Add PIC-level support to Clang.

[jhibbits]

Summary

This distinguishes between -fpic and -fPIC now, with the additions in LLVM for
PIC level support.

[jhibbits]

ParseStmtAsm.cpp was missing, fix that as well.

[• rafael]

lib/CodeGen/BackendUtil.cpp

428

Don't you want to produce an error if -pic-level is not 1 or 2?

[jhibbits]

Update to use the Module PIC Level API.

[• rafael]

lib/CodeGen/CodeGenModule.cpp

401 ↗

(On Diff #16293)

We use llvm_unreachble instead of assert(0).

[jhibbits]

lib/CodeGen/CodeGenModule.cpp

401 ↗

(On Diff #16293)

d'oh, fail :(

[jhibbits]

Use llvm_unreachable() instead of assert(0).

[• rafael]

LGTM with a nit.

lib/CodeGen/CodeGenModule.cpp

395 ↗

(On Diff #16295)

You can fold the variable declaration into the if:

if (uint32_t PLevel = Context.getLangOpts().PICLevel) {

[rnk]

lib/CodeGen/BackendUtil.cpp

428

It's too easy for the user to try to do something like clang -cc1 -pic-level 3 t.c and crash the compiler with assert or llvm_unreachable. We should either clamp the level to [0-2] or issue a diagnostic in lib/Frontend/CompilerInvocation.cpp.

[jhibbits]

Thanks for the review, Rafael!

lib/CodeGen/CodeGenModule.cpp

395 ↗

(On Diff #16295)

That may be legal C++, but it makes me really uncomfortable, and makes it (trivially, I guess) less readable, I think.

[jhibbits]

Closed by commit rL222227 (authored by @jhibbits).

[• rafael]

rafael wrote:

Don't you want to produce an error if -pic-level is not 1 or 2?

It's too easy for the user to try to do something like clang -cc1 -pic-level 3 t.c and crash the compiler with assert or llvm_unreachable. We should either clamp the level to [0-2] or issue a diagnostic in lib/Frontend/CompilerInvocation.cpp.

I don't think -cc1 options are considered user visible. Having another
value in here means a bug somewhere else in clang.

Cheers,
Rafael

lib/CodeGen/BackendUtil.cpp

TargetMachine *EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
 
   CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
   switch (CodeGenOpts.OptimizationLevel) {
   default: break;
   case 0: OptLevel = CodeGenOpt::None; break;
   case 3: OptLevel = CodeGenOpt::Aggressive; break;
   }
 
+  llvm::PICLevel::Level PL = llvm::PICLevel::Default;
+  switch (LangOpts.PICLevel) {
+  default: break;
+  case 1: PL = llvm::PICLevel::Small; break;
+  case 2: PL = llvm::PICLevel::Large; break;
+  }
+
   llvm::TargetOptions Options;
 
   Options.ThreadModel =
     llvm::StringSwitch<llvm::ThreadModel::Model>(CodeGenOpts.ThreadModel)
       .Case("posix", llvm::ThreadModel::POSIX)
       .Case("single", llvm::ThreadModel::Single);
 
   if (CodeGenOpts.DisableIntegratedAS)
TargetMachine *EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
   Options.MCOptions.MCSaveTempLabels = CodeGenOpts.SaveTempLabels;
   Options.MCOptions.MCUseDwarfDirectory = !CodeGenOpts.NoDwarfDirectoryAsm;
   Options.MCOptions.MCNoExecStack = CodeGenOpts.NoExecStack;
   Options.MCOptions.MCFatalWarnings = CodeGenOpts.FatalWarnings;
   Options.MCOptions.AsmVerbose = CodeGenOpts.AsmVerbose;
 
   TargetMachine *TM = TheTarget->createTargetMachine(Triple, TargetOpts.CPU,
                                                      FeaturesStr, Options,
-                                                     RM, CM, OptLevel);
+                                                     RM, CM, OptLevel, PL);
 
   return TM;
 }
 
 bool EmitAssemblyHelper::AddEmitPasses(BackendAction Action,
                                        formatted_raw_ostream &OS) {
 
   // Create the code generator passes.

lib/Parse/ParseStmtAsm.cpp

StmtResult Parser::ParseMicrosoftAsmStatement(SourceLocation AsmLoc) {
   std::unique_ptr<llvm::MCInstrInfo> MII(TheTarget->createMCInstrInfo());
   std::unique_ptr<llvm::MCObjectFileInfo> MOFI(new llvm::MCObjectFileInfo());
   std::unique_ptr<llvm::MCSubtargetInfo> STI(
       TheTarget->createMCSubtargetInfo(TT, "", ""));
 
   llvm::SourceMgr TempSrcMgr;
   llvm::MCContext Ctx(MAI.get(), MRI.get(), MOFI.get(), &TempSrcMgr);
   MOFI->InitMCObjectFileInfo(TT, llvm::Reloc::Default, llvm::CodeModel::Default,
-                             Ctx);
+                             llvm::PICLevel::Default, Ctx);
   std::unique_ptr<llvm::MemoryBuffer> Buffer =
       llvm::MemoryBuffer::getMemBuffer(AsmString, "<MS inline asm>");
 
   // Tell SrcMgr about this buffer, which is what the parser will pick up.
   TempSrcMgr.AddNewSourceBuffer(std::move(Buffer), llvm::SMLoc());
 
   std::unique_ptr<llvm::MCStreamer> Str(createNullStreamer(Ctx));
   std::unique_ptr<llvm::MCAsmParser> Parser(

tools/driver/cc1as_main.cpp

static bool ExecuteAssembler(AssemblerInvocation &Opts,
 
   // FIXME: This is not pretty. MCContext has a ptr to MCObjectFileInfo and
   // MCObjectFileInfo needs a MCContext reference in order to initialize itself.
   std::unique_ptr<MCObjectFileInfo> MOFI(new MCObjectFileInfo());
 
   MCContext Ctx(MAI.get(), MRI.get(), MOFI.get(), &SrcMgr);
   // FIXME: Assembler behavior can change with -static.
   MOFI->InitMCObjectFileInfo(Opts.Triple,
-                             Reloc::Default, CodeModel::Default, Ctx);
+                             Reloc::Default, CodeModel::Default,
+                             PICLevel::Default, Ctx);
   if (Opts.SaveTemporaryLabels)
     Ctx.setAllowTemporaryLabels(false);
   if (Opts.GenDwarfForAssembly)
     Ctx.setGenDwarfForAssembly(true);
   if (!Opts.DwarfDebugFlags.empty())
     Ctx.setDwarfDebugFlags(StringRef(Opts.DwarfDebugFlags));
   if (!Opts.DwarfDebugProducer.empty())
     Ctx.setDwarfDebugProducer(StringRef(Opts.DwarfDebugProducer));