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      1 //===--- TargetRegistry.cpp - Target registration -------------------------===//
      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 #include "llvm/Support/TargetRegistry.h"
     11 #include "llvm/ADT/STLExtras.h"
     12 #include "llvm/ADT/StringRef.h"
     13 #include "llvm/Support/Host.h"
     14 #include "llvm/Support/raw_ostream.h"
     15 #include <cassert>
     16 #include <vector>
     17 using namespace llvm;
     18 
     19 // Clients are responsible for avoid race conditions in registration.
     20 static Target *FirstTarget = 0;
     21 
     22 TargetRegistry::iterator TargetRegistry::begin() {
     23   return iterator(FirstTarget);
     24 }
     25 
     26 const Target *TargetRegistry::lookupTarget(const std::string &ArchName,
     27                                            Triple &TheTriple,
     28                                            std::string &Error) {
     29   // Allocate target machine.  First, check whether the user has explicitly
     30   // specified an architecture to compile for. If so we have to look it up by
     31   // name, because it might be a backend that has no mapping to a target triple.
     32   const Target *TheTarget = 0;
     33   if (!ArchName.empty()) {
     34     for (TargetRegistry::iterator it = TargetRegistry::begin(),
     35            ie = TargetRegistry::end(); it != ie; ++it) {
     36       if (ArchName == it->getName()) {
     37         TheTarget = &*it;
     38         break;
     39       }
     40     }
     41 
     42     if (!TheTarget) {
     43       Error = "error: invalid target '" + ArchName + "'.\n";
     44       return 0;
     45     }
     46 
     47     // Adjust the triple to match (if known), otherwise stick with the
     48     // given triple.
     49     Triple::ArchType Type = Triple::getArchTypeForLLVMName(ArchName);
     50     if (Type != Triple::UnknownArch)
     51       TheTriple.setArch(Type);
     52   } else {
     53     // Get the target specific parser.
     54     std::string TempError;
     55     TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), TempError);
     56     if (TheTarget == 0) {
     57       Error = ": error: unable to get target for '"
     58             + TheTriple.getTriple()
     59             + "', see --version and --triple.\n";
     60       return 0;
     61     }
     62   }
     63 
     64   return TheTarget;
     65 }
     66 
     67 const Target *TargetRegistry::lookupTarget(const std::string &TT,
     68                                            std::string &Error) {
     69   // Provide special warning when no targets are initialized.
     70   if (begin() == end()) {
     71     Error = "Unable to find target for this triple (no targets are registered)";
     72     return 0;
     73   }
     74   const Target *Best = 0, *EquallyBest = 0;
     75   unsigned BestQuality = 0;
     76   for (iterator it = begin(), ie = end(); it != ie; ++it) {
     77     if (unsigned Qual = it->TripleMatchQualityFn(TT)) {
     78       if (!Best || Qual > BestQuality) {
     79         Best = &*it;
     80         EquallyBest = 0;
     81         BestQuality = Qual;
     82       } else if (Qual == BestQuality)
     83         EquallyBest = &*it;
     84     }
     85   }
     86 
     87   if (!Best) {
     88     Error = "No available targets are compatible with this triple, "
     89       "see -version for the available targets.";
     90     return 0;
     91   }
     92 
     93   // Otherwise, take the best target, but make sure we don't have two equally
     94   // good best targets.
     95   if (EquallyBest) {
     96     Error = std::string("Cannot choose between targets \"") +
     97       Best->Name  + "\" and \"" + EquallyBest->Name + "\"";
     98     return 0;
     99   }
    100 
    101   return Best;
    102 }
    103 
    104 void TargetRegistry::RegisterTarget(Target &T,
    105                                     const char *Name,
    106                                     const char *ShortDesc,
    107                                     Target::TripleMatchQualityFnTy TQualityFn,
    108                                     bool HasJIT) {
    109   assert(Name && ShortDesc && TQualityFn &&
    110          "Missing required target information!");
    111 
    112   // Check if this target has already been initialized, we allow this as a
    113   // convenience to some clients.
    114   if (T.Name)
    115     return;
    116 
    117   // Add to the list of targets.
    118   T.Next = FirstTarget;
    119   FirstTarget = &T;
    120 
    121   T.Name = Name;
    122   T.ShortDesc = ShortDesc;
    123   T.TripleMatchQualityFn = TQualityFn;
    124   T.HasJIT = HasJIT;
    125 }
    126 
    127 const Target *TargetRegistry::getClosestTargetForJIT(std::string &Error) {
    128   const Target *TheTarget = lookupTarget(sys::getDefaultTargetTriple(), Error);
    129 
    130   if (TheTarget && !TheTarget->hasJIT()) {
    131     Error = "No JIT compatible target available for this host";
    132     return 0;
    133   }
    134 
    135   return TheTarget;
    136 }
    137 
    138 static int TargetArraySortFn(const void *LHS, const void *RHS) {
    139   typedef std::pair<StringRef, const Target*> pair_ty;
    140   return ((const pair_ty*)LHS)->first.compare(((const pair_ty*)RHS)->first);
    141 }
    142 
    143 void TargetRegistry::printRegisteredTargetsForVersion() {
    144   std::vector<std::pair<StringRef, const Target*> > Targets;
    145   size_t Width = 0;
    146   for (TargetRegistry::iterator I = TargetRegistry::begin(),
    147        E = TargetRegistry::end();
    148        I != E; ++I) {
    149     Targets.push_back(std::make_pair(I->getName(), &*I));
    150     Width = std::max(Width, Targets.back().first.size());
    151   }
    152   array_pod_sort(Targets.begin(), Targets.end(), TargetArraySortFn);
    153 
    154   raw_ostream &OS = outs();
    155   OS << "  Registered Targets:\n";
    156   for (unsigned i = 0, e = Targets.size(); i != e; ++i) {
    157     OS << "    " << Targets[i].first;
    158     OS.indent(Width - Targets[i].first.size()) << " - "
    159       << Targets[i].second->getShortDescription() << '\n';
    160   }
    161   if (Targets.empty())
    162     OS << "    (none)\n";
    163 }
    164