ARMSubtarget.cpp revision d3dd50fec00fbbb76edbfaff4d613f1248d21c9e 
1//===-- ARMSubtarget.cpp - ARM Subtarget Information ------------*- C++ -*-===//
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 implements the ARM specific subclass of TargetSubtarget.
11//
12//===----------------------------------------------------------------------===//
13
14#include "ARMSubtarget.h"
15#include "ARMGenSubtarget.inc"
16#include "llvm/GlobalValue.h"
17#include "llvm/Target/TargetOptions.h"
18#include "llvm/Support/CommandLine.h"
19using namespace llvm;
20
21static cl::opt<bool>
22ReserveR9("arm-reserve-r9", cl::Hidden,
23          cl::desc("Reserve R9, making it unavailable as GPR"));
24static cl::opt<bool>
25UseNEONFP("arm-use-neon-fp",
26          cl::desc("Use NEON for single-precision FP"),
27          cl::init(false), cl::Hidden);
28
29ARMSubtarget::ARMSubtarget(const std::string &TT, const std::string &FS,
30                           bool isT)
31  : ARMArchVersion(V4T)
32  , ARMFPUType(None)
33  , UseNEONForSinglePrecisionFP(UseNEONFP)
34  , IsThumb(isT)
35  , ThumbMode(Thumb1)
36  , PostRAScheduler(false)
37  , IsR9Reserved(ReserveR9)
38  , stackAlignment(4)
39  , CPUString("generic")
40  , TargetType(isELF) // Default to ELF unless otherwise specified.
41  , TargetABI(ARM_ABI_APCS) {
42  // default to soft float ABI
43  if (FloatABIType == FloatABI::Default)
44    FloatABIType = FloatABI::Soft;
45
46  // Determine default and user specified characteristics
47
48  // Parse features string.
49  CPUString = ParseSubtargetFeatures(FS, CPUString);
50
51  // Set the boolean corresponding to the current target triple, or the default
52  // if one cannot be determined, to true.
53  unsigned Len = TT.length();
54  unsigned Idx = 0;
55
56  if (Len >= 5 && TT.substr(0, 4) == "armv")
57    Idx = 4;
58  else if (Len >= 6 && TT.substr(0, 5) == "thumb") {
59    IsThumb = true;
60    if (Len >= 7 && TT[5] == 'v')
61      Idx = 6;
62  }
63  if (Idx) {
64    unsigned SubVer = TT[Idx];
65    if (SubVer > '4' && SubVer <= '9') {
66      if (SubVer >= '7') {
67        ARMArchVersion = V7A;
68      } else if (SubVer == '6') {
69        ARMArchVersion = V6;
70        if (Len >= Idx+3 && TT[Idx+1] == 't' && TT[Idx+2] == '2')
71          ARMArchVersion = V6T2;
72      } else if (SubVer == '5') {
73        ARMArchVersion = V5T;
74        if (Len >= Idx+3 && TT[Idx+1] == 't' && TT[Idx+2] == 'e')
75          ARMArchVersion = V5TE;
76      }
77      if (ARMArchVersion >= V6T2)
78        ThumbMode = Thumb2;
79    }
80  }
81
82  // Thumb2 implies at least V6T2.
83  if (ARMArchVersion < V6T2 && ThumbMode >= Thumb2)
84    ARMArchVersion = V6T2;
85
86  if (Len >= 10) {
87    if (TT.find("-darwin") != std::string::npos)
88      // arm-darwin
89      TargetType = isDarwin;
90  }
91
92  if (TT.find("eabi") != std::string::npos)
93    TargetABI = ARM_ABI_AAPCS;
94
95  if (isAAPCS_ABI())
96    stackAlignment = 8;
97
98  if (isTargetDarwin())
99    IsR9Reserved = ReserveR9 | (ARMArchVersion < V6);
100
101  if (!isThumb() || hasThumb2())
102    PostRAScheduler = true;
103
104  // Set CPU specific features.
105  if (CPUString == "cortex-a8") {
106    // On Cortext-a8, it's faster to perform some single-precision FP
107    // operations with NEON instructions.
108    if (UseNEONFP.getPosition() == 0)
109      UseNEONForSinglePrecisionFP = true;
110  }
111}
112
113/// GVIsIndirectSymbol - true if the GV will be accessed via an indirect symbol.
114bool
115ARMSubtarget::GVIsIndirectSymbol(GlobalValue *GV, Reloc::Model RelocM) const {
116  if (RelocM == Reloc::Static)
117    return false;
118
119  // GV with ghost linkage (in JIT lazy compilation mode) do not require an
120  // extra load from stub.
121  bool isDecl = GV->isDeclaration() && !GV->hasNotBeenReadFromBitcode();
122
123  if (!isTargetDarwin()) {
124    // Extra load is needed for all externally visible.
125    if (GV->hasLocalLinkage() || GV->hasHiddenVisibility())
126      return false;
127    return true;
128  } else {
129    if (RelocM == Reloc::PIC_) {
130      // If this is a strong reference to a definition, it is definitely not
131      // through a stub.
132      if (!isDecl && !GV->isWeakForLinker())
133        return false;
134
135      // Unless we have a symbol with hidden visibility, we have to go through a
136      // normal $non_lazy_ptr stub because this symbol might be resolved late.
137      if (!GV->hasHiddenVisibility())  // Non-hidden $non_lazy_ptr reference.
138        return true;
139
140      // If symbol visibility is hidden, we have a stub for common symbol
141      // references and external declarations.
142      if (isDecl || GV->hasCommonLinkage())
143        // Hidden $non_lazy_ptr reference.
144        return true;
145
146      return false;
147    } else {
148      // If this is a strong reference to a definition, it is definitely not
149      // through a stub.
150      if (!isDecl && !GV->isWeakForLinker())
151        return false;
152
153      // Unless we have a symbol with hidden visibility, we have to go through a
154      // normal $non_lazy_ptr stub because this symbol might be resolved late.
155      if (!GV->hasHiddenVisibility())  // Non-hidden $non_lazy_ptr reference.
156        return true;
157    }
158  }
159
160  return false;
161}
162