lib/VMCore/InlineAsm.cpp

   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 "llvm/InlineAsm.h"
  15 #include "llvm/DerivedTypes.h"
  16 #include <algorithm>
  17 #include <cctype>
  18 using namespace llvm;
  19
  20 // Implement the first virtual method in this class in this file so the
  21 // InlineAsm vtable is emitted here.
  22 InlineAsm::~InlineAsm() {
  23 }
  24
  25
  26 // NOTE: when memoizing the function type, we have to be careful to handle the
  27 // case when the type gets refined.
  28
  29 InlineAsm *InlineAsm::get(const FunctionType *Ty, const StringRef &AsmString,
  30                           const StringRef &Constraints, bool hasSideEffects) {
  31   // FIXME: memoize!
  32   return new InlineAsm(Ty, AsmString, Constraints, hasSideEffects);
  33 }
  34
  35 InlineAsm::InlineAsm(const FunctionType *Ty, const StringRef &asmString,
  36                      const StringRef &constraints, bool hasSideEffects)
  37   : Value(PointerType::getUnqual(Ty),
  38           Value::InlineAsmVal),
  39     AsmString(asmString),
  40     Constraints(constraints), HasSideEffects(hasSideEffects) {
  41
  42   // Do various checks on the constraint string and type.
  43   assert(Verify(Ty, constraints) && "Function type not legal for constraints!");
  44 }
  45
  46 const FunctionType *InlineAsm::getFunctionType() const {
  47   return cast<FunctionType>(getType()->getElementType());
  48 }
  49
  50 /// Parse - Analyze the specified string (e.g. "==&{eax}") and fill in the
  51 /// fields in this structure.  If the constraint string is not understood,
  52 /// return true, otherwise return false.
  53 bool InlineAsm::ConstraintInfo::Parse(const StringRef &Str,
  54                      std::vector<InlineAsm::ConstraintInfo> &ConstraintsSoFar) {
  55   StringRef::iterator I = Str.begin(), E = Str.end();
  56
  57   // Initialize
  58   Type = isInput;
  59   isEarlyClobber = false;
  60   MatchingInput = -1;
  61   isCommutative = false;
  62   isIndirect = false;
  63
  64   // Parse prefixes.
  65   if (*I == '~') {
  66     Type = isClobber;
  67     ++I;
  68   } else if (*I == '=') {
  69     ++I;
  70     Type = isOutput;
  71   }
  72
  73   if (*I == '*') {
  74     isIndirect = true;
  75     ++I;
  76   }
  77
  78   if (I == E) return true;  // Just a prefix, like "==" or "~".
  79
  80   // Parse the modifiers.
  81   bool DoneWithModifiers = false;
  82   while (!DoneWithModifiers) {
  83     switch (*I) {
  84     default:
  85       DoneWithModifiers = true;
  86       break;
  87     case '&':     // Early clobber.
  88       if (Type != isOutput ||      // Cannot early clobber anything but output.
  89           isEarlyClobber)          // Reject &&&&&&
  90         return true;
  91       isEarlyClobber = true;
  92       break;
  93     case '%':     // Commutative.
  94       if (Type == isClobber ||     // Cannot commute clobbers.
  95           isCommutative)           // Reject %%%%%
  96         return true;
  97       isCommutative = true;
  98       break;
  99     case '#':     // Comment.
 100     case '*':     // Register preferencing.
 101       return true;     // Not supported.
 102     }
 103
 104     if (!DoneWithModifiers) {
 105       ++I;
 106       if (I == E) return true;   // Just prefixes and modifiers!
 107     }
 108   }
 109
 110   // Parse the various constraints.
 111   while (I != E) {
 112     if (*I == '{') {   // Physical register reference.
 113       // Find the end of the register name.
 114       StringRef::iterator ConstraintEnd = std::find(I+1, E, '}');
 115       if (ConstraintEnd == E) return true;  // "{foo"
 116       Codes.push_back(std::string(I, ConstraintEnd+1));
 117       I = ConstraintEnd+1;
 118     } else if (isdigit(*I)) {     // Matching Constraint
 119       // Maximal munch numbers.
 120       StringRef::iterator NumStart = I;
 121       while (I != E && isdigit(*I))
 122         ++I;
 123       Codes.push_back(std::string(NumStart, I));
 124       unsigned N = atoi(Codes.back().c_str());
 125       // Check that this is a valid matching constraint!
 126       if (N >= ConstraintsSoFar.size() || ConstraintsSoFar[N].Type != isOutput||
 127           Type != isInput)
 128         return true;  // Invalid constraint number.
 129
 130       // If Operand N already has a matching input, reject this.  An output
 131       // can't be constrained to the same value as multiple inputs.
 132       if (ConstraintsSoFar[N].hasMatchingInput())
 133         return true;
 134
 135       // Note that operand #n has a matching input.
 136       ConstraintsSoFar[N].MatchingInput = ConstraintsSoFar.size();
 137     } else {
 138       // Single letter constraint.
 139       Codes.push_back(std::string(I, I+1));
 140       ++I;
 141     }
 142   }
 143
 144   return false;
 145 }
 146
 147 std::vector<InlineAsm::ConstraintInfo>
 148 InlineAsm::ParseConstraints(const StringRef &Constraints) {
 149   std::vector<ConstraintInfo> Result;
 150
 151   // Scan the constraints string.
 152   for (StringRef::iterator I = Constraints.begin(),
 153          E = Constraints.end(); I != E; ) {
 154     ConstraintInfo Info;
 155
 156     // Find the end of this constraint.
 157     StringRef::iterator ConstraintEnd = std::find(I, E, ',');
 158
 159     if (ConstraintEnd == I ||  // Empty constraint like ",,"
 160         Info.Parse(std::string(I, ConstraintEnd), Result)) {
 161       Result.clear();          // Erroneous constraint?
 162       break;
 163     }
 164
 165     Result.push_back(Info);
 166
 167     // ConstraintEnd may be either the next comma or the end of the string.  In
 168     // the former case, we skip the comma.
 169     I = ConstraintEnd;
 170     if (I != E) {
 171       ++I;
 172       if (I == E) { Result.clear(); break; }    // don't allow "xyz,"
 173     }
 174   }
 175
 176   return Result;
 177 }
 178
 179
 180 /// Verify - Verify that the specified constraint string is reasonable for the
 181 /// specified function type, and otherwise validate the constraint string.
 182 bool InlineAsm::Verify(const FunctionType *Ty, const StringRef &ConstStr) {
 183   if (Ty->isVarArg()) return false;
 184
 185   std::vector<ConstraintInfo> Constraints = ParseConstraints(ConstStr);
 186
 187   // Error parsing constraints.
 188   if (Constraints.empty() && !ConstStr.empty()) return false;
 189
 190   unsigned NumOutputs = 0, NumInputs = 0, NumClobbers = 0;
 191   unsigned NumIndirect = 0;
 192
 193   for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
 194     switch (Constraints[i].Type) {
 195     case InlineAsm::isOutput:
 196       if ((NumInputs-NumIndirect) != 0 || NumClobbers != 0)
 197         return false;  // outputs before inputs and clobbers.
 198       if (!Constraints[i].isIndirect) {
 199         ++NumOutputs;
 200         break;
 201       }
 202       ++NumIndirect;
 203       // FALLTHROUGH for Indirect Outputs.
 204     case InlineAsm::isInput:
 205       if (NumClobbers) return false;               // inputs before clobbers.
 206       ++NumInputs;
 207       break;
 208     case InlineAsm::isClobber:
 209       ++NumClobbers;
 210       break;
 211     }
 212   }
 213
 214   switch (NumOutputs) {
 215   case 0:
 216     if (Ty->getReturnType() != Type::VoidTy) return false;
 217     break;
 218   case 1:
 219     if (isa<StructType>(Ty->getReturnType())) return false;
 220     break;
 221   default:
 222     const StructType *STy = dyn_cast<StructType>(Ty->getReturnType());
 223     if (STy == 0 || STy->getNumElements() != NumOutputs)
 224       return false;
 225     break;
 226   }
 227
 228   if (Ty->getNumParams() != NumInputs) return false;
 229   return true;
 230 }
 231