ARMSubtarget.cpp revision bfae1fd1fce97e73299e8ad67a22ae18de5112e9 
1//===-- ARMSubtarget.cpp - ARM Subtarget Information ----------------------===//
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 TargetSubtargetInfo.
11//
12//===----------------------------------------------------------------------===//
13
14#include "ARMSubtarget.h"
15#include "ARMBaseRegisterInfo.h"
16#include "llvm/GlobalValue.h"
17#include "llvm/Target/TargetSubtargetInfo.h"
18#include "llvm/Support/CommandLine.h"
19
20#define GET_SUBTARGETINFO_TARGET_DESC
21#define GET_SUBTARGETINFO_CTOR
22#include "ARMGenSubtargetInfo.inc"
23
24using namespace llvm;
25
26static cl::opt<bool>
27ReserveR9("arm-reserve-r9", cl::Hidden,
28          cl::desc("Reserve R9, making it unavailable as GPR"));
29
30static cl::opt<bool>
31DarwinUseMOVT("arm-darwin-use-movt", cl::init(true), cl::Hidden);
32
33static cl::opt<bool>
34StrictAlign("arm-strict-align", cl::Hidden,
35            cl::desc("Disallow all unaligned memory accesses"));
36
37ARMSubtarget::ARMSubtarget(const std::string &TT, const std::string &CPU,
38                           const std::string &FS)
39  : ARMGenSubtargetInfo(TT, CPU, FS)
40  , ARMProcFamily(Others)
41  , HasV4TOps(false)
42  , HasV5TOps(false)
43  , HasV5TEOps(false)
44  , HasV6Ops(false)
45  , HasV6T2Ops(false)
46  , HasV7Ops(false)
47  , HasVFPv2(false)
48  , HasVFPv3(false)
49  , HasVFPv4(false)
50  , HasNEON(false)
51  , UseNEONForSinglePrecisionFP(false)
52  , SlowFPVMLx(false)
53  , HasVMLxForwarding(false)
54  , SlowFPBrcc(false)
55  , InThumbMode(false)
56  , HasThumb2(false)
57  , IsMClass(false)
58  , NoARM(false)
59  , PostRAScheduler(false)
60  , IsR9Reserved(ReserveR9)
61  , UseMovt(false)
62  , SupportsTailCall(false)
63  , HasFP16(false)
64  , HasD16(false)
65  , HasHardwareDivide(false)
66  , HasT2ExtractPack(false)
67  , HasDataBarrier(false)
68  , Pref32BitThumb(false)
69  , AvoidCPSRPartialUpdate(false)
70  , HasRAS(false)
71  , HasMPExtension(false)
72  , FPOnlySP(false)
73  , AllowsUnalignedMem(false)
74  , Thumb2DSP(false)
75  , stackAlignment(4)
76  , CPUString(CPU)
77  , TargetTriple(TT)
78  , TargetABI(ARM_ABI_APCS) {
79  // Determine default and user specified characteristics
80  if (CPUString.empty())
81    CPUString = "generic";
82
83  // Insert the architecture feature derived from the target triple into the
84  // feature string. This is important for setting features that are implied
85  // based on the architecture version.
86  std::string ArchFS = ARM_MC::ParseARMTriple(TT);
87  if (!FS.empty()) {
88    if (!ArchFS.empty())
89      ArchFS = ArchFS + "," + FS;
90    else
91      ArchFS = FS;
92  }
93  ParseSubtargetFeatures(CPUString, ArchFS);
94
95  // Thumb2 implies at least V6T2. FIXME: Fix tests to explicitly specify a
96  // ARM version or CPU and then remove this.
97  if (!HasV6T2Ops && hasThumb2())
98    HasV4TOps = HasV5TOps = HasV5TEOps = HasV6Ops = HasV6T2Ops = true;
99
100  // Initialize scheduling itinerary for the specified CPU.
101  InstrItins = getInstrItineraryForCPU(CPUString);
102
103  // After parsing Itineraries, set ItinData.IssueWidth.
104  computeIssueWidth();
105
106  if (TT.find("eabi") != std::string::npos)
107    // FIXME: We might want to separate AAPCS and EABI. Some systems, e.g.
108    // Darwin-EABI conforms to AACPS but not the rest of EABI.
109    TargetABI = ARM_ABI_AAPCS;
110
111  if (isAAPCS_ABI())
112    stackAlignment = 8;
113
114  if (!isTargetIOS())
115    UseMovt = hasV6T2Ops();
116  else {
117    IsR9Reserved = ReserveR9 | !HasV6Ops;
118    UseMovt = DarwinUseMOVT && hasV6T2Ops();
119    SupportsTailCall = !getTargetTriple().isOSVersionLT(5, 0);
120  }
121
122  if (!isThumb() || hasThumb2())
123    PostRAScheduler = true;
124
125  // v6+ may or may not support unaligned mem access depending on the system
126  // configuration.
127  if (!StrictAlign && hasV6Ops() && isTargetDarwin())
128    AllowsUnalignedMem = true;
129}
130
131/// GVIsIndirectSymbol - true if the GV will be accessed via an indirect symbol.
132bool
133ARMSubtarget::GVIsIndirectSymbol(const GlobalValue *GV,
134                                 Reloc::Model RelocM) const {
135  if (RelocM == Reloc::Static)
136    return false;
137
138  // Materializable GVs (in JIT lazy compilation mode) do not require an extra
139  // load from stub.
140  bool isDecl = GV->hasAvailableExternallyLinkage();
141  if (GV->isDeclaration() && !GV->isMaterializable())
142    isDecl = true;
143
144  if (!isTargetDarwin()) {
145    // Extra load is needed for all externally visible.
146    if (GV->hasLocalLinkage() || GV->hasHiddenVisibility())
147      return false;
148    return true;
149  } else {
150    if (RelocM == Reloc::PIC_) {
151      // If this is a strong reference to a definition, it is definitely not
152      // through a stub.
153      if (!isDecl && !GV->isWeakForLinker())
154        return false;
155
156      // Unless we have a symbol with hidden visibility, we have to go through a
157      // normal $non_lazy_ptr stub because this symbol might be resolved late.
158      if (!GV->hasHiddenVisibility())  // Non-hidden $non_lazy_ptr reference.
159        return true;
160
161      // If symbol visibility is hidden, we have a stub for common symbol
162      // references and external declarations.
163      if (isDecl || GV->hasCommonLinkage())
164        // Hidden $non_lazy_ptr reference.
165        return true;
166
167      return false;
168    } else {
169      // If this is a strong reference to a definition, it is definitely not
170      // through a stub.
171      if (!isDecl && !GV->isWeakForLinker())
172        return false;
173
174      // Unless we have a symbol with hidden visibility, we have to go through a
175      // normal $non_lazy_ptr stub because this symbol might be resolved late.
176      if (!GV->hasHiddenVisibility())  // Non-hidden $non_lazy_ptr reference.
177        return true;
178    }
179  }
180
181  return false;
182}
183
184unsigned ARMSubtarget::getMispredictionPenalty() const {
185  // If we have a reasonable estimate of the pipeline depth, then we can
186  // estimate the penalty of a misprediction based on that.
187  if (isCortexA8())
188    return 13;
189  else if (isCortexA9())
190    return 8;
191
192  // Otherwise, just return a sensible default.
193  return 10;
194}
195
196void ARMSubtarget::computeIssueWidth() {
197  unsigned allStage1Units = 0;
198  for (const InstrItinerary *itin = InstrItins.Itineraries;
199       itin->FirstStage != ~0U; ++itin) {
200    const InstrStage *IS = InstrItins.Stages + itin->FirstStage;
201    allStage1Units |= IS->getUnits();
202  }
203  InstrItins.IssueWidth = 0;
204  while (allStage1Units) {
205    ++InstrItins.IssueWidth;
206    // clear the lowest bit
207    allStage1Units ^= allStage1Units & ~(allStage1Units - 1);
208  }
209  assert(InstrItins.IssueWidth <= 2 && "itinerary bug, too many stage 1 units");
210}
211
212bool ARMSubtarget::enablePostRAScheduler(
213           CodeGenOpt::Level OptLevel,
214           TargetSubtargetInfo::AntiDepBreakMode& Mode,
215           RegClassVector& CriticalPathRCs) const {
216  Mode = TargetSubtargetInfo::ANTIDEP_CRITICAL;
217  CriticalPathRCs.clear();
218  CriticalPathRCs.push_back(&ARM::GPRRegClass);
219  return PostRAScheduler && OptLevel >= CodeGenOpt::Default;
220}
221