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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 &TT,
     27                                            std::string &Error) {
     28   // Provide special warning when no targets are initialized.
     29   if (begin() == end()) {
     30     Error = "Unable to find target for this triple (no targets are registered)";
     31     return 0;
     32   }
     33   const Target *Best = 0, *EquallyBest = 0;
     34   unsigned BestQuality = 0;
     35   for (iterator it = begin(), ie = end(); it != ie; ++it) {
     36     if (unsigned Qual = it->TripleMatchQualityFn(TT)) {
     37       if (!Best || Qual > BestQuality) {
     38         Best = &*it;
     39         EquallyBest = 0;
     40         BestQuality = Qual;
     41       } else if (Qual == BestQuality)
     42         EquallyBest = &*it;
     43     }
     44   }
     45 
     46   if (!Best) {
     47     Error = "No available targets are compatible with this triple, "
     48       "see -version for the available targets.";
     49     return 0;
     50   }
     51 
     52   // Otherwise, take the best target, but make sure we don't have two equally
     53   // good best targets.
     54   if (EquallyBest) {
     55     Error = std::string("Cannot choose between targets \"") +
     56       Best->Name  + "\" and \"" + EquallyBest->Name + "\"";
     57     return 0;
     58   }
     59 
     60   return Best;
     61 }
     62 
     63 void TargetRegistry::RegisterTarget(Target &T,
     64                                     const char *Name,
     65                                     const char *ShortDesc,
     66                                     Target::TripleMatchQualityFnTy TQualityFn,
     67                                     bool HasJIT) {
     68   assert(Name && ShortDesc && TQualityFn &&
     69          "Missing required target information!");
     70 
     71   // Check if this target has already been initialized, we allow this as a
     72   // convenience to some clients.
     73   if (T.Name)
     74     return;
     75 
     76   // Add to the list of targets.
     77   T.Next = FirstTarget;
     78   FirstTarget = &T;
     79 
     80   T.Name = Name;
     81   T.ShortDesc = ShortDesc;
     82   T.TripleMatchQualityFn = TQualityFn;
     83   T.HasJIT = HasJIT;
     84 }
     85 
     86 const Target *TargetRegistry::getClosestTargetForJIT(std::string &Error) {
     87   const Target *TheTarget = lookupTarget(sys::getHostTriple(), Error);
     88 
     89   if (TheTarget && !TheTarget->hasJIT()) {
     90     Error = "No JIT compatible target available for this host";
     91     return 0;
     92   }
     93 
     94   return TheTarget;
     95 }
     96 
     97 static int TargetArraySortFn(const void *LHS, const void *RHS) {
     98   typedef std::pair<StringRef, const Target*> pair_ty;
     99   return ((const pair_ty*)LHS)->first.compare(((const pair_ty*)RHS)->first);
    100 }
    101 
    102 void TargetRegistry::printRegisteredTargetsForVersion() {
    103   std::vector<std::pair<StringRef, const Target*> > Targets;
    104   size_t Width = 0;
    105   for (TargetRegistry::iterator I = TargetRegistry::begin(),
    106        E = TargetRegistry::end();
    107        I != E; ++I) {
    108     Targets.push_back(std::make_pair(I->getName(), &*I));
    109     Width = std::max(Width, Targets.back().first.size());
    110   }
    111   array_pod_sort(Targets.begin(), Targets.end(), TargetArraySortFn);
    112 
    113   raw_ostream &OS = outs();
    114   OS << "  Registered Targets:\n";
    115   for (unsigned i = 0, e = Targets.size(); i != e; ++i) {
    116     OS << "    " << Targets[i].first;
    117     OS.indent(Width - Targets[i].first.size()) << " - "
    118       << Targets[i].second->getShortDescription() << '\n';
    119   }
    120   if (Targets.empty())
    121     OS << "    (none)\n";
    122 }
    123