1 //===-- TargetSelect.cpp - Target Chooser Code ----------------------------===//
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 // This just asks the TargetRegistry for the appropriate target to use, and
11 // allows the user to specify a specific one on the commandline with -march=x,
12 // -mcpu=y, and -mattr=a,-b,+c. Clients should initialize targets prior to
13 // calling selectTarget().
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/ExecutionEngine/ExecutionEngine.h"
18 #include "llvm/ADT/Triple.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/MC/SubtargetFeature.h"
21 #include "llvm/Support/CommandLine.h"
22 #include "llvm/Support/Host.h"
23 #include "llvm/Support/TargetRegistry.h"
24 #include "llvm/Target/TargetMachine.h"
25 
26 using namespace llvm;
27 
28 TargetMachine *EngineBuilder::selectTarget() {
29   Triple TT;
30 
31   // MCJIT can generate code for remote targets, but the old JIT and Interpreter
32   // must use the host architecture.
33   if (UseMCJIT && WhichEngine != EngineKind::Interpreter && M)
34     TT.setTriple(M->getTargetTriple());
35   else {
36     TT.setTriple(LLVM_HOSTTRIPLE);
37 #if defined(__APPLE__)
38 #if defined(__LP64__)
39     if (TT.isArch32Bit())
40       TT = TT.get64BitArchVariant();
41 #else
42     if (TT.isArch64Bit())
43       TT = TT.get32BitArchVariant();
44 #endif
45 #endif // APPLE
46   }
47   return selectTarget(TT, MArch, MCPU, MAttrs);
48 }
49 
50 /// selectTarget - Pick a target either via -march or by guessing the native
51 /// arch.  Add any CPU features specified via -mcpu or -mattr.
52 TargetMachine *EngineBuilder::selectTarget(const Triple &TargetTriple,
53                               StringRef MArch,
54                               StringRef MCPU,
55                               const SmallVectorImpl<std::string>& MAttrs) {
56   Triple TheTriple(TargetTriple);
57   if (TheTriple.getTriple().empty())
58     TheTriple.setTriple(sys::getDefaultTargetTriple());
59 
60   // Adjust the triple to match what the user requested.
61   const Target *TheTarget = 0;
62   if (!MArch.empty()) {
63     for (TargetRegistry::iterator it = TargetRegistry::begin(),
64            ie = TargetRegistry::end(); it != ie; ++it) {
65       if (MArch == it->getName()) {
66         TheTarget = &*it;
67         break;
68       }
69     }
70 
71     if (!TheTarget) {
72       if (ErrorStr)
73         *ErrorStr = "No available targets are compatible with this -march, "
74                     "see -version for the available targets.\n";
75       return 0;
76     }
77 
78     // Adjust the triple to match (if known), otherwise stick with the
79     // requested/host triple.
80     Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
81     if (Type != Triple::UnknownArch)
82       TheTriple.setArch(Type);
83   } else {
84     std::string Error;
85     TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
86     if (TheTarget == 0) {
87       if (ErrorStr)
88         *ErrorStr = Error;
89       return 0;
90     }
91   }
92 
93   // Package up features to be passed to target/subtarget
94   std::string FeaturesStr;
95   if (!MAttrs.empty()) {
96     SubtargetFeatures Features;
97     for (unsigned i = 0; i != MAttrs.size(); ++i)
98       Features.AddFeature(MAttrs[i]);
99     FeaturesStr = Features.getString();
100   }
101 
102   // Allocate a target...
103   TargetMachine *Target = TheTarget->createTargetMachine(TheTriple.getTriple(),
104                                                          MCPU, FeaturesStr,
105                                                          Options,
106                                                          RelocModel, CMModel,
107                                                          OptLevel);
108   assert(Target && "Could not allocate target machine!");
109   return Target;
110 }
111