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->getContext()), 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(
  51       PointerType::getUnqual(FTy->getContext()), Key);
  52 }
  53
  54 void InlineAsm::destroyConstant() {
  55   getType()->getContext().pImpl->InlineAsms.remove(this);
  56   delete this;
  57 }
  58
  59 FunctionType *InlineAsm::getFunctionType() const {
  60   return FTy;
  61 }
  62
  63 void InlineAsm::collectAsmStrs(SmallVectorImpl<StringRef> &AsmStrs) const {
  64   StringRef AsmStr(AsmString);
  65   AsmStrs.clear();
  66
  67   // TODO: 1) Unify delimiter for inline asm, we also meet other delimiters
  68   // for example "\0A", ";".
  69   // 2) Enhance StringRef. Some of the special delimiter ("\0") can't be
  70   // split in StringRef. Also empty StringRef can not call split (will stuck).
  71   if (AsmStr.empty())
  72     return;
  73   AsmStr.split(AsmStrs, "\n\t", -1, false);
  74 }
  75
  76 /// Parse - Analyze the specified string (e.g. "==&{eax}") and fill in the
  77 /// fields in this structure.  If the constraint string is not understood,
  78 /// return true, otherwise return false.
  79 bool InlineAsm::ConstraintInfo::Parse(StringRef Str,
  80                      InlineAsm::ConstraintInfoVector &ConstraintsSoFar) {
  81   StringRef::iterator I = Str.begin(), E = Str.end();
  82   unsigned multipleAlternativeCount = Str.count('|') + 1;
  83   unsigned multipleAlternativeIndex = 0;
  84   ConstraintCodeVector *pCodes = &Codes;
  85
  86   // Initialize
  87   isMultipleAlternative = multipleAlternativeCount > 1;
  88   if (isMultipleAlternative) {
  89     multipleAlternatives.resize(multipleAlternativeCount);
  90     pCodes = &multipleAlternatives[0].Codes;
  91   }
  92   Type = isInput;
  93   isEarlyClobber = false;
  94   MatchingInput = -1;
  95   isCommutative = false;
  96   isIndirect = false;
  97   currentAlternativeIndex = 0;
  98
  99   // Parse prefixes.
 100   if (*I == '~') {
 101     Type = isClobber;
 102     ++I;
 103
 104     // '{' must immediately follow '~'.
 105     if (I != E && *I != '{')
 106       return true;
 107   } else if (*I == '=') {
 108     ++I;
 109     Type = isOutput;
 110   } else if (*I == '!') {
 111     ++I;
 112     Type = isLabel;
 113   }
 114
 115   if (*I == '*') {
 116     isIndirect = true;
 117     ++I;
 118   }
 119
 120   if (I == E) return true;  // Just a prefix, like "==" or "~".
 121
 122   // Parse the modifiers.
 123   bool DoneWithModifiers = false;
 124   while (!DoneWithModifiers) {
 125     switch (*I) {
 126     default:
 127       DoneWithModifiers = true;
 128       break;
 129     case '&':     // Early clobber.
 130       if (Type != isOutput ||      // Cannot early clobber anything but output.
 131           isEarlyClobber)          // Reject &&&&&&
 132         return true;
 133       isEarlyClobber = true;
 134       break;
 135     case '%':     // Commutative.
 136       if (Type == isClobber ||     // Cannot commute clobbers.
 137           isCommutative)           // Reject %%%%%
 138         return true;
 139       isCommutative = true;
 140       break;
 141     case '#':     // Comment.
 142     case '*':     // Register preferencing.
 143       return true;     // Not supported.
 144     }
 145
 146     if (!DoneWithModifiers) {
 147       ++I;
 148       if (I == E) return true;   // Just prefixes and modifiers!
 149     }
 150   }
 151
 152   // Parse the various constraints.
 153   while (I != E) {
 154     if (*I == '{') {   // Physical register reference.
 155       // Find the end of the register name.
 156       StringRef::iterator ConstraintEnd = std::find(I+1, E, '}');
 157       if (ConstraintEnd == E) return true;  // "{foo"
 158       pCodes->push_back(std::string(StringRef(I, ConstraintEnd + 1 - I)));
 159       I = ConstraintEnd+1;
 160     } else if (isdigit(static_cast<unsigned char>(*I))) { // Matching Constraint
 161       // Maximal munch numbers.
 162       StringRef::iterator NumStart = I;
 163       while (I != E && isdigit(static_cast<unsigned char>(*I)))
 164         ++I;
 165       pCodes->push_back(std::string(StringRef(NumStart, I - NumStart)));
 166       unsigned N = atoi(pCodes->back().c_str());
 167       // Check that this is a valid matching constraint!
 168       if (N >= ConstraintsSoFar.size() || ConstraintsSoFar[N].Type != isOutput||
 169           Type != isInput)
 170         return true;  // Invalid constraint number.
 171
 172       // If Operand N already has a matching input, reject this.  An output
 173       // can't be constrained to the same value as multiple inputs.
 174       if (isMultipleAlternative) {
 175         if (multipleAlternativeIndex >=
 176             ConstraintsSoFar[N].multipleAlternatives.size())
 177           return true;
 178         InlineAsm::SubConstraintInfo &scInfo =
 179           ConstraintsSoFar[N].multipleAlternatives[multipleAlternativeIndex];
 180         if (scInfo.MatchingInput != -1)
 181           return true;
 182         // Note that operand #n has a matching input.
 183         scInfo.MatchingInput = ConstraintsSoFar.size();
 184         assert(scInfo.MatchingInput >= 0);
 185       } else {
 186         if (ConstraintsSoFar[N].hasMatchingInput() &&
 187             (size_t)ConstraintsSoFar[N].MatchingInput !=
 188                 ConstraintsSoFar.size())
 189           return true;
 190         // Note that operand #n has a matching input.
 191         ConstraintsSoFar[N].MatchingInput = ConstraintsSoFar.size();
 192         assert(ConstraintsSoFar[N].MatchingInput >= 0);
 193         }
 194     } else if (*I == '|') {
 195       multipleAlternativeIndex++;
 196       pCodes = &multipleAlternatives[multipleAlternativeIndex].Codes;
 197       ++I;
 198     } else if (*I == '^') {
 199       // Multi-letter constraint
 200       // FIXME: For now assuming these are 2-character constraints.
 201       pCodes->push_back(std::string(StringRef(I + 1, 2)));
 202       I += 3;
 203     } else if (*I == '@') {
 204       // Multi-letter constraint
 205       ++I;
 206       unsigned char C = static_cast<unsigned char>(*I);
 207       assert(isdigit(C) && "Expected a digit!");
 208       int N = C - '0';
 209       assert(N > 0 && "Found a zero letter constraint!");
 210       ++I;
 211       pCodes->push_back(std::string(StringRef(I, N)));
 212       I += N;
 213     } else {
 214       // Single letter constraint.
 215       pCodes->push_back(std::string(StringRef(I, 1)));
 216       ++I;
 217     }
 218   }
 219
 220   return false;
 221 }
 222
 223 /// selectAlternative - Point this constraint to the alternative constraint
 224 /// indicated by the index.
 225 void InlineAsm::ConstraintInfo::selectAlternative(unsigned index) {
 226   if (index < multipleAlternatives.size()) {
 227     currentAlternativeIndex = index;
 228     InlineAsm::SubConstraintInfo &scInfo =
 229       multipleAlternatives[currentAlternativeIndex];
 230     MatchingInput = scInfo.MatchingInput;
 231     Codes = scInfo.Codes;
 232   }
 233 }
 234
 235 InlineAsm::ConstraintInfoVector
 236 InlineAsm::ParseConstraints(StringRef Constraints) {
 237   ConstraintInfoVector Result;
 238
 239   // Scan the constraints string.
 240   for (StringRef::iterator I = Constraints.begin(),
 241          E = Constraints.end(); I != E; ) {
 242     ConstraintInfo Info;
 243
 244     // Find the end of this constraint.
 245     StringRef::iterator ConstraintEnd = std::find(I, E, ',');
 246
 247     if (ConstraintEnd == I ||  // Empty constraint like ",,"
 248         Info.Parse(StringRef(I, ConstraintEnd-I), Result)) {
 249       Result.clear();          // Erroneous constraint?
 250       break;
 251     }
 252
 253     Result.push_back(Info);
 254
 255     // ConstraintEnd may be either the next comma or the end of the string.  In
 256     // the former case, we skip the comma.
 257     I = ConstraintEnd;
 258     if (I != E) {
 259       ++I;
 260       if (I == E) {
 261         Result.clear();
 262         break;
 263       } // don't allow "xyz,"
 264     }
 265   }
 266
 267   return Result;
 268 }
 269
 270 static Error makeStringError(const char *Msg) {
 271   return createStringError(errc::invalid_argument, Msg);
 272 }
 273
 274 Error InlineAsm::verify(FunctionType *Ty, StringRef ConstStr) {
 275   if (Ty->isVarArg())
 276     return makeStringError("inline asm cannot be variadic");
 277
 278   ConstraintInfoVector Constraints = ParseConstraints(ConstStr);
 279
 280   // Error parsing constraints.
 281   if (Constraints.empty() && !ConstStr.empty())
 282     return makeStringError("failed to parse constraints");
 283
 284   unsigned NumOutputs = 0, NumInputs = 0, NumClobbers = 0;
 285   unsigned NumIndirect = 0, NumLabels = 0;
 286
 287   for (const ConstraintInfo &Constraint : Constraints) {
 288     switch (Constraint.Type) {
 289     case InlineAsm::isOutput:
 290       if ((NumInputs-NumIndirect) != 0 || NumClobbers != 0 || NumLabels != 0)
 291         return makeStringError("output constraint occurs after input, "
 292                                "clobber or label constraint");
 293
 294       if (!Constraint.isIndirect) {
 295         ++NumOutputs;
 296         break;
 297       }
 298       ++NumIndirect;
 299       [[fallthrough]]; // We fall through for Indirect Outputs.
 300     case InlineAsm::isInput:
 301       if (NumClobbers)
 302         return makeStringError("input constraint occurs after clobber "
 303                                "constraint");
 304       ++NumInputs;
 305       break;
 306     case InlineAsm::isClobber:
 307       ++NumClobbers;
 308       break;
 309     case InlineAsm::isLabel:
 310       if (NumClobbers)
 311         return makeStringError("label constraint occurs after clobber "
 312                                "constraint");
 313
 314       ++NumLabels;
 315       break;
 316     }
 317   }
 318
 319   switch (NumOutputs) {
 320   case 0:
 321     if (!Ty->getReturnType()->isVoidTy())
 322       return makeStringError("inline asm without outputs must return void");
 323     break;
 324   case 1:
 325     if (Ty->getReturnType()->isStructTy())
 326       return makeStringError("inline asm with one output cannot return struct");
 327     break;
 328   default:
 329     StructType *STy = dyn_cast<StructType>(Ty->getReturnType());
 330     if (!STy || STy->getNumElements() != NumOutputs)
 331       return makeStringError("number of output constraints does not match "
 332                              "number of return struct elements");
 333     break;
 334   }
 335
 336   if (Ty->getNumParams() != NumInputs)
 337     return makeStringError("number of input constraints does not match number "
 338                            "of parameters");
 339
 340   // We don't have access to labels here, NumLabels will be checked separately.
 341   return Error::success();
 342 }