lib/Support/TargetRegistry.cpp

   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/Target/TargetRegistry.h"
  11 #include "llvm/System/Host.h"
  12 #include <cassert>
  13 using namespace llvm;
  14
  15 // Clients are responsible for avoid race conditions in registration.
  16 static Target *FirstTarget = 0;
  17
  18 TargetRegistry::iterator TargetRegistry::begin() {
  19   return iterator(FirstTarget);
  20 }
  21
  22 const Target *TargetRegistry::lookupTarget(const std::string &TT,
  23                                            std::string &Error) {
  24   // Provide special warning when no targets are initialized.
  25   if (begin() == end()) {
  26     Error = "Unable to find target for this triple (no targets are registered)";
  27     return 0;
  28   }
  29   const Target *Best = 0, *EquallyBest = 0;
  30   unsigned BestQuality = 0;
  31   for (iterator it = begin(), ie = end(); it != ie; ++it) {
  32     if (unsigned Qual = it->TripleMatchQualityFn(TT)) {
  33       if (!Best || Qual > BestQuality) {
  34         Best = &*it;
  35         EquallyBest = 0;
  36         BestQuality = Qual;
  37       } else if (Qual == BestQuality)
  38         EquallyBest = &*it;
  39     }
  40   }
  41
  42   if (!Best) {
  43     Error = "No available targets are compatible with this triple";
  44     return 0;
  45   }
  46
  47   // Otherwise, take the best target, but make sure we don't have two equally
  48   // good best targets.
  49   if (EquallyBest) {
  50     Error = std::string("Cannot choose between targets \"") +
  51       Best->Name  + "\" and \"" + EquallyBest->Name + "\"";
  52     return 0;
  53   }
  54
  55   return Best;
  56 }
  57
  58 void TargetRegistry::RegisterTarget(Target &T,
  59                                     const char *Name,
  60                                     const char *ShortDesc,
  61                                     Target::TripleMatchQualityFnTy TQualityFn,
  62                                     bool HasJIT) {
  63   assert(Name && ShortDesc && TQualityFn &&
  64          "Missing required target information!");
  65
  66   // Check if this target has already been initialized, we allow this as a
  67   // convenience to some clients.
  68   if (T.Name)
  69     return;
  70
  71   // Add to the list of targets.
  72   T.Next = FirstTarget;
  73   FirstTarget = &T;
  74
  75   T.Name = Name;
  76   T.ShortDesc = ShortDesc;
  77   T.TripleMatchQualityFn = TQualityFn;
  78   T.HasJIT = HasJIT;
  79 }
  80
  81 const Target *TargetRegistry::getClosestTargetForJIT(std::string &Error) {
  82   const Target *TheTarget = lookupTarget(sys::getHostTriple(), Error);
  83
  84   if (TheTarget && !TheTarget->hasJIT()) {
  85     Error = "No JIT compatible target available for this host";
  86     return 0;
  87   }
  88
  89   return TheTarget;
  90 }
  91