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       "see -version for the available targets.";
45     return 0;
46   }
47 
48   // Otherwise, take the best target, but make sure we don't have two equally
49   // good best targets.
50   if (EquallyBest) {
51     Error = std::string("Cannot choose between targets \"") +
52       Best->Name  + "\" and \"" + EquallyBest->Name + "\"";
53     return 0;
54   }
55 
56   return Best;
57 }
58 
59 void TargetRegistry::RegisterTarget(Target &T,
60                                     const char *Name,
61                                     const char *ShortDesc,
62                                     Target::TripleMatchQualityFnTy TQualityFn,
63                                     bool HasJIT) {
64   assert(Name && ShortDesc && TQualityFn &&
65          "Missing required target information!");
66 
67   // Check if this target has already been initialized, we allow this as a
68   // convenience to some clients.
69   if (T.Name)
70     return;
71 
72   // Add to the list of targets.
73   T.Next = FirstTarget;
74   FirstTarget = &T;
75 
76   T.Name = Name;
77   T.ShortDesc = ShortDesc;
78   T.TripleMatchQualityFn = TQualityFn;
79   T.HasJIT = HasJIT;
80 }
81 
82 const Target *TargetRegistry::getClosestTargetForJIT(std::string &Error) {
83   const Target *TheTarget = lookupTarget(sys::getHostTriple(), Error);
84 
85   if (TheTarget && !TheTarget->hasJIT()) {
86     Error = "No JIT compatible target available for this host";
87     return 0;
88   }
89 
90   return TheTarget;
91 }
92 
93