Wire up primitive support in the assembler backend for writing .o files

directly on the mac.  This is very early, doesn't support relocations and
has a terrible hack to avoid .machine from being printed, but despite
that it generates an bitwise-identical-to-cctools .o file for stuff like 
this:

  define i32 @test() nounwind { ret i32 42 }

I don't plan to continue pushing this forward, but if anyone else was
interested in doing it, it should be really straight-forward.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119136 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/CMakeLists.txt

@@ -13,6 +13,7 @@ tablegen(PPCGenCallingConv.inc -gen-callingconv)
 tablegen(PPCGenSubtarget.inc -gen-subtarget)
 
 add_llvm_target(PowerPCCodeGen
+  PPCAsmBackend.cpp
   PPCAsmPrinter.cpp
   PPCBranchSelector.cpp
   PPCCodeEmitter.cpp

lib/Target/PowerPC/PPC.h

@@ -15,6 +15,8 @@
 #ifndef LLVM_TARGET_POWERPC_H
 #define LLVM_TARGET_POWERPC_H
 
+#include <string>
+
 // GCC #defines PPC on Linux but we use it as our namespace name
 #undef PPC
 
@@ -30,6 +32,7 @@ namespace llvm {
   class MCCodeEmitter;
   class MCContext;
   class TargetMachine;
+  class TargetAsmBackend;
   
   FunctionPass *createPPCBranchSelectionPass();
   FunctionPass *createPPCISelDag(PPCTargetMachine &TM);
@@ -37,6 +40,7 @@ namespace llvm {
                                             JITCodeEmitter &MCE);
   MCCodeEmitter *createPPCMCCodeEmitter(const Target &, TargetMachine &TM,
                                         MCContext &Ctx);
+  TargetAsmBackend *createPPCAsmBackend(const Target &, const std::string &);
   
   void LowerPPCMachineInstrToMCInst(const MachineInstr *MI, MCInst &OutMI,
                                     AsmPrinter &AP);

lib/Target/PowerPC/PPCAsmBackend.cpp

@@ -0,0 +1,104 @@
+//===-- PPCAsmBackend.cpp - PPC Assembler Backend -------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Target/TargetAsmBackend.h"
+#include "PPC.h"
+#include "PPCFixupKinds.h"
+#include "llvm/MC/MCSectionMachO.h"
+#include "llvm/MC/MCObjectFormat.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/Target/TargetRegistry.h"
+#include "llvm/Support/MachO.h"
+using namespace llvm;
+
+namespace {
+  class PPCAsmBackend : public TargetAsmBackend {
+  public:
+    PPCAsmBackend(const Target &T) : TargetAsmBackend(T) {}
+    
+    bool MayNeedRelaxation(const MCInst &Inst) const {
+      // FIXME.
+      return false;
+    }
+    
+    void RelaxInstruction(const MCInst &Inst, MCInst &Res) const {
+      // FIXME.
+      assert(0 && "RelaxInstruction() unimplemented");
+    }
+    
+    bool WriteNopData(uint64_t Count, MCObjectWriter *OW) const {
+      // FIXME: Zero fill for now. That's not right, but at least will get the
+      // section size right.
+      for (uint64_t i = 0; i != Count; ++i)
+        OW->Write8(0);
+      return true;
+    }      
+    
+    unsigned getPointerSize() const {
+      StringRef Name = TheTarget.getName();
+      if (Name == "ppc64") return 8;
+      assert(Name == "ppc32" && "Unknown target name!");
+      return 4;
+    }
+  };
+} // end anonymous namespace
+
+
+// FIXME: This should be in a separate file.
+namespace {
+  class DarwinPPCAsmBackend : public PPCAsmBackend {
+    MCMachOObjectFormat Format;
+  public:
+    DarwinPPCAsmBackend(const Target &T) : PPCAsmBackend(T) {
+      HasScatteredSymbols = true;
+    }
+    
+    virtual const MCObjectFormat &getObjectFormat() const {
+      return Format;
+    }
+    
+    void ApplyFixup(const MCFixup &Fixup, MCDataFragment &DF,
+                    uint64_t Value) const {
+      assert(0 && "UNIMP");
+    }
+    
+    bool isVirtualSection(const MCSection &Section) const {
+      const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
+      return (SMO.getType() == MCSectionMachO::S_ZEROFILL ||
+              SMO.getType() == MCSectionMachO::S_GB_ZEROFILL ||
+              SMO.getType() == MCSectionMachO::S_THREAD_LOCAL_ZEROFILL);
+    }
+    
+    MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
+      bool is64 = getPointerSize() == 8;
+      return createMachObjectWriter(OS, /*Is64Bit=*/is64,
+                                    is64 ? MachO::CPUTypePowerPC64 : 
+                                    MachO::CPUTypePowerPC64,
+                                    MachO::CPUSubType_POWERPC_ALL,
+                                    /*IsLittleEndian=*/false);
+    }
+    
+    virtual bool doesSectionRequireSymbols(const MCSection &Section) const {
+      return false;
+    }
+  };
+} // end anonymous namespace
+
+
+
+
+TargetAsmBackend *llvm::createPPCAsmBackend(const Target &T,
+                                            const std::string &TT) {
+  switch (Triple(TT).getOS()) {
+  case Triple::Darwin:
+    return new DarwinPPCAsmBackend(T);
+  default:
+    return 0;
+  }
+}

lib/Target/PowerPC/PPCAsmPrinter.cpp

@@ -438,7 +438,10 @@ void PPCDarwinAsmPrinter::EmitStartOfAsmFile(Module &M) {
   if (Subtarget.isPPC64() && Directive < PPC::DIR_970)
     Directive = PPC::DIR_64;
   assert(Directive <= PPC::DIR_64 && "Directive out of range.");
-  OutStreamer.EmitRawText("\t.machine " + Twine(CPUDirectives[Directive]));
+  
+  // FIXME: This is a total hack, finish mc'izing the PPC backend.
+  if (OutStreamer.hasRawTextSupport())
+    OutStreamer.EmitRawText("\t.machine " + Twine(CPUDirectives[Directive]));
 
   // Prime text sections so they are adjacent.  This reduces the likelihood a
   // large data or debug section causes a branch to exceed 16M limit.

lib/Target/PowerPC/PPCTargetMachine.cpp

@@ -15,6 +15,7 @@
 #include "PPCMCAsmInfo.h"
 #include "PPCTargetMachine.h"
 #include "llvm/PassManager.h"
+#include "llvm/MC/MCStreamer.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Target/TargetRegistry.h"
 #include "llvm/Support/FormattedStream.h"
@@ -29,6 +30,20 @@ static MCAsmInfo *createMCAsmInfo(const Target &T, StringRef TT) {
   
 }
 
+// This is duplicated code. Refactor this.
+static MCStreamer *createMCStreamer(const Target &T, const std::string &TT,
+                                    MCContext &Ctx, TargetAsmBackend &TAB,
+                                    raw_ostream &OS,
+                                    MCCodeEmitter *Emitter,
+                                    bool RelaxAll) {
+  switch (Triple(TT).getOS()) {
+  case Triple::Darwin:
+    return createMachOStreamer(Ctx, TAB, OS, Emitter, RelaxAll);
+  default:
+    return NULL;
+  }
+}
+
 extern "C" void LLVMInitializePowerPCTarget() {
   // Register the targets
   RegisterTargetMachine<PPC32TargetMachine> A(ThePPC32Target);  
@@ -40,6 +55,15 @@ extern "C" void LLVMInitializePowerPCTarget() {
   // Register the MC Code Emitter
   TargetRegistry::RegisterCodeEmitter(ThePPC32Target, createPPCMCCodeEmitter);
   TargetRegistry::RegisterCodeEmitter(ThePPC64Target, createPPCMCCodeEmitter);
+  
+  
+  // Register the asm backend.
+  TargetRegistry::RegisterAsmBackend(ThePPC32Target, createPPCAsmBackend);
+  TargetRegistry::RegisterAsmBackend(ThePPC64Target, createPPCAsmBackend);
+  
+  // Register the object streamer.
+  TargetRegistry::RegisterObjectStreamer(ThePPC32Target, createMCStreamer);
+  TargetRegistry::RegisterObjectStreamer(ThePPC64Target, createMCStreamer);
 }