Add a new virtual EmitStartOfAsmFile method to the AsmPrinter and use this

to emit target-specific things at the beginning of the asm output.  This
fixes a problem for PPC, where the text sections are not being kept together
as expected.  The base class doInitialization code calls DW->BeginModule()
which emits a bunch of DWARF section directives.  The PPC doInitialization
code then emits all the TEXT section directives, with the intention that they
will be kept together. But as I understand it, the Darwin assembler treats
the default TEXT section as a special case and moves it to the beginning of
the file, which means that all those DWARF sections are in the middle of
the text.  With this change, the EmitStartOfAsmFile hook is called before
the DWARF section directives are emitted, so that all the PPC text section
directives come out right at the beginning of the file.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83176 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/AsmPrinter.h

@@ -169,6 +169,10 @@ namespace llvm {
     /// call this implementation.
     bool doInitialization(Module &M);
 
+    /// EmitStartOfAsmFile - This virtual method can be overridden by targets
+    /// that want to emit something at the start of their file.
+    virtual void EmitStartOfAsmFile(Module &M) {}
+    
     /// EmitEndOfAsmFile - This virtual method can be overridden by targets that
     /// want to emit something at the end of their file.
     virtual void EmitEndOfAsmFile(Module &M) {}

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -110,8 +110,8 @@ bool AsmPrinter::doInitialization(Module &M) {
   if (MAI->doesAllowNameToStartWithDigit())
     Mang->setSymbolsCanStartWithDigit(true);
   
-  GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
-  assert(MI && "AsmPrinter didn't require GCModuleInfo?");
+  // Allow the target to emit any magic that it wants at the start of the file.
+  EmitStartOfAsmFile(M);
 
   if (MAI->hasSingleParameterDotFile()) {
     /* Very minimal debug info. It is ignored if we emit actual
@@ -120,6 +120,8 @@ bool AsmPrinter::doInitialization(Module &M) {
     O << "\t.file\t\"" << M.getModuleIdentifier() << "\"\n";
   }
 
+  GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
+  assert(MI && "AsmPrinter didn't require GCModuleInfo?");
   for (GCModuleInfo::iterator I = MI->begin(), E = MI->end(); I != E; ++I)
     if (GCMetadataPrinter *MP = GetOrCreateGCPrinter(*I))
       MP->beginAssembly(O, *this, *MAI);

lib/Target/ARM/AsmPrinter/ARMAsmPrinter.cpp

@@ -149,8 +149,8 @@ namespace {
 
     void printMachineInstruction(const MachineInstr *MI);
     bool runOnMachineFunction(MachineFunction &F);
-    bool doInitialization(Module &M);
     bool doFinalization(Module &M);
+    void EmitStartOfAsmFile(Module &M);
 
     /// EmitMachineConstantPoolValue - Print a machine constantpool value to
     /// the .s file.
@@ -1043,8 +1043,7 @@ void ARMAsmPrinter::printMachineInstruction(const MachineInstr *MI) {
   O << '\n';
 }
 
-bool ARMAsmPrinter::doInitialization(Module &M) {
-
+void ARMAsmPrinter::EmitStartOfAsmFile(Module &M) {
   if (Subtarget->isTargetDarwin()) {
     Reloc::Model RelocM = TM.getRelocationModel();
     if (RelocM == Reloc::PIC_ || RelocM == Reloc::DynamicNoPIC) {
@@ -1064,8 +1063,6 @@ bool ARMAsmPrinter::doInitialization(Module &M) {
     }
   }
 
-  bool Result = AsmPrinter::doInitialization(M);
-
   // Use unified assembler syntax mode for Thumb.
   if (Subtarget->isThumb())
     O << "\t.syntax unified\n";
@@ -1102,8 +1099,6 @@ bool ARMAsmPrinter::doInitialization(Module &M) {
 
     // FIXME: Should we signal R9 usage?
   }
-
-  return Result;
 }
 
 void ARMAsmPrinter::PrintGlobalVariable(const GlobalVariable* GVar) {

lib/Target/Alpha/AsmPrinter/AlphaAsmPrinter.cpp

@@ -56,7 +56,7 @@ namespace {
     void printBaseOffsetPair(const MachineInstr *MI, int i, bool brackets=true);
     void PrintGlobalVariable(const GlobalVariable *GVar);
     bool runOnMachineFunction(MachineFunction &F);
-    bool doInitialization(Module &M);
+    void EmitStartOfAsmFile(Module &M);
 
     bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
                          unsigned AsmVariant, const char *ExtraCode);
@@ -193,14 +193,12 @@ bool AlphaAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
   return false;
 }
 
-bool AlphaAsmPrinter::doInitialization(Module &M)
-{
-  if(TM.getSubtarget<AlphaSubtarget>().hasCT())
+void AlphaAsmPrinter::EmitStartOfAsmFile(Module &M) {
+  if (TM.getSubtarget<AlphaSubtarget>().hasCT())
     O << "\t.arch ev6\n"; //This might need to be ev67, so leave this test here
   else
     O << "\t.arch ev6\n";
   O << "\t.set noat\n";
-  return AsmPrinter::doInitialization(M);
 }
 
 void AlphaAsmPrinter::PrintGlobalVariable(const GlobalVariable *GVar) {

lib/Target/Mips/AsmPrinter/MipsAsmPrinter.cpp

@@ -85,7 +85,7 @@ namespace {
     static const char *getRegisterName(unsigned RegNo);
 
     bool runOnMachineFunction(MachineFunction &F);
-    bool doInitialization(Module &M);
+    void EmitStartOfAsmFile(Module &M);
   };
 } // end of anonymous namespace
 
@@ -408,7 +408,7 @@ printFCCOperand(const MachineInstr *MI, int opNum, const char *Modifier) {
   O << Mips::MipsFCCToString((Mips::CondCode)MO.getImm()); 
 }
 
-bool MipsAsmPrinter::doInitialization(Module &M) {
+void MipsAsmPrinter::EmitStartOfAsmFile(Module &M) {
   // FIXME: Use SwitchSection.
   
   // Tell the assembler which ABI we are using
@@ -421,8 +421,6 @@ bool MipsAsmPrinter::doInitialization(Module &M) {
 
   // return to previous section
   O << "\t.previous" << '\n'; 
-
-  return AsmPrinter::doInitialization(M);
 }
 
 void MipsAsmPrinter::PrintGlobalVariable(const GlobalVariable *GVar) {

lib/Target/PowerPC/AsmPrinter/PPCAsmPrinter.cpp

@@ -381,8 +381,8 @@ namespace {
     }
 
     bool runOnMachineFunction(MachineFunction &F);
-    bool doInitialization(Module &M);
     bool doFinalization(Module &M);
+    void EmitStartOfAsmFile(Module &M);
 
     void getAnalysisUsage(AnalysisUsage &AU) const {
       AU.setPreservesAll();
@@ -862,7 +862,7 @@ bool PPCDarwinAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
 }
 
 
-bool PPCDarwinAsmPrinter::doInitialization(Module &M) {
+void PPCDarwinAsmPrinter::EmitStartOfAsmFile(Module &M) {
   static const char *const CPUDirectives[] = {
     "",
     "ppc",
@@ -885,9 +885,6 @@ bool PPCDarwinAsmPrinter::doInitialization(Module &M) {
   assert(Directive <= PPC::DIR_64 && "Directive out of range.");
   O << "\t.machine " << CPUDirectives[Directive] << '\n';
 
-  bool Result = AsmPrinter::doInitialization(M);
-  assert(MMI);
-
   // Prime text sections so they are adjacent.  This reduces the likelihood a
   // large data or debug section causes a branch to exceed 16M limit.
   TargetLoweringObjectFileMachO &TLOFMacho = 
@@ -907,8 +904,6 @@ bool PPCDarwinAsmPrinter::doInitialization(Module &M) {
                                       16, SectionKind::getText()));
   }
   OutStreamer.SwitchSection(getObjFileLowering().getTextSection());
-
-  return Result;
 }
 
 void PPCDarwinAsmPrinter::PrintGlobalVariable(const GlobalVariable *GVar) {