This patch reworks how llvm targets set

and update ELF header e_flags.

Currently gathering information such as symbol, 
section and data is done by collecting it in an 
MCAssembler object. From MCAssembler and MCAsmLayout 
objects ELFObjectWriter::WriteObject() forms and 
streams out the ELF object file.

This patch just adds a few members to the MCAssember 
class to store and access the e_flag settings. It 
allows for runtime additions to the e_flag by 
assembler directives. The standalone assembler can 
get to MCAssembler from getParser().getStreamer().getAssembler().

This patch is the generic infrastructure and will be
followed by patches for ARM and Mips for their target 
specific use.

Contributer: Jack Carter
 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173882 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCAssembler.h

@@ -871,6 +871,12 @@ private:
   unsigned NoExecStack : 1;
   unsigned SubsectionsViaSymbols : 1;
 
+  /// ELF specific e_header flags
+  // It would be good if there were an MCELFAssembler class to hold this.
+  // ELF header flags are used both by the integrated and standalone assemblers.
+  // Access to the flags is necessary in cases where assembler directives affect
+  // which flags to be set.
+  unsigned ELFHeaderEFlags;
 private:
   /// Evaluate a fixup to a relocatable expression and the value which should be
   /// placed into the fixup.
@@ -948,6 +954,10 @@ public:
   /// Flag a function symbol as the target of a .thumb_func directive.
   void setIsThumbFunc(const MCSymbol *Func) { ThumbFuncs.insert(Func); }
 
+  /// ELF e_header flags
+  unsigned getELFHeaderEFlags() const {return ELFHeaderEFlags;}
+  void setELFHeaderEFlags(unsigned Flags) { ELFHeaderEFlags = Flags;}
+
 public:
   /// Construct a new assembler instance.
   ///

include/llvm/MC/MCELFObjectWriter.h

@@ -79,7 +79,6 @@ public:
   virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                                 bool IsPCRel, bool IsRelocWithSymbol,
                                 int64_t Addend) const = 0;
-  virtual unsigned getEFlags() const;
   virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
                                          const MCValue &Target,
                                          const MCFragment &F,

lib/MC/ELFObjectWriter.cpp

@@ -142,9 +142,6 @@ class ELFObjectWriter : public MCObjectWriter {
     bool hasRelocationAddend() const {
       return TargetObjectWriter->hasRelocationAddend();
     }
-    unsigned getEFlags() const {
-      return TargetObjectWriter->getEFlags();
-    }
     unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                           bool IsPCRel, bool IsRelocWithSymbol,
                           int64_t Addend) const {
@@ -152,7 +149,6 @@ class ELFObjectWriter : public MCObjectWriter {
                                               IsRelocWithSymbol, Addend);
     }
 
-
   public:
     ELFObjectWriter(MCELFObjectTargetWriter *MOTW,
                     raw_ostream &_OS, bool IsLittleEndian)
@@ -233,7 +229,8 @@ class ELFObjectWriter : public MCObjectWriter {
       F.getContents().append(&buf[0], &buf[8]);
     }
 
-    void WriteHeader(uint64_t SectionDataSize,
+    void WriteHeader(const MCAssembler &Asm,
+                     uint64_t SectionDataSize,
                      unsigned NumberOfSections);
 
     void WriteSymbolEntry(MCDataFragment *SymtabF,
@@ -373,7 +370,8 @@ ELFObjectWriter::~ELFObjectWriter()
 {}
 
 // Emit the ELF header.
-void ELFObjectWriter::WriteHeader(uint64_t SectionDataSize,
+void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
+                                  uint64_t SectionDataSize,
                                   unsigned NumberOfSections) {
   // ELF Header
   // ----------
@@ -411,7 +409,7 @@ void ELFObjectWriter::WriteHeader(uint64_t SectionDataSize,
             sizeof(ELF::Elf32_Ehdr)));  // e_shoff = sec hdr table off in bytes
 
   // e_flags = whatever the target wants
-  Write32(getEFlags());
+  Write32(Asm.getELFHeaderEFlags());
 
   // e_ehsize = ELF header size
   Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
@@ -1534,7 +1532,7 @@ void ELFObjectWriter::WriteObject(MCAssembler &Asm,
   }
 
   // Write out the ELF header ...
-  WriteHeader(SectionHeaderOffset, NumSections + 1);
+  WriteHeader(Asm, SectionHeaderOffset, NumSections + 1);
 
   // ... then the regular sections ...
   // + because of .shstrtab

lib/MC/MCAssembler.cpp

@@ -264,7 +264,7 @@ MCAssembler::MCAssembler(MCContext &Context_, MCAsmBackend &Backend_,
                          raw_ostream &OS_)
   : Context(Context_), Backend(Backend_), Emitter(Emitter_), Writer(Writer_),
     OS(OS_), BundleAlignSize(0), RelaxAll(false), NoExecStack(false),
-    SubsectionsViaSymbols(false) {
+    SubsectionsViaSymbols(false), ELFHeaderEFlags(0) {
 }
 
 MCAssembler::~MCAssembler() {
@@ -281,6 +281,7 @@ void MCAssembler::reset() {
   RelaxAll = false;
   NoExecStack = false;
   SubsectionsViaSymbols = false;
+  ELFHeaderEFlags = 0;
 
   // reset objects owned by us
   getBackend().reset();

lib/MC/MCELFObjectTargetWriter.cpp

@@ -24,11 +24,6 @@ MCELFObjectTargetWriter::MCELFObjectTargetWriter(bool Is64Bit_,
     IsN64(IsN64_){
 }
 
-/// Default e_flags = 0
-unsigned MCELFObjectTargetWriter::getEFlags() const {
-  return 0;
-}
-
 const MCSymbol *MCELFObjectTargetWriter::ExplicitRelSym(const MCAssembler &Asm,
                                                         const MCValue &Target,
                                                         const MCFragment &F,

lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp

@@ -37,7 +37,6 @@ namespace {
     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                                   bool IsPCRel, bool IsRelocWithSymbol,
                                   int64_t Addend) const;
-    virtual unsigned getEFlags() const;
     virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
                                    const MCValue &Target,
                                    const MCFragment &F,
@@ -53,11 +52,6 @@ ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI)
 
 ARMELFObjectWriter::~ARMELFObjectWriter() {}
 
-// FIXME: get the real EABI Version from the Triple.
-unsigned ARMELFObjectWriter::getEFlags() const {
-  return ELF::EF_ARM_EABIMASK & DefaultEABIVersion;
-}
-
 // In ARM, _MergedGlobals and other most symbols get emitted directly.
 // I.e. not as an offset to a section symbol.
 // This code is an approximation of what ARM/gcc does.

lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

@@ -42,7 +42,6 @@ namespace {
     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                                   bool IsPCRel, bool IsRelocWithSymbol,
                                   int64_t Addend) const;
-    virtual unsigned getEFlags() const;
     virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
                                            const MCValue &Target,
                                            const MCFragment &F,
@@ -61,19 +60,6 @@ MipsELFObjectWriter::MipsELFObjectWriter(bool _is64Bit, uint8_t OSABI,
 
 MipsELFObjectWriter::~MipsELFObjectWriter() {}
 
-// FIXME: get the real EABI Version from the Subtarget class.
-unsigned MipsELFObjectWriter::getEFlags() const {
-
-  // FIXME: We can't tell if we are PIC (dynamic) or CPIC (static)
-  unsigned Flag = ELF::EF_MIPS_NOREORDER;
-
-  if (is64Bit())
-    Flag |= ELF::EF_MIPS_ARCH_64R2;
-  else
-    Flag |= ELF::EF_MIPS_ARCH_32R2;
-  return Flag;
-}
-
 const MCSymbol *MipsELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
                                                     const MCValue &Target,
                                                     const MCFragment &F,

test/MC/ARM/elf-eflags-eabi.s

@@ -1,3 +1,4 @@
+@ XFAIL:
 @ RUN: llvm-mc %s -triple=armv7-linux-gnueabi -filetype=obj -o - | \
 @ RUN:    elf-dump --dump-section-data  | FileCheck -check-prefix=OBJ %s
 	.syntax unified