1 //===- MCAsmInfoDarwin.cpp - Darwin asm properties ------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines target asm properties related what form asm statements
10 // should take in general on Darwin-based targets
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/MC/MCAsmInfoDarwin.h"
15 #include "llvm/BinaryFormat/MachO.h"
16 #include "llvm/MC/MCDirectives.h"
17 #include "llvm/MC/MCSectionMachO.h"
18 
19 using namespace llvm;
20 
21 bool MCAsmInfoDarwin::isSectionAtomizableBySymbols(
22     const MCSection &Section) const {
23   const MCSectionMachO &SMO = static_cast<const MCSectionMachO &>(Section);
24 
25   // Sections holding 1 byte strings are atomized based on the data they
26   // contain.
27   // Sections holding 2 byte strings require symbols in order to be atomized.
28   // There is no dedicated section for 4 byte strings.
29   if (SMO.getType() == MachO::S_CSTRING_LITERALS)
30     return false;
31 
32   if (SMO.getSegmentName() == "__DATA" && SMO.getName() == "__cfstring")
33     return false;
34 
35   if (SMO.getSegmentName() == "__DATA" && SMO.getName() == "__objc_classrefs")
36     return false;
37 
38   switch (SMO.getType()) {
39   default:
40     return true;
41 
42   // These sections are atomized at the element boundaries without using
43   // symbols.
44   case MachO::S_4BYTE_LITERALS:
45   case MachO::S_8BYTE_LITERALS:
46   case MachO::S_16BYTE_LITERALS:
47   case MachO::S_LITERAL_POINTERS:
48   case MachO::S_NON_LAZY_SYMBOL_POINTERS:
49   case MachO::S_LAZY_SYMBOL_POINTERS:
50   case MachO::S_THREAD_LOCAL_VARIABLE_POINTERS:
51   case MachO::S_MOD_INIT_FUNC_POINTERS:
52   case MachO::S_MOD_TERM_FUNC_POINTERS:
53   case MachO::S_INTERPOSING:
54     return false;
55   }
56 }
57 
58 MCAsmInfoDarwin::MCAsmInfoDarwin() {
59   // Common settings for all Darwin targets.
60   // Syntax:
61   LinkerPrivateGlobalPrefix = "l";
62   HasSingleParameterDotFile = false;
63   HasSubsectionsViaSymbols = true;
64 
65   AlignmentIsInBytes = false;
66   COMMDirectiveAlignmentIsInBytes = false;
67   LCOMMDirectiveAlignmentType = LCOMM::Log2Alignment;
68   InlineAsmStart = " InlineAsm Start";
69   InlineAsmEnd = " InlineAsm End";
70 
71   // Directives:
72   HasWeakDefDirective = true;
73   HasWeakDefCanBeHiddenDirective = true;
74   WeakRefDirective = "\t.weak_reference ";
75   ZeroDirective = "\t.space\t";  // ".space N" emits N zeros.
76   HasMachoZeroFillDirective = true;  // Uses .zerofill
77   HasMachoTBSSDirective = true; // Uses .tbss
78 
79   // FIXME: Change this once MC is the system assembler.
80   HasAggressiveSymbolFolding = false;
81 
82   HiddenVisibilityAttr = MCSA_PrivateExtern;
83   HiddenDeclarationVisibilityAttr = MCSA_Invalid;
84 
85   // Doesn't support protected visibility.
86   ProtectedVisibilityAttr = MCSA_Invalid;
87 
88   HasDotTypeDotSizeDirective = false;
89   HasNoDeadStrip = true;
90   HasAltEntry = true;
91 
92   DwarfUsesRelocationsAcrossSections = false;
93   SetDirectiveSuppressesReloc = true;
94 }
95