Remove support for 10.4 Tiger from AsmPrinter

[gchatelet]

Summary

I stumbled on this while trying to tighten Alignment in MCStreamer (D138705).
From the wikipedia page, last release of MacOSX Tiger was released 15 years ago and is not supported anymore by Apple.

Relevant commit : https://github.com/llvm/llvm-project/commit/9f06f911d197577b80d208a167980833b4fb9ad5#diff-17b326b45ef392288420bed274616afa7df81b27576c96723b3c25f5198dc398

[lattner]

Nice, seems overdue. Tiger (10.4.10) was the first release to ship LLVM as part of the OS, so special memories there :-). Thanks for cleaning this up!

[gchatelet]

rebase and fix formatting

[gchatelet]

In D138707#3951630, @lattner wrote:

Nice, seems overdue. Tiger (10.4.10) was the first release to ship LLVM as part of the OS, so special memories there :-). Thanks for cleaning this up!

🙂

llvm/include/llvm/MC/MCObjectFileInfo.h

 #include <array>
 
 namespace llvm {
 class MCContext;
 class MCSection;
 
 class MCObjectFileInfo {
 protected:
-  /// True if .comm supports alignment.  This is a hack for as long as we
-  /// support 10.4 Tiger, whose assembler doesn't support alignment on comm.
-  bool CommDirectiveSupportsAlignment = false;
-
   /// True if target object file supports a weak_definition of constant 0 for an
   /// omitted EH frame.
   bool SupportsWeakOmittedEHFrame = false;
 
   /// True if the target object file supports emitting a compact unwind section
   /// without an associated EH frame section.
   bool SupportsCompactUnwindWithoutEHFrame = false;
 
public:
   }
   bool getSupportsCompactUnwindWithoutEHFrame() const {
     return SupportsCompactUnwindWithoutEHFrame;
   }
   bool getOmitDwarfIfHaveCompactUnwind() const {
     return OmitDwarfIfHaveCompactUnwind;
   }
 
-  bool getCommDirectiveSupportsAlignment() const {
-    return CommDirectiveSupportsAlignment;
-  }
-
   unsigned getFDEEncoding() const { return FDECFIEncoding; }
 
   unsigned getCompactUnwindDwarfEHFrameOnly() const {
     return CompactUnwindDwarfEHFrameOnly;
   }
 
   virtual unsigned getTextSectionAlignment() const { return 4; }
   MCSection *getTextSection() const { return TextSection; }

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

NamedRegionTimer T(HI.TimerName, HI.TimerDescription,
                        TimePassesIsEnabled);
     HI.Handler->setSymbolSize(GVSym, Size);
   }
 
   // Handle common symbols
   if (GVKind.isCommon()) {
     if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
     // .comm _foo, 42, 4
-    const bool SupportsAlignment =
-        getObjFileLowering().getCommDirectiveSupportsAlignment();
-    OutStreamer->emitCommonSymbol(GVSym, Size,
-                                  SupportsAlignment ? Alignment.value() : 0);
+    OutStreamer->emitCommonSymbol(GVSym, Size, Alignment.value());
     return;
   }
 
   // Determine to which section this global should be emitted.
   MCSection *TheSection = getObjFileLowering().SectionForGlobal(GV, GVKind, TM);
 
   // If we have a bss global going to a section that supports the
   // zerofill directive, do so here.
if (MAI->getLCOMMDirectiveAlignmentType() != LCOMM::NoAlignment) {
       // .lcomm _foo, 42
       OutStreamer->emitLocalCommonSymbol(GVSym, Size, Alignment.value());
       return;
     }
 
     // .local _foo
     OutStreamer->emitSymbolAttribute(GVSym, MCSA_Local);
     // .comm _foo, 42, 4
-    const bool SupportsAlignment =
-        getObjFileLowering().getCommDirectiveSupportsAlignment();
-    OutStreamer->emitCommonSymbol(GVSym, Size,
-                                  SupportsAlignment ? Alignment.value() : 0);
+    OutStreamer->emitCommonSymbol(GVSym, Size, Alignment.value());
     return;
   }
 
   // Handle thread local data for mach-o which requires us to output an
   // additional structure of data and mangle the original symbol so that we
   // can reference it later.
   //
   // TODO: This should become an "emit thread local global" method on TLOF.

llvm/lib/MC/MCObjectFileInfo.cpp

void MCObjectFileInfo::initMachOMCObjectFileInfo(const Triple &T) {
   case EmitDwarfUnwindType::Default:
     OmitDwarfIfHaveCompactUnwind =
         T.isWatchABI() || SupportsCompactUnwindWithoutEHFrame;
     break;
   }
 
   FDECFIEncoding = dwarf::DW_EH_PE_pcrel;
 
-  // .comm doesn't support alignment before Leopard.
-  if (T.isMacOSX() && T.isMacOSXVersionLT(10, 5))
-    CommDirectiveSupportsAlignment = false;
-
   TextSection // .text
     = Ctx->getMachOSection("__TEXT", "__text",
                            MachO::S_ATTR_PURE_INSTRUCTIONS,
                            SectionKind::getText());
   DataSection // .data
       = Ctx->getMachOSection("__DATA", "__data", 0, SectionKind::getData());
 
   // BSSSection might not be expected initialized on msvc.
EHFrameSection =
                                            COFF::IMAGE_SCN_MEM_READ,
                           SectionKind::getData());
 
   // Set the `IMAGE_SCN_MEM_16BIT` flag when compiling for thumb mode.  This is
   // used to indicate to the linker that the text segment contains thumb instructions
   // and to set the ISA selection bit for calls accordingly.
   const bool IsThumb = T.getArch() == Triple::thumb;
 
-  CommDirectiveSupportsAlignment = true;
-
   // COFF
   BSSSection = Ctx->getCOFFSection(
       ".bss", COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
                   COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
       SectionKind::getBSS());
   TextSection = Ctx->getCOFFSection(
       ".text",
       (IsThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0) |

 MCObjectFileInfo::~MCObjectFileInfo() = default;
 
 void MCObjectFileInfo::initMCObjectFileInfo(MCContext &MCCtx, bool PIC,
                                             bool LargeCodeModel) {
   PositionIndependent = PIC;
   Ctx = &MCCtx;
 
   // Common.
-  CommDirectiveSupportsAlignment = true;
   SupportsWeakOmittedEHFrame = true;
   SupportsCompactUnwindWithoutEHFrame = false;
   OmitDwarfIfHaveCompactUnwind = false;
 
   FDECFIEncoding = dwarf::DW_EH_PE_absptr;
 
   CompactUnwindDwarfEHFrameOnly = 0;