lib/Target/TargetAsmInfo.cpp

   1 //===-- TargetAsmInfo.cpp - Asm Info ---------------------------------------==//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file defines target asm properties related what form asm statements
  11 // should take.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Constants.h"
  16 #include "llvm/GlobalVariable.h"
  17 #include "llvm/Function.h"
  18 #include "llvm/Module.h"
  19 #include "llvm/Type.h"
  20 #include "llvm/Target/TargetAsmInfo.h"
  21 #include "llvm/Target/TargetOptions.h"
  22 #include "llvm/Support/Dwarf.h"
  23 #include <cctype>
  24 #include <cstring>
  25
  26 using namespace llvm;
  27
  28 TargetAsmInfo::TargetAsmInfo() :
  29   TextSection("\t.text"),
  30   DataSection("\t.data"),
  31   BSSSection("\t.bss"),
  32   TLSDataSection("\t.section .tdata,\"awT\",@progbits"),
  33   TLSBSSSection("\t.section .tbss,\"awT\",@nobits"),
  34   ZeroFillDirective(0),
  35   NonexecutableStackDirective(0),
  36   NeedsSet(false),
  37   MaxInstLength(4),
  38   PCSymbol("$"),
  39   SeparatorChar(';'),
  40   CommentString("#"),
  41   GlobalPrefix(""),
  42   PrivateGlobalPrefix("."),
  43   JumpTableSpecialLabelPrefix(0),
  44   GlobalVarAddrPrefix(""),
  45   GlobalVarAddrSuffix(""),
  46   FunctionAddrPrefix(""),
  47   FunctionAddrSuffix(""),
  48   PersonalityPrefix(""),
  49   PersonalitySuffix(""),
  50   NeedsIndirectEncoding(false),
  51   InlineAsmStart("#APP"),
  52   InlineAsmEnd("#NO_APP"),
  53   AssemblerDialect(0),
  54   StringConstantPrefix(".str"),
  55   ZeroDirective("\t.zero\t"),
  56   ZeroDirectiveSuffix(0),
  57   AsciiDirective("\t.ascii\t"),
  58   AscizDirective("\t.asciz\t"),
  59   Data8bitsDirective("\t.byte\t"),
  60   Data16bitsDirective("\t.short\t"),
  61   Data32bitsDirective("\t.long\t"),
  62   Data64bitsDirective("\t.quad\t"),
  63   AlignDirective("\t.align\t"),
  64   AlignmentIsInBytes(true),
  65   TextAlignFillValue(0),
  66   SwitchToSectionDirective("\t.section\t"),
  67   TextSectionStartSuffix(""),
  68   DataSectionStartSuffix(""),
  69   SectionEndDirectiveSuffix(0),
  70   ConstantPoolSection("\t.section .rodata"),
  71   JumpTableDataSection("\t.section .rodata"),
  72   JumpTableDirective(0),
  73   CStringSection(0),
  74   StaticCtorsSection("\t.section .ctors,\"aw\",@progbits"),
  75   StaticDtorsSection("\t.section .dtors,\"aw\",@progbits"),
  76   FourByteConstantSection(0),
  77   EightByteConstantSection(0),
  78   SixteenByteConstantSection(0),
  79   ReadOnlySection(0),
  80   GlobalDirective("\t.globl\t"),
  81   SetDirective(0),
  82   LCOMMDirective(0),
  83   COMMDirective("\t.comm\t"),
  84   COMMDirectiveTakesAlignment(true),
  85   HasDotTypeDotSizeDirective(true),
  86   UsedDirective(0),
  87   WeakRefDirective(0),
  88   WeakDefDirective(0),
  89   HiddenDirective("\t.hidden\t"),
  90   ProtectedDirective("\t.protected\t"),
  91   AbsoluteDebugSectionOffsets(false),
  92   AbsoluteEHSectionOffsets(false),
  93   HasLEB128(false),
  94   HasDotLocAndDotFile(false),
  95   SupportsDebugInformation(false),
  96   SupportsExceptionHandling(false),
  97   DwarfRequiresFrameSection(true),
  98   GlobalEHDirective(0),
  99   SupportsWeakOmittedEHFrame(true),
 100   DwarfSectionOffsetDirective(0),
 101   DwarfAbbrevSection(".debug_abbrev"),
 102   DwarfInfoSection(".debug_info"),
 103   DwarfLineSection(".debug_line"),
 104   DwarfFrameSection(".debug_frame"),
 105   DwarfPubNamesSection(".debug_pubnames"),
 106   DwarfPubTypesSection(".debug_pubtypes"),
 107   DwarfStrSection(".debug_str"),
 108   DwarfLocSection(".debug_loc"),
 109   DwarfARangesSection(".debug_aranges"),
 110   DwarfRangesSection(".debug_ranges"),
 111   DwarfMacInfoSection(".debug_macinfo"),
 112   DwarfEHFrameSection(".eh_frame"),
 113   DwarfExceptionSection(".gcc_except_table"),
 114   DebugInfoRequireFrameMoveInfo(true),
 115   AsmTransCBE(0) {
 116 }
 117
 118 TargetAsmInfo::~TargetAsmInfo() {
 119 }
 120
 121 /// Measure the specified inline asm to determine an approximation of its
 122 /// length.
 123 /// Comments (which run till the next SeparatorChar or newline) do not
 124 /// count as an instruction.
 125 /// Any other non-whitespace text is considered an instruction, with
 126 /// multiple instructions separated by SeparatorChar or newlines.
 127 /// Variable-length instructions are not handled here; this function
 128 /// may be overloaded in the target code to do that.
 129 unsigned TargetAsmInfo::getInlineAsmLength(const char *Str) const {
 130   // Count the number of instructions in the asm.
 131   bool atInsnStart = true;
 132   unsigned Length = 0;
 133   for (; *Str; ++Str) {
 134     if (*Str == '\n' || *Str == SeparatorChar)
 135       atInsnStart = true;
 136     if (atInsnStart && !isspace(*Str)) {
 137       Length += MaxInstLength;
 138       atInsnStart = false;
 139     }
 140     if (atInsnStart && strncmp(Str, CommentString, strlen(CommentString))==0)
 141       atInsnStart = false;
 142   }
 143
 144   return Length;
 145 }
 146
 147 unsigned TargetAsmInfo::PreferredEHDataFormat(DwarfEncoding::Target Reason,
 148                                               bool Global) const {
 149   return dwarf::DW_EH_PE_absptr;
 150 }
 151
 152 static bool isSuitableForBSS(const GlobalVariable *GV) {
 153   if (!GV->hasInitializer())
 154     return true;
 155
 156   // Leave constant zeros in readonly constant sections, so they can be shared
 157   Constant *C = GV->getInitializer();
 158   return (C->isNullValue() && !GV->isConstant() && !NoZerosInBSS);
 159 }
 160
 161 SectionKind::Kind
 162 TargetAsmInfo::SectionKindForGlobal(const GlobalValue *GV) const {
 163   // Early exit - functions should be always in text sections.
 164   if (isa<Function>(GV))
 165     return SectionKind::Text;
 166
 167   const GlobalVariable* GVar = dyn_cast<GlobalVariable>(GV);
 168   bool isThreadLocal = GVar->isThreadLocal();
 169   assert(GVar && "Invalid global value for section selection");
 170
 171   SectionKind::Kind kind;
 172   if (isSuitableForBSS(GVar)) {
 173     // Variable can be easily put to BSS section.
 174     return (isThreadLocal ? SectionKind::ThreadBSS : SectionKind::BSS);
 175   } else if (GVar->isConstant() && !isThreadLocal) {
 176     // Now we know, that varible has initializer and it is constant. We need to
 177     // check its initializer to decide, which section to output it into. Also
 178     // note, there is no thread-local r/o section.
 179     Constant *C = GVar->getInitializer();
 180     if (C->ContainsRelocations())
 181       kind = SectionKind::ROData;
 182     else {
 183       const ConstantArray *CVA = dyn_cast<ConstantArray>(C);
 184       // Check, if initializer is a null-terminated string
 185       if (CVA && CVA->isCString())
 186         kind = SectionKind::RODataMergeStr;
 187       else
 188         kind = SectionKind::RODataMergeConst;
 189     }
 190   }
 191
 192   // Variable is not constant or thread-local - emit to generic data section.
 193   return (isThreadLocal ? SectionKind::ThreadData : SectionKind::Data);
 194 }