155       StringRef::iterator ConstraintEnd = std::find(I+1, E, '}');
 156       if (ConstraintEnd == E) return true;  // "{foo"
 157       pCodes->push_back(std::string(StringRef(I, ConstraintEnd + 1 - I)));
 158       I = ConstraintEnd+1;
 159     } else if (isdigit(static_cast<unsigned char>(*I))) { // Matching Constraint
 160       // Maximal munch numbers.
 161       StringRef::iterator NumStart = I;
 162       while (I != E && isdigit(static_cast<unsigned char>(*I)))
 163         ++I;
 164       pCodes->push_back(std::string(StringRef(NumStart, I - NumStart)));
 165       unsigned N = atoi(pCodes->back().c_str());
 166       // Check that this is a valid matching constraint!
 167       if (N >= ConstraintsSoFar.size() || ConstraintsSoFar[N].Type != isOutput||
 168           Type != isInput)
 169         return true;  // Invalid constraint number.
 170
 171       // If Operand N already has a matching input, reject this.  An output
 172       // can't be constrained to the same value as multiple inputs.
 173       if (isMultipleAlternative) {
 174         if (multipleAlternativeIndex >=
 175             ConstraintsSoFar[N].multipleAlternatives.size())
 176           return true;
 177         InlineAsm::SubConstraintInfo &scInfo =
 178           ConstraintsSoFar[N].multipleAlternatives[multipleAlternativeIndex];
 179         if (scInfo.MatchingInput != -1)
 180           return true;
 181         // Note that operand #n has a matching input.
 182         scInfo.MatchingInput = ConstraintsSoFar.size();
 183         assert(scInfo.MatchingInput >= 0);
 184       } else {
 185         if (ConstraintsSoFar[N].hasMatchingInput() &&
 186             (size_t)ConstraintsSoFar[N].MatchingInput !=
 187                 ConstraintsSoFar.size())
 188           return true;
 189         // Note that operand #n has a matching input.
 190         ConstraintsSoFar[N].MatchingInput = ConstraintsSoFar.size();
 191         assert(ConstraintsSoFar[N].MatchingInput >= 0);
 192         }
 193     } else if (*I == '|') {
 194       multipleAlternativeIndex++;
 195       pCodes = &multipleAlternatives[multipleAlternativeIndex].Codes;
 196       ++I;
 197     } else if (*I == '^') {
 198       // Multi-letter constraint
 199       // FIXME: For now assuming these are 2-character constraints.
 200       pCodes->push_back(std::string(StringRef(I + 1, 2)));
 201       I += 3;
 202     } else if (*I == '@') {
 203       // Multi-letter constraint
 204       ++I;
 205       unsigned char C = static_cast<unsigned char>(*I);
 206       assert(isdigit(C) && "Expected a digit!");
 207       int N = C - '0';
 208       assert(N > 0 && "Found a zero letter constraint!");
 209       ++I;
 210       pCodes->push_back(std::string(StringRef(I, N)));
 211       I += N;
 212     } else {
 213       // Single letter constraint.
 214       pCodes->push_back(std::string(StringRef(I, 1)));
 215       ++I;
 216     }
 217   }
 218
 219   return false;
 220 }
 221
 222 /// selectAlternative - Point this constraint to the alternative constraint
 223 /// indicated by the index.
 224 void InlineAsm::ConstraintInfo::selectAlternative(unsigned index) {
 225   if (index < multipleAlternatives.size()) {
 226     currentAlternativeIndex = index;
 227     InlineAsm::SubConstraintInfo &scInfo =
 228       multipleAlternatives[currentAlternativeIndex];
 229     MatchingInput = scInfo.MatchingInput;
 230     Codes = scInfo.Codes;
 231   }
 232 }
 233
 234 InlineAsm::ConstraintInfoVector
 235 InlineAsm::ParseConstraints(StringRef Constraints) {
 236   ConstraintInfoVector Result;
 237
 238   // Scan the constraints string.
 239   for (StringRef::iterator I = Constraints.begin(),
 240          E = Constraints.end(); I != E; ) {
 241     ConstraintInfo Info;
 242
 243     // Find the end of this constraint.
 244     StringRef::iterator ConstraintEnd = std::find(I, E, ',');
 245
 246     if (ConstraintEnd == I ||  // Empty constraint like ",,"
 247         Info.Parse(StringRef(I, ConstraintEnd-I), Result)) {
 248       Result.clear();          // Erroneous constraint?
 249       break;
 250     }
 251
 252     Result.push_back(Info);
 253
 254     // ConstraintEnd may be either the next comma or the end of the string.  In
 255     // the former case, we skip the comma.
 256     I = ConstraintEnd;
 257     if (I != E) {
 258       ++I;
 259       if (I == E) {
 260         Result.clear();
 261         break;
 262       } // don't allow "xyz,"
 263     }
 264   }
 265
 266   return Result;
 267 }
 268
 269 static Error makeStringError(const char *Msg) {
 270   return createStringError(errc::invalid_argument, Msg);
 271 }
 272
 273 Error InlineAsm::verify(FunctionType *Ty, StringRef ConstStr) {
 274   if (Ty->isVarArg())
 275     return makeStringError("inline asm cannot be variadic");
 276
 277   ConstraintInfoVector Constraints = ParseConstraints(ConstStr);
 278
 279   // Error parsing constraints.
 280   if (Constraints.empty() && !ConstStr.empty())
 281     return makeStringError("failed to parse constraints");
 282
 283   unsigned NumOutputs = 0, NumInputs = 0, NumClobbers = 0;
 284   unsigned NumIndirect = 0, NumLabels = 0;
 285
 286   for (const ConstraintInfo &Constraint : Constraints) {
 287     switch (Constraint.Type) {
 288     case InlineAsm::isOutput:
 289       if ((NumInputs-NumIndirect) != 0 || NumClobbers != 0 || NumLabels != 0)
 290         return makeStringError("output constraint occurs after input, "
 291                                "clobber or label constraint");
 292
 293       if (!Constraint.isIndirect) {
 294         ++NumOutputs;
 295         break;
 296       }
 297       ++NumIndirect;
 298       [[fallthrough]]; // We fall through for Indirect Outputs.
 299     case InlineAsm::isInput:
 300       if (NumClobbers)
 301         return makeStringError("input constraint occurs after clobber "
 302                                "constraint");
 303       ++NumInputs;
 304       break;
 305     case InlineAsm::isClobber:
 306       ++NumClobbers;
 307       break;
 308     case InlineAsm::isLabel:
 309       if (NumClobbers)
 310         return makeStringError("label constraint occurs after clobber "
 311                                "constraint");
 312
 313       ++NumLabels;
 314       break;
 315     }
 316   }
 317
 318   switch (NumOutputs) {
 319   case 0:
 320     if (!Ty->getReturnType()->isVoidTy())
 321       return makeStringError("inline asm without outputs must return void");
 322     break;
 323   case 1:
 324     if (Ty->getReturnType()->isStructTy())
 325       return makeStringError("inline asm with one output cannot return struct");
 326     break;
 327   default:
 328     StructType *STy = dyn_cast<StructType>(Ty->getReturnType());
 329     if (!STy || STy->getNumElements() != NumOutputs)
 330       return makeStringError("number of output constraints does not match "
 331                              "number of return struct elements");
 332     break;
 333   }
 334
 335   if (Ty->getNumParams() != NumInputs)
 336     return makeStringError("number of input constraints does not match number "
 337                            "of parameters");
 338
 339   // We don't have access to labels here, NumLabels will be checked separately.
 340   return Error::success();
 341 }