lib/ExecutionEngine/TargetSelect.cpp

   1 //===-- TargetSelect.cpp - Target Chooser Code ----------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This just asks the TargetRegistry for the appropriate target to use, and
  10 // allows the user to specify a specific one on the commandline with -march=x,
  11 // -mcpu=y, and -mattr=a,-b,+c. Clients should initialize targets prior to
  12 // calling selectTarget().
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "llvm/ADT/Triple.h"
  17 #include "llvm/ExecutionEngine/ExecutionEngine.h"
  18 #include "llvm/IR/Module.h"
  19 #include "llvm/MC/SubtargetFeature.h"
  20 #include "llvm/Support/Host.h"
  21 #include "llvm/Support/TargetRegistry.h"
  22 #include "llvm/Target/TargetMachine.h"
  23
  24 using namespace llvm;
  25
  26 TargetMachine *EngineBuilder::selectTarget() {
  27   Triple TT;
  28
  29   // MCJIT can generate code for remote targets, but the old JIT and Interpreter
  30   // must use the host architecture.
  31   if (WhichEngine != EngineKind::Interpreter && M)
  32     TT.setTriple(M->getTargetTriple());
  33
  34   return selectTarget(TT, MArch, MCPU, MAttrs);
  35 }
  36
  37 /// selectTarget - Pick a target either via -march or by guessing the native
  38 /// arch.  Add any CPU features specified via -mcpu or -mattr.
  39 TargetMachine *EngineBuilder::selectTarget(const Triple &TargetTriple,
  40                               StringRef MArch,
  41                               StringRef MCPU,
  42                               const SmallVectorImpl<std::string>& MAttrs) {
  43   Triple TheTriple(TargetTriple);
  44   if (TheTriple.getTriple().empty())
  45     TheTriple.setTriple(sys::getProcessTriple());
  46
  47   // Adjust the triple to match what the user requested.
  48   const Target *TheTarget = nullptr;
  49   if (!MArch.empty()) {
  50     auto I = find_if(TargetRegistry::targets(),
  51                      [&](const Target &T) { return MArch == T.getName(); });
  52
  53     if (I == TargetRegistry::targets().end()) {
  54       if (ErrorStr)
  55         *ErrorStr = "No available targets are compatible with this -march, "
  56                     "see -version for the available targets.\n";
  57       return nullptr;
  58     }
  59
  60     TheTarget = &*I;
  61
  62     // Adjust the triple to match (if known), otherwise stick with the
  63     // requested/host triple.
  64     Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
  65     if (Type != Triple::UnknownArch)
  66       TheTriple.setArch(Type);
  67   } else {
  68     std::string Error;
  69     TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
  70     if (!TheTarget) {
  71       if (ErrorStr)
  72         *ErrorStr = Error;
  73       return nullptr;
  74     }
  75   }
  76
  77   // Package up features to be passed to target/subtarget
  78   std::string FeaturesStr;
  79   if (!MAttrs.empty()) {
  80     SubtargetFeatures Features;
  81     for (unsigned i = 0; i != MAttrs.size(); ++i)
  82       Features.AddFeature(MAttrs[i]);
  83     FeaturesStr = Features.getString();
  84   }
  85
  86   // FIXME: non-iOS ARM FastISel is broken with MCJIT.
  87   if (TheTriple.getArch() == Triple::arm &&
  88       !TheTriple.isiOS() &&
  89       OptLevel == CodeGenOpt::None) {
  90     OptLevel = CodeGenOpt::Less;
  91   }
  92
  93   // Allocate a target...
  94   TargetMachine *Target =
  95       TheTarget->createTargetMachine(TheTriple.getTriple(), MCPU, FeaturesStr,
  96                                      Options, RelocModel, CMModel, OptLevel,
  97                                      /*JIT*/ true);
  98   Target->Options.EmulatedTLS = EmulatedTLS;
  99   Target->Options.ExplicitEmulatedTLS = true;
 100
 101   assert(Target && "Could not allocate target machine!");
 102   return Target;
 103 }