TargetRegistry.cpp revision 4bd03abe593222b26e84066223feb321bf738625 
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>
13using namespace llvm;
14
15// Clients are responsible for avoid race conditions in registration.
16static Target *FirstTarget = 0;
17
18TargetRegistry::iterator TargetRegistry::begin() {
19  return iterator(FirstTarget);
20}
21
22const 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
58void 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
81const 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
92