lib/ExecutionEngine/TargetSelect.cpp

   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/ADT/Triple.h"
  18 #include "llvm/ExecutionEngine/ExecutionEngine.h"
  19 #include "llvm/IR/Module.h"
  20 #include "llvm/MC/SubtargetFeature.h"
  21 #include "llvm/Support/Host.h"
  22 #include "llvm/Support/TargetRegistry.h"
  23 #include "llvm/Target/TargetMachine.h"
  24
  25 using namespace llvm;
  26
  27 TargetMachine *EngineBuilder::selectTarget() {
  28   Triple TT;
  29
  30   // MCJIT can generate code for remote targets, but the old JIT and Interpreter
  31   // must use the host architecture.
  32   if (WhichEngine != EngineKind::Interpreter && M)
  33     TT.setTriple(M->getTargetTriple());
  34
  35   return selectTarget(TT, MArch, MCPU, MAttrs);
  36 }
  37
  38 /// selectTarget - Pick a target either via -march or by guessing the native
  39 /// arch.  Add any CPU features specified via -mcpu or -mattr.
  40 TargetMachine *EngineBuilder::selectTarget(const Triple &TargetTriple,
  41                               StringRef MArch,
  42                               StringRef MCPU,
  43                               const SmallVectorImpl<std::string>& MAttrs) {
  44   Triple TheTriple(TargetTriple);
  45   if (TheTriple.getTriple().empty())
  46     TheTriple.setTriple(sys::getProcessTriple());
  47
  48   // Adjust the triple to match what the user requested.
  49   const Target *TheTarget = nullptr;
  50   if (!MArch.empty()) {
  51     auto I = find_if(TargetRegistry::targets(),
  52                      [&](const Target &T) { return MArch == T.getName(); });
  53
  54     if (I == TargetRegistry::targets().end()) {
  55       if (ErrorStr)
  56         *ErrorStr = "No available targets are compatible with this -march, "
  57                     "see -version for the available targets.\n";
  58       return nullptr;
  59     }
  60
  61     TheTarget = &*I;
  62
  63     // Adjust the triple to match (if known), otherwise stick with the
  64     // requested/host triple.
  65     Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
  66     if (Type != Triple::UnknownArch)
  67       TheTriple.setArch(Type);
  68   } else {
  69     std::string Error;
  70     TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
  71     if (!TheTarget) {
  72       if (ErrorStr)
  73         *ErrorStr = Error;
  74       return nullptr;
  75     }
  76   }
  77
  78   // Package up features to be passed to target/subtarget
  79   std::string FeaturesStr;
  80   if (!MAttrs.empty()) {
  81     SubtargetFeatures Features;
  82     for (unsigned i = 0; i != MAttrs.size(); ++i)
  83       Features.AddFeature(MAttrs[i]);
  84     FeaturesStr = Features.getString();
  85   }
  86
  87   // FIXME: non-iOS ARM FastISel is broken with MCJIT.
  88   if (TheTriple.getArch() == Triple::arm &&
  89       !TheTriple.isiOS() &&
  90       OptLevel == CodeGenOpt::None) {
  91     OptLevel = CodeGenOpt::Less;
  92   }
  93
  94   // Allocate a target...
  95   TargetMachine *Target =
  96       TheTarget->createTargetMachine(TheTriple.getTriple(), MCPU, FeaturesStr,
  97                                      Options, RelocModel, CMModel, OptLevel,
  98                                      /*JIT*/ true);
  99   Target->Options.EmulatedTLS = EmulatedTLS;
 100   Target->Options.ExplicitEmulatedTLS = true;
 101
 102   assert(Target && "Could not allocate target machine!");
 103   return Target;
 104 }